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THE GEOMORPHIC AND ECOLOGICAL INFLUENCE OF LARGE WOODY DEBRIS IN
STREAMS AND RIVERS
by
Neil S. Lassettre ([email protected]) Department of Landscape Architecture and Environmental Planning
University of California Berkeley, CA 94720 USA
Richard R. Harris ([email protected])
Department of Environmental Science, Policy, and Management University of California
Berkeley, CA 94720-3114
March 2001 Abstract. Large pieces of wood, such as logs, stumps, and large branches are an important ecological component of streams flowing through coast redwood (Sequoia sempervirens) forests of Northern California. The distribution and abundance, geomorphic role, and ecological role of large woody debris (LWD) vary through the channel network. This review summarizes pertinent literature and describes how the physical and ecological characteristics of wood change from small to large streams. Streamside and in-channel management practices influence LWD recruitment and transport processes, and significantly alter its functions. Management decisions can be better defined through a process-based classification that describes the influence of wood through the channel network.
Introduction Logs, stumps, and branches that enter and are transported by rivers and streams are important influences on channel morphology and aquatic ecology. Large woody debris (LWD), generally defined as wood ≥ 10 cm diameter and ≥ 1 m length, obstructs streamflow, stores and distributes sediment, and creates channel features, such as pools, riffles, and waterfalls. Wood intercepts organic matter traveling downstream, allowing this material to be processed by instream organisms. Macroinvertebrates and fish occupy and use pools and riffles as habitat, and sediment deposition provides sites for riparian forest regeneration.
The ecological importance of wood is not limited to the instream environment. On the forest floor, woody debris is both a nutrient source and a habitat element for plants, insects, and vertebrates. In estuaries and near shore ocean environments, LWD provides nursery habitat, protection, and a nutrient source for various organisms. Reviews by Harmon et al. (1986), Sedell et al. (1988), and Triska and Cromack (1980) thoroughly treat these topics.
This review focuses on the instream geomorphic and ecological roles of LWD, highlighting effects occurring at the reach level and basin-wide along the channel network from headwaters to large rivers. When possible, the examples are drawn from redwood (Sequoia sempervirens) ecosystems. However, since such examples do not exist for every situation, studies from other systems are used to demonstrate basic concepts, while recognizing possible local differences.
This literature survey is divided into six general subject areas: 1) characteristics, distribution, and transport of LWD, 2) LWD and channel morphology; 3) LWD and stream ecology; 4) management impacts on LWD; 5) synthesis and a proposal for stream classification and; 6) management recommendations. The first section examines regional LWD loading, general trends of log size through the stream network, and the influences and mechanisms of LWD transport. Section two discusses the influence of LWD on sediment storage, channel dimension and stability, and basin-wide effects of wood on pool formation. Section three explores how wood affects nutrient retention, the distribution of macroinvertebrates and salmonids, and the presence of riparian forest patches. The fourth section looks at how timber harvest, flood control, and road maintenance affect the distribution and abundance of instream LWD. The fifth section includes a synthesis of the morphological and ecological effects occurring throughout the channel network. This synthesis results in a proposed designation of LWD influence zones based on channel size and gradient. The last section provides a discussion on how timber harvest and road maintenance may be modified to accommodate LWD input and transport.
In the course of preparing this review, all available literature concerning LWD in stream systems, regardless of geographic location, was consulted. A listing and summary of interesting results from all studies is contained in the appendix (Tables A-1 through A-13).
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Characteristics, Distribution, and Transport of LWD LWD loading and distribution. Large woody debris loading refers to the weight or volume of wood per square meter of stream channel (kg/m2 or m3/m2). Along the Pacific Coast, streams flowing through the redwood forests of Northern California exhibit the highest levels of instream wood loading (Table 1, Harmon et al. 1986, Bilby and Bisson 1998). Massive redwood logs contribute huge amounts of biomass to stream channels, and in some reaches loading is dominated by a single piece of woody debris (Tally 1980). LWD loading generally decreases as one moves to more northern forests, with southeastern Alaska streams that flow through sitka spruce forests (Picea sitchensis) displaying the lowest abundance of instream wood (Table 1, Bilby and Bisson 1998). When compared with other regions across North America, forests of the Pacific Coast have the greatest levels of terrestrial and aquatic woody debris (Harmon et al. 1986).
Table 1. Loading of LWD (m3/m2) in streams flowing through unmanaged forests along the Pacific Coast from Northern California to Southeastern Alaska. Loading is greatest in coast redwood (Sequoia sempervirens) systems of Northern California and generally decreases as one moves to more northern forests.
LOCATION FOREST TYPE LOADING REFERENCE Alaska • Sitka spruce (Picea sitchensis), western
hemlock (Tsuga heterophylla), • 0.019 m3/m2 Harmon et al. 1986
Alaska • Sitka spruce (Picea sitchensis), western hemlock (Tsuga heterophylla), red alder (Alnus rubra)
• 0.061 m3/m2 Robison and Beschta 1990
British Columbia, Canada
• Sitka spruce (Picea sitchensis), western hemlock (Tsuga heterophylla)
• 0.068 m3/m2 Harmon et al. 1986
Oregon • Douglas fir (Pseudotsuga menziesii) • 0.057 m3/m2 Harmon et al. 1986 Northern California • Douglas fir (Pseudotsuga menziesii) • 0.028 m3/m2 Harmon et al. 1986 Northern California • Coast Redwood (Sequoia sempervirens) • 0.155 m3/m2 Harmon et al. 1986 Northern California • Coast redwood (Sequoia sempervirens) • 0.181 m3/m2 Keller and MacDonald 1983
Within a stream network, the abundance and distribution of LWD is strongly influenced by channel size and dominant input mechanism (Bilby and Ward 1989, Beechie and Sibley 1997). Debris loading is greatest in low order streams (smallest) and generally decreases in the downstream direction (Figure 1, Keller and Swanson 1979, Keller et al. 1985, Lienkaemper and Swanson 1987, Robison and Beschta 1990, Montgomery et al. 1995). Narrow, low order channels lack the streamflow necessary to transport and redistribute most fallen logs (Swanson and Lienkaemper 1978). Wood enters through windthrow, bank erosion, and mass wasting, and unless transported by debris torrents or flood flows, remains randomly distributed in the channel (Table 2, Swanson et al. 1976, Keller and Swanson 1979). Logs may remain stationary for long periods of time (greater than 200 years in some cases), but will eventually leave through transport, or decay from decomposition and physical abrasion (Tally 1980, Harmon et al. 1986, Murphy and Koski 1989).
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Table 2. The distribution and mechanisms of LWD input and transport from low to high order streams. Jams range from randomly oriented single pieces to large, clumped accumulations within the stream and on bars and floodplains. In small streams, wood enters and moves along the stream primarily during heavy storms, which trigger landslides and provide adequate flow to transport logs. In larger streams and rivers, LWD mobility increases, leaving wood in distinct jams in the water or on bars.
LOW ORDERS INTERMEDIATE ORDERS HIGH ORDERS DISTRIBUTION • Random
• Single piece • Clumped in jams within
streams • Clumped in jams on bars
and floodplains INPUT MECHANISMS
• Windthrow • Bank erosion • Mass Wasting
• Windthrow • Bank erosion • Fluvial transport
• Bank erosion • Fluvial transport
TRANSPORT MECHANISMS
• Debris flows • Flood flows
• Flotation
• Flotation
Figure 1. Schematic representation of the general trend of LWD characteristics along the channel network. Debris loading and jam frequency is highest in small, low order streams and generally decreases in higher orders. The piece size, jam size, and transport tend to increase along the same gradient. The relationship shows that small channels contain more wood per channel area than large channels, but larger channels have a greater capacity to transport and redistribute LWD pieces.
Intermediate order channels are wide and deep enough to move and redistribute in-channel wood (Swanson and Lienkaemper 1978, Bilby and Ward 1989). The main input mechanisms are windthrow, bank erosion, and fluvial transport from upstream reaches (Table 2, Keller and Swanson 1979). Wood accumulates within the channel or on meander bends in irregularly spaced but distinct jams that have profound influence on stream morphology and ecology (Fetherston et al. 1995, Abbe and Montgomery 1996, Hogan et al. 1998). Jam frequency (number of jams per meter) decreases as channels become larger and are more able to transport wood, while at the same time the size of LWD jams increases (Keller and Tally 1979, Bisson et al. 1987). The trend of increasing LWD jam size down the channel network runs counter to the trend of decreasing LWD loading, however, both are a consequence of the increasing capacity of streams to transport wood (Figure 1).
In high order streams, most wood enters through bank undercutting and fluvial transport. The wood deposits on gravel bars or terraces along the river margin (Table 2, Keller and
LOADING JAM FREQUENCY
High
Low
DISTANCE FROM HEADWATERS
PIECE SIZE JAM SIZE TRANSPORT
High
Low
4
Swanson 1979, Bisson et al. 1987). Wood collecting on bars or islands is frequently out of contact with the low flow channel and may have a limited effect on channel morphology (Keller and Swanson 1979). Fluvially deposited LWD still provides important ecological services for salmonids, such as escape cover, and for riparian forest development (Harmon et al. 1986, Fetherston et al. 1995). In low gradient rivers and streams, channel width and sinuosity are main factors controlling the abundance and distribution of LWD accumulations (Nakamura and Swanson 1994). Wide, unconstrained reaches bordered by floodplains and terraces possess abundant storage and depositional sites for transported logs. Reaches flowing through wide valleys develop secondary channels at the base of terraces and along valley walls that trap wood mobilized during large floods. The mouths of secondary channels may be significant LWD storage sites (Swanson and Lienkaemper 1979, Nakamura and Swanson 1994). Constrained reaches have less extensive floodplain and valley regions and are thus less able to accumulate LWD. Another factor contributing to greater abundance of LWD in sinuous channels is riparian forest development. Riparian forests develop on floodplains and terraces, providing a direct source of wood to stream channels (Lienkaemper and Swanson 1979, Nakamura and Swanson 1994). Confined channels also have a greater capacity to transport wood downstream during high flows (Keller and Swanson 1979).
LWD size and volume. As LWD loading decreases down the channel network, the average size (length and diameter) and volume of instream wood increases (Figure 1, Bilby and Ward 1989, 1991). Channel width is a dominant influence on measures of LWD loading, as it is directly related to channel area (Beechie and Sibley 1997). Low order streams have small channel area and a low capacity to transport in-channel wood, leading to high debris loads. Channel width also controls the average size of wood in streams (Bilby and Ward 1989, 1991, Robison and Beschta 1990). Stable pieces of wood remain stationary during normal to high flows. As channels become wider and deeper, the average size of a stable piece of wood increases. Pieces shorter than bankfull width and with a diameter less than bankfull depth are more likely to be transported out of a reach by streamflow (Bilby 1984, Braudrick et al. 1997). In progressively larger channels, a larger proportion of small pieces is removed, leading to a greater average size of in-channel LWD (Bisson et al. 1987, Bilby and Ward 1989).
Influences on LWD transport. The stability of LWD depends on the physical characteristics of the piece and piece orientation within the channel. Log length and diameter are major controls on the movement of wood in rivers and streams (Swanson et al. 1976, Bilby 1984, Nakamura and Swanson 1994). Most transported pieces are shorter than bankfull width, indicating that length may be a rough estimate of wood susceptibility to transport (Bilby 1984, Lienkaemper and Swanson 1987, Nakamura and Swanson 1994). Shorter pieces move more easily than longer pieces, as they encounter fewer instream obstructions and have less contact with bank regions, leaving fewer opportunities for pieces to deposit and accumulate (Bilby 1984). In low to intermediate order streams (3 m to 25 m bankfull width), Lienkaemper and Swanson (1987) found that all transported pieces travelling more than 10 m were shorter than bankfull width. Nakamura and Swanson (1994) also observed that most transported pieces were shorter than bankfull width, while 20% of un-transported pieces were longer than bankfull width. Rootwads increase the stability of logs by increasing the surface area available for
5
snagging on instream obstructions and potentially increasing log diameter to greater than the average bankfull depth (Sedell et al. 1988).
Log position influences the degree to which a piece is exposed to streamflow and potentially transported. Important positional factors contributing to the stability of in-channel wood are the percent of the piece anchored to the bank, the proportion of the piece in the water, and the angle of orientation to flow (Bryant 1983). Burial of one end in the streambed or along the banks reduces piece exposure to streamflow and significantly increases LWD stability. Pieces buried at both ends are extremely stable and may remain in place for decades (Bilby 1984). Increased stability also results when LWD only partially resides in the stream, with one end either buried or simply resting above the bankfull channel.
Within the channel, pieces oriented increasingly perpendicular to flow are transported more easily than pieces oriented in a downstream direction (Bryant 1983). Bryant (1983) observed a southeastern Alaska stream and developed criteria that identified the most stable pieces of wood as those with 70% of their mass anchored to the stream bank, 15% of their mass touching the water, both ends buried, and oriented 30 degrees to flow. However, precise relationships between physical characteristics, piece orientation, and wood transport are yet to be established. Braudrick and Grant (2000) performed flume experiments with pieces shorter than bankfull width and found that orientation to flow, presence of a rootwad, log density, and log diameter were the most influential factors in LWD transport. Braudrick et al. (1997) simulated wood movement through a system, using flume experiments, and observed three distinct transport regimes based on the degree of piece congestion. The transport regime depended on the rate of log input compared to stream discharge. The results showed that low order channels with high rates of wood input and relatively low discharge have a congested transport regime, while high order channels with low wood input rates and greater discharge are uncongested.
LWD transport mechanisms. The mechanisms of wood transport vary down the stream network with respect to channel size (Table 2, Keller and Swanson 1979). Small, steep, low order tributaries primarily move wood through debris torrents triggered during heavy rainfall and flood flows (Swanson et al. 1976, Keller and Swanson 1979, Nakamura and Swanson 1993). Debris flows usually originate in 1st and 2nd order channels with bank slopes that exceed 50%; torrents are rare in intermediate order streams with moderately sloping banks (Swanson et al. 1976, Swanson and Lienkaemper 1978). Torrents bring material from hillslopes into stream channels, transporting logs and sediment short distances to form large accumulations, or transport wood and sediment over longer distances to be deposited in lower gradient reaches (Keller and Swanson 1979). In some cases, debris flows scour existing in-channel debris and sediment, leaving a bedrock channel that is devoid of complexity (Swanson et al. 1976, Swanson and Lienkaemper 1978). In intermediate to high order channels, flotation is the main transport mechanism. Flotation of logs occurs infrequently in small channels, mainly during unusually high flows that also trigger debris torrents (Swanson et al. 1976, Singer and Swanson 1983). The transport of wood during elevated flows is most common in larger streams, and is an important LWD recruitment mechanism in reaches that have relatively low input of trees from the adjacent riparian forest (Keller and Swanson 1979).
6
LWD and Channel Morphology Sediment storage. Logs and stumps deflect streamflow, creating low energy environments that encourage the deposition of sediment upstream of the obstruction (Lisle 1986b). Anchored or attached pieces can protect and strengthen streambanks, which serves to reduce rates of bank erosion and sediment delivery into the channel (Keller and Swanson 1979). LWD obstructions create sediment storage sites that buffer the movement of bedload sediment through a system. In low order streams, in-channel LWD produces open storage sites that collect and store sediment during high flows (Keller et al. 1985). The storage capacity of these LWD-created sites can be quite large. Tally (1980) estimated that wood stored 200 years worth of bedload in undisturbed reaches flowing through Redwood National Park, with space for another 100 years worth of sediment yield. In the Oregon Coast Ranges, Swanson et al. (1976) estimated that the sediment yield of forested streams was less than 10% of the material in storage, and found that in one 100 m section of stream, wood trapped and stored 230m3 of sediment. The storage capacity of LWD has also been observed in Idaho batholith streams, where logs accounted for 34% of channel obstructions and 50% of sediment storage (Megahan 1982).
The displacement or removal of log steps significantly increases sediment transport out of low order stream reaches. Removal of wood from streams reduces the amount of available storage sites and decreases streambed roughness, leading to higher rates of sediment transport. Winter high flows transported 5000m3 of sediment out of a 250 m stream reach in western Washington after Beschta (1979) experimentally removed all pieces of in-channel wood. Bilby (1981) removed wood from a New Hampshire stream and saw a 500% increase in sediment export over the next year. In steep mountain reaches, log steps are a natural influence on hydraulic geometry and play an important role in channel slope adjustment (Swanson et al. 1976, Keller and Swanson 1979, Tally 1980, Heede 1985a, b). Log steps removed from an Arizona stream were eventually replaced by gravel bars, which assumed control over the drop in elevation (Heede 1985a,b). Increased bedload movement of coarse sediment was required to offset the removal of naturally occurring log steps.
The relative contribution of LWD obstructions to sediment storage decreases down the stream network (Figure 2, Table 3). In channels <7 m wide, Bilby and Ward (1989) found that 40% of debris pieces were associated with sediment accumulations. An examination of progressively wider streams (with decreasing gradient) revealed that <30% of debris pieces in channels between 7 m to 10 m, and <20% of debris pieces in channels >10 m were associated with sediment accumulations. Thus, in high gradient reaches, LWD obstructions have a greater role in bedload storage and in controlling the release of sediment (Nakamura and Swanson 1993). Logs are the primary structural component in the formation of step pools that dissipate stream energy, forming low energy depositional sites just upstream of the created waterfall and on the margins of the resulting plunge pool (Heede 1972, Bilby and Bisson 1998).
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Table 3. The predominant storage sites and pool types associated with LWD from low to high order streams. Step pools form in small channels and accumulate sediment just upstream of the obstruction. In wider streams, accumulations obstruct flow and create low energy depositional environments downstream. Large rivers accumulate sediment in hydraulically formed floodplains and gravel bars.
LOW ORDERS INTERMEDIATE ORDERS HIGH ORDERS STORAGE SITES • Upstream of log steps • Downstream of single
pieces and log steps • Floodplains and gravel
bars POOL TYPES • Step pools • LWD formed lateral scour • Hydraulically formed
lateral scour
Narrow, low order streams often lack significant floodplains and gravel bars, which are important sediment storage sites for intermediate to high orders. In wider streams and large rivers, obstructions create zones of locally high shear stress and a low energy depositional site just downstream (Table 3, Lisle 1986b, Fetherston et al. 1995, Abbe and Montgomery 1996). These channel margin gravel bars and mid-channel islands accumulate additional LWD and sediment, allowing surfaces to build in elevation. The surfaces are sites for riparian regeneration and forest development, further stabilizing the accumulated sediment (Fetherston et al. 1995, Abbe and Montgomery 1996).
In low gradient reaches, wood has a limited effect over sediment accumulation and transport, mainly providing temporary storage (Figure 2, Table 3, Nakamura and Swanson 1993). Large woody debris may actually limit sediment storage by influencing and retarding floodplain and bar development (Smith et al. 1993b). LWD deflects the channel thalweg, resulting in irregular wood controlled lateral scour and increased local sediment export (Smith et al. 1993b, Nakamura and Swanson 1993). After removing log obstructions from a southeastern Alaska stream, Smith et al. (1993b) observed that streamflow initially mobilized sediment causing an increase in net sediment yield. After the channel re-adjusted, the loss of turbulence and increased resistance associated with bar formation resulted in a more regular sequence of bars that stored greater amounts of sediment.
8
Figure 2. Schematic representation of the general trend of the effects of LWD on channel morphology along the stream network. The sediment storage capacity, influence on channel gradient, and influence on pool formation is greatest in small streams and decreases in higher orders. The influence of LWD on channel width increases along the same gradient, but has a limited effect on the width of large rivers.
Channel dimension. The presence of LWD influences local channel gradient and channel width. In low orders, logs form steps that create waterfalls where the stream abruptly drops in elevation. The presence of steps and waterfalls dissipates stream energy, making the stream less able to transport sediment (Heede 1985a, b). Step forming LWD accounts for 30% to 80% of the elevation drop in moderate to steep gradient streams along the coasts of Northern California and Oregon (Swanson et al. 1976, Keller and Swanson 1979, Keller and Tally 1979). As channel gradient decreases, and channels widen, fewer pieces of wood are able to span the channel and form steps, decreasing the occurrence of waterfalls and lessening the control LWD has on elevation (Figure 2, Keller et al. 1985, Bilby and Ward 1989). In very steep reaches, however, wood may rest on top of large boulders and have a limited effect on sediment storage, waterfall formation, and gradient control (Keller and Tally 1979).
LWD increases local channel width in streams not confined by bedrock (Figure 2, Swanson et al. 1976, Bryant 1980, 1983). Sediment deposits upstream of wood accumulations, or downstream of wood accumulations in low gradient reaches, widen and decrease channel depth (Keller and Swanson 1979). Partially spanning fallen trees deflect the thalweg laterally, causing the stream current to diverge and widen the stream channel (Bisson et al. 1987). In moderate to low gradient streams along the Pacific Coast, studies show that the scour around single pieces of wood and large jams widens the channel by 50% to 200% over average bankfull width (Keller et al. 1985, Keller and Swanson 1979, Bryant 1980, 1983, Nakamura and Swanson 1993). In low gradient southeastern Alaska streams, Robison and Beschta (1990) found that the difference in average bankfull width between streams was best explained by the volume of LWD per 100 m of channel in study reaches. Streams with the greatest volume of wood along their length were the widest.
SEDIMENT STORAGE CHANNEL GRADIENT POOL FORMATION
High
Low
DISTANCE FROM HEADWATERS
CHANNEL WIDTH
High
Low
9
In low to intermediate orders, large jams of wood have the greatest overall influence on channel morphology, while individual pieces influence the bed between jams (Hogan et al. 1998). LWD jams are initiated by the presence of key pieces that are of sufficient length and width to trap transported logs. Jams persist for many years, and as they age, channel morphology increases in complexity (Hogan et al. 1998). After formation, sediment accumulates upstream of the jam, initially resulting in a less complex, sediment laden channel. As wood ages and decays, the porosity of the jam increases, creating differential scour and diverse channel forms that become more complex as the jam further deteriorates. Old growth forests have relatively low rates of jam formation, thus jams of varying age, and a complex channel morphology. Harvested or disturbed basins have accelerated rates of jam formation, thus jam age is less varied, leading to a less complex channel morphology (Hogan et al. 1998). Local stream gradients upstream of reaches controlled by key-LWD or LWD jams are lower than channel averages, contributing to a stepped profile, and local channel widths upstream of key-LWD of LWD jams can be significantly greater (Nakamura and Swanson 1993).
Influence on channel stability. LWD stabilizes channels by dissipating stream energy, armoring stream banks, and creating sites of local scour and fill (Keller and Swanson 1979). In low order streams, log steps create cascades, which reduce available energy by increasing channel roughness and leave less energy to erode and scour bed and banks (Heede 1985a, b). Steps are a major control on bank stability, and removal or reduction in size and abundance of these features through management or timber harvest can destabilize channels (Beschta 1979, Adenlof and Wohl 1994). After removing log steps from reaches in low to intermediate sized streams, Beschta (1979) and Bilby (1984) observed severe erosion that completely modified the stream channel through scour and fill. In low gradient alluvial reaches, wood and boulder obstructions act to stabilize the location of pools and bars during high flow (Lisle 1986b). The obstructions create backwater eddies, which are low energy depositional sites that reduce local shear stress and stabilize bed material (Smith et al. 1993a, b).
LWD also contributes to channel instability. Logs divert streamflow and force lateral cutting in streams with minimal bedrock influence (Keller and Swanson 1979, Swanson and Lienkaemper 1979). Lateral stream erosion leads to bank undercutting and eventual slumping into the channel. In streams impacted by debris flows, wood and sediment accumulations divert flow against adjacent steep banks and can initiate failure of the affected hillslope (Swanson et al. 1976). Wood carried by flood flows reduces bank cohesion by battering low banks and severely abrading streamside vegetation (Swanson and Lienkaemper 1979). In high orders, large jams commonly induce channel migration and cause major changes in streambed topography (Hickin 1984, Nakamura and Swanson 1993).
Influence on pool formation. In step-pool and plane bedded (steep to moderate gradient) stream reaches, wood obstructions are the primary element in pool formation (Figure 2, Montgomery et al. 1995, Abbe and Montgomery 1996, Beechie and Sibley 1997, Montgomery and Buffington 1997). Step-pool and plane bedded reaches are found in steep to moderate gradients, and studies along the Pacific Coast show that 20% to 80% of pools are formed in association with LWD (Lisle 1986b, Andrus et al. 1988, Carlson et
10
al. 1990, Robison and Beschta 1990, Nakamura and Swanson 1994, Montgomery et al. 1995, Wood-Smith and Buffington 1996, Montgomery and Buffington 1997).
In narrow, steep gradient streams, a large proportion of fallen logs fully span the channel and obstruct streamflow to form cascades and plunge pools (Table 3, Bilby and Ward 1989, 1991, Robison and Beschta 1990, Richmond and Fausch 1995). Other instream obstructions, such as boulders, are active in the formation of cascades and plunge pools, but wood exerts the greatest control over pool creation (Keller and Swanson 1979).
In wider, low gradient streams, fewer logs are able to span the channel, so most pieces extend partway across and are oriented diagonal to flow (Gregory et al. 1993, Richmond and Fausch 1995). Scour pools form adjacent to partially spanning pieces, as streamflow is forced under and around obstructions. Dominant pool types shift from step-pools to scour pools down the channel network from step-pool to plane bedded reaches (Table 3, Bilby and Ward 1989, 1991, Robison and Beschta 1990, Richmond and Fausch 1995). Bilby and Ward (1989) surveyed western Washington streams and found that plunge pools were the most common (40%) pool type in streams <7 m bankfull width, while scour pools were the most common (60%) pool types in stream >10 m bankfull width. Bilby and Ward (1991) witnessed the same general shift in pool types among both logged and undisturbed basins.
Further down the channel network, in pool-riffle reaches, the interaction between streamflow and sediment transport is the most important element in pool formation (Leopold et al. 1964, Montgomery and Buffington 1997). The presence of wood has a lesser effect on pool formation and the frequency of LWD associated pools generally decreases with increasing channel width (Bilby and Ward 1991). In stream gradients ranging from 0.01 to 0.05, Montgomery et al. (1995) and Beechie and Sibley (1997) found a strong relationship between the number of pools and LWD loading, while in stream gradients <0.01 to <0.02 the relationship was significantly weaker. Smith et al. (1993a, b) removed wood from a low gradient southeastern Alaska stream and found that pool spacing was similar before and after. The results indicate that in low gradient rivers and streams, hydraulic factors rather than channel obstructions exert a greater control over the formation of pools (Swanson and Lienkaemper 1978, Montgomery et al. 1995, Beechie and Sibley 1997). In very large rivers, most wood deposits in the active channel on bars, islands, or in secondary channels, out of contact with the low flow water surface (Piegay et al. 1999). In these cases, pool formation in the main channel may be independent of LWD presence, but wood along shallow channel margins or in small secondary channels does create pools that are important refuge for salmonids (Bisson et al. 1987).
LWD and Stream Ecology Nutrient dynamics. Allochthonous material from the riparian forest is a primary energy source for undisturbed rivers and streams (Gregory et al. 1991). Wood obstructions potentially store large amounts of externally derived organic matter (Figure 3). In Rocky Mountain streams of various successional stages, Trotter (1990) found that reaches with LWD stored twice as much organic matter as reaches where wood was experimentally removed. Bilby and Likens (1980) removed LWD from a low order stream in New
11
Hampshire and observed significant increases in the export of dissolved organic carbon (18% increase), fine particulate organic matter (<1mm; 638% increase), and coarse particulate organic matter (>1mm; 138% increase). During high discharges, the same reaches showed a 500% increase in the export of fine particulate organic matter and coarse particulate organic matter (Bilby 1981).
Salmon carcasses are an important source of organic matter for stream systems (Cederholm and Petersen 1985, Cederholm et al. 1989). In western Washington streams, twenty-two species of mammals and birds were found to consume coho salmon (Oncorhynchus kisutch) carcasses (Cederholm et al. 1989). Woody debris plays an important role in making nutrients from dead fish available by preventing the rapid transport of carcasses downstream. Cederholm and Petersen (1985) found a positive relationship between LWD loading and the number of retained coho salmon carcasses. Branches and logs physically obstruct the movement of dead fish, and the distance a carcass drifted downstream in a controlled release experiment was inversely related to the amount of LWD. In a separate experiment, pools were the most common carcass deposition sites and most pools that retained dead fish were formed by LWD (Cederholm et al. 1989).
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Figure 3. Schematic representation of the general trend of the effects of LWD on stream ecology down channel network. Wood-associated nutrient storage and insect abundance is highest in small, low order streams and generally decreases in higher orders. The importance of LWD for salmonid habitat is equally important throughout the basin, although the role of wood varies. Wood decomposes more quickly in the terrestrial environment, and hence more quickly in higher orders where LWD frequently resides partway or completely out of the channel. The influence of LWD on riparian forest development decreases with increasing channel confinement that reduces active floodplain area.
Accumulations of organic matter behind log debris dams are sites for the uptake of nutrients. The sediment associated with LWD is high in organic matter content and maintains locally elevated respiration rates. Hedin (1990) found that community respiration was three times higher in sediment behind log debris dams than elsewhere on the streambed. As an attachment substrate for microorganisms that uptake nutrients, wood debris is active in nitrogen and phosphorous removal (Aumen et al. 1990).
Wood is a potential nutrient source for stream ecosystems. Logs contribute fine particulate organic matter through macroinvertebrate processing and physical abrasion. In streams with high debris loads, logs are a greater source of fine particulate organic matter than leaves or pine needles (Ward and Aumen 1986). The physical production of fine particulate organic matter is greatest in winter, when logs are shattered by high flow and through collisions with mobilized substrate.
