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Hat Creek Restoration Project. Prepared by. Geomorphic Assessment and Preliminary Plans for Woody Debris Placement and Recreation Access Improvements. Prepared for. California Trout. Project area/objectives. PROJECT AREA Highway 299 upstream to Powerhouse riffle. OBJECTIVES - PowerPoint PPT Presentation
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Hat Creek Restoration Project
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Prepared by
Geomorphic Assessment and Preliminary Plans for Woody Debris Placement and Recreation Access
Improvements
Prepared forCalifornia
Trout
Project area/objectives
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
PROJECT AREA• Highway 299 upstream to
Powerhouse riffle
OBJECTIVES• Provide geomorphic
background for restoration activities
• Develop designs for recreation improvements
• Develop designs for introduction of large woody debris
PRESENTATION OUTLINE• Geomorphic overview• Large wood restoration• Recreation/access
improvements
Restoration approach/study methods
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
PROCESS-BASED RESTORATION• Replicate the geomorphic and ecosystem processes
that create habitat• Identify and describe processes• Identify human disturbance
METHODS• Review existing information• Stream walk survey• Topographic surveys• Field surveys of existing wood, and
potential wood placement areas• Review of instream wood inventory
conducted by CalTrout
WHY THIS APPROACH?• Target species likely to
show a positive response• Restoration measures less
likely to have negative unintended consequences
• Restoration measures more likely to function over long-term
Geomorphic processes: water and sediment
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Channel form is a reflection of the balance between flow and sediment
Source: Rosgen 1996
Water
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Flow very consistent over time
• Floods are not large• Hydropower has
limited, short-term effects
• Agricultural diversion lowers spring flood peaks, spring-summer flow
Sources: Kondolf et al. 1994
Sediment: suspended sediment
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
SOURCES• Bank erosion, overland
flows• Episodic, short-term
inputs from large-scale events
• Human disturbances that increase erosion have likely increased suspended sediment supply, but supply relatively low
EFFECTS OF DISTURBANCE• Increased sedimentation
in low velocity areas• Limited effect on channel
form, but may impact ecology
Sediment: bedload supply
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Large body of prior work due to concerns about sediment wave: Kondolf et al. 1994; Cook and Ellis 1998; Cook 2000)
• Bedload mostly sand; larger sediment generally can’t be transported due to low slope and lack of large floods
Source: Kondolf et al. 1994
TYPICAL SOURCES• Streambank erosion• Erosion of tributaries• Mass wasting upstream
in bypass reaches• General conclusions:
none of these sources account for bedload
Sediment: bedload supply
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Volcanic events can dramatically increase bedload supply—1915 eruption
• Transport through the system influences the bedload supply to the project area
• Flatter areas store sediment, affecting the rate of sediment supply and the size of sediment delivered to the project area
• Result—over decades following a volcanic event, increase in bedload supply rates to the project area
• Long intervening periods with low rates of sediment supply
Source: Kondolf et al. 1994
Recent sediment wave: influence of human disturbance
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Little effect on overall magnitude of supply
• Hydropower modifications have disrupted sediment transport in the system
• Likely a link between Baum Lake and the Powerhouse 2 bypass reach (Cook 2000)
• Channelization upstream of Cassel in 1950’s likely increased sediment supply, either by increasing transport capacity, erosion of the channelized reach, or both
• Episodic increases in sediment likely a natural process
Channel sediment reponse
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Hat Creek has limited transport capability due to consistent flow and low slope
• During periods of high sediment supply, transport capacity is exceeded and channel aggrades
Source: Rosgen 1996
Recent sediment wave
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Increased sediment supply resulted in a sediment wave over decadal time scales
• At any point in the channel, the wave caused an aggradation-degradation event as it passed
• Total sediment volume in wave 60,000 cy; aggradation average about 1.5 ft (Kondolf et al. 1994)
• Wave has mostly passed through upper half of project area, crest likely around Wood Duck Island; passes out of project area 2010-2040 (Cook 2000)
Channel form
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Cross section rectangular, high width-depth ratio
• Relatively uniform width and depth• Peaty streambanks in low marshy
areas• Erosion rates low during periods of
low sediment supply
HUMAN DISTURBANCE• Introduction of muskrats
significantly increased streambank erosion rates and channel widening--possibly exacerbated by grazing
• Old Carbon Bridge may have caused widening downstream
• Riparian shrubs may have been reduced by grazing
Channel form and periods of high sediment supply
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
CHANNEL FORM• Depth variable in space and
time• Width may increase due to
higher streambank erosion rates (powerhouse riffle island, Cook 2000)
• Avulsion possible during severe events (backwaters in historic aerials, Cook 2000)
• During recent wave, bank instability caused by muskrats may have increased widening
• Widened areas may retain portions of the wave in narrow, longitudinal bars
ECOLOGICAL RESPONSES• Burial of aquatic vegetation• Aquatic vegetation reestablishment
constrained due to high bed mobility• Reduction in habitat diversity and
complexity
Model of channel function
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Infrequent, large-scale waves of sediment occur naturally• Resulting ADE may last decades• High rates of streambank erosion during aggradation may
result in widening, or side channels and avulsion during severe events
• As sediment supply decreases, backwater areas fill in with aquatic and emergent vegetation, creating peat and low-lying streambanks
• Narrow longitudinal bars may persist in widened areas after wave passage, likely to be eventually colonized by aquatic and emergent vegetation and resulting in narrowing
Woody debris-processes of large wood recruitment
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
POSSIBLE MODES OF LARGE WOOD
RECRUITMENT TO STREAMS
• Tree fall• Bank erosion• Wind throw• Soil saturation• Snow load• Fire• Disease
• Floating• Mass wasting
Large wood: recruitment in the project area
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Trees found on streambanks in much of lower half of project area
• Swampy areas unlikely to grow large trees
Large wood: human disturbance and wood supply
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Timber harvest likely removed potentially recruitable trees
• Subsequent grazing and management favored conversion to meadows
• Areas that are currently meadow may have historically had scattered large trees
• Current load of large wood (@5 pieces in the project area, CalTrout surveys) are likely lower than would have occurred naturally
Large wood: restoration opportunities
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
GEOMORPHIC EFFECTS• Work with existing
process of narrowing in wide areas
ECOLOGIC EFFECTS• Increase instream
habitat diversity and complexity
• Provide stable substrates for aquatic plant colonization
• Loafing habitat for turtles
• Substrates for macroinvertebrates
Large wood: habitat diversity and complexity I
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Large wood: habitat diversity and complexity II
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Large wood: habitat diversity and complexity III
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Large wood: preliminary wood plan
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
• Large woody debris loading can vary substantially between streams, even those with similar surrounding forest types, climate, and disturbance histories (Morris 2008)
• Final density and location determined by budget, aesthetics, fishing access, etc.
Design/Construction Considerations
• Mimic natural tree throw
• Rootwads will assure stability
• Disturbance of cultural resources
• Construction access/disturbance
Large wood: preliminary wood plan
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
STREAMBANK STABILIZATION
• Use of wood or other revetments to stabilize streambanks is not recommended
• Consider biotechnical treatments such as high-density willow planting
• Control of muskrats should be considered
Recreation Improvements I
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Recreation Improvements II
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Recreation Improvements III
Hat Creek Restoration Project HatRAC Presentation October 29, 2013
Recreation Improvements IV
Hat Creek Restoration Project HatRAC Presentation October 29, 2013