WaterQualityBuffersforWatersandWetlands

2008Nor’easter:IndianRiverBay

ProgressTowardsPollutionReductionGoalsfortheInlandBays

1,471

2,427

Nitrogen(lbs.perday)

Achieved Remaining

93

Phosphorus(lbs.perday)

Achieved

WaterQualityBuffersare…natural areas between development and wetlands or waterbodies; they are managed for the primary purposes of:

1.sustainable removal of pollutants entering wetlands or waterbodies,

2. to protect wetlands or waterbodies against encroachment and physical alterations, and

3. to allow wetlands or waterbodies to maximize their own natural capacities to reduce pollution.

Forested Buffer

~ 200’

BufferConsiderations

• Extent• Vegetation• FieldDitches• Views• ApprovalandEnforcement• Width

Headwaters(smallstreams)makeup~75%oftotalwaterwaylength

Headwatersaremoreefficientatremovingpollutionthanlargerstreams

Turf

Forest

VegetationType

Turfvs.Forest

• Forestedbuffersremove36%morenitrogenonaveragethangrassedbuffers

• Forestedbufferstakeup11– 37lbsofnitrogenand2– 5lbsofphosphorusperacreperyearintowood

• Soilorganicmatterisovertwiceashighinforestedbuffers

• Forestedbuffersimproveinstreamprocessingofnutrients

• Forestedbufferssupportwildlifehabitatanddon’tcontributepollution

Effect of Buffer Width on Nitrogen Removalfrom 17 Atlantic Coastal Plain Riparian Buffers

Buffer Width (ft.)

0 100 200 300

% N

itrog

en R

emov

al

-60

-40

-20

0

20

40

60

80

100

120

140

y=-7915.6564+((8015.6442x)/(0.1813+x))Rsqr = 0.67p = 0.0005---- = 95% Confidence Int.

EffectofBufferWidthonNitrogenRemovalfor17AtlanticCoastalPlainRiparianBuffers

BAY

MARSH

UPLAND

BAY

MARSH

UPLAND

BAY

MARSH

UPLAND

DEVELOPMENT

BAY

MARSH

UPLAND

DEVELOPMENT

BAY

MARSH

UPLAND

DEVELOPMENT

BAY

MARSH

UPLAND

DEVELOPMENT

SHORELINE ARMOR

BAY

MARSH

UPLAND

DEVELOPMENT

SHORELINE ARMOR

BAY

MARSH

UPLAND

DEVELOPMENT

SHORELINE ARMOR

BAY

MARSH

UPLAND

DEVELOPMENT

Mouth of Guinea Creek

Bay ShorelineUpland/Wetland Boundary

Bay ShorelineUpland/Wetland Boundary

Slope of Adjacent Upland Indian River BayRehoboth

BayGradual (<0.08 rise/run) 5.25 ft/yr 6.07 ft/yr

Steep (>0.09 rise/run) 1.44 ft/yr 0.82 ft/yr

Rates of tidal wetland migration derived from metric mapping analysis 1926-1989

FieldDitches

ApprovalandEnforcement

NewCastleCo.,DE

KentCo.,DE

SussexCo.,DE

NewJersey MarylandCriticalAreas

CIBAdequate

CIBOptimum

TidalWetlands&Waters

100ft. 100ft. 50ft. 300ft. 200ft. 80-300ft. 150-500ft.

NontidalWetlands 50ft. 25ft. 0ft. 0– 150ft. 25ft. 50 100

Headwaters 100ft. 50ft. 0ft. 300ft. 100ft. 35- 80 35-150

Larger/PerennialWaterways

100ft.or50ft.fromfloodplain

100ft. 0– 50ft. 300ft. 100ft. 80 150

VegetationType Natural/Forest

Natural

/Forest

Natural/

Forest

ExistingVegetationorNatural

/Forest

Natural

/Forest

Natural

/Forest

Natural

/Forest

VegetationPreservation

Existingnativevegetation

Existingnaturalbuffers

Existingnaturalbuffers

Existingvegetation

Existingnatural

vegetation

Existingnativevegetation

Existingnativevegetation

BufferMgmt.Plan No No No Yes Yes Yes Yes

BufferOrdinanceComparison

AnalysisofRecommendationsAppliedtoDevelopments

• 11randomlyselectedPLUSapplications:’04-’06.

l Separated into large (>75th percentile) & small projects (<50th

percentile) and by watershed region

l Estimated % developable acreage as buffer by waterbody type and buffer alternative

WellDrainedRegion

PoorlyDrainedRegion

Results• Onaverage,bufferswerewithinrangeofcurrentCountyopenspacerequirements

• Adequate=13.8%ofdevelopableacreage• Optimum=33.2%ofdevelopableacreage

• Siteswithtidalwetlandsbylowlyinguplandshadverylargeareasasbuffers

• Encouragefillingorintegrationintostormwatercontrolsthoseditchesunnecessaryfordrainage.

• Smallerbufferwidthsshouldbeafforded(>35’)onshallowditches(<3ftdeep)toallowbufferingofotherfeatures

Site Characteristics

Adequate A

lternative

Optim

um A

lternative

Applying R

ecomm

endations: Bethany W

oods

Acreage 12Developable Ac. 9% Dev. Ac. in Buffer (Adequate) 61% Dev. Ac. in Buffer (Optimum) 89

TidalNontidal Wtlnds

Nontidal WaterwayNontidal WetlandTidal Wetlands

Buffer TypesWaterbody Type

Development

Major Ditches

Site Characteristics

Adequate A

lternative

Optim

um A

lternative

Acreage 314Developable Ac. 309% Dev. Ac. in Buffer (Adequate) 1.8% Dev. Ac. in Buffer (Optimum) 3.7

TidalNontidal Wtlnds

Nontidal WaterwayNontidal WetlandTidal Wetlands

Buffer TypesWaterbody Type

Development

ApplyingRecommendations:Bridlew

ood

Indian River Bay Rehoboth Bay

Upland Buffer Width

Gradual Slope

Steep Slope

Gradual Slope

Steep Slope

50’ 10 35 8 6175’ 14 52 12 91100’ 19 69 17 122200’ 38 139 33 244300’ 57 208 49 366400’ 76 278 66 488500’ 95 347 82 610

Yearsbuffersofdifferentwidthsareestimatedtoprovideprotectiontotidalwetlands

derived from metric mapping analysis 1926-1989