The decomposition of wood into basic nutrient forms occurs very slowly in water (Sedell et al. 1988). Fungi and macroinvertebrate decomposers require an aerobic environment, but waterlogging prevents the deep penetration of oxygen into the wood interior. Pieces partly submerged beneath the water surface show variable rates of decomposition, with sections exposed to air breaking down more rapidly. In small streams that are shallow and narrow, wood is partly or completely submerged only during the high flows of winter and spring. Wood decomposition rates may be much more rapid in the summer, when pieces are exposed to air (Sedell et al. 1988). Intermediate stream orders are wide and deep enough to submerge logs during high and low flow periods, and may have relatively slow wood decomposition rates. In large rivers, wood is deposited on banks and islands frequently out of contact with the water surface, possibly encouraging rapid rates of LWD break down (Figure 3).
NUTRIENT STORAGE INSECT ABUNDANCE
High
Low
DISTANCE FROM HEADWATERS
WOOD DECOMPOSITION FOREST DEVELOPMENT
High
Low
SALMONID HABITAT
13
Physical abrasion and macroinvertebrate grazing gradually expose more wood surface area and increase oxygen penetration. As logs decompose, the concentration of essential nutrients, such as nitrogen, increases partly through nitrogen fixation (Sedell et al. 1988). The nitrogen fixation occurring on fallen wood may account for 5% to 10% of the annual nitrogen supplied to streams (Sedell et al. 1988).
Macroinvertebrates. The macroinvertebrate fauna associated with LWD ranges from obligate restriction to purely opportunistic use (Dudley and Anderson 1982). In coastal and Cascades Oregon streams, Dudley and Anderson (1982) found 45 taxa closely associated with wood and over 80 taxa facultatively associated. Obligate groups are mostly xylophagous and rely on wood as a direct nutrient source. Obligates are mainly comprised of borers and gougers, which remove and process log particles. Most obligate groups are found on soft, rotten wood or grooved, textured wood with a large surface area. Major xylophagous species are the wood gouging caddisfly Heteroplectron californicum and elmid beetle Lara avara. Anderson et al. (1978) found caddisflies to be the most conspicuous and diverse wood associated insects, however, the density and abundance of L. avara was more strongly associated with the amount of wood available, irrespective of stream size. Higher densities of xylophagous insects occur on hardwoods than on conifers (Anderson et al. 1978). Hardwoods have a higher nutritional value due to greater microbial activity and nitrogen content (Sedell et al. 1988). Two possible mechanisms for wood exploitation by macroinvertebrates are consumption to obtain digestible carbon and nitrogen from microbial flora to meet energy and nutrient requirements, and cultivation and retention of a gut flora to provide nutrients and aid in digestion of wood fiber (Anderson et al. 1978).
Facultative groups use wood as an attachment substrate for filter feeding and grazing, as refugia during high flows and protection from predators, and as an oviposition site. Wood acts as a stable feeding platform for net spinning caddisflies and may channel flow along surface features to maximize filter-feeding efficiency (Dudley and Anderson 1982, Harmon et al. 1986). Wood is also used in case construction, particularly by Limnephilidae caddisflies (Merritt and Cummins 1996). Smooth, firm wood is a suitable attachment site for filter feeders and macroinvertebrates grazing on biofilm (Dudley and Anderson 1982). In New York, Hax and Golladay (1993) found macroinvertebrate densities on wood substrates to be higher than densities on leaves and other detritus. Densities were correlated with the amount of biofilm, which was highest on logs. Biofilm is a food source for grazing aquatic insects. Collector/gatherers occurred in higher proportions on leaves, while collector/filterers preferred wood attachment sites.
The primary basis of association for most facultative taxa is cover from predators and refuge from abiotic stress (Dudley and Anderson 1982). Grooves and cracks support high densities of macroinvertebrates presumably seeking escape cover, as many times predators dominate the total biomass within these microhabitats. Most groups are found on grooved or textured surfaces (Dudley and Anderson 1982). In Australia, O'Connor (1991) compared different wood surfaces and found that grooved snags supported higher densities of aquatic insects. The results supported a habitat complexity hypothesis predicting an increase in species richness with increasing habitat complexity. Physically complex substrates provide more habitat opportunities for algae, microbes, and
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macroinvertebrates. Depositional sites upstream of log obstructions may support locally high macroinvertebrate densities as organisms gather to process organic material. Log obstructions also act as refugia during high discharge by creating areas of low water flux and low bedflow (Palmer 1996). These areas retain existing populations and encourage deposit of drifting organisms.
Caddisflies and Diptera commonly pupate in moist or saturated logs in the channel or along the stream margin (Harmon et al. 1986). Limnephilid caddisflies deposit egg masses on damp wood, while hydropsychids prefer submerged branches or overhanging wood.
The sequence of colonizers on a newly fallen piece of wood follows the stage of decay (Sedell et al. 1988). Fresh logs are primarily attachment substrates for algae and microbes, which in turn support populations in the grazer and collector/gatherer functional feeding groups. Early colonizers include chironomid midges and scraping mayflies, such as Cinygma spp. and Ironodes spp. (Merritt and Cummins 1996). As wood decays through decomposition and physical abrasion, populations of xylophagous macroinvertebrates colonize the wood surface. Gougers and borers, such as the caddisfly H. californicum and the elmid beetle L. avara, graze on the soft wood, creating a mottled surface, which increases the surface area available for algae attachment and speeds microbial decomposition. In later stages of decay, chironomid and tipulid (Liposothrix spp.) detrivores continue decomposition into basic nutrient elements. However, the role of aquatic macroinvertebrates in wood decomposition and processing is limited compared to terrestrial insects, with aquatic organisms consuming less than 5% of all available wood (Pereira et al. 1982, Sedell et al. 1988).
The abundance and community structure of wood associated macroinvertebrates changes in relation to stream characteristics (Table 4, Dudley and Anderson 1982). High gradient reaches with coarse substrates and exposed logs support an abundant fauna of xylophilous insects, comprised of borers, gougers, scrapers, and groups colonizing wood surfaces and crevices. In moderate gradient reaches, the accumulation of silt and fine organic matter excludes many gougers, borers, and scrapers, limiting the fauna to collectors and predators. In large rivers, physical abrasion diminishes most populations. Additionally, wood may be deposited on high banks and terraces, out of contact with the water surface and unavailable to aquatic invertebrates (Dudley and Anderson 1982, Piegay et al. 1999).
Table 4. Wood associated insect fauna and role of LWD in salmonid habitat from low to high order streams. Coarse substrates, high debris loads, and exposed logs support an abundance of aquatic insects in high order streams. The accumulation of fine silt and sediment and deposit of wood out of the channel in lower gradients excludes most wood associated insects. The role of wood in salmonid habitat varies with channel width and gradient.
LOW ORDERS INTERMEDIATE ORDERS HIGH ORDERS INSECT FAUNA • Borers
• Gougers • Scrapers • Collectors • Predators
• Collectors • Predators
• Limited, wood out of channel
ROLE IN SALMONID HABITAT
• Pool formation • Cover
• Pool formation • Cover • Spawning
• Cover
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Salmonids. Along the Pacific Coast, wood is crucial in creating and maintaining the area and complexity of salmonid habitat (Figure 3, Table 4, Bisson et al. 1987). An important role of LWD in forming salmonid habitat is the creation of pools. Pools provide fish with a low energy environment to minimize energy expenditures in running water, provide maximum exposure to drifting food organisms, and are used as escape cover by individuals avoiding predators (Bisson et al. 1987, Bjornn and Reiser 1991). In moderate to high gradient streams, LWD is a primary factor controlling channel morphology, particularly pool formation (Keller and Swanson 1979, Beechie and Sibley 1997). Most pools are formed in association with LWD and wood-formed pools occupy a large proportion of the total stream surface area and total stream volume (Fausch and Northcote 1992, Crispin et al. 1993). Other instream obstructions, such as boulders, interact with flowing water to form pools. However, in addition to altering bed morphology, debris-formed pools provide other habitat values, such as cover and nutrient trapping, not offered by boulder-formed pools. Thus, streams with high volumes of wood typically support higher fish densities. In southeastern Alaska, summer periphyton biomass and the volume of instream debris best modeled the winter density of coho salmon and LWD volume alone best modeled the summer and winter density of Dolly Varden (Murphy et al. 1986).
Large woody debris obstructions also create zones of differential scour and deposit, leading to the creation of gravel bars, which are used by salmonids as spawning habitat. After adding logs to western Oregon streams, House and Boehne (1986) observed a 25-fold increase in gravel bar area. In a separate study, Crispin et al. (1993) observed a 4-fold increase in coho salmon (Oncorhynchus kisutch) spawning activity.
In the early to mid twentieth century, managers manipulated trout populations by installing log structures in order to increase habitat area and wood cover (Tarzwell 1937, Boussu 1954). Recent studies use manipulation to demonstrate the influence of woody debris loading on salmonid populations and fish biomass. Stream reaches with reduced levels of in-channel wood support lower salmonid populations compared to reaches with near natural LWD loading. Despite using selective techniques to remove wood from a southeastern Alaska stream and observing no significant changes in average channel width or depth, Dolloff (1986) found that the abundance of coho salmon and Dolly Varden (Salvelinus malma) was lower in cleared reaches. Similarly, Bryant (1985) found that the densities of coho salmon, steelhead trout (O. mykiss), and Dolly Varden were consistently lower in reaches with reduced LWD loading. Coho fry were particularly sensitive to the presence of wood, decreasing in density as the volume of individual LWD accumulations decreased. After removing LWD, Elliott (1986) noted a decrease in benthos abundance and an elimination of most instream overhead cover. The reduced food supply and increased susceptibility to displacement in high flows contributed to the numerical decline of Dolly Varden. Log structures installed in northern Colorado streams increased pool volume and total cover, which encouraged immigration of fish from nearby unmanipulated reaches, leading to increases in the abundance and biomass of age 2+ brook trout (S. fontinalis), brown trout (S. trutta), and rainbow trout (Gowan and Fausch 1996).
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An important function of instream wood is providing high flow refuge during winter. Salmonids prefer logs, tree roots, and undercut banks as cover, and streams with abundant cover elements support high winter densities of fish (Heifetz et al. 1986, Tschaplinski and Hartman 1986, Dolloff and Reeves 1990, Bjornn and Reiser 1991). Ideal winter cover sites combine low velocity, shade, and three-dimensional complexity (McMahon and Hartman 1989). Quinn and Peterson (1996) found that overwintering survival of coho was correlated with LWD abundance and volume and habitat complexity at the end of the summer, prior to winter high flows. Cederholm et al. (1997) found little or no change in spring and fall coho populations after log additions, but saw a significant increase in winter populations. The results indicate the importance of LWD in providing winter habitat. In high flows, reaches with an abundance of complex, LWD created pools retain the greatest amount of fish (Harvey 1998).
Salmonids occupy stream positions adjacent to structures that increase habitat complexity (Murphy et al. 1986). In British Columbia, 99% of coho fry and 83% of steelhead parr occupied positions near mid-channel rootwads in drought, normal, and high flow conditions (Shirvell 1990). Coho remained near the shore, while steelhead preferred more distant wood associated sites. An artificial channel experiment showed that coho abundance increased in areas of high overhead cover complexity (McMahon and Hartman 1989). Young of the year fish prefer LWD derived lateral habitats. Moore and Gregory (1988) increased lateral habitat by 2.4-fold through the addition of woody debris and increased the number of age 0 cutthroat trout (O. clarki) by 2-fold. McMahon and Holtby (1992) found that complex woody debris pieces also influence the distribution and abundance of fish in streams and estuaries. Eighty percent of coho smolts occurred within 1 m of debris pieces and 95% occurred within 2 m of debris pieces. The results support the need to retain LWD for smolt production in both habitat types.
Riparian habitat. The age structure of floodplain riparian forests reflects the history of LWD deposition and fluvial disturbance. In moderate to steep gradient streams of the Pacific Northwest, LWD parallel or oblique to flow influences the development of forested floodplains (Fetherston et al. 1995). Downed logs trap alluvium and colluvium in upstream near-bank sites, providing areas for riparian seedling establishment. The logs create low velocity environments where sediment and organic material deposit, speeding soil development and providing nutrients for riparian stands. Woody debris additionally provides nutrients as nurse logs for young trees, and in this capacity also creates an elevated establishment site that minimizes competition between seedlings and other forest floor vegetation. Established forests eventually contribute LWD back to the stream during disturbance events, continuing the process of riparian forest development (Bilby and Bisson 1998).
In exposed channel bars, LWD protects downstream riparian sites by obstructing streamflow and shielding vegetation from high flows, allowing species such as alder to become established (Sedell et al. 1988). The sediment deposition, nutrient deposition, and protection afforded by LWD helps streamside vegetation quickly reach a mature stage and better withstand floods.
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As channel confinement increases, the influence of LWD on riparian forest development and distribution lessens due to a general decrease in the size of wood-associated sediment deposition sites (Figure 3, Bilby and Ward 1989, Bilby and Bisson 1998). Narrow channels also lack extensive floodplain area and are more prone to debris flows that remove soil and vegetation, further limiting riparian forest development (Fetherston et al. 1995, Bilby and Bisson 1998).
In low to moderate gradient reaches, wood accumulates in large distinct jams within the channel and on the floodplain, providing abundant sites for forest establishment (Bisson et al. 1987, Abbe and Montgomery 1996). In northwest Washington, Abbe and Montgomery (1996) observed a diverse riparian forest structure dotted with anomalous old growth patches. The old growth patches were associated with LWD accumulations located in alluvial terrain characterized by frequent disturbance. The accumulations formed around key member logs, which were originally the largest streamside trees, creating distinct, stable LWD jams. Downstream of these bar area jams (BAJs), three factors facilitate the development of riparian forest: 1) local flow deceleration and decreased basal shear stress, 2) sediment deposition, 3) abundant accumulation of organic matter. Log jams create upstream arcuate gravel bars and downstream central gravel bars, which become sites for forest patch establishment and are stable as long as the wood accumulations exist. The observation of forest patches within the zone of active channel migration suggests that some LWD structures provide long-term refugia for floodplain riparian communities and remain stable despite repeated integration into the active channel.
Management Impacts on LWD Timber harvest. Timber harvest activities in streamside forests can directly affect wood input (Table 5, Swanson and Lienkaemper 1978, Bilby and Bisson 1998). Clearcut logging, often with minimal buffer strips surrounding the stream channel, was a common management practice throughout the Pacific Northwest and Alaska until the early to late 1980s (Dominguez and Cederholm 2000). The harvesting of streamside forests may temporarily reduce or eliminate LWD recruitment to the stream (Bryant 1980). The recovery time for input to return to pre-harvest conditions may be quite long. Fifty years after logging, debris from the current stand of a western Oregon stream contributed only 14% of total LWD volume and only 7% of the wood from the current stand contributed to pool formation (Andrus et al. 1988). The results indicate that some second growth stands must grow at least 50 years before trees contribute LWD in sizes and amounts similar to old growth forests. A decay model calibrated in southeastern Alaska predicted a 70% reduction in wood 90 years after clear-cutting, and that full recovery exceeded 250 years (Murphy and Koski 1989).
Logs derived from second growth forests are smaller in diameter and have less volume than old growth LWD, contributing to lower instream loading in logged streams (Bilby and Ward 1991, Ralph et al. 1994). Second growth wood loads tend to be comprised of deciduous riparian species and small conifers that degrade more easily and have less of an effect on long-term channel morphology (Dominguez and Cederholm 2000).
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A comparison between unlogged, moderately, and intensively logged catchments found that undisturbed streams contained more logs in the largest size categories (>50 cm diameter) than managed streams (Ralph et al. 1994). Intensively harvested streams displayed reduced average pool depth and area, and a significantly lower proportion of stream area occupied by pool habitat. These characteristics were related to the smaller size of in-channel wood and a modified spatial distribution where a large proportion of logs were located out of the low flow channel or did not interact with stream flow.
Table 5. The effect of certain management practices on the characteristics and abundance of LWD within stream systems. Timber harvest temporarily reduces input or changes the physical characteristics of subsequent inputs. Flood control and road maintenance activities generally result in the removal of in-channel wood.
MANAGEMENT PRACTICE
EFFECT REFERENCES
• Temporary reduction in LWD input Bryant 1980, Andrus 1988, Murphy and Koski 1989
• Second growth input smaller, less rot resistant with less profound effects on physical habitat
Bilby and Ward 1991, Wood-Smith and Buffington 1996, Ralph et al. 1994
• Removal of logging residue simplifies physical habitat by failing to distinguish between naturally occurring habitat-forming logs and leftover material
Swanson et al. 1976, Swanson and Lienkaemper 1978, Beschta 1979, Bryant 1980, Keller and MacDonald 1983, Bilby 1984, Bisson et al. 1987, Bilby and Ward 1989
• Extremely large amounts of logging material reduces intragravel flow, increases biological oxygen demand, reduces space available for invertebrates, and blocks fish migration
Hall and Lantz 1968, Narver 1970, Brown 1974
• Destabilization of hillslopes and increase in debris avalanches
Swanson and Lienkaemper 1978
• Narrow buffer strips (<20 m to 30 m) potentially reduce wood input
McDade et al. 1990, Van Sickle and Gregory 1990
Timber harvest
• Buffer strips adjacent to clearcuts have higher occurrence of windthrow and are depleted of large wood sources rapidly
Reid and Hilton 1998
• Remove wood to decrease channel roughness, increase conveyance, and maintain flood capacity
Marzolf 1978, Young 1991, Gippel et al. 1996
Flood control and road maintenance
• Remove wood and clear jams to keep culverts and bridges free of debris and reduce structural damage during storms
Singer and Swanson 1983, Diehl 1997
Streams flowing through second growth forests have a lower frequency of LWD associated pools and fewer channel spanning logs than old growth streams, leading to a scour pool dominated system (Bilby and Ward 1991). Thus, in low to mid-order streams the percentage of LWD formed waterfalls and the control of wood on gradient is decreased by timber harvest. Old growth logs are larger and retain more bedload sediment and fine organic debris. Fine organic debris influences the physical characteristics of large jams and may contribute to an increased diversity of pool types in old growth streams (Bilby and Ward 1991). Changes in wood loading and abundance significantly alter stream morphology. Wood-Smith and Buffington (1993) showed that pool frequency, pool depth, and local shear stress were significantly different in logged versus unlogged streams.
Near-stream logging influences natural LWD input processes. Depending on the method, harvest activities destabilize hillslopes and increase the likelihood of debris avalanches (Swanson and Lienkaemper 1978). Buffer strips are a common technique to reduce logging effects on forests and streams. Most LWD inputs come from within 20 m to 30
19
m of the stream channel and buffers more narrow than this zone of input potentially reduce the amount of available logs (McDade et al. 1990, Van Sickle and Gregory 1990). Buffer strips adjacent to clearcuts are exposed to higher wind velocities, increasing the occurrence of windthrown logs to the stream channel (Reid and Hilton 1998). Higher rates of windthrow may lead to rapid depletion of available wood from the remaining adjacent forest, increasing short-term LWD input, but decreasing long-term input.
Woody debris clearance. During logging operations, leftover woody material accumulates on hillslopes and within streams. Historically in the Pacific Northwest, salvage logging operations removed instream wood to recover leftover material (Bisson et al. 1987). Many regulations also recommended the removal of log jams, which were perceived by fisheries biologists as impediments to anadromous fish migration. Such activities proceeded without rigorous evaluation to distinguish between natural and logging derived LWD, or between naturally occurring logjams and unnatural barriers to fish migration. Many pieces of wood were unnecessarily removed leading to the simplification of physical habitat (Bilby and Bisson 1998).
Stream cleaning reduces the abundance of large stable, habitat forming logs, leaving smaller pieces that are more easily mobilized in moderate to high flows (Swanson et al. 1976, Swanson and Lienkaemper 1978, Bryant 1980, Keller and MacDonald 1983). These small pieces collect behind remaining large logs and build massive debris dams that impede flow and increase rates of lateral stream erosion. The mobilized LWD also weakens existing stable logjams, contributing to dam failure and the initiation of debris torrents.
In moderate to high gradient streams, logs play an important role in bedload storage (Figure 2), and the removal of LWD eliminates potential storage sites (Beschta 1979, Bilby 1984, Bilby and Ward 1989). The decrease in storage capacity and subsequent release of sediment simplifies physical habitat by filling in the deepest pools, reducing pool area, and smoothing channel gradient (Sullivan et al. 1987, Dominguez and Cederholm 2000). Debris removal affects salmonid populations by decreasing the amount of available hydraulic cover available during winter high flows, and by reducing stream wetted width and perimeter (Dolloff 1986, Elliott 1986). Undisturbed reaches have more available habitat area, contain greater supplies of food, and contain more fish of all sizes than altered reaches. Smaller fish and less available hydraulic cover combine to cause an increase in the displacement of fish in high flows. Streams with reduced levels of LWD, either from instream removal or streamside harvest that decreases wood input are often modified with artificial structures designed to mimic the hydraulic and habitat forming effects of LWD (House and Boehne 1986, Riley and Fausch 1995, Wallace et al. 1995).
Alternatively, an excessive amount of logging material left in the stream may be damaging to fish populations. Fine debris lying on the gravel surface impedes interchange between intragravel flow and surface water, reducing subsurface dissolved oxygen levels (Hall and Lantz 1969, Narver 1970, Brown 1974). Reduced oxygen availability retards the development of salmonid embryos within the gravel. The decomposition of wood increases biological oxygen demand, further reducing available
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dissolved oxygen (Narver 1970). Tannins and lignin-like substances released by wood decomposition produce yellow and brown pigments that absorb photosynthetically active radiation, possibly reducing periphyton growth. Small pieces of wood and bark occupy interstitial pores, reducing the available living space for stream invertebrates (Narver 1970). Very large human induced accumulations of wood prevent upstream migration of anadromous salmonids (Brown 1974). Much historical management of LWD in logged streams concentrated on the removal of excess debris to allow fish passage (Bilby and Bisson 1998).
Flood control and road maintenance. In systems influenced by human infrastructure, road maintenance and flood control activities affect the abundance of large wood (Table 5). Logs and riparian vegetation increase channel roughness, reduce conveyance, and are commonly removed by managers to maintain flood capacity (Marzolf 1978, Singer and Swanson 1983, Young 1991, Gippel et al. 1996). Wood mobilized during high flows frequently becomes trapped on channel spanning bridges and culverts, leading to road overtopping and eventual structure failure. Managers clear jams to keep structures free of obstructions and reduce damage to river crossings. Such management may completely eliminate LWD or remove only the largest pieces that pose the greatest hazard, but which are most important to habitat formation.
Synthesis and a Proposal for Stream Classification Synthesis. The geomorphic and ecological effects of LWD gradually change downstream through the channel network (Figures 2 and 3). The abundance of wood in a stream or river reflects the balance between wood entering and wood leaving a particular reach (Keller and Swanson 1979). The main controls on the geomorphic effects of LWD are piece size, channel gradient, and channel width. The ecological effect of LWD arises from log characteristics and channel morphology. Logs trap and retain nutrients, create habitat for fish and new riparian growth, and act as a direct nutrient source and attachment site for aquatic insects. This review has thus far concentrated on geomorphic and ecological effects as they occur in varying stream orders. The effects of LWD in stream systems may be better understood when integrated with existing process-based stream classification systems to create a classification based on the influence of instream wood. Such a classification system will aid in the management of instream LWD and help determine the sensitivity of stream channels to changes in LWD characteristics.
Montgomery and Buffington (1997) developed a channel classification system based on geomorphic processes. The system integrates channel processes with the spatial arrangement of specific reach morphologies. In channels composed of alluvial substrates, they identify several reach morphologies that occur in a downstream direction with reducing gradient: cascade, step-pool, plane-bed, and pool-riffle (Figure 4, Table 6). The reach morphologies reflect basin wide trends in sediment transport and storage capacity. Higher gradient reaches have a high transport capacity relative to sediment supply and function as transport zones that deliver sediment to lower gradient reaches. Reach substrate and morphology result from the balance between sediment supply and transport capacity. Other reach types arise when external influences, such as LWD, are present in stream channels and affect sediment input and output processes.
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In some cases, LWD obstructions force sediment-poor bedrock channels into becoming alluvial channels, owing to the sediment storage capacity of in-channel wood. Montgomery and Buffington (1997) recognize two forced reach morphologies in alluvial channels: forced pool riffle, and forced step pool. The forced morphologies extend beyond the range of free forming analogous channel types into higher and lower gradient sections (Figure 4). Forced pool-riffle reaches span the gradient range for pool-riffle and plane-bed reaches and arise when most pools and bars form in response to LWD obstructions. Forced step-pool reaches arise when most elevation controlling steps are formed by channel spanning logs. The recognition of forced-reach morphologies as distinct types acknowledges the control LWD has on bed morphology.
Table 6. The gradient range and general characteristics of reach morphologies in alluvial channels (Data taken from Bisson and Montgomery 1996 and Montgomery and Buffington 1997).
CASCADE STEP-POOL PLANE-BED POOL RIFFLE GRADIENT • 0.08 to 0.30 • 0.04 to 0.08 • 0.01 to 0.04 • 0.001 to 0.02
BEDMATERIAL • Boulder • Cobble/boulder • Gravel/cobble • Gravel
CONFINEMENT • Confined • Confined • Variable • Unconfined
Figure 4. Generalized long profile of alluvial channels showing spatial arrangement of reach morphologies, including forced step-pool and forced pool-riffle morphologies. Forced morphologies extend beyond the gradient range of free-formed counterparts. Gradient ranges of forced morphologies depicted above are interpreted from Montgomery et al. (1995) and Beechie and Sibley (1997). The classifications are based on geomorphic processes and reflect basin wide trends in sediment transport and storage (Figure adapted from Montgomery and Buffington 1997).
The river continuum concept is an ecological framework that describes adjustments of the biological community in response to physical conditions (Figure 5, Vannote et al. 1980). Energy sources and processes change systematically from headwaters to large rivers. Low order streams tend to be narrow and shaded by streamside vegetation, resulting in low rates of instream autotrophic growth. Headwater communities rely on allochthonous inputs from leaves, pine needles, and pieces of wood as energy sources. In these reaches, the autotrophic production to heterotrophic respiration ratio (P:R) is less than one, and is reflected in algal and macroinvertebrate community structure. Algal growth is limited and the macroinvertebrate community is comprised mainly of shredder and collector
cascade
pool-riffle
step-pool
plane-bed
DISTANCE FROM HEADWATERS
forced pool-riffle
forced step-pool
22
functional feeding groups, which process external inputs. In intermediate order streams, channel widening reduces overhead canopy cover allowing rates of autotrophic production to exceed respiration (P:R >1). Periphyton is the dominant energy source and macroinvertebrates shift to grazers and collectors. Grazers scrape and process algae from solid surfaces, such as boulders and logs. In large rivers, shade is further reduced and channels become wider and deeper, but generally more turbid. The high turbidity and increased depth reduces light penetration and autotrophic production (P:R <1). Dissolved material and fine particles transported from upstream are the dominant energy sources and macroinvertebrate communities are comprised mainly of collectors.
The role of LWD is not explicitly addressed within the river continuum concept. However, the influence of wood on nutrient retention and macroinvertebrate communities is quite important (Bilby and Likens 1980, Wallace et al. 1995). As nutrients travel downstream, they are incorporated by stream organisms. After incorporation, processed nutrients are eventually released and again become available for uptake by stream organisms. The process by which nutrients are used and released, called spiraling, is influenced by the presence of LWD. Fallen logs delay the transport of sediment and organic matter downstream. By physically obstructing particulate and dissolved nutrients, LWD reduces the spiraling length, or distance between uptake and release (Bilby and Likens 1980, Newbold et al. 1982). Without storage behind wood accumulations, allochthonous input is transported downstream without being reduced into smaller particles by physical and biological action. Unobstructed material may be unavailable to organisms, such as macroinvertebrates, in intermediate to high order streams (Vannote et al. 1980, Bisson et al. 1987). Wood obstructions store large amounts of organic matter, the primary energy source in undisturbed streams. Thus, the presence of wood obstructions has an effect on available nutrients and biological community structure. Down the channel network the storage capacity of LWD decreases, but wood may act as growth substrate for periphyton, an attachment site for filter feeders, or as a direct food source, further influencing macroinvertebrate community structure (Dudley and Anderson 1982, Bilby and Ward 1989). In large rivers, where woody debris deposits on banks and terraces largely out of contact with the water surface, the influence on macroinvertebrate community structure and nutrient availability is limited. Unlike Montgomery and Buffington (1997) reach morphologies, the river continuum concept does not recognize ecological stream reaches that are forced by woody debris obstructions. Considering the above relations, stream ecology is most sensitive to the influence of LWD in low to intermediate stream orders.
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Figure 5. The relationship between channel width, canopy, respiration, and macroinvertebrate community structure. As channels increase in width, the relative shading by riparian canopy decreases, and turbidity, caused by concentration of suspended sediment, increases. In narrow streams, the autotrophic production to heterotrophic respiration ratio is less than 1, as most production comes from allochthonous inputs. As the stream widens and shade decreases, water is clear enough to support periphyton growth and autochthonous production dominates. In large channels, turbidity and depth reduce algal growth, and production is allochthonous input transported from upstream. The relative proportion of macroinvertebrate functional feeding groups changes in response to the dominant energy source. Collectors and shredders process leafy input in small channels, grazers scrape periphyton from substrates in mid-order reaches, and collectors gather transported material in high order rivers (figure adapted from Vannote et al. 1980).
