Water Quality Buffers for Waters and Wetlands

Transcription

1 Water Quality Buffers for Waters and Wetlands

2 2008 Nor easter: Indian River Bay

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5 Progress Towards Pollution Reduction Goals for the Inland Bays Phosphorus (lbs. per day) Nitrogen (lbs. per day) 1,471 2, Achieved Achieved Remaining

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13 Water Quality Buffers are 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.

14 Forested Buffer ~ 200

15 Buffer Considerations Extent Vegetation Field Ditches Views Approval and Enforcement Width

16 Headwaters(small streams) make up ~75% of total waterway length Headwaters are more efficient at removing pollution than larger streams

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19 Turf Vegetation Type Turf vs. Forest Forest Forested buffers remove 36% more nitrogen on average than grassed buffers Forested buffers take up lbs of nitrogen and 2 5 lbs of phosphorus per acre per year into wood Soil organic matter is over twice as high in forested buffers Forested buffers improve instream processing of nutrients Forested buffers support wildlife habitat and don t contribute pollution

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22 Effect of Buffer Width on Nitrogen Removal for 17 Atlantic Coastal Plain Riparian Buffers Effect of Buffer Width on Nitrogen Removal from 17 Atlantic Coastal Plain Riparian Buffers % Nitrogen Removal y= (( x)/( x)) Rsqr = 0.67 p = = 95% Confidence Int Buffer Width (ft.)

23 MARSH UPLAND BAY

24 MARSH UPLAND BAY

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27 DEVELOPMENT MARSH UPLAND BAY

28 DEVELOPMENT MARSH UPLAND BAY

29 DEVELOPMENT MARSH UPLAND BAY

30 DEVELOPMENT MARSH UPLAND BAY SHORELINE ARMOR

31 DEVELOPMENT MARSH UPLAND BAY SHORELINE ARMOR

32 MARSH DEVELOPMENT UPLAND BAY SHORELINE ARMOR

33 DEVELOPMENT MARSH UPLAND BAY

34 Mouth of Guinea Creek Bay Shoreline Upland/Wetland Boundary

35 Rates of tidal wetland migration derived from metric mapping analysis Slope of Adjacent Upland Indian River Bay Rehoboth Bay Gradual (<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

36 Field Ditches

37 Approval and Enforcement

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42 Tidal Wetlands & Waters New Castle Co., DE Kent Co., DE Sussex Co., DE New Jersey Maryland Critical Areas CIB Adequate CIB Optimum 100 ft. 100 ft. 50 ft. 300 ft. 200 ft ft ft. Nontidal Wetlands 50 ft. 25 ft. 0 ft ft. 25 ft Headwaters 100 ft. 50 ft. 0 ft. 300 ft. 100 ft Larger/Perennial Waterways Vegetation Type Vegetation Preservation Buffer Ordinance Comparison 100 ft. or 50 ft. from floodplain Natural/ Forest Existing native vegetation 100 ft ft. 300 ft. 100 ft Natural /Forest Existing natural buffers Natural/ Forest Existing natural buffers Existing Vegetation or Natural /Forest Existing vegetation Natural /Forest Existing natural vegetation Natural /Forest Existing native vegetation Buffer Mgmt. Plan No No No Yes Yes Yes Yes Natural /Forest Existing native vegetation

43 Analysis of Recommendations Applied to Developments 11 randomly selected PLUS applications: l Separated into large (>75 th percentile) & small projects (<50 th percentile) and by watershed region l Estimated % developable acreage as buffer by waterbody type and buffer alternative Well Drained Region Poorly Drained Region

44 Results On average, buffers were within range of current County open space requirements Adequate = 13.8% of developable acreage Optimum = 33.2% of developable acreage Sites with tidal wetlands by low lying uplands had very large areas as buffers Encourage filling or integration into stormwater controls those ditches unnecessary for drainage. Smaller buffer widths should be afforded (>35 ) on shallow ditches (< 3 ft deep) to allow buffering of other features

45 Applying Recommendations: Bethany Woods Site Characteristics Adequate Alternative Acreage 12 Developable Ac. 9 % Dev. Ac. in Buffer (Adequate) 61 % Dev. Ac. in Buffer (Optimum) 89 Development Waterbody Type Tidal Nontidal Wtlnds Major Ditches Optimum Alternative Buffer Types Nontidal Waterway Nontidal Wetland Tidal Wetlands

46 Applying Recommendations: Bridlewood Site Characteristics Adequate Alternative Acreage 314 Developable Ac. 309 % Dev. Ac. in Buffer (Adequate) 1.8 % Dev. Ac. in Buffer (Optimum) 3.7 Development Waterbody Type Tidal Nontidal Wtlnds Optimum Alternative Buffer Types Nontidal Waterway Nontidal Wetland Tidal Wetlands

47 Years buffers of different widths are estimated to provide protection to tidal wetlands Indian River Bay Rehoboth Bay Upland Buffer Width Gradual Slope Steep Slope Gradual Slope Steep Slope derived from metric mapping analysis