A stream classification proposal. Managers should emphasize restoring and maintaining habitat-forming processes associated with large wood (Beechie and Bolton 1999). Figures 6 and 7 describe a new classification system derived from this review of scientific literature (Figures 2 and 3) and existing process based geomorphic and ecological classifications (Figures 4 and 5). These wood influence zones, based upon position within the channel network, should not be confused with influence zones described by Robison and Beschta (1990) and O'Connor and Ziemer (1989), which are based on lateral channel position. Low to intermediate order reaches make up the single piece/debris flow zone where closely spaced, solitary logs and debris flows have the greatest effect on channel morphology and ecology. Single pieces falling across the channel accumulate sediment and allochthonous material in upstream storage sites, and in general are the major control on morphology and ecology in small streams (Montgomery and Buffington 1997). Wood moves infrequently, but usually in catastrophic bursts triggered by heavy storms. Such events may transport massive amounts of LWD downstream and cause landslides and debris flows that bring wood into the channel (Swanson et al. 1976, Singer and Swanson 1983). In very steep gradients, solitary logs may lie above the channel, resting on large boulders, having minimal effect on channel
CANOPY COVER
High
Low
DISTANCE FROM HEADWATERS
CHANNEL WIDTH TURBIDITY
High
Low
PRODUCTION/RESPIRATION
P/R < 1
P/R > 1
P/R < 1
Shredders
Grazers
Collectors
Predators
Shredders
GrazersCollectors
Predators
Predators
Collectors
24
morphology (Keller and Tally 1979). However, the sediment storage capacity of log obstructions may also force high gradient bedrock channels into an alluvial reach morphology or cascade channels into a forced step-pool morphology (Montgomery et al. 1996, Montgomery and Buffington 1997).
Intermediate order streams comprise the intermediate jam zone (Figure 6). Larger channels have the capacity to redistribute wood in irregularly spaced jams. Wood generally occurs in multiple piece jams and the spacing between accumulations increases downstream. The relative confinement influences the predominant pool type and reach morphology (Figure 7). Confined channels have limited floodplain area, thus wood deposits within the channel, building jams that create a forced step-pool reach morphology. Highly confined channels have a greater capacity to transport wood downstream, and may have low wood loading, minimizing log influence on morphology and ecology (Bilby and Bisson 1998). Moderately confined to unconfined channels have floodplains and gravel bars that act as LWD storage sites. The channel margin location of LWD jams encourages the formation of lateral scour pools within a forced pool-riffle reach morphology. The intermediate jam zone then can be further classified into moderately confined and unconfined subtypes that produce different possible reach morphologies.
Higher order streams and rivers make up the large jam zone (Figure 6). Wide, deep channels transport and deposit wood on floodplains and gravel bars within the active channel, but may be out of contact with the water surface (Figure 7). Jams in this zone tend to be the largest within the channel network, but are widely spaced and have a limited effect on gradient and sediment storage. Most sediment is stored in geomorphic elements, such as floodplains and terraces. Channel margin deposits of wood encourage the formation of lateral scour pools within a forced pool-riffle morphology. Woody debris jams provide salmonids with hydraulic and escape cover during seasonal migrations. Possibly the most important role of LWD in the large jam zone is riparian forest development. Large jams provide sites for vegetation colonization, forest island growth, and forest floodplain development (Fetherston et al. 1995).
Management Recommendations Forest management. Possibly the first step in improving the management of LWD in California stream systems is to recognize the different roles it plays in different parts of the watershed. The stream classification proposed above explicitly does that. It is equally important to understand the mechanisms by which LWD gets into streams, its potential for stability and the limitations on managers for recruiting and maintaining LWD. Timber harvest in and near streamside zones can potentially influence direct inputs of LWD to streams and can also influence indirect inputs through mechanisms such as inner gorge landslides and debris flows. However, timber harvesting in streamside zones probably has more significance on small to intermediate streams. In upper watershed areas, removal of forest from unstable upland sites that periodically contribute large quantities of LWD associated with mass wasting can also have lasting impacts. In view of these issues, the current system of regulating streamside management based on stream size, i.e., larger streams get more protection, may not achieve the desired results.
25
Figure 6. Location of LWD influence zones in relation to general trends occurring along the channel network and in context to geomorphic and ecological classification systems (figures adapted from Vannote et al. 1980 and Montgomery and Buffington 1997).
SEDIMENT STORAGE CHANNEL GRADIENT POOL FORMATION
High
Low
CHANNEL WIDTH
High
Low
NUTRIENT STORAGE INSECT ABUNDANCE
High
Low
High
Low
WOOD DECOMPOSITION FOREST DEVELOPMENT
SALMONID HABITAT
pool-riffle
step-pool
cascade
plane-bed
forced pool-riffle
forced step-pool
SINGLE PIECE/DEBRIS
JAM ZONE INTERMEDIATE
JAM ZONE LARGE JAM
ZONE
DISTANCE FROM HEADWATERS
P/R < 1 P/R < 1
P/R > 1
CHANNEL WIDTH TURBIDITY
PRODUCTION/RESPIRATION
High High
Low Low
CANOPY COVER
26
Figure 7. The general characteristics of LWD influence zones. Single pieces and debris flows dominate in small streams, while progressively larger jams dominate in higher orders. Intermediate jam zones can be further classified according to channel entrenchment, with confined reaches tending toward step-pool morphologies and unconfined reaches tending toward pool-riffle morphologies.
To ensure future supplies of LWD to stream channels, buffer strips serving as reservoirs of wood supply should be wide enough to encompass the zone of LWD input, typically within 20 m to 30 m of the stream channel (Lienkaemper and Swanson 1987, McDade et al. 1990, Van Sickle and Gregory 1990). Some researchers have argued for larger buffers, based on susceptibility of buffer strips next to clear-cuts to blow-down and rapid depletion of available streamside wood (Reid and Hilton 1998). The use of a selectively logged fringe buffer adjacent to the streamside buffer may serve to reduce abnormally high rates of windthrow and preserve natural input rates. Any selective cutting within buffer strips should leave an abundant supply of the largest trees for recruitment (Murphy and Koski 1989, Abbe and Montgomery 1996). Large in this context refers to trees that can produce LWD big enough to interact with flow and influence channel morphology. To be cautious, the very largest trees should always be retained (Fetherston et al. 1995, Abbe and Montgomery 1996). There is no formula for determining the amount of wood required in a given stream so conservative judgment is warranted. Species, diameter, and wood decay rates influence the amount of wood recruitment potentially necessary (Murphy and Koski 1989).
SINGLE PIECE/DEBRIS FLOW ZONE
DISTRIBUTION • Random • Single piece
INPUT MECHANISMS
• Windthrow • Bank erosion • Mass Wasting
TRANSPORT MECHANISMS
• Debris flows • Flood flows
STORAGE SITES • Upstream of log steps
POOL TYPES • Step pools WOOD ASSOCIATED INSECT FAUNA
• Borers • Gougers • Scrapers • Collectors • Predators
ROLE IN SALMONID HABITAT
• Pool formation • Cover
INTERMEDIATE JAM ZONE
CONFINED DISTRIBUTION • Clumped in
jams within streams INPUT MECHANISMS
• Windthrow • Bank erosion • Fluvial
transport TRANSPORT MECHANISMS
• Flotation
STORAGE SITES • Single logs and log jams
POOL TYPES • Step pools WOOD ASSOCIATED INSECT FAUNA
• Collectors • Predators
ROLE IN SALMONID HABITAT
• Pool formation • Cover • Spawning
UNCONFINED DISTRIBUTION • Clumped in
jams within streams INPUT MECHANISMS
• Windthrow • Bank erosion • Fluvial
transport TRANSPORT MECHANISMS
• Flotation
STORAGE SITES • Single logs and log jams
POOL TYPES • LWD formed lateral scour
WOOD ASSOCIATED INSECT FAUNA
• Collectors • Predators
ROLE IN SALMONID HABITAT
• Pool formation • Cover • Spawning
LARGE JAM ZONE DISTRIBUTION • Clumped in
jams on bars and floodplains
INPUT MECHANISMS
• Bank erosion • Fluvial
transport TRANSPORT MECHANISMS
• Flotation
STORAGE SITES • Flood plains and gravel bars
POOL TYPES • Hydraulically formed lateral scour
WOOD ASSOCIATED INSECT FAUNA
• Limited, wood out of channel
ROLE IN SALMONID HABITAT
• Cover
LWD INFLUENCE ZONES
27
Table 7. The possible management implications of preserving LWD input, transport, and presence within the stream channel. MANAGEMENT
PRACTICE IMPLICATION REFERENCES
• Buffer strips should be wider than zone of LWD input McDade et al. 1991, Van Sickle and Gregory 1990
• Fringe buffers can protect streamside buffers from premature wood depletion
Reid and Hilton 1998
• Selective management in buffers should consider future input required based on instream surveys
Bilby and Ward 1989, Murphy and Koski 1989
• Selective management should leave large trees that will be stable and influence channel morphology
Fetherston et al. 1995, Abbe and Montgomery 1996
• Active management of buffer zones can increase recruitment of certain species and sizes of wood
Beechie and Sibley 1997
• Removal of logging debris best dealt with by selective removal
Bryant 1983, Bilby 1984, Gurnell et al. 1995
• Knowledge of habitat conditions, and the size and abundance of LWD required to maintain conditions must be considered when removing instream wood
Bryant 1983, Bilby 1984
Timber harvest
• Characteristics of unmanaged streams should guide re-introduction of wood
Smith et al. 1993a, b, Montgomery et al. 1995, Abbe and Montgomery 1996, Beechie and Sibley 1997, Montgomery and Buffington 1997
• Must gain quantitative understanding of effect of wood on flood heights and how moves through a system
Young 1991, Braudrick et al. 1997, Braudrick and Grant 2000
• Design and modify bridges and culverts to allow for passage of woody debris
Diehl 1997, Flanagan et al. 1998
Flood control and road maintenance
• Develop management that recognizes ecological value and impact of wood on human infrastructure and public safety
Singer and Swanson 1983, Piegay and Landon 1997
Forest managers should seek to increase the recruitment of certain species, primarily conifers which produce the largest and longest lasting LWD. This may involve active management of deciduous riparian zones to promote conifer establishment and growth (Beechie and Sibley 1997). This strategy should be considered in relation to position within the channel network. Small channels (<10 m width) can form pools around smaller pieces of wood (<20 cm), such as alder logs. Large to intermediate channels require greater diameter logs to form pools (>60 cm). Data on variations in the size and amount of woody debris with changing stream size could be used to develop plans for numbers and sizes of trees to be achieved (Bilby and Ward 1989).
LWD clearance. In cases where logging debris is to be removed from a stream, it is best dealt with by selective maintenance to ensure channel stability and ecological function (Gurnell et al. 1995). An adequate amount of leftover LWD is essential to maintain wood related habitat structure (Lisle 1986a). Uncleaned streams flowing through logged or clear-cut reaches may exhibit higher levels of wood debris loading and subsequently have a greater abundance of LWD associated habitats (Lisle 1986a, Lisle and Napolitano 1998). Froehlich (1973) found that some harvest methods increased in-channel LWD abundance by >1000% over natural levels. In southeastern Alaska, Lisle (1986a) found that debris dams were more frequent in clear-cut reaches that were not cleaned after harvest than in undisturbed reaches. The clear-cut reaches showed greater residual pool depth and length, and the remaining LWD stored more bedload sediment than logs in undisturbed reaches. Leftover wood eventually deteriorates through decomposition and physical abrasion and streams eventually decrease in physical complexity if LWD is not replaced through natural inputs (Lisle and Napolitano 1998).
28
Indiscriminate removal of in-channel LWD for any reason can have major influence on channel processes (Beschta 1979, Bilby 1984). Knowledge of habitat conditions and the size and abundance of stable LWD required to create and maintain these conditions are considerations when removing instream wood. Bilby (1984) developed a dichotomous key based on local channel conditions and size of LWD to determine whether to remove or leave logs in the channel. Bryant (1983) used an inventory of piece length, percent of piece in the water, angle of orientation to flow, and location of anchor point to determine piece stability and suggested general removal guidelines based on the age of debris and stream gradient.
LWD placement. In streams with a paucity of LWD, re-introduction or placement of logs as instream structures provides a short-term solution to maintain wood created habitats until natural recruitment processes recover (Sullivan et al. 1987, Gurnell et al. 1995). The characteristics of unmanaged streams, such as the variability in species, size, and spacing of LWD accumulations and the goals of the project should guide the re-introduction of wood (Dominguez and Cederholm 2000). Dominguez and Cederholm (2000) developed a flow chart for determining candidate streams for rehabilitation based on fish habitat needs and characteristics of the stream and surrounding forest. Any logs added should be structured to mimic effects of natural obstructions in streams. Due to its random location, all stable logs may not be active in pool formation (Montgomery et al. 1995). Through careful placement of existing logs, managers may be able to engineer jam configurations that more efficiently enhance pool formation. The sensitivity of stream channels to wood addition varies with channel gradient. Moderate gradient reaches are highly sensitive to the presence of LWD (Sullivan et al. 1987, Montgomery et al. 1995, Abbe and Montgomery 1996, Beechie and Sibley 1997, Montgomery and Buffington 1997). Beechie and Sibley (1997) predict that increases in log abundance will lead to more rapid increase in the number of pools and pool area in moderate slope channels than in lower slope channels. The presence of pools in low gradient reaches may be independent of LWD presence (Smith et al. 1993a, b). The placement of instream structures maintains pools in the short-term, but ignores dynamic ecological and physical processes. Improved management of streamside forests offers the most promise for developing valuable and productive riparian systems (Elmore and Beschta 1989). Effective management of LWD will depend on information relating vegetative and physical characteristics of riparian areas to input of LWD (Bilby and Ward 1989).
Flood control and road maintenance. Flood control programs that encourage the removal of woody debris rarely undergo technical scrutiny, and do not always have a significant effect on flood levels (Williams and Swanson 1989, Young 1991, Dudley et al. 1998). Channel roughness depends on many factors, and the claims of reduced frequency and duration of over bank flooding, used to justify debris removal, are not unequivocally proven in the field (Gippel 1995). In Australia, Young (1991) found that the average amount of wood in lowland rivers seldom had a significant effect on flood levels, and suggested that larger pieces may be rearranged for hydraulic reasons and habitat preservation. Clearance of wood to maintain bridges and culverts is usually undertaken during low flow conditions, yet much wood enters streams and rivers during storms, through debris avalanches, bank erosion, and windthrow, reducing the effectiveness of removal programs (Singer and Swanson 1983). The use of hydraulic
29
models may aid in the planning of debris management programs. However, in re-introducing LWD to stream channels as part of riparian restoration or instream habitat enhancement, managers must understand the geomorphic context of wood function to guide the effective placement for long-term log stability (Braudrick et al. 1997). A quantitative understanding of wood movement is needed to assess stability of re-introduced wood and to prevent unstable logs from becoming a safety hazard.
The alternative is to design bridges and culverts that allow passage of woody debris. Diehl (1997) examined drift damage to bridges across the United States and suggested adequate freeboard, wide spans, solid piers, rounded pier noses, and pier placement out of the path of drift to reduce jam accumulation. Flanagan et al. (1998) suggested methods to determine the potential of culvert crossings to impede downstream movement of logs based on the ratio of culvert width to channel width (w*), degree of upstream widening and stream approach angle to the culvert. Culverts with w* <1 are prone to clogging. Channel widening immediately upstream of culverts encourages ponding and creates eddies that orient wood perpendicular to flow and promote formation of large jams. In streams approaching crossings at a severe angle, wood cannot rotate parallel to flow and is less likely to pass through the culvert. Surveys on the size distribution of instream wood should also be included in studies assessing log passing capacity and considered before construction or modification of structures (Singer and Swanson 1983).
The management of wood in basins that are directly influenced by human infrastructure must balance ecological and safety concerns. Piegay and Landon (1997) proposed a system that recognizes the impact of LWD on public safety and human infrastructure, and the ecological value of wood. The sectored LWD maintenance plan was based on mapping of three areas: 1) woody debris supply areas, 2) areas where log jam formation is most probable, 3) areas of floodplain occupation to determine human vulnerability to flooding. The plan allowed for recruitment of LWD and the formation of jams in areas that posed little safety hazard. Intensive maintenance of instream wood occurred near flood prone areas and upstream of bridges.
Conclusion Pieces of large wood are an important component in the ecology of streams flowing through the forests of Northern California. The physical and ecological roles of logs, stumps, and large branches vary through the channel network. In designing a management plan, one must not only consider the various roles, but also the processes by which LWD enters and is transported downstream. The LWD influence zones described in this paper could be used to define management objectives regarding forest management (LWD input), flood control and road maintenance (LWD transport), and instream rehabilitation projects (LWD loading). More specific management objectives must come from an understanding of habitat requirements and the limiting factors of sensitive species, and the characteristics of individual streams. The uncertain nature of ecological studies requires adequate monitoring, the results of which should be integrated into an adaptive management process that is designed by managers to maintain or improve ecological processes.
30
APP
EN
DIX
Tabl
e A
-1.
The
char
acte
ristic
s an
d di
strib
utio
n of
LW
D in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k lo
catio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Wes
tern
Ore
gon
• 0.
10 to
0.3
0 ch
anne
l gra
dien
ts
• LW
D in
sm
all s
tream
s ra
ndom
ly d
istri
bute
d •
LWD
eas
ily tr
ansp
orte
d in
larg
er ri
vers
lead
ing
to s
ize
sorti
ng a
nd a
ccum
ulat
ions
in
dist
inct
jam
s
Swan
son
et a
l. 19
76
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• D
ebris
load
ing
high
est i
n sm
all,
stee
p st
ream
s, d
ecre
asin
g do
wns
tream
•
In 1
st a
nd 2
nd o
rder
stre
ams
LWD
rand
omly
loca
ted
beca
use
stre
ams
too
smal
l to
redi
strib
ute
• In
3rd
to 5
th o
rder
stre
ams
flow
s la
rge
enou
gh to
redi
strib
ute
debr
is to
form
dis
tinct
ac
cum
ulat
ions
that
dire
ctly
affe
ct c
hann
el w
idth
•
In la
rge
river
s LW
D th
row
n on
isla
nds
or o
n ba
nks,
hav
ing
little
influ
ence
on
chan
nel,
exce
pt d
urin
g hi
gh fl
ows
Swan
son
and
Lien
kaem
per
1978
Indi
ana
Nor
th C
arol
ina
Ore
gon
• 0.
001
to 0
.40
chan
nel g
radi
ents
•
Load
ing
(kg/
m2 ) d
ecre
ased
with
incr
easi
ng c
hann
el w
idth
, wat
ersh
ed a
rea,
stre
am
orde
r, an
d de
crea
sing
cha
nnel
gra
dien
t Ke
ller a
nd S
wan
son
1979
Nor
thw
est
Cal
iforn
ia
• 0.
01 to
0.4
0 ch
anne
l gra
dien
ts
• 1.
0 km
2 to 2
7 km
2 dra
inag
e ar
eas
• 2nd
thro
ugh
4th o
rder
stre
ams
• R
edw
ood
debr
is u
sual
ly d
omin
ates
tota
l loa
ding
•
Load
ing
(m3 /m
2 ) dec
reas
ed a
s dr
aina
ge a
rea
and
wid
th in
crea
sed
• D
ebris
acc
umul
atio
ns in
low
er re
ache
s la
rger
, mor
e co
mpl
ex, a
nd s
pace
d fu
rther
ap
art t
han
in u
pper
reac
hes
Kelle
r and
Tal
ly 1
979,
Tal
ly
1980
, Kel
ler a
nd M
acD
onal
d 19
83, K
elle
r et a
l. 19
85
New
Eng
land
•
1.5
m to
7m
wid
e ch
anne
ls
• Fr
eque
ncy
of d
ebris
dam
s de
crea
sed
from
1st o
rder
(20
to 4
0 da
ms
per 1
00m
) to
2nd
orde
r (10
to 1
5 da
ms
per 1
00m
) to
3rd o
rder
(1to
6 d
ams
per 1
00m
) stre
ams
Like
ns a
nd B
ilby
1982
Wes
tern
Ore
gon
• 0.
03 to
0.3
7 ch
anne
l gra
dien
ts
• 3.
5 m
to 2
4 m
ban
kful
l wid
ths
• 0.
1 km
2 to 6
1 km
2 dra
inag
e ar
eas
• 1st
thro
ugh
5th o
rder
stre
ams
• Am
ount
of L
WD
gen
eral
ly d
ecre
ased
from
sm
all t
o la
rge
chan
nels
Li
enka
empe
r and
Sw
anso
n 19
87
Wes
tern
W
ashi
ngto
n •
0.13
cha
nnel
gra
dien
t (<7
m
chan
nel w
idth
) •
0.08
cha
nnel
gra
dien
t (7m
to 1
0m
chan
nel w
idth
) •
0.03
cha
nnel
gra
dien
t (>1
0m
chan
nel w
idth
)
• M
ean
diam
eter
, len
gth,
and
vol
ume
of L
WD
incr
ease
d w
ith in
crea
sing
cha
nnel
wid
th
• Fr
eque
ncy
of o
ccur
renc
e (#
pie
ces/
m) d
ecre
ased
with
incr
easi
ng c
hann
el w
idth
•
Cha
nges
rela
ted
to in
crea
sed
capa
city
of l
arge
r stre
ams
to m
ove
woo
d do
wns
tream
•
Hig
her p
ropo
rtion
of w
ood
inpu
t rem
aine
d in
the
stre
am c
hann
el a
s st
ream
siz
e de
crea
sed
Bilb
y an
d W
ard
1989
Sout
heas
t Ala
ska
• <0
.03
chan
nel g
radi
ents
•
0.7
km2 to
55
km2 d
rain
age
area
s •
1st th
roug
h 4th
ord
er s
tream
s
• Ab
unda
nce
of L
WD
and
vol
ume
per c
hann
el le
ngth
(m3 /m
) inc
reas
ed w
ith in
crea
sing
st
ream
siz
e •
LWD
load
ing
(m3 /m
2 ) dec
reas
ed w
ith in
crea
sing
ban
kful
l wid
th
Rob
ison
and
Bes
chta
199
0
Wes
tern
W
ashi
ngto
n •
3 m
to 2
4 m
ban
kful
l cha
nnel
w
idth
s •
Aver
age
LWD
vol
ume
incr
ease
d w
ith in
crea
sing
stre
am s
ize
(ban
kful
l wid
th)
• LW
D a
bund
ance
(# p
iece
s/m
) dec
reas
ed w
ith in
crea
sing
ban
kful
l wid
th
Bilb
y an
d W
ard
1991
Uni
ted
King
dom
•
110
km2 d
rain
age
area
•
Den
sity
of L
WD
jam
s (n
umbe
r of d
ams
per 1
00m
and
num
ber o
f dam
s pe
r 500
m)
decr
ease
d do
wns
tream
from
hea
dwat
ers
and
with
incr
easi
ng c
hann
el w
idth
•
Abun
danc
e of
par
tial s
pann
ing
dam
s in
crea
sed
in d
owns
tream
dire
ctio
n •
Deb
ris lo
adin
g (k
g/m
2 ) dec
reas
ed in
dow
nstre
am d
irect
ion
Gre
gory
et a
l. 19
93
Sout
heas
tern
Fr
ance
•
0.00
12 to
0.0
018
chan
nel g
radi
ents
•
3700
km
2 dra
inag
e ar
ea
• 6th
ord
er ri
ver
• LW
D d
iffer
entia
lly d
epos
ited
on b
anks
dep
endi
ng o
n flo
w a
nd fo
rest
con
ditio
ns
Pieg
ay 1
993
Wes
tern
Ore
gon
• 0.
022
aver
age
chan
nel g
radi
ent
• 23
m a
vera
ge c
hann
el w
idth
•
60 k
m2 d
rain
age
area
• C
hann
el w
idth
and
sin
uosi
ty w
ere
mai
n fa
ctor
s co
ntro
lling
LWD
sup
ply
and
dist
ribut
ion
• N
umbe
r and
vol
ume
of L
WD
hig
hest
in w
ide
sinu
ous
reac
hes
Nak
amur
a an
d Sw
anso
n 19
94
31
Tabl
e A
-1.
The
char
acte
ristic
s an
d di
strib
utio
n of
LW
D in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k lo
catio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
• 5th
ord
er c
hann
el
Sout
hwes
t Ala
ska
Wes
tern
W
ashi
ngto
n
• 0.
002
to 0
.085
cha
nnel
gra
dien
ts
• 2.
5m to
38m
cha
nnel
wid
ths
• N
umbe
r of L
WD
pie
ces
per m
2 dec
reas
ed w
ith in
crea
sing
cha
nnel
wid
th
• Lo
gs in
larg
er c
hann
els
wer
e m
ore
read
ily tr
ansp
orte
d •
Inve
rse
prop
ortio
nalit
y be
twee
n po
ol s
paci
ng a
nd L
WD
freq
uenc
y
Mon
tgom
ery
et a
l. 19
95
Nor
th C
entra
l C
olor
ado
• 0.
005
to 0
.065
cha
nnel
gra
dien
ts
• 4
m to
10
m b
ankf
ull w
idth
•
2 km
2 to 3
0 km
2 dra
inag
e ar
eas
• 1st
thro
ugh
3rd o
rder
stre
ams
• Ab
unda
nce
(pie
ces
of L
WD
/ m) g
reat
er in
sm
alle
r stre
ams
whe
n so
rted
by d
rain
age
area
and
wid
th
• Lo
wer
per
cent
age
of p
iece
s sp
anne
d ch
anne
l in
larg
er s
tream
s (s
orte
d by
dra
inag
e ar
ea a
nd w
idth
) tha
n in
sm
alle
r stre
ams
• Pe
rcen
tage
of L
WD
lyin
g pe
rpen
dicu
lar t
o st
ream
cha
nnel
dec
reas
ed w
ith in
crea
sing
dr
aina
ge a
rea
• Pe
rcen
tage
of d
ebris
pie
ces
in w
ette
d ch
anne
l dec
reas
ed in
larg
er s
tream
s •
Perc
enta
ge o
f LW
D a
bove
wet
ted
chan
nels
incr
ease
d in
sm
alle
r stre
ams
• LW
D ra
ndom
ly d
istri
bute
d in
stre
ams
<5.0
m w
idth
and
clu
mpe
d in
to ja
ms
in >
5.0
m
in w
idth
Ric
hmon
d an
d Fa
usch
199
5
Nor
thw
est
Was
hing
ton
• 0.
002
to 0
.05
chan
nel g
radi
ents
•
5 m
to 2
0 m
cha
nnel
wid
ths
• 2
km2 to
120
km
2 dr
aina
ge a
reas
• Lo
adin
g an
d ab
unda
nce
decr
ease
d w
ith in
crea
sing
cha
nnel
wid
th
• C
hann
el w
idth
is d
omin
ant i
nflu
ence
on
num
ber o
f pie
ces
of L
WD
/m2
Beec
hie
and
Sibl
ey 1
997
Sout
heas
tern
Fr
ance
•
0.00
12 to
0.0
018
chan
nel g
radi
ents
•
3700
km
2 dra
inag
e ar
ea
• 6th
ord
er ri
ver
• LW
D d
istri
butio
n on
mea
nder
ban
ks re
late
d to
ang
le o
f ban
k to
flow
, hei
ght o
f flo
w,
and
pres
ence
of s
econ
dary
cha
nnel
s Pi
egay
and
Mar
ston
199
8
Spai
n •
0.08
to 0
.157
5 ch
anne
l gra
dien
ts
• 3
m to
8 m
cha
nnel
wid
ths
• 0.
4 km
2 to 6
4 km
2 dra
inag
e ar
eas
• 1st
thro
ugh
3rd o
rder
stre
ams
• Ab
unda
nce
and
load
ing
decr
ease
d in
dow
nstre
am d
irect
ion
Elos
egi e
t al.
1999
Sout
heas
tern
Fr
ance
•
0.00
3 to
0.0
08 c
hann
el g
radi
ents
•
1650
km
2 dra
inag
e ar
ea
• M
ost L
WD
in a
ctiv
e ch
anne
l on
high
bar
s •
LWD
dep
osit
cont
rolle
d by
dep
osit
site
mor
phol
ogy
and
prox
imity
of L
WD
sou
rces
Pi
egay
et a
l. 19
99
32
Tabl
e A
-2.
The
mob
ility
and
trans
port
mec
hani
sms
of L
WD
in v
ario
us g
eogr
aphi
c lo
catio
ns a
nd c
hann
el p
ositi
ons
(arra
nged
in c
hron
olog
ical
ord
er).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Wes
tern
Ore
gon
• 0.
10 to
0.3
0 ch
anne
l gra
dien
ts
• Ab
ility
of s
tream
s an
d riv
ers
to m
ove
LWD
dep
ends
on
size
of r
iver
and
woo
d di
men
sion
s •
Larg
e riv
ers
trans
port
mos
t LW
D, w
hile
sm
all s
tream
s m
ove
only
sm
all d
ebris
sho
rt di
stan
ces
befo
re d
epos
ition
on
chan
nel o
bstru
ctio
ns
• Ve
ry la
rge
debr
is in
sm
all c
hann
els
trans
porte
d th
roug
h de
bris
torre
nts
• To
rrent
s ra
re in
>2nd
to 3
rd o
rder
stre
ams,
as
stee
p gr
adie
nts
are
requ
ired
to m
ove
debr
is
Swan
son
et a
l. 19
76
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• D
ebris
mov
es th
roug
h flo
tatio
n at
hig
h flo
ws
or th
roug
h de
bris
flow
s •
Deb
ris fl
ows
orig
inat
e in
1st a
nd 2
nd o
rder
cha
nnel
s (>
50%
gra
dien
t, <0
.2 k
m2
drai
nage
are
as)
• 3rd
to 5
th o
rder
stre
ams
(4 k
m2 to
60
km2 d
rain
age
area
s) w
ide
enou
gh to
floa
t lar
ge
debr
is a
nd d
ebris
jam
s at
hig
h flo
ws
Swan
son
and
Lien
kaem
per
1978
East
ern
Was
hing
ton
• 0.
015
chan
nel g
radi
ent
• 11
.5 m
ban
kful
l wid
th
• LW
D m
ovem
ent d
epen
ded
on le
ngth
and
dia
met
er o
f woo
d •
Dis
tanc
e tra
vele
d by
LW
D in
vers
ely
rela
ted
to p
iece
leng
th
• An
chor
ed p
iece
s m
ore
stab
le in
hig
h flo
ws
Bilb
y 19
84
Indi
ana
Nor
th C
arol
ina
Ore
gon
• 0.
001
to 0
.40
chan
nel g
radi
ents
•
Deb
ris to
rrent
s m
ain
trans
port
mec
hani
sm in
sm
all,
high
gra
dien
t stre
ams
• Fl
otat
ion
mai
n tra
nspo
rt m
echa
nism
in la
rge,
low
gra
dien
t stre
ams
Kelle
r and
Sw
anso
n 19
79
Wes
tern
Ore
gon
• 0.
03 to
0.3
7 ch
anne
l gra
dien
ts
• 3.
5 m
to 2
4 m
ban
kful
l wid
ths
• 0.
1 km
2 to 6
1 km
2 dra
inag
e ar
eas
• 1st
thro
ugh
5th o
rder
stre
ams
• W
ood
mov
emen
t occ
urre
d in
larg
er s
tream
s du
ring
mon
itorin
g pe
riod
• D
ista
nce
mov
ed d
epen
ded
on p
iece
leng
th in
rela
tion
to b
ankf
ull w
idth
•
All p
iece
s m
ovin
g >1
0 m
wer
e sh
orte
r tha
n ba
nkfu
ll w
idth
Lien
kaem
per a
nd S
wan
son
1987
Wes
tern
Ore
gon
• 0.
03 to
0.2
1 ch
anne
l gra
dien
ts
• 7
m to
25
m b
ankf
ull w
idth
s •
2nd th
roug
h 5th
ord
er s
tream
s
• D
ebris
flow
s re
dist
ribut
ed L
WD
in s
teep
, low
- ord
er s
tream
s •
Floo
ds re
dist
ribut
ed L
WD
in m
ediu
m to
hig
h or
der s
tream
s N
akam
ura
and
Swan
son
1993
Wes
tern
Ore
gon
• 0.
019
to 0
.028
cha
nnel
gra
dien
ts
• 9
m to
71
m c
hann
el w
idth
s •
5th o
rder
stre
ams
• M
ost t
rans
porte
d pi
eces
sho
rter t
han
bank
full
wid
th
• 20
% o
f unt
rans
porte
d pi
eces
long
er th
an b
ankf
ull w
idth
•
LWD
leng
th to
cha
nnel
wid
th u
sefu
l mea
sure
of s
usce
ptib
ility
to tr
ansp
ort
Nak
amur
a an
d Sw
anso
n 19
94
Wyo
min
g •
0.04
1 to
0.0
55 c
hann
el g
radi
ents
•
6.4
m to
7 m
low
flow
cha
nnel
w
idth
s
• LW
D le
ss s
tabl
e in
bur
ned
drai
nage
due
to in
crea
sed
runo
ff an
d pe
ak fl
ows,
and
de
crea
sed
bank
sta
bilit
y Yo
ung
1994
NA
• N
A •
Unc
onge
sted
, sem
i-con
gest
ed, a
nd c
onge
sted
woo
d tra
nspo
rt ba
sed
on ra
tio o
f log
in
put (
Qlo
g) to
stre
am d
isch
arge
(Qw)
• Pr
opos
ed a
bilit
y of
cha
nnel
to re
tain
woo
d is
func
tion
of d
ebris
roug
hnes
s, w
hich
va
ries
with
cha
nnel
and
log
dim
ensi
ons
Brau
dric
k et
al.
1997
Spai
n •
0.08
to 0
.157
5 ch
anne
l gra
dien
ts
• 3
m to
14
m b
ankf
ull w
idth
s •
0.8
km2 to
69
km2 d
rain
age
area
s •
1st th
roug
h 3rd
ord
er s
tream
s
• Lo
adin
g(m
3 /m2 ) d
ecre
ased
in d
owns
tream
dire
ctio
n •
Log
mob
ility
incr
ease
d in
larg
er s
tream
s El
oseg
i et a
l. 19
99
33
Tabl
e A
-3.
The
effe
ct o
f LW
D o
n th
e st
orag
e an
d tra
nspo
rt of
bed
load
in v
ario
us g
eogr
aphi
c lo
catio
ns a
nd c
hann
el n
etw
ork
posi
tions
(arra
nged
in c
hron
olog
ical
ord
er).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Wes
tern
Ore
gon
• 0.
10 to
0.3
0 ch
anne
l gra
dien
ts
• LW
D a
ccum
ulat
ions
trap
ped
230
m3 o
f sed
imen
t in
100
m re
ach
Swan
son
et a
l. 19
76
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• An
nual
sed
imen
t yie
ld le
ss th
at 1
0% o
f mat
eria
l in
stor
age
• W
oody
mat
eria
l prim
ary
stor
age
elem
ent
Swan
son
and
Lien
kaem
per 1
978
Nor
ther
n C
alifo
rnia
•
0.01
to 0
.048
cha
nnel
gra
dien
ts
• 6.
4 m
to 9
.6 m
cha
nnel
wid
ths
• D
ebris
sto
red
sedi
men
t com
pris
ed 4
0% o
f cha
nnel
are
a
Kelle
r and
Tal
ly 1
979,
Ta
lly 1
980,
Kel
ler a
nd
Mac
Don
ald
1983
, Kel
ler
et a
l. 19
85
Wes
tern
W
ashi
ngto
n •
0.07
cha
nnel
gra
dien
t •
Acce
lera
ted
eros
ion
of s
tore
d se
dim
ent (
5000
m3 ) a
fter L
WD
rem
oval
from
250
m re
ach
Besc
hta
1979
New
Ham
pshi
re
• 0.
21 a
vera
ge c
hann
el g
radi
ent
• 3.
0 m
ave
rage
cha
nnel
wid
th
• 50
0% in
crea
se in
the
expo
rt of
sto
red
sedi
men
t afte
r rem
oval
of L
WD
Bi
lby
1981
Cen
tral I
daho
•
0.21
ave
rage
cha
nnel
gra
dien
t •
5.0
m a
vera
ge c
hann
el w
idth
•
1st th
roug
h 3rd
ord
er s
tream
s
• Lo
gs a
ccou
nted
for 5
0% o
f tot
al s
edim
ent s
tore
d an
d 34
% o
f all
chan
nel o
bstru
ctio
ns
Meg
ahan
198
2
East
ern
Was
hing
ton
• 0.
015
chan
nel g
radi
ent
• 11
.5 m
ban
kful
l wid
th
• R
educ
tion
in s
edim
ent s
tora
ge (i
ncre
ased
sco
ur) a
fter l
oggi
ng a
nd s
tream
cle
anin
g Bi
lby
1984
Ariz
ona
• 0.
07 to
0.0
9 ch
anne
l gra
dien
ts
• R
emov
al o
f log
ste
ps le
d to
incr
ease
d be
dloa
d m
ovem
ent
• Lo
g st
eps
even
tual
ly re
plac
ed g
rave
l bar
s H
eede
198
5a, 1
985b
Nor
ther
n C
alifo
rnia
•
0.00
6 to
0.0
14 c
hann
el g
radi
ents
•
12 m
ave
rage
cha
nnel
wid
th
• LW
D o
bstru
ctio
ns s
tabi
lize
grav
el c
hann
els
by c
ontro
lling
loca
tion
of p
ools
and
bar
s Li
sle
1986
a
Alas
ka
• 0.
01 to
0.0
9 ch
anne
l gra
dien
ts
• 2
m to
6 m
act
ive
chan
nel w
idth
•
Deb
ris a
cted
to s
tore
sed
imen
t thr
ough
the
crea
tion
of lo
w-e
nerg
y de
posi
tiona
l en
viro
nmen
ts
Lisl
e 19
86b
Wes
tern
W
ashi
ngto
n •
0.13
cha
nnel
gra
dien
t (<7
m
chan
nel w
idth
) •
0.08
cha
nnel
gra
dien
t (7
m to
10
m
chan
nel w
idth
) •
0.03
cha
nnel
gra
dien
t (>1
0 m
ch
anne
l wid
th)
• 40
% o
f LW
D a
ssoc
iate
d w
ith s
edim
ent a
ccum
ulat
ions
in 0
.13
chan
nel g
radi
ent (
<7 m
ch
anne
l wid
th)
• <3
0% o
f LW
D a
ssoc
iate
d w
ith s
edim
ent a
ccum
ulat
ions
in 0
.08
chan
nel g
radi
ent (
7 m
to
10 m
cha
nnel
wid
th)
• <2
0% o
f LW
D a
ssoc
iate
d w
ith s
edim
ent a
ccum
ulat
ions
in 0
.03
chan
nel g
radi
ent (
>10
m
chan
nel w
idth
)
Bilb
y an
d W
ard
1989
Wes
tern
W
ashi
ngto
n •
3 m
to 2
4 m
ban
kful
l cha
nnel
w
idth
s •
Sedi
men
t ret
entio
n by
LW
D d
ecre
ased
with
incr
easi
ng s
tream
siz
e •
Amou
nt o
f sed
imen
t ret
aine
d w
as a
ssoc
iate
d w
ith a
ge a
nd v
olum
e of
woo
d Bi
lby
and
War
d 19
91
Wes
tern
Ore
gon
• 0.
03 to
0.2
1 ch
anne
l gra
dien
ts
• 7
m to
25
m b
ankf
ull w
idth
s •
2nd th
roug
h 5th
ord
er s
tream
s
• LW
D w
as d
omin
ant s
edim
ent s
tora
ge c
ontro
l in
mod
erat
e to
ste
ep s
tream
s •
LWD
pro
vide
d te
mpo
rary
sed
imen
t sto
rage
in lo
w g
radi
ent r
each
es
Nak
amur
a an
d Sw
anso
n 19
93
Sout
heas
t Ala
ska
• 0.
01 a
vera
ge c
hann
el g
radi
ent
• 3.
9 m
ave
rage
cha
nnel
wid
th
• Fo
ur fo
ld in
crea
se in
bed
load
tran
spor
t and
ban
kful
l flo
w a
fter L
WD
rem
oval
Sm
ith e
t al.
1993
a
Sout
heas
t Ala
ska
• 0.
008
to 0
.010
cha
nnel
gra
dien
ts
• 4
m a
vera
ge c
hann
el w
idth
•
Initi
al in
crea
se in
bed
load
tran
spor
t afte
r LW
D re
mov
al
• C
hann
el re
adju
sted
to fo
rm s
erie
s of
regu
larly
spa
ced
bars
Sm
ith e
t al.
1993
b
Col
orad
o •
0.11
ave
rage
cha
nnel
gra
dien
t •
3.5
m a
vera
ge c
hann
el w
idth
•
LWD
maj
or c
ontro
l on
the
stor
age
and
rele
ase
of b
edlo
ad
Aden
lof a
nd W
ohl 1
994
Wes
tern
W
ashi
ngto
n •
0.10
to 0
.15
chan
nel g
radi
ents
•
3 m
to 4
m c
hann
el w
idth
s •
LWD
maj
or c
ontro
l on
sedi
men
t sto
rage
and
tran
spor
t O
'Con
nor 1
994
Belg
ium
•
0.04
6 ch
anne
l gra
dien
t •
0.75
m c
hann
el w
idth
•
2nd o
rder
stre
am
• Lo
g ja
ms
redu
ced
mov
emen
t and
tran
spor
t of b
ed m
ater
ial
Assa
ni a
nd P
etit
1995
Nor
thea
st
Cal
iforn
ia
• 0.
02 to
0.0
8 ch
anne
l gra
dien
ts
• 2
m to
12
m b
ankf
ull w
idth
•
LWD
min
imal
effe
ct o
n se
dim
ent s
tora
ge
Berg
et a
l. 19
98
Nor
thw
est
Was
hing
ton
• 0.
24 a
vera
ge c
hann
el g
radi
ent
• 2.
7 m
ave
rage
cha
nnel
wid
th
• LW
D m
ain
com
pone
nt o
f sed
imen
t sto
ring
obst
ruct
ions
G
rizze
l and
Wol
ff 19
98
34
Tabl
e A
-4.
The
effe
ct o
f LW
D o
n ch
anne
l dim
ensi
on in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
W
este
rn O
rego
n •
0.10
to 0
.30
chan
nel g
radi
ents
•
LWD
con
trolle
d 30
% to
50%
of d
rop
in e
leva
tion
• LW
D c
ause
d pr
onou
nced
loca
l wid
enin
g of
stre
ams
Swan
son
et a
l. 19
76
Indi
ana
Nor
th C
arol
ina
Ore
gon
• 0.
001
to 0
.40
chan
nel g
radi
ents
•
Scou
r aro
und
jam
s in
crea
sed
chan
nel w
idth
by
mor
e th
an 5
0%
• In
low
gra
dien
t stre
ams
LWD
con
tribu
ted
to fo
rmat
ion
of m
eand
er c
utof
fs
• In
hig
h gr
adie
nt s
tream
s se
dim
ent s
tora
ge b
y ch
anne
l spa
nnin
g w
ood
crea
ted
step
ped
prof
ile
• LW
D c
ontro
ls 3
0% to
80%
of d
rop
in e
leva
tion
Kelle
r and
Sw
anso
n 19
79
Nor
thw
est
Cal
iforn
ia
• 0.
01 to
0.4
0 ch
anne
l gra
dien
ts
• 1.
0 km
2 to 2
7 km
2 dra
inag
e ar
eas
• 2nd
thro
ugh
4th o
rder
stre
ams
• W
idth
at d
ebris
acc
umul
atio
ns w
as tw
o or
mor
e tim
es g
reat
er th
an c
hara
cter
istic
wid
th
of c
hann
el
• 60
% o
f dro
p in
ele
vatio
n as
soci
ated
with
LW
D s
teps
•
Exte
nsiv
e po
nded
sed
imen
t ups
tream
LW
D
• W
ood
had
less
effe
ct o
n el
evat
ion
in s
teep
er s
ectio
ns w
here
deb
ris re
sts
of a
bove
bo
ulde
rs
• LW
D c
reat
ed v
arie
ty o
f cha
nnel
dep
ths
• Ef
fect
on
elev
atio
n de
crea
sed
with
dec
reas
ing
chan
nel g
radi
ent
Kelle
r and
Tal
ly 1
979,
Tal
ly
1980
, Kel
ler a
nd
Mac
Don
ald
1983
, Kel
ler e
t al
. 198
5
Sout
heas
t Ala
ska
• 42
km
2 dra
inag
e ar
ea
• LW
D s
igni
fican
t inf
luen
ce o
n ch
anne
l wid
th, a
nd p
ool a
nd b
ar lo
catio
n Br
yant
198
0 So
uthe
ast A
lask
a •
15 k
m2 to
75
km2 d
rain
age
area
s •
4th th
roug
h 5th
ord
er s
tream
s •
LWD
acc
umul
atio
ns d
ecre
ased
30
year
s af
ter l
oggi
ng
• LW
D in
fluen
ced
chan
nel w
idth
, and
poo
l and
bar
loca
tion
Brya
nt 1
983
Ariz
ona
• 0.
07 to
0.0
9 ch
anne
l gra
dien
ts
• Lo
g st
eps
cont
rolle
d ch
anne
l gra
dien
t in
stee
p st
ream
s •
LWD
par
t of n
atur
al h
ydra
ulic
geo
met
ry o
f ste
ep s
tream
s H
eede
198
5a, b
Sout
heas
t Ala
ska
• <0
.03
chan
nel g
radi
ents
•
0.7
km2 to
55
km2 d
rain
age
area
s •
1st th
roug
h 4th
ord
er s
tream
s
• Va
riatio
ns in
loca
l ban
kful
l wid
th a
ssoc
iate
d w
ith v
olum
e of
inst
ream
LW
D
Rob
ison
and
Bes
chta
199
0
Wes
tern
Ore
gon
• 0.
03 to
0.2
1 ch
anne
l gra
dien
ts
• 7
m to
25
m b
ankf
ull w
idth
s •
2nd th
roug
h 5th
ord
er s
tream
s
• W
idth
s up
stre
am o
f key
LW
D a
nd L
WD
jam
s w
ider
than
cha
nnel
ave
rage
s in
med
ium
or
der c
hann
els
• G
radi
ents
ups
tream
of k
ey L
WD
and
LW
D ja
ms
low
er th
an c
hann
el a
vera
ges
in
med
ium
ord
er c
hann
els
• C
hann
els
with
key
LW
D a
re 1
.5 ti
mes
wid
er th
an c
hann
els
with
out k
ey L
WD
Nak
amur
a an
d Sw
anso
n 19
93
Uni
ted
King
dom
•
11 k
m2 d
rain
age
area
•
LWD
acc
umul
atio
ns c
ontri
bute
d to
ban
k su
bsid
ence
lead
ing
to w
iden
ing
in s
tream
ch
anne
l D
avis
and
Gre
gory
199
4
Coa
stal
Brit
ish
Col
umbi
a, C
anad
a •
0.01
to 0
.07
chan
nel g
radi
ents
•
10 m
to 3
0 m
ban
kful
l wid
ths
• 1
km2 to
28
km2 d
rain
age
area
s
• LW
D ja
ms
grea
test
influ
ence
on
over
all c
hann
el m
orph
olog
y •
Indi
vidu
al p
iece
s im
porta
nt to
cha
nnel
mor
phol
ogy
and
smal
l sca
le fe
atur
es b
etw
een
jam
s •
Cha
nnel
s in
crea
sed
in c
ompl
exity
as
LWD
jam
s ag
e an
d de
terio
rate
•
Old
gro
wth
fore
sts
had
low
rate
of j
am fo
rmat
ion,
lead
ing
to ja
ms
of v
ario
us a
ges
and
com
plex
cha
nnel
form
s •
Dis
turb
ed fo
rest
s ha
ve a
ccel
erat
ed ra
tes
of ja
m fo
rmat
ion,
alte
ring
chan
nel
mor
phol
ogy
Hog
an e
t al.
1998
35
Tabl
e A
-5.
The
effe
ct o
f LW
D o
n po
ol fo
rmat
ion
and
spac
ing
in v
ario
us g
eogr
aphi
c lo
catio
ns a
nd c
hann
el n
etw
ork
posi
tions
(arra
nged
in c
hron
olog
ical
ord
er).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• In
ste
ep s
tream
s, L
WD
mai
n fa
ctor
in d
eter
min
ing
char
acte
r of a
quat
ic h
abita
t •
In lo
w g
radi
ent s
tream
s, h
ydra
ulic
fact
ors
regu
late
d aq
uatic
hab
itat
Swan
son
and
Lien
kaem
per
1978
N
orth
wes
t C
alifo
rnia
•
0.01
to 0
.048
cha
nnel
gra
dien
ts
• 1.
0 km
2 to 2
7 km
2 dra
inag
e ar
eas
• 2nd
thro
ugh
4th o
rder
stre
ams
• D
ebris
enh
ance
d po
ols
incr
ease
d in
abu
ndan
ce w
ith in
crea
sing
cha
nnel
gra
dien
t •
Pool
spa
cing
dec
reas
ed w
ith in
crea
sing
gra
dien
t Ke
ller a
nd T
ally
197
9, T
ally
19
80, K
elle
r and
Mac
Don
ald
1983
, Kel
ler e
t al.
1985
So
uthe
ast A
lask
a •
0.00
1 to
0.0
3 ch
anne
l gra
dien
t •
2nd th
roug
h 4th
ord
er s
tream
s •
Mos
t poo
ls fo
rmed
by
debr
is
• Po
ol v
olum
e an
d de
bris
vol
ume
dire
ctly
cor
rela
ted
Mur
phy
et a
l. 19
86
Nor
thw
est
Cal
iforn
ia
• 0.
006
to 0
.014
cha
nnel
gra
dien
ts
• 12
m a
vera
ge c
hann
el w
idth
•
26 k
m2 d
rain
age
area
• LW
D m
ajor
com
pone
nt in
poo
l for
mat
ion
and
long
-ter m
cha
nnel
sta
bilit
y Li
sle
1986
a
Alas
ka
• 0.
01 to
0.0
9 ch
anne
l gra
dien
ts
• 2
m to
6 m
act
ive
chan
nel w
idth
•
0.5
km2 to
2.0
km
2 dra
inag
e ar
eas
• D
ebris
form
ed 4
6% o
f poo
ls in
fore
sted
reac
hes
• D
ebris
form
ed 8
6% o
f poo
ls in
cle
ar-c
ut s
tream
s du
e to
hig
her d
ebris
load
s Li
sle
1986
b
Wes
tern
Ore
gon
• 0.
02 to
0.0
6 ch
anne
l gra
dien
ts
• 5.
5 m
to 8
m b
ankf
ull w
idth
s •
6.5
km2 d
rain
age
area
• 70
% o
f all
pool
s cr
eate
d pr
imar
ily b
y w
oody
deb
ris
Andr
us e
t al.
1988
Wes
tern
W
ashi
ngto
n •
0.13
cha
nnel
gra
dien
t (<7
m
chan
nel w
idth
) •
0.08
cha
nnel
gra
dien
t (7
m to
10
m
chan
nel w
idth
) •
0.03
cha
nnel
gra
dien
t (>1
0 m
ch
anne
l wid
th)
• Pl
unge
poo
l mos
t com
mon
(40%
) of a
ll LW
D fo
rmed
poo
ls in
stre
ams
<7m
•
Scou
r poo
ls m
ost c
omm
on (6
0%) o
f all
LWD
form
ed p
ools
in s
tream
s >1
0m
Bilb
y an
d W
ard
1989
East
ern
Ore
gon
• 0.
02 to
0.0
7 ch
anne
l gra
dien
ts
• 2
m to
6 m
ban
kful
l wid
th
• 7
km2 to
25
km2 d
rain
age
area
s
• D
ebris
ass
ocia
ted
with
64%
of p
ools
in a
ll st
udy
stre
ams
Car
lson
et a
l. 19
90
Sout
heas
t Ala
ska
• <0
.03
chan
nel g
radi
ents
•
0.7
km2 to
55
km2 d
rain
age
area
s •
1st th
roug
h 4th
ord
er s
tream
s
• LW
D fo
rmed
65%
to 7
5% o
f all
pool
s •
Shift
in p
ool t
ypes
from
plu
nge
to la
tera
l sco
ur in
sm
all t
o la
rge
stre
ams
Rob
ison
and
Bes
chta
199
0
Wes
tern
W
ashi
ngto
n •
3 m
to 2
4 m
ban
kful
l cha
nnel
w
idth
s •
Freq
uenc
y of
LW
D a
ssoc
iate
d po
ols
decr
ease
d w
ith in
crea
sing
stre
am s
ize
• Ty
pe o
f poo
ls a
ssoc
iate
d w
ith L
WD
cha
nged
with
stre
am s
ize:
sco
ur p
ools
incr
ease
d an
d pl
unge
poo
ls d
ecre
ased
with
incr
easi
ng s
tream
siz
e
Bilb
y an
d W
ard
1991
Wes
tern
Te
nnes
see
• 13
,000
km
2 dra
inag
e ar
ea
• Ph
ysic
al h
abita
t div
ersi
ty s
trong
ly c
orre
late
d w
ith p
rese
nce
of L
WD
Sh
ield
s an
d Sm
ith 1
992
Sout
heas
t Ala
ska
• 0.
008
to 0
.01
chan
nel g
radi
ents
•
4 m
ave
rage
cha
nnel
wid
ths
• 1.
5 km
2 dra
inag
e ar
ea
• Po
ol s
paci
ng s
imila
r bef
ore
and
afte
r LW
D re
mov
al
• Po
ols
form
ed b
y no
n-er
odib
le o
bstru
ctio
ns b
ut la
cked
cov
er a
nd h
ydra
ulic
com
plex
ity
of w
ood
form
ed p
ools
Smith
et a
l. 19
93a,
b
Wes
tern
Ore
gon
• 0.
022
aver
age
chan
nel g
radi
ent
• 23
m a
vera
ge c
hann
el w
idth
•
60 k
m2 d
rain
age
area
•
5th o
rder
cha
nnel
• 17
% o
f LW
D in
wid
e si
nuou
s ch
anne
ls a
ffect
ed p
ool f
orm
atio
n, 2
to 5
tim
es h
ighe
r th
an o
ther
cha
nnel
type
s N
akam
ura
and
Swan
son
1994
Sout
hwes
t Ala
ska
Wes
tern
W
ashi
ngto
n
• 0.
002
to 0
.085
cha
nnel
gra
dien
ts
• 2.
5 to
38
m c
hann
el w
idth
s •
73%
of p
ools
form
ed b
y LW
D
• 40
% o
f woo
d in
fluen
ced
pool
form
atio
n •
Pool
spa
cing
inve
rsel
y re
late
d to
LW
D lo
adin
g in
pla
ne-b
ed, p
ool-r
iffle
, and
forc
ed
pool
riffl
e ch
anne
ls.
• Po
ol s
paci
ng in
crea
sed
with
incr
easi
ng c
hann
el w
idth
•
>0.0
1 gr
adie
nt c
hann
els:
poo
l for
mat
ion
sens
itive
to L
WD
load
ing
• <0
.01
grad
ient
cha
nnel
s: p
ool f
orm
atio
n no
t as
sens
itive
to L
WD
load
ing
Mon
tgom
ery
et a
l. 19
95
36
Tabl
e A
-5.
The
effe
ct o
f LW
D o
n po
ol fo
rmat
ion
and
spac
ing
in v
ario
us g
eogr
aphi
c lo
catio
ns a
nd c
hann
el n
etw
ork
posi
tions
(arra
nged
in c
hron
olog
ical
ord
er).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Nor
th C
entra
l C
olor
ado
• 0.
005
to 0
.065
cha
nnel
gra
dien
ts
• 4
m to
10
m b
ankf
ull w
idth
•
2 km
2 to 3
0 km
2 dra
inag
e ar
eas
• 1st
thro
ugh
3rd o
rder
stre
ams
• 76
% o
f poo
ls fo
rmed
by
LWD
•
4% to
20%
of L
WD
form
ed p
ools
•
Hig
her p
ropo
rtion
of L
WD
in s
mal
ler s
tream
s fo
rmed
poo
ls
• LW
D p
erpe
ndic
ular
to fl
ow in
sm
all s
tream
s •
LWD
dia
gona
l to
flow
in la
rge
stre
ams
Ric
hmon
d an
d Fa
usch
199
5
Nor
thw
est
Was
hing
ton
• 0.
005
to 0
.01
chan
nel g
radi
ents
•
30 m
to 8
0 m
ban
kful
l wid
ths
• 75
km
2 to 2
25 k
m2 d
rain
age
area
s
• 70
% o
f all
obse
rved
poo
ls a
ssoc
iate
d w
ith L
WD
jam
s •
LWD
ass
ocia
ted
pool
s pr
ovid
e ot
her h
abita
t val
ues
(cov
er a
nd n
utrie
nt tr
appi
ng) n
ot
asso
ciat
ed w
ith p
ools
form
ed o
ther
way
s
Abbe
and
Mon
tgom
ery
1996
Nor
thw
este
rn
Nev
ada
• 0.
02 to
0.0
4 ch
anne
l gra
dien
ts
• 10
% o
f LW
D p
iece
s fo
rmed
poo
ls
• LW
D p
ositi
ve e
ffect
s on
poo
l for
mat
ion
and
qual
ity
Mye
rs a
nd S
wan
son
1996
a,
b So
uthw
est A
lask
a •
0.00
17 to
0.0
224
chan
nel g
radi
ents
•
4 m
to 2
5 m
ban
kful
l wid
ths
• 1
km2 to
40
km2 d
rain
age
area
s
• LW
D a
ssoc
iate
d w
ith 8
0% o
f poo
ls in
und
istu
rbed
stre
ams
• LW
D a
ssoc
iate
d w
ith 5
5% o
f poo
ls in
dis
turb
ed s
tream
s W
ood-
Smith
and
Buf
fingt
on
1996
Nor
thw
est
Was
hing
ton
• 0.
002
to 0
.05
chan
nel g
radi
ents
•
5 m
to 2
0 m
cha
nnel
wid
ths
• 2
km2 to
120
km
2 dra
inag
e ar
eas
• Po
ol fo
rmat
ion
in m
oder
ate
to s
teep
slo
pe c
hann
els
high
ly s
ensi
tive
to p
rese
nce
of
LWD
•
Pool
s in
low
slo
pe c
hann
els
form
ed b
y m
echa
nism
s ot
her t
han
LWD
Beec
hie
and
Sibl
ey 1
997
Sout
hwes
t Virg
inia
•
0.01
to 0
.06
chan
nel g
radi
ents
•
5 m
ave
rage
cha
nnel
wid
th
• N
umbe
r of p
ools
in lo
w g
radi
ent r
each
es in
crea
sed
afte
r LW
D a
dditi
ons
• N
umbe
r of p
ools
in h
igh
grad
ient
reac
hes
unch
ange
d af
ter L
WD
add
ition
s
Hild
erbr
and
et a
l. 19
97
Uni
ted
King
dom
•
0.01
3 av
erag
e ch
anne
l gra
dien
t •
2 m
to 5
m b
ankf
ull w
idth
•
Pool
s cl
osel
y as
soci
ated
with
LW
D
• C
hann
els
with
LW
D h
ave
mor
e po
ols
than
cha
nnel
s w
ithou
t LW
D
Gur
nell
and
Swee
t 199
8
Sout
heas
tern
Fr
ance
•
0.00
3 to
0.0
08 c
hann
el g
radi
ents
•
1650
km
2 dra
inag
e ar
ea
• Fe
w p
ools
ass
ocia
ted
with
LW
D
• Po
ol s
ize
inde
pend
ent o
f LW
D m
ass
• LW
D a
ccum
ulat
ions
mod
erat
ely
influ
ence
d ch
anne
l mor
phol
ogy
Pieg
ay e
t al.
1999
37
Tabl
e A
-6.
The
effe
ct o
f LW
D o
n nu
trien
t dyn
amic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
LO
CAT
ION
R
ESU
LTS
REF
EREN
CES
N
ew H
amps
hire
•
0.21
cha
nnel
gra
dien
t •
3 m
ave
rage
cha
nnel
wid
th
• 1st
thro
ugh
3rd o
rder
stre
ams
• In
crea
se in
org
anic
car
bon
trans
port
afte
r woo
d re
mov
al
• 18
% in
crea
se in
DO
C e
xpor
t, 63
2% in
crea
se in
FPO
C e
xpor
t, 13
8% in
crea
se in
C
POM
exp
ort a
fter w
ood
rem
oval
•
Dec
reas
e in
num
ber o
f deb
ris d
ams
dow
n th
e st
ream
net
wor
k: 3
3.5
per 1
00 m
(1st
orde
r), 1
3.7
per 1
00m
(2nd
ord
er),
2.5
per 1
00m
(3rd
ord
er)
Bilb
y an
d Li
kens
198
0
New
Ham
pshi
re
• 0.
21 c
hann
el g
radi
ent
• 3m
ave
rage
ban
kful
l wid
th
• 2nd
ord
er s
tream
• In
crea
se in
FPO
M a
nd C
POM
(500
%) e
xpor
t dur
ing
high
dis
char
ge a
fter L
WD
re
mov
al
• Tw
igs
and
FPO
M a
re im
porta
nt fo
r ret
entio
n of
mat
ter,
fillin
g cr
acks
and
hol
es in
da
ms
to m
ake
them
wat
ertig
ht a
nd in
crea
se h
ydra
ulic
effe
ctiv
enes
s •
Dec
reas
e in
LW
D c
ontro
l on
elev
atio
n fro
m 1
st th
roug
h 3rd
ord
er s
tream
s: 5
2% o
f el
evat
ion
drop
con
trolle
d by
woo
d in
1st o
rder
stre
ams,
46%
of e
leva
tion
drop
co
ntro
lled
by w
ood
in 2
nd o
rder
stre
ams,
10%
of e
leva
tion
drop
con
trolle
d by
woo
d in
3rd
ord
er s
tream
s
Bilb
y 19
81
Nor
thw
est
Was
hing
ton
• 0.
014
(0.0
1 to
0.0
2) c
hann
el
grad
ient
s •
7.7
km2 b
asin
are
a
• G
ener
al p
ositi
ve tr
end
in L
WD
/m2 a
nd n
umbe
r of c
oho
salm
on (O
ncor
hync
hus
kisu
tch)
car
cass
es re
tain
ed
• C
arca
sses
impo
rtant
sou
rce
of n
utrie
nts
for a
quat
ic a
nd te
rrest
rial o
rgan
ism
s
Ced
erho
lm a
nd P
eter
son
1985
Wes
tern
Ore
gon
• 0.
10 c
hann
el g
radi
ent
• 6
km2 d
rain
age
area
•
Woo
dy d
ebris
is s
ourc
e fo
r app
roxi
mat
ely
90g/
m/y
r fin
e pa
rticu
late
org
anic
mat
ter
(FPO
M)
• Fo
r sys
tem
s w
ith la
rge
accu
mul
atio
n of
LW
D a
nd F
WD
, woo
d pr
oces
sing
can
be
sign
ifica
nt s
ourc
e of
FPO
M p
ool
• FP
OM
from
woo
d po
tent
ial t
o be
gre
ater
than
that
gen
erat
ed fr
om le
af a
nd n
eedl
e lit
ter p
roce
ssin
g •
Prod
uctio
n of
FPO
M g
reat
er in
win
ter f
rom
phy
sica
l abr
asio
n
War
d an
d Au
men
198
6
Paci
fic N
orth
wes
t, U
SA
• N
/A
• W
ood
deco
mpo
ses
mor
e sl
owly
in w
ater
than
on
land
•
Wat
erlo
ggin
g pr
even
ts d
eep
pene
tratio
n of
O2 i
n w
ood
• D
ecom
posi
tion
incr
ease
s as
gra
zing
or a
bras
ion
incr
ease
s; a
llow
s O
2 to
pene
trate
w
ood
• C
once
ntra
tion
of c
arbo
n an
d ni
troge
n in
crea
ses
as w
ood
deco
mpo
ses
• In
crea
se in
nitr
ogen
con
cent
ratio
n as
car
bon
use
incr
ease
s, a
nd th
roug
h ni
troge
n fix
ing
mic
roor
gani
sms
• N
itrog
en fi
xatio
n on
woo
d ac
coun
ts fo
r 5%
to 1
0% o
f ann
ual n
itrog
en s
uppl
y to
st
ream
•
Slow
dec
ompo
sitio
n of
inst
ream
woo
d in
fluen
ces
stab
ility
of L
WD
and
max
imiz
es
role
in h
abita
t for
mat
ion
Sede
ll et
al.
1988
Nor
thw
est
Was
hing
ton
• Lo
w g
radi
ent
• 15
m to
24
m c
hann
el w
idth
•
3rd o
rder
stre
ams
• D
ista
nce
carc
asse
s dr
ifted
inve
rsel
y re
late
d to
deb
ris lo
ads
• La
rge
and
smal
l org
anic
deb
ris m
ost i
mpo
rtant
inst
ream
rete
ntio
n el
emen
t for
ca
rcas
ses
• LW
D fo
rmed
poo
ls w
ere
mos
t im
porta
nt c
arca
ss d
epos
ition
site
Ced
erho
lm e
t al.
1989
Nor
ther
n O
rego
n •
N/A
•
At re
ach
scal
e w
ood
not s
igni
fican
t in
Nitr
ogen
and
Pho
spho
rous
upt
ake
• At
sm
alle
r sca
les,
woo
dy d
ebris
act
ive
in N
itrog
en a
nd P
hosp
horo
us re
mov
al fr
om
wat
er
• W
oody
deb
ris p
rovi
des
surfa
ce a
rea
for m
icro
orga
nism
s th
at u
ptak
e nu
trien
ts
Aum
en e
t al.
1990
38
Tabl
e A
-6.
The
effe
ct o
f LW
D o
n nu
trien
t dyn
amic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
LO
CAT
ION
R
ESU
LTS
REF
EREN
CES
N
ew H
amps
hire
•
N/A
•
Org
anic
deb
ris d
ams
impo
rtant
site
s of
org
anic
mat
ter r
eten
tion
and
accu
mul
atio
n •
Com
mun
ity re
spira
tion
3 tim
es h
ighe
r (23
4mg
C/m
2 /day
) in
sedi
men
t ass
ocia
ted
with
or
gani
c de
bris
dam
s •
Org
anic
mat
ter c
onte
nt (u
p to
5 c
m d
epth
) sig
nific
antly
hig
her i
n se
dim
ent a
ssoc
iate
d w
ith d
ebris
dam
s (a
vera
ge =
1.7
kg/m
2 ) •
Res
ults
sug
gest
deb
ris d
ams
are
foca
l site
s of
met
abol
ic a
ctiv
ity in
thes
e he
adw
ater
st
ream
s •
Met
abol
ic a
ctiv
ity m
ay b
e un
dere
stim
ated
, as
mea
sure
d to
a d
epth
of o
nly
5cm
Hed
in 1
990
New
Mex
ico
• 0.
17 to
0.1
9 ch
anne
l gra
dien
ts
• R
each
es w
ith w
ood
stor
ed m
ore
orga
nic
mat
ter t
han
reac
hes
with
out w
ood
• D
ecre
ase
in a
vera
ge v
eloc
ity a
nd in
crea
se in
stre
am w
idth
and
dep
th a
fter w
ood
addi
tion
• In
crea
se in
ave
rage
vel
ocity
and
dec
reas
e in
ave
rage
wid
th a
nd d
epth
afte
r woo
d re
mov
al
• Pa
rticl
e re
tent
ion
rate
s in
crea
sed
in s
tream
s w
ith d
ams
or w
ood
• D
ams
stop
ped
parti
cles
, def
lect
ed fl
ow, c
hang
ed w
ater
vel
ocity
, and
alte
red
wid
th
and
dept
h of
the
stre
am
• R
eten
tion
may
dep
end
on c
hann
el s
tabi
lity;
rete
ntio
n de
crea
ses
with
dec
reas
ing
chan
nel s
tabi
lity
Trot
ter 1
990
39
Tabl
e A
-7.
The
effe
ct o
f LW
D o
n aq
uatic
mac
roin
verte
brat
es in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
LO
CAT
ION
R
ESU
LTS
REF
EREN
CES
O
rego
n •
0.01
7 to
0.3
5 ch
anne
l gra
dien
ts
• LW
D lo
adin
g (k
g/m
2 ) dec
reas
ed w
ith in
crea
sing
stre
am o
rder
•
Cad
disf
ly w
ere
mos
t con
spic
uous
and
div
erse
inse
cts
on w
ood
• Tr
icho
pter
a (H
eter
ople
ctro
n ca
lifor
nicu
m) a
nd C
oleo
pter
a (L
ara
avar
a) w
ere
maj
or
inve
rtebr
ates
ass
ocia
ted
with
woo
d su
bstra
tes
• L.
ava
ra s
trong
ly a
ssoc
iate
d w
ith a
mou
nt o
f woo
d av
aila
ble,
irre
spec
tive
of s
tream
si
ze
• Lo
wer
inse
ct b
iom
ass
on w
ood
com
pare
d to
leaf
pac
k •
Two
poss
ible
mec
hani
sms
for w
ood
expl
oita
tion:
1) w
ood
cons
umpt
ion
to o
btai
n di
gest
ible
car
bon
and
nitro
gen
from
mic
robi
al fl
ora,
2) c
ultiv
atio
n an
d re
tent
ion
of g
ut
flora
Ande
rson
et a
l. 19
78
Was
hing
ton
O
rego
n C
alifo
rnia
• N
/A
• C
ontin
uum
of f
auna
l ass
ocia
tion
on L
WD
rang
es fr
om o
blig
ate
rest
rictio
n to
pur
ely
oppo
rtuni
stic
use
•
Sequ
ence
of c
olon
ists
par
alle
l sta
te o
f woo
d de
cay
• H
igh
grad
ient
trib
utar
ies
had
reas
onab
ly g
ood
faun
a of
bor
ers/
goug
ers
and
seve
ral
othe
r gro
ups
•
Whe
re g
radi
ent d
ecre
ased
, silt
atio
n an
d ac
cum
ulat
ion
of o
rgan
ic fi
ne p
artic
les
excl
uded
man
y go
uger
s an
d sc
rape
rs; m
uch
woo
d bu
ried
whe
re D
O w
as lo
w a
nd
fung
al a
ctiv
ity lo
w
• In
mai
n st
em, a
bras
ion
dim
inis
hed
the
role
of i
nver
tebr
ates
in w
ood
degr
adat
ion,
mos
t w
ood
occu
rred
in la
rge
jam
s, d
epos
ited
on s
hore
, and
was
una
vaila
ble
to a
quat
ic
form
s •
Woo
d as
soci
ated
inve
rtebr
ate
com
mun
ity a
nd it
s im
pact
on
woo
d w
as d
epen
dent
on
phys
ical
regi
me
• W
ood
qual
ity a
nd te
xtur
e im
porta
nt in
det
erm
inin
g sp
ecie
s co
loni
zatio
n •
66%
of c
lose
ly a
ssoc
iate
d gr
oups
(obl
igat
e) fo
und
in s
oft,
rotte
n w
ood,
30%
on
groo
ved,
text
ured
woo
d, a
nd <
10%
on
firm
sub
stra
tes
• 20
% o
f fac
ulta
tive
grou
ps fo
und
in s
oft,
rotte
n w
ood,
70%
on
groo
ved,
text
ured
woo
d,
and
10%
on
firm
woo
d •
Func
tiona
l fee
ding
gro
ups
asso
ciat
ed w
ith w
ood
text
ure;
sm
ooth
sur
face
s fo
r at
tach
men
t (fil
tere
rs) a
nd g
raze
rs, s
oft w
ood
form
bor
ers
• Fa
culta
tive
spec
ies
may
use
woo
d m
ore
as re
fuge
from
pre
datio
n th
an fo
r atta
chm
ent
Dud
ley
and
Ande
rson
198
2
Was
hing
ton
O
rego
n C
alifo
rnia
• N
/A
• Fe
edin
g is
mai
n pr
oces
s af
fect
ing
inse
ct m
edia
ted
fragm
enta
tion
• M
ost i
mpo
rtant
inse
cts
in d
egra
datio
n pr
oces
s ar
e bo
rers
and
gou
gers
•
Com
pare
d to
terre
stria
l situ
atio
ns, d
iver
sity
and
den
sity
of b
orer
s an
d go
uger
s is
low
du
e to
lack
of O
2
Pere
ira e
t al.
1982
Sout
heas
t Ala
ska
• 1.
9 m
ave
rage
cha
nnel
wid
th
• 9
km2 c
hann
el w
idth
•
6.5
km lo
ng
• Be
ntho
s de
nsity
, # o
f drif
t inv
erte
brat
es, a
nd #
of i
nver
tebr
ates
eat
en b
y D
olly
Var
den
(S. m
alm
a) d
ecre
ased
afte
r woo
d re
mov
al
• Be
ntho
s bi
omas
s de
crea
sed
by o
ne-th
ird d
urin
g tre
atm
ent p
hase
•
Inve
rtebr
ate
drift
dec
reas
ed s
igni
fican
tly a
fter d
ebris
rem
oval
•
Deb
ris u
sed
as s
ubst
rate
s us
ed b
y al
l ben
thic
taxa
, rem
oval
dire
ctly
redu
ced
abun
danc
e of
ben
thos
Ellio
tt 19
86
40
Tabl
e A
-7.
The
effe
ct o
f LW
D o
n aq
uatic
mac
roin
verte
brat
es in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
LO
CAT
ION
R
ESU
LTS
REF
EREN
CES
Pa
cific
Nor
thw
est,
USA
•
N/A
•
Lite
ratu
re re
view
•
Sequ
ence
of c
olon
ists
par
alle
ls s
tage
of d
ecay
•
New
woo
d is
prim
arily
hab
itat f
or a
lgae
, mic
robe
s, g
raze
rs, a
n co
llect
ors
• C
olon
izat
ion
prom
otes
dec
ompo
sitio
n an
d co
loni
zatio
n by
woo
d sh
redd
ers
(cad
disf
lies,
sto
nefli
es)
• Te
xtur
ed s
urfa
ce p
rovi
des
habi
tat f
or o
rgan
ism
s •
Fung
al g
row
th a
nd e
ffect
of w
ood
bore
rs s
peed
s de
cay
• D
etriv
ores
and
ear
thw
orm
s co
ntin
ue d
ecom
posi
tion
• Th
ree
mos
t im
porta
nt w
ood
proc
esso
rs c
onsu
me
only
2%
of a
ll av
aila
ble
woo
d
Sede
ll et
al.
1988
Arka
nsas
•
1st th
roug
h 3rd
ord
er s
tream
s •
Tric
hopt
era
foun
d in
gre
ater
den
sitie
s in
ben
thic
hab
itats
than
on
LWD
, but
thre
e fa
milie
s fo
und
in g
reat
er d
ensi
ties
on L
WD
•
Woo
d as
soci
ated
Tric
hopt
eran
s fo
und
on h
ighl
y de
caye
d w
ood
and
on L
WD
with
ro
ugh
text
ure,
pro
vidi
ng a
ttach
men
t site
s fo
r net
spi
nnin
g ca
ddis
flies
Philli
ps 1
994
Nor
th C
arol
ina
• 0.
03 to
0.0
6 ch
anne
l gra
dien
ts
• Po
ol fo
rmat
ion
afte
r log
add
ition
•
Inve
rtebr
ate
abun
danc
e an
d bi
omas
s in
crea
sed
sign
ifica
ntly
afte
r log
add
ition
•
Scra
per a
nd c
olle
ctor
/filte
rer a
bund
ance
incr
ease
d af
ter l
og a
dditi
on
• Se
cond
ary
prod
uctio
n of
scr
aper
s an
d fil
tere
rs d
ecre
ased
•
Shift
s in
func
tiona
l gro
up a
bund
ance
and
bio
mas
s ac
cent
uate
the
impo
rtanc
e of
loca
l ab
iotic
fact
ors
in p
atch
stru
ctur
e of
inve
rtebr
ate
com
mun
ities
Wal
lace
et a
l. 19
95
Vict
oria
, Aus
tralia
•
N/A
•
Top
of s
nags
sup
porte
d m
ore
mac
roin
verte
brat
es s
peci
es th
an o
ther
sur
face
s •
Gro
oved
sna
gs s
uppo
rted
sign
ifica
ntly
mor
e m
acro
inve
rtebr
ates
•
Res
ults
of s
tudy
sho
w im
porta
nce
of s
nag
habi
tat i
n st
ream
s an
d riv
ers
• R
esul
ts s
uppo
rt ha
bita
t com
plex
ity h
ypot
hesi
s w
here
spe
cies
rich
ness
incr
ease
s w
ith
habi
tat c
ompl
exity
O'C
onno
r 199
1
New
Yor
k •
30 m
to 5
0 m
cha
nnel
wid
th
• 4th
ord
er s
tream
•
Inve
rtebr
ate
dens
ities
gre
ater
on
woo
d th
an o
n le
aves
•
Filte
rers
dis
prop
ortio
nate
ly c
olon
ized
woo
d an
d co
llect
or/g
athe
rer f
avor
ed le
aves
•
Larg
er p
erce
ntag
e of
scr
aper
s on
leav
es th
an o
n w
ood
• D
ensi
ties
corre
late
d w
ith b
iofil
m d
evel
opm
ent,
whi
ch w
as g
reat
er o
n w
ood
• As
woo
d so
ftene
d th
roug
h ph
ysic
al a
nd b
iolo
gica
l for
ces,
woo
d be
cam
e m
ore
phys
ical
ly c
ompl
ex, o
fferin
g m
ore
mic
roha
bita
ts
• Su
rface
com
plex
ity a
nd s
tabi
lity
cont
ribut
ed to
incr
ease
d ta
xon
dens
ity o
n w
ood
Hax
and
Gol
lada
y 19
93
Nor
ther
n Vi
rgin
ia
• 20
m a
vera
ge c
hann
el w
idth
•
4th o
rder
stre
am
• D
ebris
dam
s st
ored
fine
sed
imen
t and
leaf
y de
bris
•
Abun
danc
e of
Chi
rono
mid
and
Cop
epod
beh
ind
dam
s le
ss li
kely
to d
eclin
e du
ring
flood
s •
Oth
er p
atch
type
s sh
owed
75%
to 9
5% re
duct
ions
in C
hiro
nom
id a
nd C
opep
od
abun
danc
e af
ter f
lood
s •
Deb
ris re
mov
al d
id n
ot im
pede
faun
al re
cove
ry
• R
esul
ts s
ugge
st d
ebris
dam
s as
soci
ated
with
fine
sed
imen
t and
leaf
y de
bris
hav
e po
tent
ial t
o ac
t as
refu
gia
durin
g hi
gh fl
ow
• Pa
tche
s ac
cum
ulat
ing
anim
als
wer
e ch
arac
teriz
ed b
y lo
w w
ater
flux
and
low
bed
flow
, lik
ely
cont
ribut
ing
to re
tent
ion
or p
assi
ve d
epos
ition
of a
nim
als
Palm
er 1
996
Sout
hwes
t Virg
inia
•
0.01
to 0
.06
chan
nel g
radi
ents
•
5 m
ave
rage
cha
nnel
wid
th
• Be
nthi
c m
acro
inve
rtebr
ate
abun
danc
e di
d no
t inc
reas
e af
ter l
og a
dditi
ons
• N
et a
bund
ance
of P
leco
pter
a, C
oleo
pter
a, T
richo
pter
a, a
nd O
ligoc
haet
a de
crea
sed
whi
le E
phem
erop
tera
incr
ease
d w
ith in
crea
se in
poo
l are
a
Hild
erbr
and
et a
l. 19
97
41
Tabl
e A
-8.
The
effe
ct o
f LW
D o
n fis
h (p
redo
min
antly
sal
mon
ids)
hab
itat a
nd p
opul
atio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al
orde
r).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Mic
higa
n •
N/A
•
Log
stru
ctur
es in
crea
sed
habi
tat a
rea
and
incr
ease
d Br
ook
trout
(Sal
velin
us fo
ntin
alis
) ab
unda
nce
Tarz
wel
l 193
7
Mon
tana
•
1 m
cha
nnel
wid
th
• Ab
unda
nce
and
biom
ass
of B
rook
trou
t (Sa
lvel
inus
font
inal
is),
rain
bow
trou
t (O
ncor
hync
hus
myk
iss)
, bro
wn
trout
(Sal
mo
trutta
) inc
reas
ed a
fter a
dditi
on o
f arti
ficia
l w
ood
cove
r •
Abun
danc
e an
d bi
omas
s de
crea
sed
afte
r bru
shy
cove
r rem
oval
Bous
su 1
954
Briti
sh C
olum
bia,
C
olum
bia
• 10
km
2 dra
inag
e ar
ea
• Ar
eas
with
logs
, und
ercu
t ban
ks, a
nd d
eep
pool
s fil
led
with
upt
urne
d tre
e ro
ots
(and
ot
her f
ores
t deb
ris) c
onta
ined
coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h)
Tsch
aplin
ski a
nd H
artm
an
1983
Cen
tral I
llinoi
s •
>0.0
01 c
hann
el g
radi
ent
• 3
m to
5 m
cha
nnel
wid
th
• M
ore
spec
ies,
mor
e in
divi
dual
s, a
nd la
rger
fish
cap
ture
d in
reac
hes
with
woo
d •
Hig
her i
nver
tebr
ate
abun
danc
e in
reac
hes
with
woo
d •
Fish
pre
fere
nce
for d
ebris
fille
d re
ache
s re
late
d w
ith fo
od a
vaila
bilit
y •
Woo
d pr
ovid
ed s
ubst
rate
for m
acro
inve
rtebr
ates
•
Woo
d pl
ays
mul
tidim
ensi
onal
role
in s
truct
ure
and
func
tion
of s
tream
eco
syst
ems
Ange
rmei
er a
nd K
arr 1
984
Paci
fic N
orth
wes
t •
N/A
•
Lite
ratu
re re
view
on
hist
oric
al p
roce
sses
and
man
agem
ent o
f LW
D, g
eom
orph
ic
func
tions
, cha
nnel
mor
phol
ogy,
influ
ence
on
fish
habi
tat,
and
man
agem
ent o
f LW
D
inpu
ts in
to s
tream
s
Sede
ll et
al.
1988
Sout
heas
t Ala
ska
• 4th
thr
ough
5th o
rder
stre
ams
• D
olly
Var
den
(Sal
velin
us m
alm
a), s
teel
head
trou
t (O
ncor
hync
hus
myk
iss)
, coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h)
• W
here
deb
ris a
bsen
t, de
nsiti
es o
f coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) c
onsi
sten
tly
low
er
• Ba
ckw
ater
s an
d si
de c
hann
els
asso
ciat
ed w
ith L
WD
had
hig
her d
ensi
ties
of c
oho
salm
on (O
ncor
hync
hus
kisu
tch)
than
mai
n ch
anne
l are
as w
ith d
ebris
•
Den
sity
of c
oho
salm
on (O
ncor
hync
hus
kisu
tch)
fry
decr
ease
d as
siz
e of
ac
cum
ulat
ion
decr
ease
d •
Mid
-cha
nnel
deb
ris, r
egar
dles
s of
siz
e su
ppor
ted
low
er d
ensi
ties
of c
oho
salm
on
(Onc
orhy
nchu
s ki
sutc
h) th
an ro
otw
ads
alon
g th
e ba
nk
Brya
nt 1
985
Sout
heas
t Ala
ska
• 0.
035
to 0
.05
chan
nel g
radi
ents
•
2 m
ave
rage
cha
nnel
wid
ths
• N
o si
gnifi
cant
diff
eren
ce in
ave
rage
cha
nnel
dep
th o
r wid
th b
etw
een
clea
red
and
uncl
eare
d re
ache
s •
In g
ener
al, u
ncle
aned
stre
am s
ectio
ns c
onta
ined
mor
e fis
h of
all
size
s th
an c
lear
ed
sect
ions
•
Des
pite
use
d of
sel
ectiv
e te
chni
ques
, num
bers
and
pro
duct
ion
of b
oth
coho
sal
mon
(O
ncor
hync
hus
kisu
tch)
and
Dol
ly V
arde
n (S
alve
linus
mal
ma)
wer
e re
duce
d by
re
mov
al o
f LW
D
Dol
loff
1986
Sout
heas
t Ala
ska
• 1.
9 m
ave
rage
cha
nnel
wid
th
• 9
km2 c
hann
el w
idth
•
6.5
km lo
ng
• R
emov
al o
f log
ging
deb
ris re
duce
d w
ette
d w
idth
and
are
as fr
om 8
74 m
2 an
d 72
6 m
2 •
Dol
ly V
arde
n (S
alve
linus
mal
ma)
pop
ulat
ion
decr
ease
d fro
m 7
48 to
100
, tw
o ye
ars
afte
r deb
ris re
mov
al
• D
ecre
ase
in fi
sh s
ize
afte
r cle
aran
ce
• Be
fore
deb
ris re
mov
al, f
ish
occu
pied
mid
cha
nnel
poo
ls a
nd ta
ngle
s of
deb
ris
• Af
ter r
emov
al, f
ish
occu
pied
bac
kwat
ers
and
stre
am m
argi
ns
• R
emov
al o
f log
ging
deb
ris c
hang
ed m
orph
olog
y, b
riefly
redu
ced
food
sup
ply
and
elim
inat
ed m
ost c
over
, red
ucin
g #
and
mea
n le
ngth
of f
ish,
leav
ing
smal
l fis
h su
scep
tible
to d
ispl
acem
ent
• D
ecre
ase
in b
enth
os a
bund
ance
, red
uced
am
ount
of f
ood
eate
n by
Dol
ly V
arde
n (S
alve
linus
mal
ma)
and
may
hav
e co
ntrib
uted
to n
umer
ical
dec
line
Ellio
tt 19
86
42
Tabl
e A
-8.
The
effe
ct o
f LW
D o
n fis
h (p
redo
min
antly
sal
mon
ids)
hab
itat a
nd p
opul
atio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al
orde
r).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Sout
heas
tern
Al
aska
•
0.02
to 0
.03
chan
nel g
radi
ents
•
2nd th
roug
h 4th
ord
er s
tream
s •
Mos
t fis
h, re
gard
less
of s
peci
es o
r age
, wer
e in
poo
ls
• Am
ount
s of
LW
D a
nd c
obbl
e si
gnifi
cant
ly in
crea
sed
in o
ccup
ied
pool
than
in
unoc
cupi
ed p
ools
•
LWD
cau
sed
73%
of a
ll po
ols
• Ju
veni
le s
alm
onid
s (in
win
ter)
pref
erre
d po
ol w
ith c
over
(upt
urne
d ro
ots,
acc
umul
atio
n of
logs
, cob
ble
subs
trate
) •
Amou
nt o
f pre
ferre
d w
inte
r hab
itat d
epen
ded
on a
mou
nt o
f LW
D
• C
lear
cut r
each
es h
ad le
ss L
WD
and
less
poo
l are
a •
Buffe
r stri
ps p
rote
ct h
abita
t by
prov
idin
g LW
D
Hei
fietz
et a
l. 19
86
Ore
gon
• 9.
3 km
2 dra
inag
e ar
ea
• 0.
03 a
vera
ge c
hann
el g
radi
ent
• Fe
wer
pie
ces
of L
WD
in lo
gged
sec
tion
(6 p
iece
s pe
r 100
m) c
ompa
red
to in
un
dist
urbe
d se
ctio
n (4
6 pi
eces
per
100
m)
• LW
D m
ost i
mpo
rtant
fact
or c
ontro
lling
diffe
renc
es in
cha
nnel
mor
phol
ogy:
LW
D
crea
ted
stai
r ste
p m
orph
olog
y, s
econ
dary
cha
nnel
s, a
nd m
eand
ers
• U
ndis
turb
ed s
ectio
ns, L
WD
impr
oved
poo
l qua
lity
and
# of
poo
ls
• Af
ter L
WD
add
ition
s, g
rave
l abu
ndan
ce in
crea
sed
by 2
33%
, gra
vel a
rea
incr
ease
d 25
fo
ld
• 3
times
mor
e co
ho (O
ncor
hync
hus
kisu
tch)
(0.8
8/m
2 ) and
ste
elhe
ad (O
ncor
hync
hus
myk
iss)
(0.5
9/m
2 ) in
undi
stur
bed
sect
ions
•
Posi
tive
corre
latio
n be
twee
n fis
h po
pula
tions
(spa
wni
ng a
nd re
arin
g ha
bita
t) an
d LW
D
Hou
se a
nd B
oehn
e 19
86
Alas
ka
• 0.
01 to
0.0
9 ch
anne
l gra
dien
ts
• 2
m to
6 m
cha
nnel
wid
ths
• 0.
5 km
2 to 2
km
2 dra
inag
e ar
ea
• D
ebris
dam
freq
uenc
y co
rrela
ted
with
deb
ris lo
adin
g •
Deb
ris d
ams
form
ed 8
6% o
f poo
ls in
cle
arcu
t rea
ches
and
47%
of p
ools
in u
nfor
este
d re
ache
s •
Deb
ris d
ams
effe
ctiv
e at
mai
ntai
ning
dep
th in
low
flow
(res
idua
l dep
th)
Lisl
e 19
86a
Was
hing
ton
• 28
0 km
tota
l stre
am le
ngth
for
basi
n •
Salm
onid
dis
appe
aran
ce a
fter M
ount
St H
elen
s er
uptio
n •
LWD
rela
ted
habi
tats
mad
e up
1%
of t
otal
in n
ew c
hann
els,
6%
to 1
2% in
old
affe
cted
ch
anne
ls, a
nd 1
2% to
16%
in o
ld u
naffe
cted
cha
nnel
s •
Stre
ams
with
littl
e am
ount
of L
WD
, als
o ha
d de
crea
sed
amou
nt o
f poo
l are
a •
Deb
ris p
rodu
ces
cove
r but
als
o re
duce
s w
ater
vel
ocity
Mar
tin e
t al.
1986
Briti
sh C
olum
bia,
C
anad
a •
Artif
icia
l cha
nnel
s 4.
9 m
(l) b
y 0.
9 m
(w) b
y 0.
6 m
(d)
• C
oho
salm
on (O
ncor
hync
hus
kisu
tch)
abu
ndan
ce in
crea
sed
as c
over
com
plex
ity
incr
ease
d •
Win
ter c
over
for c
oho
(Onc
orhy
nchu
s ki
sutc
h) c
ombi
ned
low
vel
ocity
, sha
de, a
nd 3
di
men
sion
al c
ompl
exity
McM
ahon
and
Har
tman
19
89
Sout
heas
tern
Al
aska
•
0.10
to 0
.30
chan
nel g
radi
ent
• 5
m to
7 m
cha
nnel
wid
th
• W
inte
r coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) fr
y de
nsity
bes
t mod
eled
by
sum
mer
pe
riphy
ton
biom
ass
and
volu
me
of in
stre
am d
ebris
•
Parr
abun
dant
whe
re d
ebris
was
abu
ndan
t •
In b
oth
sum
mer
and
win
ter,
dens
ity o
f Dol
ly V
arde
n (S
alve
linus
mal
ma)
par
r dire
ctly
re
late
d to
LW
D v
olum
e •
Cov
er (L
WD
and
und
ercu
t ban
ks) m
ore
impo
rtant
for a
ll pa
rr in
win
ter
Mur
phy
et a
l. 19
86
Briti
sh C
olum
bia,
C
anad
a •
10 k
m2 d
rain
age
area
•
Red
uctio
n in
vol
ume
and
stab
ility
of L
WD
2 y
ears
afte
r log
ging
•
Afte
r log
ging
, buf
ferin
g of
stre
am e
nerg
y re
duce
d, c
ohes
ion
of s
tream
bank
s re
duce
d •
Incr
ease
in s
and
led
to re
duce
d gr
avel
qua
lity
and
decr
ease
d si
tes
avai
labl
e fo
r chu
m
(Onc
orhy
nchu
s ke
ta) a
nd c
oho
salm
on (O
ncor
hync
hus
kisu
tch)
spa
wni
ng
• Be
tter g
row
th b
y yo
ung
coho
sal
mon
(Onc
orhy
nchu
s ki
sutc
h) a
nd c
utth
roat
trou
t (O
ncor
hync
hus
clar
ki)
• LW
D p
rovi
ded
over
win
ter c
over
•
Dec
reas
ed d
ensi
ties
of c
oho
(Onc
orhy
nchu
s ki
sutc
h) le
d to
fast
er g
row
th ra
te, l
arge
r si
ze, a
nd h
ighe
r win
ter s
urvi
val
Har
tman
et a
l. 19
87
43
Tabl
e A
-8.
The
effe
ct o
f LW
D o
n fis
h (p
redo
min
antly
sal
mon
ids)
hab
itat a
nd p
opul
atio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al
orde
r).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Ore
gon
• 0.
10 a
vera
ge c
hann
el g
radi
ent
• 3.
2 av
erag
e ch
anne
l wid
th
• 5.
4 km
2 dra
inag
e ar
ea
• 3rd
ord
er s
tream
• 2.
4 fo
ld in
crea
se in
late
ral h
abita
t gav
e 2.
2 fo
ld in
crea
se in
num
ber o
f age
-0 c
utth
roat
tro
ut (O
ncor
hync
hus
clar
ki)
• 86
% re
duct
ion
in la
tera
l hab
itat g
ave
83%
redu
ctio
n in
age
0 c
utth
roat
trou
t (O
ncor
hync
hus
clar
ki)
• Si
gnifi
cant
ly h
ighe
r tro
ut p
rodu
ctio
n in
late
ral h
abita
t of m
anip
ulat
ed s
ectio
n th
an in
co
ntro
l sec
tion
and
LWD
redu
ced
sect
ions
(95%
and
24%
) •
Func
tiona
l lat
eral
hab
itat c
omes
from
LW
D in
tera
ctio
n w
ith s
tream
bed
Moo
re a
nd G
rego
ry 1
988
Sout
heas
t Ala
ska
• <2
m w
ide
stre
ams
• Lo
gs, b
ranc
hes,
und
ercu
t ban
ks, d
ense
ove
rhea
d ve
geta
tion,
and
larg
e bo
ulde
rs w
ere
prim
ary
type
s of
cov
er u
sed
by c
oho
salm
on (O
ncor
hync
hus
kisu
tch)
and
Dol
ly
Vard
en (S
alve
linus
mal
ma)
of a
ll ag
e cl
asse
s
Dol
loff
and
Ree
ves
1990
Briti
sh C
olum
bia,
C
anad
a •
108
km2 d
rain
age
area
•
Coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) fr
y (9
9%) a
nd s
teel
head
(Onc
orhy
nchu
s m
ykis
s) p
arr (
83%
) occ
upie
d po
sitio
ns n
ear m
id-c
hann
el a
rtific
ial r
ootw
ads
in a
ll flo
w
cond
ition
s (d
roug
ht, n
orm
al, a
nd fl
ood)
•
Coh
o pr
efer
red
near
sho
re p
iece
s, w
hile
ste
elhe
ad p
refe
rred
mor
e di
stan
t site
s •
Youn
g fis
h pr
efer
red
slow
wat
er (8
0%) a
nd lo
w li
ght (
20%
) env
ironm
ents
for
prot
ectio
n fro
m h
igh
curre
nts
and
pred
ator
s
Shirv
ell 1
990
Briti
sh C
olum
bia,
C
anad
a •
0.00
5 to
0.0
4 ch
anne
l gra
dien
ts
• 2
m to
5 m
ave
rage
ban
kful
l wid
th
• 1.
03 to
1.3
7 si
nuos
ity
• Se
ctio
ns w
ith L
WD
rem
oved
wer
e le
ss s
inuo
us, w
ider
and
sha
llow
er a
nd h
ad le
ss
cove
r for
fish
than
una
ltere
d se
ctio
ns
• Po
ols
wer
e 9%
to 2
5% o
f tot
al v
olum
e at
bas
eflo
w in
rem
oval
sec
tions
, 61%
to 6
9% o
f to
tal v
olum
e in
una
ltere
d se
ctio
ns
• N
umbe
r of p
iece
s of
LW
D d
irect
ly in
fluen
cing
cha
nnel
mor
phol
ogy
was
gre
ater
in
unal
tere
d se
ctio
ns
• LW
D fo
rmed
72%
to 8
0% o
f poo
ls in
all
sect
ions
•
Dep
ths
of p
ools
gre
ater
in u
nalte
red
sect
ions
•
Afte
r sur
face
flow
cea
sed
in s
umm
er, 9
6% o
f poo
l vol
ume
asso
ciat
ed w
ith L
WD
•
In h
ighe
r gra
dien
t rea
ches
(0.0
15 to
0.0
4 gr
adie
nt) m
ost w
ood
orie
nted
per
pend
icul
ar
to fl
ow
• In
low
er g
radi
ent r
each
es (>
0.01
5) m
uch
high
er p
erce
ntag
e (4
0%) o
f dia
gona
l or
ient
atio
n •
Stan
ding
cro
p of
age
1+
and
olde
r sal
mon
ids
was
muc
h lo
wer
in c
lear
ed s
ectio
ns th
an
in u
nalte
red
sect
ions
•
Biom
ass
of a
ge 1
+ an
d ol
der f
ish
corre
late
d w
ith p
ool v
olum
e, s
ectio
n vo
lum
e, m
ean
dept
h, a
nd le
ngth
of o
verh
ead
cove
r •
Fish
bio
mas
s st
rong
ly c
orre
late
d w
ith p
ool v
olum
e an
d de
pth
• U
ncle
ared
sec
tions
had
five
tim
es th
e cu
rrent
sta
ndin
g cr
op in
cle
ared
sec
tions
Faus
ch a
nd N
orth
cote
199
2
Briti
sh C
olum
bia,
C
anad
a •
Buffe
red,
cle
arcu
t, es
tuar
ine
reac
hes
• LW
D in
fluen
ced
abun
danc
e of
coh
o sm
olts
(Onc
orhy
nchu
s ki
sutc
h) in
stre
am a
nd
estu
ary
• C
oho
smol
t (O
ncor
hync
hus
kisu
tch)
dis
tribu
tion
high
ly c
lum
ped
arou
nd d
ebris
; 80%
w
ithin
5 m
of d
ebris
; 95%
with
in 1
m
• Su
ppor
ts th
e ne
ed to
reta
in L
WD
for s
mol
t hab
itat i
n st
ream
s an
d es
tuar
ies
McM
ahon
and
Hol
tby
1992
Ore
gon
• 27
km
2 dra
inag
e ar
ea
• 5th
ord
er s
tream
•
Stre
am s
urfa
ce a
rea
and
wat
er v
olum
e in
crea
sed
74%
and
168
% a
fter l
og a
dditi
on
• Su
rface
are
a of
poo
l and
off
chan
nel h
abita
t inc
reas
ed in
trea
ted
sect
ions
•
Spaw
ning
act
ivity
four
tim
es h
ighe
r in
trea
ted
sect
ion
Cris
pin
et a
l. 19
93
Albe
rta, C
anad
a •
23 m
cha
nnel
wid
th
• 0.
5 m
cha
nnel
dep
th
• 57
1 km
2 dra
inag
e ar
ea
• 4th
ord
er s
tream
• Fr
y de
nsiti
es h
ighe
r in
sect
ions
with
fine
woo
dy d
ebris
(FW
D) a
dditi
ons
• FW
D m
ay h
ave
prov
ided
stru
ctur
ally
com
plex
hab
itat,
used
as
refu
ge fr
om p
reda
tors
an
d as
site
s fro
m w
hich
fora
ging
fora
ys b
egan
Cul
p et
al.
1996
44
Tabl
e A
-8.
The
effe
ct o
f LW
D o
n fis
h (p
redo
min
antly
sal
mon
ids)
hab
itat a
nd p
opul
atio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al
orde
r).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Mar
ylan
d •
Sube
stua
rine
envi
ronm
ent
• D
ensi
ties
of e
pibe
nthi
c fis
h in
crea
sed
sign
ifica
ntly
in s
ites
with
LW
D
• LW
D p
rovi
ded
refu
ge fr
om p
reda
tion
for e
pibe
nthi
c fis
h an
d in
verte
brat
es
Ever
ett a
nd R
uiz
1993
Nor
th C
arol
ina
• 0.
045
to 0
.06
chan
nel g
radi
ents
•
4 m
to 5
m c
hann
el w
idth
•
7 km
2 to 2
1 km
2 wat
ersh
ed a
rea
• 1st
thro
ugh
3rd o
rder
stre
am
• H
ighe
r abu
ndan
ce o
f LW
D in
und
istu
rbed
stre
ams
• U
ndis
turb
ed re
ache
s ha
d 32
% to
46%
of h
abita
t uni
ts a
ssoc
iate
d w
ith L
WD
•
Broo
k tro
ut (S
alve
linus
font
inal
is),
rain
bow
trou
t (O
ncor
hync
hus
myk
iss)
, bro
wn
trout
(S
alm
o tru
tta) h
ad h
ighe
r den
sity
and
bio
mas
s in
und
istu
rbed
reac
hes
with
LW
D
• La
rger
ave
rage
siz
e of
LW
D in
und
istu
rbed
reac
hes
• M
ore
pool
s an
d rif
fles
of s
mal
ler s
ize
in u
ndis
turb
ed re
ache
s
Fleb
be a
nd D
ollo
ff 19
95
Nor
ther
n C
olor
ado
• 0.
01 to
0.0
24 c
hann
el g
radi
ents
•
3 m
to 6
m c
hann
el w
idth
s •
Pool
vol
ume
incr
ease
d af
ter d
rop
stru
ctur
es in
stal
led
• Am
ount
of c
over
incr
ease
d si
gnifi
cant
ly a
fter a
dditi
on o
f log
dro
p st
ruct
ures
•
Trea
tmen
t sec
tions
wer
e de
eper
and
had
low
er v
eloc
ity th
an c
ontro
l sec
tions
•
Abun
danc
e an
d bi
omas
s of
age
2 a
nd o
lder
incr
ease
d si
gnifi
cant
ly a
fter i
nsta
llatio
n of
dr
op s
truct
ures
•
Log
drop
stru
ctur
es in
crea
sed
abun
danc
e of
adu
lt br
ook
trout
(Sal
velin
us fo
ntin
alis
) an
d po
ssib
ly s
urvi
val,
alth
ough
dat
a no
t con
clus
ive
Rile
y an
d Fa
usch
199
5
Was
hing
ton
• 2.
4 m
cha
nnel
wid
th (a
rtific
ial
chan
nels
) •
Foun
d no
evi
denc
e th
at s
umm
er p
opul
atio
ns w
ere
attra
cted
to b
rush
y de
bris
, nor
did
th
e pr
esen
ce o
f bru
sh in
fluen
ce s
urvi
val o
r gro
wth
, com
para
ble
to fr
ee ra
ngin
g co
ho
salm
on (O
ncor
hync
hus
kisu
tch)
•
Affin
ity o
f coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) fo
r woo
dy d
ebris
incr
ease
s in
win
ter
Spal
ding
et a
l. 19
95
Nor
ther
n C
olor
ado
• 0.
01 to
0.0
3 ch
anne
l gra
dien
ts
• 3
m to
6 m
ave
rage
cha
nnel
wid
th
• Po
ol v
olum
e an
d to
tal c
over
incr
ease
d af
ter L
WD
add
ition
•
Abun
danc
e an
d bi
omas
s of
adu
lt of
bro
ok tr
out (
Sal
velin
us fo
ntin
alis
), br
own
trout
(S
alm
o tru
tta),
rain
bow
trou
t (O
ncor
hync
hus
myk
iss)
incr
ease
d in
man
ipul
ated
re
ache
s •
Incr
ease
d ab
unda
nce
and
biom
ass
resu
lted
from
imm
igra
tion
from
sur
roun
ding
re
ache
s •
Log
wei
rs in
crea
sed
abun
danc
e an
d bi
omas
s of
fish
in th
e ab
senc
e of
any
m
anag
emen
t lim
itatio
ns
Gow
an a
nd F
ausc
h 19
96
Was
hing
ton
• 0.
002
to 0
.015
cha
nnel
gra
dien
ts
• 38
km
2 dra
inag
e ar
ea
• Po
ol s
paci
ng s
igni
fican
tly c
orre
late
d w
ith L
WD
abu
ndan
ce
• Su
rviv
al o
f coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) c
orre
late
d w
ith L
WD
abu
ndan
ce a
nd
volu
me
• Po
sitiv
e re
latio
nshi
p be
twee
n ha
bita
t com
plex
ity (a
bund
ance
of L
WD
and
poo
l sp
acin
g) a
t the
end
of t
he s
umm
er a
nd o
verw
inte
r sur
viva
l
Qui
nn a
nd P
eter
son
1996
Wyo
min
g •
2 m
to 5
m c
hann
el w
idth
•
39%
of p
ools
form
ed b
y LW
D, 6
4% o
f cut
thro
at tr
out (
Onc
orhy
nchu
s cl
arki
) rel
ocat
ed
to th
ese
pool
s Yo
ung
1996
Was
hing
ton
• 0.
02 c
hann
el g
radi
ent
• 10
.0 m
cha
nnel
wid
th
• 3rd
ord
er s
tream
• Po
ol a
rea
incr
ease
d af
ter L
WD
add
ition
•
Abun
danc
e of
coh
o sa
lmon
(Onc
orhy
nchu
s ki
sutc
h) d
urin
g sp
ring
and
win
ter s
how
ed
no re
spon
se to
enh
ance
men
t •
Win
ter a
bund
ance
of c
oho
(Onc
orhy
nchu
s ki
sutc
h) in
crea
sed
sign
ifica
ntly
afte
r en
hanc
emen
t
Ced
erho
lm e
t al.
1997
Nor
ther
n C
alifo
rnia
•
0.02
2 ch
anne
l gra
dien
t •
27.5
km
2 dra
inag
e ar
ea
• 3rd
ord
er s
tream
• Po
ols
form
ed b
y LW
D s
cour
con
tain
ed m
ore
cutth
roat
trou
t (O
ncor
hync
hus
clar
ki)
(0.2
5/m
) tha
n po
ols
form
ed b
y bo
ulde
r sco
ur (0
.16/
m)
• R
eten
tion
of c
utth
roat
trou
t (O
ncor
hync
hus
clar
ki) g
reat
est i
n co
mpl
ex (L
WD
) poo
ls
durin
g hi
gher
flow
s •
Pres
ence
of L
WD
had
littl
e of
no
effe
ct o
n tro
ut m
ovem
ent o
r gro
wth
dur
ing
low
or
mod
erat
e di
scha
rge,
food
ava
ilabi
lity
was
the
mai
n fa
ctor
con
trollin
g m
ovem
ent a
nd
grow
th
Har
vey
1998
45
Tabl
e A
-8.
The
effe
ct o
f LW
D o
n fis
h (p
redo
min
antly
sal
mon
ids)
hab
itat a
nd p
opul
atio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al
orde
r).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K P
OSI
TIO
N
RES
ULT
S R
EFER
ENC
ES
Nor
th C
arol
ina
• 0.
08 to
0.1
6 ch
anne
l gra
dien
ts
• 3.
5 m
ave
rage
cha
nnel
wid
th
• 11
.3 k
m2 d
rain
age
area
•
3rd o
rder
stre
am
• Lo
wer
deb
ris lo
adin
g (e
spec
ially
of l
arge
r siz
es) i
n di
stur
bed
reac
hes
• H
igh
prop
ortio
n of
hab
itat u
nits
form
ed w
ithou
t LW
D in
dis
turb
ed re
ache
s •
Low
pro
porti
on o
f hab
itat f
orm
ed b
y 2
or m
ore
piec
es o
f woo
d in
dis
turb
ed re
ache
s •
71%
of p
ools
and
riffl
es o
ccup
ied
by tr
out i
n di
stur
bed
reac
hes
vers
us 9
0% in
re
fere
nce
reac
hes
• H
abita
t uni
ts w
ith L
WD
sup
porte
d si
gnifi
cant
ly m
ore
trout
than
uni
ts w
ithou
t
Fleb
be 1
999
46
Tabl
e A
-9.
The
effe
ct o
f LW
D o
n rip
aria
n ha
bita
t in
vario
us g
eogr
aphi
c lo
catio
ns a
nd c
hann
el n
etw
ork
posi
tions
(arra
nged
in c
hron
olog
ical
ord
er).
LOC
ATIO
N
CH
ANN
EL N
ETW
OR
K L
OC
ATIO
N
RES
ULT
S R
EFER
ENC
ES
Paci
fic N
orth
wes
t, U
SA
• N
/A
• LW
D p
rote
cts
ripar
ian
site
s w
here
ald
er a
nd o
ther
spe
cies
bec
ome
esta
blis
hed
• Fa
llen
trees
pro
tect
veg
etat
ion
in e
xpos
ed c
hann
el b
ars
• D
owne
d tre
es p
rote
ct v
eget
atio
n an
d cr
eate
site
s w
here
sed
imen
t and
org
anic
m
ater
ial d
epos
it •
Dep
ositi
on o
f sed
imen
t and
org
anic
mat
ter b
oost
s so
il de
velo
pmen
t •
LWD
hel
ps s
tand
s re
ach
mat
ure
stag
e an
d be
tter w
ithst
and
flood
s •
Low
gra
dien
t riv
er s
egm
ents
hav
e ab
unda
nt L
WD
form
ing
depo
sitio
nal a
reas
that
pr
ovid
e si
tes
for f
utur
e flo
odpl
ains
to c
olon
ize
Sede
ll et
al.
1988
Paci
fic N
orth
wes
t, U
SA
• <0
.05
to >
0.18
cha
nnel
gra
dien
ts
• C
hang
e in
siz
e, fr
eque
ncy,
loca
tion,
and
long
evity
of d
epos
ition
al s
ites
form
ed b
y LW
D in
fluen
ces
succ
essi
onal
dyn
amic
s of
ripa
rian
vege
tatio
n •
Esta
blis
hmen
t of f
ores
ted
flood
plai
ns a
ssoc
iate
d w
ith L
WD
par
alle
l or o
bliq
ue to
ch
anne
l •
LWD
trap
s co
lluvi
um a
nd a
lluvi
al s
edim
ent
• LW
D fu
nctio
ns a
s nu
rse
logs
to p
rovi
de n
utrie
nts
and
as e
leva
ted
site
to m
inim
ize
com
petit
ion
betw
een
seed
lings
and
fore
st fl
oor v
eget
atio
n •
Nur
se lo
gs a
lso
act a
s re
fuge
of y
oung
ripa
rian
spec
ies
• As
cha
nnel
con
finem
ent i
ncre
ases
, the
influ
ence
of L
WD
on
ripar
ian
fore
st d
istri
butio
n de
crea
ses
due
to d
ecre
ase
in a
rea
of a
ctiv
e flo
odpl
ain
• Fo
rest
ed fl
oodp
lain
s co
mm
only
form
beh
ind
dow
nstre
am o
f LW
D o
n se
dim
ent
depo
sits
•
Vege
tatio
n co
loni
zes
both
LW
D a
nd lo
w v
eloc
ity z
ones
•
The
age
stru
ctur
e of
fore
sted
floo
dpla
ins
refle
cts
hist
ory
of L
WD
dep
ositi
on a
nd fl
uvia
l di
stur
banc
e •
Accu
mul
atio
ns o
f LW
D fo
rm d
epos
ition
al s
ites
whe
re v
eget
atio
n co
loni
zes
and
beco
mes
est
ablis
hed
in a
n ot
herw
ise
unho
spita
ble
fluvi
al e
nviro
nmen
t
Feth
erst
on e
t al.
1995
Nor
thw
est
Was
hing
ton
• 0.
005
to 0
.01
chan
nel g
radi
ents
•
30 m
to 8
0 m
ban
kful
l wid
th
• 75
km
2 to 2
25 k
m2 d
rain
age
area
s
• R
ipar
ian
fore
sts
alon
g la
rge
allu
vial
cha
nnel
s ge
nera
lly c
hara
cter
ized
as
youn
g an
d ho
mog
enou
s tre
e co
mm
uniti
es th
at re
flect
dis
turb
ance
•
But,
obse
rved
div
erse
ripa
rian
fore
st s
truct
ure
and
anom
alou
s gr
owth
pat
ches
•
Thre
e fa
ctor
s fa
cilit
ate
ripar
ian
fore
st d
evel
opm
ent d
owns
tream
of L
WD
bar
are
a ja
ms:
1) l
ocal
flow
dec
eler
atio
n an
d de
crea
sed
basa
l she
ar s
tress
, 2) s
edim
ent
depo
sitio
n, 3
) an
abun
dant
acc
umul
atio
n of
org
anic
mat
ter o
n th
e su
rface
•
Obs
erva
tion
of o
ld g
row
th ri
paria
n pa
tche
s w
ithin
act
ive
chan
nel m
igra
tion
sugg
ests
so
me
stru
ctur
es re
mai
n st
able
des
pite
repe
ated
inte
grat
ion
into
the
activ
e ch
anne
l •
LWD
pro
vide
long
-term
refu
gia
for f
lood
plai
n rip
aria
n co
mm
uniti
es fo
rmin
g an
omal
ous
old-
grow
th ri
paria
n fo
rest
pat
ches
in a
lluvi
al te
rrain
cha
ract
eriz
ed b
y fre
quen
t di
stur
banc
e
Abbe
and
Mon
tgom
ery
1996
47
Tabl
e A
-10.
The
effe
ct o
f tim
ber h
arve
st o
n LW
D c
hara
cter
istic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
W
este
rn O
rego
n •
0.06
to 0
.65
chan
nel g
radi
ents
•
1 m
to 1
8 m
cha
nnel
wid
ths
• 0.
02 k
m2 to
30
km2 d
rain
age
area
s
• Lo
ggin
g m
etho
ds n
ear a
nd a
cros
s dr
aina
ges
can
chan
ge th
e am
ount
and
con
ditio
n of
in
-cha
nnel
deb
ris
• C
onve
ntio
nal t
ree
fallin
g ad
ded
the
mos
t am
ount
of l
oggi
ng m
ater
ial t
o th
e st
ream
, fo
llow
ed b
y ca
ble
assi
st d
irect
iona
l fal
ling,
and
con
vent
iona
l fal
ling
with
buf
fers
•
Attit
ude
of lo
ggin
g cr
ew p
laye
d la
rges
t par
t in
dete
rmin
ing
amou
nt o
f sla
sh re
mai
ning
Froe
hlic
h 19
73
Wes
tern
Ore
gon
• 0.
10 to
0.3
0 ch
anne
l gra
dien
ts
• C
lear
cut
ting
and
stre
am c
lean
ing
may
redu
ce a
bund
ance
of l
arge
sta
ble
piec
es,
incr
ease
con
cent
ratio
n of
sm
all u
nsta
ble
piec
es th
roug
h in
put a
nd m
obiliz
atio
n of
in
stre
am L
WD
, red
ucin
g ov
eral
l inp
ut
Swan
son
et a
l. 19
76
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• Ti
mbe
r har
vest
may
incr
ease
del
iver
y of
LW
D to
stre
am c
hann
el b
y in
crea
sing
pr
obab
ility
of d
ebris
ava
lanc
hes
• Ti
mbe
r har
vest
may
alte
r siz
e an
d di
strib
utio
n on
deb
ris in
stre
ams
• In
crea
sed
occu
rrenc
e of
deb
ris to
rrent
s in
cle
ar c
ut a
reas
•
Rem
oval
of s
tabl
e la
rge
debr
is m
ay m
obiliz
e sm
alle
r log
s an
d in
itiat
e do
wns
tream
to
rrent
s •
Man
agem
ent a
ctiv
ities
redu
ce L
WD
by
thin
ning
and
har
vest
ing,
whi
ch re
duce
s lo
ng
term
deb
ris lo
adin
g
Swan
son
and
Lien
kaem
per
1978
Sout
heas
tern
Al
aska
•
42 k
m2 d
rain
age
area
•
Tim
ber h
arve
st im
pose
d ch
ange
s in
stre
am c
hann
el re
late
d to
acc
umul
atio
ns o
f LW
D
• N
atur
al a
ccum
ulat
ions
app
eare
d st
able
com
pare
d to
logg
ing
debr
is
• Ab
senc
e of
old
gro
wth
fore
st a
long
stre
amba
nk e
limin
ated
LW
D re
crui
tmen
t •
As n
atur
al a
ccum
ulat
ion
deca
ys, p
ools
may
be
repl
aced
by
riffle
s •
Nat
ural
deb
ris a
ccum
ulat
ions
are
affe
cted
by
larg
e flo
atab
le d
ebris
Brya
nt 1
980
Nor
ther
n C
alifo
rnia
•
0.01
to 0
.40
chan
nel g
radi
ents
•
1.0
km2 to
27
km2 d
rain
age
area
s •
2nd th
roug
h 4th
ord
er s
tream
s
• LW
D in
trodu
ced
durin
g h
arve
st a
re s
mal
ler a
nd m
ore
num
erou
s th
an n
atur
al in
put
• Ti
mbe
r har
vest
der
ived
pie
ces
are
mor
e m
obile
and
enc
oura
ge fa
ilure
of d
owns
tream
da
ms
• Su
bseq
uent
nat
ural
inpu
ts a
re s
mal
ler t
han
old
grow
th s
peci
es
• 2nd
gro
wth
tree
s le
ss ro
t res
ista
nt th
an o
ld g
row
th re
dwoo
ds
• Lo
adin
g in
dis
turb
ed s
tream
s is
low
er a
nd c
ompr
ised
of h
emlo
ck a
nd ta
noak
•
Dis
turb
ed w
ater
shed
s ha
d gr
eate
r am
ount
s of
deb
ris s
tore
d se
dim
ent,
refle
ctin
g th
e gr
eate
r ext
ent t
o w
hich
sto
rage
com
partm
ents
are
fille
d in
logg
ed re
ache
s
Kelle
r and
Mac
Don
ald
1983
Sout
heas
tern
Al
aska
•
0.01
to 0
.09
chan
nel g
radi
ents
•
2 m
to 6
m c
hann
el w
idth
•
0.5
to 2
.0 k
m2 d
rain
age
area
s
• D
ebris
dam
s m
ore
frequ
ent i
n cl
ear c
ut s
tream
s •
Tota
l res
idua
l poo
l len
gth
and
dept
h gr
eate
r in
clea
r cut
stre
ams
• LW
D s
tore
d m
ore
sedi
men
t in
clea
r cut
reac
hes
• R
esul
ts s
ugge
st im
porta
nce
of lo
ggin
g de
bris
and
exi
stin
g de
bris
from
cle
arcu
ts
• LW
D le
ft af
ter l
oggi
ng c
onst
itute
s av
aila
ble
supp
ly o
f woo
d cr
eate
d st
ruct
ure
• R
emov
al o
f woo
d de
plet
es L
WD
bef
ore
ripar
ian
recr
uitm
ent r
esum
es
Lisl
e 19
86a
Nor
ther
n C
alifo
rnia
•
0.04
to 0
.22
chan
nel g
radi
ents
•
1st th
roug
h 2nd
ord
er s
tream
s •
Gre
ater
abu
ndan
ce o
f org
anic
deb
ris d
ams
in c
ontro
l stre
ams
than
in s
tream
s ad
jace
nt
to c
lear
cut
s or
har
vest
ed re
ache
s •
Incr
ease
d le
vels
of L
WD
load
ing
follo
win
g ha
rves
t des
tabi
lize
exis
ting
debr
is d
ams
or
chan
ge d
am c
hara
cter
istic
s th
roug
h ad
ditio
n or
mob
ilizat
ion
of w
ood
O'C
onno
r 198
6
Wes
tern
Ore
gon
• 0.
02 to
0.0
6 ch
anne
l gra
dien
ts
• 5.
5 m
to 8
m b
ankf
ull w
idth
s •
6.5
km2 d
rain
age
area
• Af
ter l
oggi
ng, d
ebris
from
cur
rent
sta
nd c
ontri
bute
d 14
% o
f tot
al L
WD
vol
ume
and
7%
of L
WD
from
cur
rent
sta
nd c
ontri
bute
d to
poo
l for
mat
ion
• R
esul
ts in
dica
te th
at tr
ees
mus
t gro
w b
eyon
d at
leas
t 50
year
s be
fore
sta
nds
cont
ribut
e LW
D in
am
ount
s si
mila
r to
old
grow
th fo
rest
s
Andr
us e
t al.
1988
48
Tabl
e A
-10.
The
effe
ct o
f tim
ber h
arve
st o
n LW
D c
hara
cter
istic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
W
este
rn
Was
hing
ton
• 0.
13 c
hann
el g
radi
ent (
<7 m
ch
anne
l wid
th)
• 0.
08 c
hann
el g
radi
ent (
7 m
to 1
0 m
cha
nnel
wid
th)
• 0.
03 c
hann
el g
radi
ent (
>10
m
chan
nel w
idth
)
• H
ighe
r LW
D a
bund
ance
in o
ld g
row
th th
an 2
nd g
row
th o
r cle
ar c
ut
• Po
ol ty
pes
chan
ged
with
sta
nd a
ge c
lass
: sco
ur p
ools
mor
e fre
quen
t in
2nd g
row
th a
nd
clea
r cut
, and
dom
inan
t poo
l typ
es in
all
stre
am s
izes
•
Freq
uenc
y of
LW
D a
ssoc
iate
d po
ols
sign
ifica
ntly
gre
ater
in o
ld g
row
th s
ites
• Pe
rcen
t of L
WD
form
ing
wat
erfa
lls a
nd p
ropo
rtion
of e
leva
tion
drop
con
trolle
d by
LW
D
grea
test
in o
ld g
row
th s
ites
• Ar
ea o
f LW
D a
ssoc
iate
d se
dim
ent g
reat
est i
n ol
d gr
owth
site
s •
Mor
e fin
e or
gani
c de
bris
reta
ined
by
old
grow
th s
ites
• Fi
ne o
rgan
ic d
ebris
may
con
tribu
te to
the
dive
rsity
of p
ool t
ypes
in o
ld g
row
th s
tream
s •
Man
y ch
ange
s in
LW
D o
ccur
sho
rtly
afte
r (<5
yr) a
fter h
arve
st
Bilb
y an
d W
ard
1989
Sout
heas
tern
Al
aska
•
0.04
to 0
.29
chan
nel g
radi
ents
•
8.2
m to
20
m c
hann
el w
idth
•
99%
of L
WD
sou
rces
with
in 3
0 m
of c
hann
el, 3
0 m
buf
fer a
long
bot
h ba
nks
shou
ld
mai
ntai
n LW
D in
put
• M
odel
pre
dict
ed L
WD
redu
ced
by 7
0% n
inet
y ye
ars
afte
r cle
ar c
uttin
g, re
cove
ry to
pre
-lo
ggin
g le
vel e
xcee
ds 2
50 y
ears
•
Stre
amsi
de m
anag
emen
t sho
uld
prov
ide
supp
ly o
f LW
D s
tabl
e en
ough
to p
rovi
de fi
sh
habi
tat
Mur
phy
and
Kosk
i 198
9
East
ern
Ore
gon
East
ern
Was
hing
ton
• 0.
02 to
0.0
7 ch
anne
l gra
dien
ts
• 2
m to
6 m
ave
rage
cha
nnel
w
idth
s
• LW
D v
olum
e at
logg
ed s
ites
1 to
2 fo
ld h
ighe
r tha
n un
logg
ed s
ites
due
to lo
ggin
g re
sidu
e an
d bl
owdo
wn,
but
ove
rall
amou
nts
wer
e si
mila
r C
arls
on e
t al.
1990
Ore
gon
• 1st
thro
ugh
3rd o
rder
stre
ams
• 70
% o
f LW
D c
ame
from
20
m o
f cha
nnel
, 11%
cam
e fro
m 1
m o
f the
cha
nnel
•
Prob
abilis
tic m
odel
bas
ed o
n tre
e he
ight
and
den
sity
•
Mod
el u
sed
to in
terp
ret e
ffect
of w
idth
of b
uffe
r stri
ps o
n fu
ture
LW
D re
crui
tmen
t
McD
ade
et a
l. 19
90
Ore
gon
• 0.
13 c
hann
el g
radi
ent
• 12
ave
rage
ban
kful
l wid
th
• 3rd
ord
er s
tream
• Pr
obab
ilistic
mod
el p
redi
ctin
g nu
mbe
r and
vol
ume
of L
WD
inpu
t •
Inpu
ts a
ggre
gate
d w
ith re
spec
t to
dist
ance
, tre
e he
ight
, and
spe
cies
•
Dem
onst
rate
s im
porta
nce
of c
onsi
derin
g st
and
com
posi
tion,
not
just
stre
am s
ize
in
desi
gnin
g bu
ffer z
ones
Van
Sick
le a
nd G
rego
ry
1990
Sout
heas
tern
Al
aska
•
0.0
02 to
0.0
2 ch
anne
l gra
dien
ts
• 1
km2 to
30
km2 d
rain
age
area
•
4 m
to 2
5 m
cha
nnel
wid
ths
• C
hann
el u
nit d
istri
butio
n di
ffers
mar
kedl
y be
twee
n di
stur
bed
and
undi
stur
bed
site
s •
55%
of w
ette
d ch
anne
l are
a in
poo
l in
und
istu
rbed
reac
hes
and
34%
in d
istu
rbed
re
ache
s •
Diff
eren
ces
in c
hann
el u
nit d
istri
butio
n at
tribu
ted
to d
iffer
ence
in p
ool a
ssoc
iate
d w
ood
• LW
D lo
adin
g gr
eate
r in
undi
stur
bed
stre
ams
• Fr
eque
ncy
of p
ool t
ypes
diff
er b
etw
een
dist
urbe
d an
d un
dist
urbe
d re
ache
s, im
plyi
ng
effe
ct o
f lan
d us
e •
Pris
tine
chan
nel c
ondi
tion
can
be d
iscr
imin
ated
from
man
aged
cha
nnel
s by
ana
lyzi
ng
geom
orph
ic v
aria
bles
Woo
d-Sm
ith a
nd
Buffi
ngto
n 19
96
Wes
tern
W
ashi
ngto
n •
0.00
4 to
0.1
1 ch
anne
l gra
dien
ts
• 0.
5 km
2 to 1
4 km
2 dra
inag
e ar
eas
• U
nlog
ged
stre
ams
had
high
er fr
actio
n of
woo
dy d
ebris
in la
rger
siz
e ca
tego
ries
• In
tens
ive
timbe
r har
vest
ing
sign
ifica
ntly
dec
reas
ed fr
actio
n of
stre
am a
rea
in p
ools
•
Inte
nsiv
e tim
ber h
arve
st re
duce
d po
ol d
epth
and
poo
l are
a •
Inte
nsiv
ely
harv
este
d ba
sins
: 50%
of w
ood
outs
ide
low
flow
cha
nnel
, 33%
inte
ract
ed
with
flow
, 6%
com
plet
ely
with
in c
hann
el
• M
oder
atel
y ha
rves
ted
basi
n: 2
5% o
f woo
d ou
tsid
e lo
w fl
ow c
hann
el, 5
0% in
tera
cted
w
ith fl
ow, 1
9% fu
lly w
ithin
cha
nnel
•
Unl
ogge
d ba
sins
: 25%
of w
ood
outs
ide
chan
nel,
66%
inte
ract
ed w
ith c
hann
el, 3
2%
fully
in c
hann
el
• St
ream
s flo
win
g th
roug
h ol
d gr
owth
fore
sts
reta
ined
mor
e pi
eces
of s
mal
ler w
ood
• N
ewly
recr
uite
d LW
D w
as le
ss s
tabl
e in
mod
erat
e an
inte
nsel
y ha
rves
ted
stre
ams
and
less
like
ly to
con
tribu
te to
con
tribu
te to
hab
itat s
truct
ure
with
less
of a
role
in b
edlo
ad
stor
age
Ral
ph e
t al.
1994
49
Tabl
e A
-10.
The
effe
ct o
f tim
ber h
arve
st o
n LW
D c
hara
cter
istic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
N
orth
Car
olin
a •
0.01
to 0
.10
chan
nel g
radi
ents
•
5 m
to 1
1 m
cha
nnel
wid
ths
• 1st
thro
ugh
4th o
rder
stre
ams
• LW
D v
olum
e in
crea
sed
linea
rly in
stre
ams
asso
ciat
ed w
ith la
te s
ucce
ssio
nal t
hrou
gh
old
grow
th fo
rest
s •
Inst
ream
load
ings
bui
ld a
nd s
tabi
lize
in la
ter s
tage
s of
suc
cess
ion
• St
ream
s flo
win
g th
roug
h yo
unge
r for
ests
rely
on
LWD
from
sta
nd g
ener
atin
g di
stur
banc
es; i
nstre
am L
WD
not
rela
ted
to fo
rest
age
•
Amer
ican
che
stnu
t (C
asta
nea
dent
ata)
maj
or L
WD
com
pone
nt in
mid
-suc
cess
iona
l st
ream
s
Hed
man
et a
l. 1
996
Nor
ther
n C
alifo
rnia
•
4.2
km2 to
5 k
m2 d
rain
age
area
s •
LWD
incr
ease
d af
ter l
oggi
ng d
ue to
resi
dual
tree
s ad
jace
nt to
the
stre
am o
r in
buffe
r st
rips
• D
ougl
as fi
r pro
vide
d gr
eate
st a
mou
nt o
f LW
D in
sec
ond
grow
th s
yste
ms
• LW
D a
ssoc
iate
d po
ols
and
debr
is ja
ms
high
er in
logg
ed s
tream
s
Surfl
eet a
nd Z
eim
er 1
996
UK
• 0.
013
aver
age
chan
nel g
radi
ent
• 2nd
thro
ugh
3rd o
rder
stre
ams
• N
umbe
r of d
ebris
dam
s re
cove
red
7 to
8 y
ears
afte
r rem
oval
•
The
num
ber o
f hyd
raul
ical
ly a
ctiv
e da
ms
did
not r
ecov
er a
s th
e nu
mbe
r and
siz
e of
po
ols
was
low
er th
an b
efor
e re
mov
al
Gur
nell
and
Swee
t 19
98
Nor
ther
n C
alifo
rnia
•
0.02
cha
nnel
gra
dien
t •
7.7
m a
vera
ge b
ankf
ull w
idth
•
3.8
km2 d
rain
age
area
•
3rd o
rder
stre
am
• Lo
ggin
g in
crea
sed
inpu
t of L
WD
from
blo
wdo
wns
, lea
ding
to in
crea
sed
stor
age
of b
ed
mat
eria
l, in
crea
sed
num
ber a
nd to
tal v
olum
e of
poo
ls, a
nd te
mpo
raril
y in
crea
sed
fine
sedi
men
t •
Incr
ease
d LW
D v
olum
es in
crea
sed
size
and
abu
ndan
ce o
n po
ols
• In
crea
se in
LW
D a
nd L
WD
ass
ocia
ted
habi
tats
may
be
tem
pora
ry a
s in
-cha
nnel
woo
d de
cays
and
nat
ural
inpu
t sou
rces
reco
ver
• R
each
es b
orde
red
by c
lear
cuts
and
buf
fer s
trips
may
lose
sed
imen
t sto
rage
, poo
l vo
lum
e, a
nd h
abita
t com
plex
ity a
s LW
D in
puts
dec
line
Lisl
e an
d N
apol
itano
199
8
Wes
tern
W
ashi
ngto
n •
<0.0
2 ch
anne
l gra
dien
ts
• 3.
0 to
12
km2 d
rain
age
area
s •
7 m
to 1
6 m
cha
nnel
wid
th
• D
iam
eter
s of
old
gro
wth
LW
D la
rger
than
2nd
gro
wth
LW
D
• Fo
rest
ry p
ract
ices
: con
vers
ion
of o
ld g
row
th c
onife
rous
to d
ecid
uous
spe
cies
, ins
tream
sa
lvag
e, a
nd s
tream
cle
anin
g ha
ve a
ltere
d LW
D c
hara
cter
istic
s •
60%
redu
ctio
n in
LW
D fo
r log
ged
old
grow
th s
ites
betw
een
1982
and
199
3 •
Ove
r 10
year
per
iod,
num
ber o
f pie
ces
iden
tical
but
LW
D v
olum
e de
crea
sed
as a
n in
crea
se in
sec
ond
grow
th L
WD
was
insu
ffici
ent t
o of
fset
loss
of o
ld g
row
th L
WD
•
Dia
met
er o
f 2nd
gro
wth
LW
D in
crea
sed
from
198
2 to
199
3, b
ut s
till s
mal
ler t
han
old
grow
th L
WD
•
Initi
al ra
pid
loss
of o
ld L
WD
follo
win
g tim
ber h
arve
st c
ause
d by
des
tabi
lizat
ion
and
yard
ing,
cha
nnel
des
tabi
lizat
ion
and
trans
port,
and
long
-term
dec
ay
• C
hara
cter
istic
s of
LW
D fr
om s
econ
d gr
owth
LW
D m
uch
diffe
rent
from
old
gro
wth
co
nife
rs
McH
enry
et a
l. 19
98
Nor
ther
n C
alifo
rnia
•
0.08
cha
nnel
gra
dien
t •
3 m
to 2
0 m
cha
nnel
wid
th
• LW
D s
igni
fican
tly lo
wer
in re
cent
ly lo
gged
bas
ins
than
in o
ld g
row
th re
dwoo
d sy
stem
s N
apol
itano
199
8
Nor
ther
n C
alifo
rnia
•
N/A
•
Pres
ence
of c
lear
cut
s ne
xt to
buf
fer s
trips
can
incr
ease
occ
urre
nce
on w
indt
hrow
for a
di
stan
ce o
f 150
m
• R
esul
ts s
ugge
st u
se o
f a c
ore
buffe
r, gr
eate
r tha
n on
e tre
e he
ight
, fla
nked
by
a fri
nge
buffe
r to
prot
ect c
ore
buffe
r fro
m a
bnor
mal
ly h
igh
rate
s of
win
dthr
ow
Rei
d an
d H
ilton
199
8
50
Tabl
e A-
11.
The
effe
ct o
f LW
D m
anag
emen
t on
fish
habi
tat i
n va
rious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
C
entra
l Ore
gon
• 0.
71 k
m2 to
30
km2 d
rain
age
area
s •
Burn
ing
of s
lash
pos
sibl
y in
crea
sed
stre
am te
mpe
ratu
res,
resu
lting
in m
orta
lity
of
coho
and
cut
thro
at
• D
ebris
on
grav
el s
urfa
ce p
reve
nted
inte
rcha
nge
betw
een
surfa
ce a
nd in
tragr
avel
w
ater
, red
ucin
g di
ssol
ved
oxyg
en
• D
ecom
posi
tion
of d
ebris
incr
ease
d bi
olog
ical
oxy
gen
dem
and,
furth
er re
duci
ng
avai
labl
e di
ssol
ved
oxyg
en
• To
pre
vent
redu
ctio
n in
dis
solv
ed o
xyge
n, k
eep
all d
ebris
out
of c
hann
el th
roug
h us
e of
a b
uffe
r stri
p
Hal
l and
Lan
tz 1
968
Paci
fic N
orth
wes
t, U
SA
• N
/A
• Ex
cess
logg
ing
deriv
ed L
WD
may
blo
ck fi
sh p
assa
ge o
r del
ay fi
sh m
igra
tion
in v
-sh
aped
cha
nnel
s •
LWD
may
des
tabi
lize
stre
ambe
d, p
artic
ular
ly s
paw
ning
gra
vel
• Sm
all d
ebris
(woo
d fib
er, b
ark,
leav
es) f
ills in
ters
tices
of g
rave
l, re
duci
ng li
ving
spa
ce
for s
tream
inve
rtebr
ates
•
Smal
l deb
ris h
as h
igh
BOD
and
CO
D, d
ecre
asin
g di
ssol
ved
O2
conc
entra
tion
• Sm
all d
ebris
on
grav
el re
duce
s in
ters
titia
l flo
w, a
nd in
crea
ses
BOD
and
CO
D,
decr
ease
d D
O in
tragr
avel
wat
er, i
nflu
enci
ng d
epth
of e
mbr
yos
and
alev
ins
• Ta
nnin
s an
d lig
nin
like
subs
tanc
es p
rodu
ce y
ello
w a
nd b
row
n co
lors
that
cou
ld a
bsor
b ph
otos
ynth
etic
ally
act
ive
radi
atio
n w
ithin
a fe
w in
ches
of t
he s
urfa
ce
Nar
ver 1
970
Paci
fic N
orth
wes
t, U
SA
• N
/A
• Ex
cess
logg
ing
deriv
ed F
WD
may
dec
reas
ed d
isso
lved
O2,
incr
ease
BO
D, a
nd
rest
rict a
erat
ion
of w
ater
•
Exce
ss lo
ggin
g de
rived
LW
D p
rese
nts
barri
ers
to fi
sh m
ovem
ent,
can
caus
e or
co
ntrib
ute
to "f
lush
out
s," m
ass
mov
emen
ts th
at s
cour
stre
ams
to b
edro
ck a
nd re
duce
co
mpl
exity
Brow
n 19
74
Wes
tern
W
ashi
ngto
n •
0.01
to 0
.08
chan
nel g
radi
ents
•
1 km
2 to
30 k
m2 d
rain
age
area
s •
Salm
onid
bio
mas
s 1.
5 tim
es g
reat
er in
logg
ed s
ectio
ns
• Lo
gged
wat
ersh
eds
cont
aine
d hi
gher
per
cent
ages
of a
ge 0
+ st
eelh
ead
(Onc
orhy
nchu
s m
ykis
s) a
nd a
ge 0
+ cu
tthro
at (O
ncor
hync
hus
clar
ki)
• D
ebris
rem
oval
follo
win
g tim
ber h
arve
st in
crea
sed
riffle
are
a •
Juve
nile
ste
elhe
ad (O
ncor
hync
hus
myk
iss)
and
cut
thro
at (O
ncor
hync
hus
clar
ki)
poss
ibly
incr
ease
d du
e to
pre
fere
nce
for r
iffle
hab
itats
Biss
on a
nd S
edel
l 198
4
Ore
gon
• N
/A
• St
ruct
ures
incr
ease
d di
vers
ity o
f stre
ambe
d, tr
appe
d gr
avel
, cre
ated
gra
vel b
ars
and
pool
s •
Spaw
ning
occ
urre
nce
of c
oho
and
stee
lhea
d(O
ncor
hync
hus
myk
iss)
incr
ease
d in
m
odifi
ed s
ectio
ns
• C
ontro
l sec
tion
supp
orte
d hi
gher
den
sitie
s of
juve
nile
coh
o (O
ncor
hync
hus
kisu
tch)
, st
eelh
ead
(Onc
orhy
nchu
s m
ykis
s), a
nd c
utth
roat
(Onc
orhy
nchu
s cl
arki
)
Hou
se a
nd B
oehn
e 19
85
Wes
tern
W
ashi
ngto
n •
N/A
•
Wat
er tr
ansp
orta
tion
and
stor
age
of lo
gs s
ever
ely
impa
cts
phys
ical
, che
mic
al, a
nd
biol
ogic
al fu
nctio
ning
of s
tream
s Se
dell
and
Duv
all 1
985
Sout
heas
t Ala
ska
• 0.
035
to 0
.053
cha
nnel
gra
dien
t •
2 m
ave
rage
cha
nnel
wid
th
• U
ncle
aned
stre
am s
ectio
n co
ntai
ned
mor
e fis
h of
all
size
cla
sses
than
cle
aned
se
ctio
ns
• N
umbe
rs a
nd p
rodu
ctio
n of
coh
o (O
ncor
hync
hus
kisu
tch)
and
Dol
ly V
arde
n (S
alve
linus
mal
ma)
redu
ced
by L
WD
rem
oval
•
Hab
itat s
impl
ifica
tion
affe
cted
age
1+
and
olde
r fis
h m
ore
than
age
0+
• LW
D p
rovi
ded
impo
rtant
hyd
raul
ic c
over
dur
ing
win
ter
Dol
loff
1986
51
Tabl
e A-
11.
The
effe
ct o
f LW
D m
anag
emen
t on
fish
habi
tat i
n va
rious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
So
uthe
ast A
lask
a •
1.9
m a
vera
ge c
hann
el w
idth
•
9 km
2 cha
nnel
wid
th
• 6.
5 km
long
• R
emov
al lo
ggin
g de
bris
redu
ced
wet
ted
wid
th a
nd a
reas
from
874
m2 a
nd 7
26m
2 •
Dol
ly V
arde
n (S
alve
linus
mal
ma)
pop
ulat
ion
decr
ease
d fro
m 7
48 to
458
to 1
00 tw
o ye
ars
afte
r deb
ris re
mov
al
• D
ecre
ase
in fi
sh s
ize
afte
r cle
aran
ce, b
efor
e de
bris
rem
oval
, fis
h oc
cupi
ed m
id
chan
nel p
ools
and
tang
les
of d
ebris
, afte
r rem
oval
occ
upie
d ba
ckw
ater
s an
d st
ream
m
argi
ns
• R
emov
al o
f log
ging
deb
ris c
hang
ed m
orph
olog
y, b
riefly
redu
ced
food
sup
ply
and
elim
inat
ed m
ost c
over
, red
ucin
g nu
mbe
r and
mea
n le
ngth
of f
ish,
leav
ing
smal
l fis
h su
scep
tible
to d
ispl
acem
ent
• D
ecre
ase
in b
enth
os a
bund
ance
, red
uced
am
ount
of f
ood
eate
n by
Dol
ly V
arde
n (S
alve
linus
mal
ma)
and
may
hav
e co
ntrib
uted
to n
umer
ical
dec
line
Ellio
tt 19
86
Sout
heas
tern
Al
aska
•
0.02
to 0
.03
chan
nel g
radi
ents
•
2nd to
4th o
rder
stre
ams
• M
ost f
ish
rega
rdle
ss o
f spe
cies
or a
ge w
ere
in p
ools
•
Amou
nts
of L
WD
and
cob
ble
high
er in
occ
upie
d po
ols
than
in u
nocc
upie
d po
ols
• LW
D c
ause
d 73
% o
f all
pool
s •
Juve
nile
sal
mon
ids
(in w
inte
r) pr
efer
red
pool
with
cov
er (u
ptur
ned
root
s, a
ccum
ulat
ion
of lo
gs, c
obbl
e su
bstra
te)
• Am
ount
of p
refe
rred
win
ter h
abita
t dep
ends
on
amou
nt o
f LW
D
• C
lear
cut r
each
es le
ss L
WD
and
poo
l are
a •
Buffe
rs p
rote
ct h
abita
t by
prov
idin
g LW
D
Hei
fietz
et a
l. 19
86
Ore
gon
• 9.
2 km
2 dra
inag
e ar
ea
• 0.
03 a
vera
ge c
hann
el g
radi
ent
• LW
D in
logg
ed s
ectio
n (6
/100
m) s
how
ed a
n in
crea
sed
in u
ndis
turb
ed s
ectio
n (4
6/10
0m)
• LW
D m
ost i
mpo
rtant
fact
or c
ontro
lling
diffe
renc
es in
cha
nnel
mor
phol
ogy
LWD
cr
eate
d st
air s
tep
mor
phol
ogy,
sec
onda
ry c
hann
els,
and
mea
nder
s •
Und
istu
rbed
sec
tions
, LW
D im
prov
ed p
ool q
ualit
y an
d #
of p
ools
•
Afte
r LW
D a
dditi
ons,
gra
vel i
ncre
ased
by
233%
, gra
vel a
reas
incr
ease
d 25
fold
in
area
•
3 tim
es m
ore
coho
(0.8
8/m
2 ) and
ste
elhe
ad (0
.59/
m2 ) i
n un
dist
urbe
d se
ctio
ns
• Po
sitiv
e co
rrela
tion
betw
een
fish
popu
latio
ns (s
paw
ning
and
rear
ing
habi
tat)
and
LWD
Hou
se a
nd B
oehn
e 19
86
Sout
heas
tern
Al
aska
•
0.10
to 0
.30
chan
nel g
radi
ent
• 5
m to
7 m
cha
nnel
wid
th
• W
inte
r fry
den
sity
bes
t mod
eled
by
sum
mer
per
iphy
ton
biom
ass
and
volu
me
of
inst
ream
deb
ris
• Pa
rr ab
unda
nt w
here
deb
ris w
as a
bund
ant
• In
bot
h su
mm
er a
nd w
inte
r, de
nsity
of D
olly
Var
den
(Sal
velin
us m
alm
a) p
arr d
irect
ly
rela
ted
to L
WD
vol
ume
• C
over
(LW
D a
nd u
nder
cut b
anks
) mor
e im
porta
nt fo
r all
parr
in w
inte
r
Mur
phy
et a
l. 19
86
Nor
ther
n C
olor
ado
• 0.
01 to
0.0
24 c
hann
el g
radi
ents
•
3 m
to 6
m c
hann
el w
idth
s •
Pool
vol
ume
afte
r dro
p st
ruct
ures
inst
alle
d •
Amou
nt o
f cov
er in
crea
sed
sign
ifica
ntly
afte
r add
ition
of l
og d
rop
stru
ctur
es
• Tr
eatm
ent s
ectio
ns w
ere
deep
er a
nd h
ad lo
wer
vel
ocity
than
con
trol s
ectio
ns
• Ab
unda
nce
and
biom
ass
of a
ge 2
and
old
er c
utth
roat
(Onc
orhy
nchu
s cl
arki
) in
crea
sed
sign
ifica
ntly
afte
r ins
talla
tion
of d
rop
stru
ctur
es
• Lo
g dr
op s
truct
ures
incr
ease
d ab
unda
nce
of a
dult
broo
k tro
ut (S
alve
linus
font
inal
is)
and
poss
ibly
sur
viva
l, al
thou
gh d
ata
not c
oncl
usiv
e
Rile
y an
d Fa
usch
199
5
Nor
th C
arol
ina
• 0.
03 to
0.0
6 ch
anne
l gra
dien
ts
• Po
ol fo
rmat
ion
afte
r log
add
ition
•
Enha
nced
redu
ctio
n up
stre
am fr
om d
ebris
dam
s •
Inve
rtebr
ate
abun
danc
e an
d bi
omas
s in
crea
sed
sign
ifica
ntly
afte
r log
add
ition
•
Scra
per a
nd c
olle
ctor
/filte
rer a
bund
ance
incr
ease
d af
ter l
og a
dditi
on
• Se
cond
ary
prod
uctio
n of
scr
aper
s an
d fil
tere
rs d
ecre
ased
•
Shift
s in
func
tiona
l gro
up a
bund
ance
s, b
iom
ass,
and
abu
ndan
ce a
ccen
tuat
e th
e im
porta
nce
of lo
cal a
biot
ic fa
ctor
s in
stru
ctur
e of
inve
rtebr
ate
com
mun
ities
with
in
patc
hes
Wal
lace
et a
l. 19
95
52
Tabl
e A-
11.
The
effe
ct o
f LW
D m
anag
emen
t on
fish
habi
tat i
n va
rious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
N
orth
ern
Cal
iforn
ia
• 4.
2 km
2 and
4.7
km
2 dra
inag
e ar
eas
• In
crea
se in
LW
D v
olum
e af
ter t
imbe
r har
vest
•
LWD
incr
ease
d ha
bita
t are
for s
teel
head
(Onc
orhy
nchu
s m
ykis
s), c
oho
(Onc
orhy
nchu
s ki
sutc
h), a
nd P
acifi
c G
iant
sal
aman
ders
(Dic
ampt
on te
nebr
osus
) •
As lo
ggin
g de
rived
LW
D d
ecre
ases
thro
ugh
deca
y, a
nd a
s na
tura
l inp
uts
reco
ver,
habi
tat c
ondi
tions
may
not
per
sist
Nak
amot
o 19
98
Tabl
e A
-12.
The
effe
ct o
f roa
ds o
n LW
D c
hara
cter
istic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
O
rego
n •
N/A
•
Logg
ing
debr
is in
stre
am c
hann
els
is a
maj
or c
ontri
buto
r to
flood
dam
age
• Lo
ggin
g re
sidu
e te
nds
to b
e co
ncen
trate
d in
dra
ws
and
depr
essi
ons
that
car
ry w
ater
du
ring
flood
con
ditio
ns
• Pr
oble
m o
f woo
d tra
nspo
rt th
roug
h ch
anne
ls c
ompo
unde
d by
road
way
s th
at p
lace
re
stric
tion
on m
ovem
ent
• C
ulve
rts a
nd b
ridge
s ob
stru
ct w
ood
mov
emen
t and
cau
se d
amag
e to
road
sys
tem
•
Dam
age
to ro
ad s
yste
m is
maj
or it
em in
cal
cula
tion
of fl
ood
loss
es
• C
ost o
f pro
blem
is u
nkno
wn,
but
incl
uded
dam
age
to ro
ads
and
desi
gn o
f stru
ctur
es to
pa
ss d
ebris
•
Asid
e fro
m re
mov
ing
all d
ebris
, alte
rnat
ives
are
to m
odify
or b
uild
stru
ctur
es to
pas
s w
ood,
mec
hani
cally
rem
ove
larg
e ja
ms,
bui
ld ro
ads
to a
ct a
s de
bris
bar
rier
Froe
hlic
h 19
70
N/A
•
N/A
•
Cle
arin
g an
d sn
aggi
ng d
one
for t
hree
reas
ons:
dra
in fl
oodp
lain
s fo
r agr
icul
tura
l de
velo
pmen
t, pr
otec
t citi
zens
from
floo
ds, m
aint
ain
navi
gabl
e w
ater
way
s •
Cle
arin
g an
d sn
aggi
ng in
hig
h or
der s
tream
s re
duce
s ro
ughn
ess
coef
ficie
nt
Mar
zolf
1978
Wes
tern
Ore
gon
• 0.
02 to
0.5
0 ch
anne
l gra
dien
ts
• H
ighe
r lev
els
of d
ebris
torre
nt a
ctiv
ity in
are
as w
ith h
igh
road
are
a re
lativ
e to
fore
st
area
Sw
anso
n an
d Li
enka
empe
r 19
78
Cen
tral C
alifo
rnia
•
104
km2 d
rain
age
area
•
Floo
d da
mag
es s
igni
fican
tly re
duce
d if
all b
ridge
s ke
pt fr
ee o
f log
jam
s •
No
prac
tical
way
to p
reve
nt a
ll tre
es fr
om e
nter
ing
chan
nel s
ince
mos
t com
e fro
m
debr
is fl
ow tr
igge
red
by s
torm
s •
Onl
y fe
asib
le s
olut
ion
to p
reve
nt a
ccum
ulat
ion
at b
ridge
s is
to m
odify
or r
epla
ce
brid
ges
son
that
logs
will
flow
und
er w
ithou
t cat
chin
g •
Stre
am c
lear
ance
is n
ot a
sol
utio
n as
mos
t log
s co
me
form
deb
ris fl
ows
that
occ
ur
durin
g th
e st
orm
•
Stud
ies
shou
ld in
clud
e lo
g pa
ssin
g ca
paci
ty o
f all
dow
nstre
am b
ridge
s
Sing
er a
nd S
wan
son
1983
N/A
•
N/A
•
LWD
and
veg
etat
ion
rem
oved
to in
crea
se h
ydra
ulic
cap
acity
Sh
ield
s an
d N
unna
lly 1
984
Cal
iforn
ia
• N
/A
• C
lear
wat
er d
esig
n of
floo
d co
ntro
l cha
nnel
igno
res
or u
nder
estim
ates
role
of f
loat
ing
debr
is in
incr
easi
ng fl
ood
elev
atio
ns
• D
ebris
impe
des
or b
lock
s sm
all t
o m
ediu
m s
ized
cul
verts
in s
mal
l to
med
ium
siz
ed
culv
erts
in s
mal
ler s
tream
s, a
nd b
ridge
s an
d la
rger
cul
verts
in m
ain
chan
nels
, cau
sing
si
gnifi
cant
incr
ease
s in
floo
d el
evat
ions
•
Con
veya
nce
prog
ram
s th
at e
ncou
rage
rem
oval
of w
ood
rare
ly u
nder
go te
chni
cal
scru
tiny;
an
appr
oach
that
con
side
rs h
ydro
logi
c, g
eom
orph
ic, a
nd b
iolo
gica
l fac
tors
is
need
ed
Willi
ams
and
Swan
son
1989
N/A
•
N/A
•
Cro
ssin
gs s
houl
d be
des
igne
d to
tran
smit
debr
is d
owns
tream
Fu
rnis
s et
al.
1991
53
Tabl
e A
-12.
The
effe
ct o
f roa
ds o
n LW
D c
hara
cter
istic
s in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
Au
stra
lia
• 0.
46 m
(w) b
y 8
m (l
) by
0.27
(d)
artif
icia
l cha
nnel
•
The
aver
age
amou
nt o
f LW
D fo
und
in A
ustra
lian
low
land
rive
rs s
eldo
m h
as a
si
gnifi
cant
on
flood
leve
ls
• W
here
larg
e lo
g ja
ms
form
or a
t cha
nnel
con
stric
tion
will
effe
cts
be s
igni
fican
t •
Whe
re c
onsu
mpt
ive
uses
redu
ce fl
ow le
vels
, LW
D re
mov
al m
ay b
e re
quire
d m
ore
frequ
ently
to p
reve
nt ja
m fo
rmat
ion
• As
a c
ompr
omis
e be
twee
n LW
D re
mov
al fo
r hyd
raul
ic re
ason
s an
d ha
bita
t pr
eser
vatio
n, it
may
by
poss
ible
to re
arra
nge
LWD
for m
inim
al h
ydra
ulic
influ
ence
Youn
g 19
91
Aust
ralia
•
3540
km
2 dra
inag
e ar
ea
• R
esul
ts s
ugge
st th
at d
e-sn
aggi
ng w
ould
redu
ce b
ankt
op fl
ood
heig
ht b
y 0.
2%
• Av
erag
e de
bris
pie
ces
wou
ld h
ave
min
imal
influ
ence
on
flow
hyd
raul
ics,
alth
ough
la
rge
piec
es m
ay b
e si
gnifi
cant
•
Re-
intro
duct
ion
of w
ood
into
cle
ared
rive
rs u
nlik
ely
to re
sult
in lo
ss o
f con
veya
nce
Gip
pel e
t al.
1996
Uni
ted
Stat
es
• N
/A
• Fl
oatin
g de
bris
incr
ease
s la
tera
l for
ces
on b
ridge
s, p
rom
otin
g sc
our
• D
rift a
ccum
ulat
ion
depe
nds
on c
hann
el, b
asin
, and
brid
ge c
hara
cter
istic
s •
Drif
t acc
umul
ates
aga
inst
brid
ge p
iers
, and
obs
tacl
es s
epar
ated
by
narro
w g
aps
trap
drift
mos
t effe
ctiv
ely
• G
aps
betw
een
two
piec
es a
re n
ot b
lock
ed u
nles
s lo
gs c
an s
pan
pier
to p
ier
• Su
gges
ted
desi
gn fe
atur
es to
redu
ce d
rift a
ccum
ulat
ion:
ade
quat
e fre
eboa
rd, w
ide
span
s, s
olid
pie
rs, r
ound
ed p
ier n
oses
, and
pie
r pla
cem
ent o
ut o
f pat
h of
drif
t (th
alw
eg)
Die
hl 1
997
Okl
ahom
a •
N/A
•
Deb
ris e
ntra
pmen
t inc
reas
ed M
anni
ng's
n b
y 39
%
• Ef
fect
of d
ebris
on
flow
resi
stan
ce d
ecre
ased
with
incr
ease
d di
scha
rge
• R
esul
ts li
mite
d to
cha
nnel
<0.
6 m
dep
th (f
lood
plai
ns o
r low
ord
er c
hann
els)
Dud
ley
et a
l. 19
98
Cal
iforn
ia
• N
/A
• Pl
uggi
ng o
f cul
verts
by
LWD
is a
com
mon
failu
re m
echa
nism
•
Piec
es in
itiat
ing
plug
ging
are
ofte
n no
t muc
h lo
nger
than
cul
vert
diam
eter
•
Cul
verts
siz
ed e
qual
to th
e ch
anne
l wid
th w
ill pa
ss a
sig
nific
ant p
ortio
n of
woo
d •
Woo
d de
bris
cap
acity
of c
ulve
rts c
an b
e as
sess
ed b
y ta
king
ratio
of c
ulve
rt di
amet
er
to c
hann
el w
idth
(w*)
•
Cro
ssin
gs w
ith lo
w w
* val
ues
(<1)
are
pro
ne to
deb
ris p
lugg
ing
• In
let b
asin
con
figur
atio
n al
so in
fluen
ces
woo
d pl
uggi
ng; c
hann
el w
iden
ing
upst
ream
of
culv
erts
pon
ds w
ater
and
cre
ates
edd
ies
that
orie
nts
woo
d pe
rpen
dicu
lar t
o flo
w a
nd
prom
oted
acc
umul
atio
n of
deb
ris p
iece
s, fo
rmin
g la
rge
jam
s up
stre
am o
f the
cul
vert
• W
hen
chan
nel e
nter
s cu
lver
t at a
n an
gle,
woo
d ca
nnot
rota
te p
aral
lel t
o flo
w a
nd p
ass
thro
ugh
culv
erts
Flan
agan
et a
l. 19
98
54
Tabl
e A
-13.
The
impl
icat
ions
of L
WD
man
agem
ent a
ctio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
W
este
rn
Was
hing
ton
• 0.
07 c
hann
el g
radi
ent
• D
owns
tream
impa
cts
shou
ld b
e co
nsid
ered
in a
sses
sing
trad
e-of
fs a
ssoc
iate
d w
ith
debr
is re
mov
al a
nd in
crea
sed
sedi
men
tatio
n Be
scht
a 19
79
Sout
heas
t Ala
ska
• 15
km
2 to 7
5 km
2 dra
inag
e ar
eas
• 4th
thro
ugh
5th o
rder
stre
ams
• Le
ngth
of p
iece
, per
cent
of p
iece
in w
ater
, ang
le o
f orie
ntat
ion
to fl
ow, a
nd lo
catio
n of
an
chor
poi
nt a
ll in
fluen
ce s
tabi
lity
of in
stre
am w
ood
• Su
gges
t gen
eral
gui
delin
es b
ased
on
age
of d
ebris
and
stre
am g
radi
ent
Brya
nt 1
983
East
ern
Was
hing
ton
• 0.
015
chan
nel g
radi
ent
• 11
.5 m
ban
kful
l wid
th
• In
disc
rimin
ant r
emov
al o
f LW
D h
as m
ajor
sho
rt te
rm in
fluen
ces
on c
hann
el s
tabi
lity
• Kn
owle
dge
of s
ize
and
othe
r fea
ture
s co
mm
on to
sta
ble
debr
is p
rovi
ded
as b
asis
for
man
agem
ent g
uide
lines
•
Prop
osed
dic
hoto
mou
s ke
y to
det
erm
ine
whe
ther
to le
ave
or re
mov
e LW
D
Bilb
y198
4
Paci
fic N
orth
wes
t •
N/A
•
Activ
e st
ream
side
veg
etat
ion
can
incr
ease
fish
bio
mas
s by
man
agin
g fo
r lar
ger l
ight
fle
cks
and
mai
ntai
ning
inpu
t of L
WD
Se
dell
and
Swan
son
1984
Paci
fic N
orth
wes
t •
N/A
•
In w
ood
rein
trodu
ctio
n m
ust c
onsi
der t
hree
thin
gs: 1
) wha
t kin
d of
woo
d is
des
irabl
e, 2
) w
here
sho
uld
LWD
be
plac
ed, 3
) how
muc
h w
ood
is e
noug
h •
Smal
l acc
umul
atio
ns o
f var
ious
siz
ed p
iece
s of
woo
d pr
ovid
e m
ost c
ompl
ex a
nd b
est
utiliz
ed h
abita
ts in
all
size
s of
rive
rs a
nd s
tream
s •
Woo
d ac
cum
ulat
es a
t trib
utar
y ju
nctio
ns, w
here
val
ley
floor
wid
ens,
at c
hann
el b
ends
, an
d at
geo
logi
c co
nstri
ctio
ns
• St
ream
reac
hes
in w
iden
ed v
alle
y flo
ors
and
area
s be
low
trib
utar
y ju
nctio
ns c
an b
e be
tter e
nhan
ced
by in
trodu
ctio
n of
mul
tiple
tree
s in
diff
eren
t con
figur
atio
ns
Sede
ll et
al.
1988
Paci
fic N
orth
wes
t •
N/A
•
Leav
e un
dist
urbe
d bu
ffer s
trip
of o
ld g
row
th ti
mbe
r to
ensu
re lo
ng-te
rm s
uppl
y lo
ng,
larg
e di
amet
er lo
gs
• Le
ave
pred
eter
min
ed fr
actio
n of
tim
ber i
n bu
ffer s
trip
that
is a
dequ
ate
to s
atis
fy s
tream
ha
bita
t nee
ds a
nd a
llow
woo
d to
ent
er th
roug
h na
tura
l pro
cess
es
• R
emov
e tim
ber f
rom
stre
amsi
de m
anag
emen
t zon
e on
dou
ble
rota
tion
basi
s, w
here
tre
es a
re h
arve
sted
eve
ry o
ther
rota
tion
(100
to 1
50 y
ears
) •
Des
ign
and
engi
neer
buf
fers
that
mai
ntai
n LW
D in
put,
prov
ide
mix
of r
ipar
ian
spec
ies
• Va
riabl
e w
idth
buf
fers
offe
r cha
nce
to ta
ilor s
tream
side
buf
fers
to lo
cal s
tream
co
nditi
ons
• Se
lect
ivel
y lo
gged
buf
fers
mus
t lea
ve s
tabl
e lo
gs fo
r con
tribu
tion
to th
e st
ream
cha
nnel
•
LWD
is s
carc
e w
hen:
1) l
ack
of q
ualit
y po
ols
2) la
ck o
f LW
D s
tora
ge s
ites
3) p
rese
nce
of u
nsta
ble
debr
is w
hich
pos
es e
nviro
nmen
tal h
azar
d 4)
lack
of e
scap
e co
ver;
scar
city
be
st d
eter
min
ed b
y be
fore
and
afte
r stu
dies
•
LWD
is to
o ex
cess
ive
whe
n: 1
) blo
cks
fish
mig
ratio
n 2)
impa
irs w
ater
qua
lity
3)
pres
ence
of u
nsta
ble
debr
is w
hich
pos
es e
nviro
nmen
tal h
azar
d 4)
inte
rfere
nce
with
re
crea
tiona
l use
s
• N
eed
thor
ough
long
-term
test
ing
Biss
on e
t al.
1987
Paci
fic N
orth
wes
t •
N/A
•
LWD
add
ition
s ca
n be
effe
ctiv
e in
enh
anci
ng fi
sh h
abita
t in
the
shor
t-ter
m
• St
ruct
ures
mim
ic e
ffect
of n
atur
al o
bstru
ctio
ns in
stre
ams
• Th
e ne
ed fo
r stru
ctur
al e
lem
ents
var
ies
with
cha
nnel
gra
dien
t: 1)
<0.
01 g
radi
ent
chan
nels
hav
e lo
w to
mod
erat
e ne
ed, 2
) 0.0
1 to
0.0
10 g
radi
ent c
hann
els
have
hig
h ne
ed, 3
) >0.
10 g
radi
ent c
hann
els
have
low
nee
d
Sulliv
an e
t al.
1987
55
Tabl
e A
-13.
The
impl
icat
ions
of L
WD
man
agem
ent a
ctio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
W
este
rn
Was
hing
ton
• 0.
13 c
hann
el g
radi
ent (
<7 m
ch
anne
l wid
th)
• 0.
08 c
hann
el g
radi
ent (
7 m
to 1
0 m
cha
nnel
wid
th)
• 0.
03 c
hann
el g
radi
ent (
>10
m
chan
nel w
idth
)
• Pr
oced
ures
to e
nsur
e LW
D s
uppl
y m
ust c
onsi
der:
1) c
lean
ing
pres
crip
tions
leav
e ap
prop
riate
am
ount
of w
ood
of p
rope
r siz
e in
stre
am, 2
) rem
aini
ng s
tream
side
ve
geta
tion
shou
ld p
rovi
de fo
r lon
g-te
rm in
put
• LW
D d
ata
mus
t be
appl
ied
to s
imila
r stre
ams
• D
ata
on v
aria
tions
in s
ize
and
amou
nt o
f woo
dy d
ebris
with
cha
ngin
g st
ream
siz
e co
uld
be u
sed
to d
evel
op p
lans
for n
umbe
rs a
nd s
izes
of t
rees
to b
e re
tain
ed
• Ef
fect
ive
man
agem
ent w
ill de
pend
on
info
rmat
ion
rela
ting
vege
tativ
e an
d ph
ysic
al
char
acte
ristic
s of
ripa
rian
area
to in
put o
f LW
D
Bilb
y an
d W
ard
1989
N/A
•
N/A
•
Stru
ctur
es te
nd to
lock
stre
ams
into
a re
lativ
ely
fixed
loca
tion
and
cond
ition
•
Impr
oved
man
agem
ent o
f stre
amsi
de v
eget
atio
n of
fers
mos
t pro
mis
e fo
r dev
elop
ing
valu
able
and
pro
duct
ive
ripar
ian
syst
ems
Elm
ore
and
Besc
hta
1989
UK
• N
/A
• LW
D m
anag
emen
t sho
uld
be u
nder
take
n w
ith k
now
ledg
e of
nat
ural
LW
D c
ondi
tions
•
Logg
ing
shou
ld m
inim
ize
disr
uptio
n to
cha
nnel
pro
cess
es
• M
anag
emen
t sho
uld
optim
ize
mai
nten
ance
of h
abita
t and
min
imiz
e ec
olog
ical
di
stur
banc
e •
Som
e ar
eas
may
requ
ire a
dditi
on o
f LW
D
Gre
gory
and
Dav
is 1
992
N/A
•
N/A
•
No-
net l
oss
polic
y in
fore
sted
bas
ins
in te
mpe
rate
USA
sho
uld
incl
ude
four
goa
ls: 1
) m
aint
ain
geom
orph
ic c
ompl
exity
2) r
etai
n LW
D a
long
cha
nnel
3) m
aint
ain
ripar
ian
vege
tatio
n 4)
pre
serv
atio
n of
hyd
rolo
gica
l fun
ctio
n of
wat
ersh
ed
• St
ream
cla
ssifi
catio
n sy
stem
s ba
sed
on g
eom
orph
ic c
hara
cter
istic
s ca
n pr
ovid
e m
eans
of
iden
tifyi
ng c
ritic
al ri
paria
n ar
eas
for r
esou
rce
use
• To
re-e
stab
lish
larg
e rip
aria
n tre
es s
ugge
st p
lant
ing
fast
gro
win
g co
nife
rs a
nd th
inni
ng
of a
lder
(Aln
us ru
bra)
ove
rsto
ry to
pro
mot
e gr
owth
of t
rees
Brya
nt a
nd S
edel
l 199
5
N/A
•
N/A
•
Hyd
raul
ic m
odel
s ca
n be
use
d to
hel
p pl
an d
ebris
man
agem
ent p
rogr
ams
• C
hann
el ro
ughn
ess
depe
nds
on m
any
fact
ors,
it is
unl
ikel
y th
at th
e ap
proa
ch o
f m
easu
ring
chan
ges
in ro
ughn
ess
coef
ficie
nt w
ill yi
eld
univ
ersa
l rel
atio
ns b
etw
een
debr
is ty
pe, q
uant
ity, a
nd h
ydra
ulic
effe
ct
• C
laim
of r
educ
ed fr
eque
ncy
of d
urat
ion
of o
verb
ank
flood
ing
used
to ju
stify
deb
ris
rem
oval
is n
ot u
nequ
ivoc
ally
pro
ven
in fi
eld
Gip
pel 1
995
N/A
•
N/A
•
Prob
lem
of d
ebris
man
agem
ent r
esul
ting
from
logg
ing
best
dea
lt w
ith s
elec
tive
rem
oval
to
ens
ure
mai
nten
ance
of c
hann
el s
tabi
lity,
fish
acc
ess,
and
fish
hab
itat
• G
uide
lines
for r
emov
al ta
ke in
to a
ccou
nt a
mou
nt, s
ize
and
age
of d
ebris
pre
sent
•
Effe
ct o
f pre
viou
s de
bris
cle
aran
ce c
an b
e re
vers
ed b
y ad
ditio
n of
deb
ris to
the
river
•
Varia
bilit
y in
siz
e an
d sp
acin
g of
LW
D a
ccum
ulat
ions
that
occ
ur lo
cally
in u
nman
aged
ch
anne
ls s
houl
d gu
ide
intro
duct
ion
of L
WD
•
Intro
duct
ion
of L
WD
is s
hort-
term
sol
utio
n, p
rodu
ctio
n of
nat
ural
inpu
ts is
pre
fera
ble
• M
aint
ain
buffe
r zon
e to
ens
ure
supp
ly o
f woo
d •
Activ
e m
anag
emen
t of b
uffe
r zon
e ca
n yi
eld
addi
tiona
l ben
efits
suc
h as
ligh
t, te
mpe
ratu
re, f
low
, sed
imen
t tra
nspo
rt, a
nd s
edim
ent c
ondi
tions
Gur
nell
et a
l. 19
95
Sout
hwes
t Ala
ska
Wes
tern
W
ashi
ngto
n
• 0.
002
to 0
.085
cha
nnel
gra
dien
ts
• 2.
5 to
38
m c
hann
el w
idth
s •
<40%
of i
n-ch
anne
l LW
D a
ctiv
e in
poo
l for
mat
ion,
so
effe
ctiv
e rip
aria
n zo
ne
man
agem
ent m
ust c
onsi
der n
atur
al in
effic
ienc
y in
recr
uitin
g do
min
ant L
WD
•
Nat
ural
recr
uitm
ent o
f man
y lo
gs is
requ
ired
to p
rovi
de a
pie
ce th
at is
situ
ated
to fo
rm a
po
ol,
• Th
e si
ze a
nd p
lace
men
t of L
WD
may
be
engi
neer
ed to
mor
e ef
ficie
ntly
cat
alyz
e po
ol
form
atio
n •
Cou
ld u
se p
ool s
paci
ng (c
hann
el w
idth
s pe
r poo
l) ag
ains
t LW
D fr
eque
ncy
(pie
ces
per
met
er) t
o de
fine
man
agem
ent o
bjec
tives
rega
rdin
g po
ol s
paci
ng a
nd L
WD
freq
uenc
y
Mon
tgom
ery
et a
l. 19
95
56
Tabl
e A
-13.
The
impl
icat
ions
of L
WD
man
agem
ent a
ctio
ns in
var
ious
geo
grap
hic
loca
tions
and
cha
nnel
net
wor
k po
sitio
ns (a
rrang
ed in
chr
onol
ogic
al o
rder
). LO
CAT
ION
C
HAN
NEL
NET
WO
RK
PO
SITI
ON
R
ESU
LTS
REF
EREN
CES
N
orth
wes
t W
ashi
ngto
n •
0.00
5 to
0.0
1 ch
anne
l gra
dien
ts
• 30
m to
80
m b
ankf
ull w
idth
s •
75 k
m2 to
225
km
2 dra
inag
e ar
eas
• M
anag
emen
t act
iviti
es m
ust e
nsur
e ad
equa
te re
crui
tmen
t of l
arge
st L
WD
from
ripa
rian
fore
st
• Se
lect
ive
rem
oval
of l
arge
st tr
ees
from
ripa
rian
and
flood
plai
n fo
rest
s w
ill ha
ve m
ajor
im
pact
s on
in-c
hann
el h
abita
t cha
ract
eris
tics
Abbe
and
Mon
tgom
ery
1996
Nor
thw
est
Was
hing
ton
• 0.
002
to 0
.05
chan
nel g
radi
ents
•
5 m
to 2
0 m
cha
nnel
wid
ths
• 2
km2 to
120
km
2 dra
inag
e ar
eas
• Pr
edic
t dec
line
in n
umbe
r and
are
a of
poo
ls in
low
to m
oder
ate
slop
e ch
anne
ls w
ith
redu
ctio
n in
LW
D
• G
iven
sam
e de
crea
se in
LW
D, p
redi
ct g
reat
er d
ecre
ases
in n
umbe
r and
are
a of
poo
ls
in m
oder
ate
slop
e ch
anne
ls th
an lo
w s
lope
cha
nnel
s •
Expe
ct d
ecre
ases
in a
bund
ance
of s
peci
es th
at s
how
stro
ng p
refe
renc
e fo
r poo
ls a
s re
arin
g lo
catio
ns (O
ncor
hync
hus
kisu
tch)
and
incr
ease
s in
abu
ndan
ce o
f spe
cies
sui
ted
to re
arin
g in
riffl
e en
viro
nmen
ts (O
ncor
hync
hus
myk
iss)
•
Afte
r log
ging
exp
ect i
ncre
ases
in n
umbe
r and
are
a of
poo
ls to
be
mor
e ra
pid
in
mod
erat
e sl
ope
chan
nels
than
in lo
w s
lope
cha
nnel
s •
Whe
n LW
D p
iece
s pe
r met
er e
xcee
ds 0
.4, p
ool s
paci
ng is
less
sen
sitiv
e to
incr
ease
d lo
adin
g •
Foun
d re
latio
nshi
p be
twee
n ch
anne
l wid
th a
nd s
ize
of L
WD
form
ing
pool
s •
In c
hann
els
<10
m w
idth
, log
s of
20
cm d
iam
eter
form
ed p
ools
; LW
D fr
om s
econ
d gr
owth
will
form
poo
ls s
oone
r in
smal
l cha
nnel
; poo
l abu
ndan
ce m
ay in
crea
se a
fter 2
5 ye
ars
thro
ugh
inpu
ts o
f dec
iduo
us v
eget
atio
n •
In c
hann
els
20 m
wid
e, p
ools
do
not f
orm
unt
il LW
D e
xcee
ds 6
0cm
; sig
nific
ant
incr
ease
s in
poo
l num
ber a
nd a
rea
may
not
beg
in fo
r 75
year
s un
til th
e re
crui
tmen
t of
larg
e co
nife
rs
• M
ay b
e po
ssib
le to
acc
eler
ate
reco
very
of p
re-lo
ggin
g co
nditi
ons
thro
ugh
man
agem
ent
of ri
paria
n fo
rest
•
Thin
ning
may
ben
efit
larg
e st
ream
s w
hich
requ
ire la
rge
logs
to fo
rm p
ools
•
Thin
ning
may
not
ben
efit
smal
ler s
tream
s, a
s sm
all w
ood
is s
uffic
ient
to fo
rm p
ools
Beec
hie
and
Sibl
ey 1
997
N/A
•
N/A
•
Deb
ris ro
ughn
ess
coul
d be
qua
ntifi
ed fr
om a
kno
wle
dge
of c
hann
el g
eom
etry
, and
tree
he
ight
and
dia
met
er
• St
udie
s sh
ow h
ow w
ood
stru
ctur
e an
d tra
nspo
rt sh
ould
cha
nge
as a
func
tion
of p
ositi
on
with
in th
e ch
anne
l net
wor
k; th
is g
eom
orph
ic c
onte
xt n
eeds
to b
e un
ders
tood
to g
uide
ef
fect
ive
plac
emen
t of w
ood
for l
ong-
term
sta
bilit
y •
Qua
ntita
tive
unde
rsta
ndin
g of
woo
d m
ovem
ent i
s ne
eded
to a
sses
s st
abilit
y of
woo
d ad
ded,
and
to p
reve
nt c
onge
sted
tran
spor
t fro
m p
osin
g en
viro
nmen
tal h
azar
d
Brau
dric
k et
al.
1997
Sout
heas
tern
Fr
ance
•
0.02
8 to
0.0
31 c
hann
el g
radi
ents
•
1640
km
2 •
Met
hodo
logi
cal a
ppro
ache
s ca
n be
pro
pose
d to
hel
p m
anag
ers
iden
tify
reac
hes
on
whi
ch v
eget
atio
n co
rrido
rs c
ould
be
cons
erve
d, re
habi
litat
ed, o
r use
d fo
r sof
t m
aint
enan
ce
• D
evel
opm
ent o
f inc
reas
ingl
y m
atur
e rip
aria
n fo
rest
, due
in p
art t
o in
cisi
on a
nd
decr
ease
d la
tera
l mig
ratio
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57
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