Effectiveness of Non-Structural Measures in Watershed Restoration

Transcription

1 Effectiveness of Non-Structural Measures in Watershed Restoration Bill Frost, PE, D.WRE Sr. Water Resources Engineer KCI Technologies, Inc. Sparks, MD 2011 Low Impact Development Symposium Philadelphia, Pennsylvania September 25-28, 2011

2 Agenda Look at urban stormwater retrofits as one element of watershed restoration Review non-structural measures Discuss why they are an important element in stormwater management Look at how they fit in with other SWM approaches Look at case studies in watershed restoration

3 The Restoration Challenge New development Understand the design criteria Design the site and the SWM controls Build them Restoration Identify the problem Determine if it's a stormwater problem Identify the stormwater retrofits that will reduce or eliminate the problems Find enough retrofit sites to treat a significant part of the watershed Build them

4 Structural Retrofit Constraints No dry ponds to retrofit Older developments may have been built with no SWM to retrofit requirements New ponds typically require significant surface area Bioretention and filters require significant amount of space Not enough publicly-owned land for the number of retrofits needed. Site constraints Tree removal Loss of open space or recreation fields Topography Retrofit sites must be downstream of the problem area

5 Pre-Development Hydrology Atmosphere Receiving Water Evapotranspiration Vegetation Evaporation Uptake Runoff Streamflow Stream Pervious Infiltration Interflow Soil Recharge Groundwater Flow Aquifer

6 Post-Development Hydrology Receiving Water Evapotranspiration Atmosphere Vegetation Uptake Evaporation Runoff Streamflow Stream Erosion Pervious Deposition Infiltration Increased Runoff Impervious Interflow Soil Recharge Groundwater Flow Aquifer

7 Post-Development Hydrology and Loading Deposition Atmosphere Evaporation Uptake Pervious Vegetation Runoff Evapotranspiration Stream Streamflow Erosion Receiving Water Activity Buildup Impervious Increased Runoff Washoff Infiltration Non urban stormwater Agriculture Point sources Septic systems Construction Soil Recharge Interflow Aquifer Groundwater Flow

8 Stormwater Management Deposition Atmosphere Evaporation Uptake Pervious Vegetation Runoff Evapotranspiration Stream Streamflow Erosion Receiving Water Activity Buildup Impervious Increased Runoff Washoff Infiltration SWM Peak Control Sedimentation Soil Interflow Recharge Aquifer Groundwater Flow

9 Stormwater Management and LID Deposition Atmosphere Evaporation Uptake Pervious Vegetation Runoff Evapotranspiration Stream Streamflow Erosion Receiving Water Activity Buildup Impervious Increased Runoff Washoff Infiltration Uptake SWM / LID Peak Control Sedimentation Infiltration, Filtration Soil Interflow Recharge Aquifer Groundwater Flow

10 Structural: SWM / LID / Stream Restoration Deposition Atmosphere Evaporation Uptake Pervious Vegetation Runoff Evapotranspiration Stream Streamflow Stream Restoration Receiving Water Activity Buildup Impervious Increased Runoff Washoff Infiltration Uptake SWM / LID Peak Control Sedimentation Reduced Erosion Infiltration, Filtration Soil Interflow Recharge Aquifer Groundwater Flow

11 Structural and Non-Structural Vegetation Pervious Soil Aquifer Receiving Water Stream Evaporation Evapotranspiration Streamflow Infiltration Interflow Groundwater Flow Recharge Uptake Impervious Atmosphere Activity SWM / LID Peak Control Sedimentation Uptake Infiltration, Filtration Runoff Stream Restoration Deposition Source Control Reduced Buildup Runoff Reduction Reduced Erosion Reduced Washoff

12 Non-Structural Measures - Source Controls Nutrient Management Lawn care outreach Pet waste outreach Composting Material Management Dumpster maintenance Outdoor material storage Cleanup Litter / trash enforcement Street sweeping Catch basin cleaning Illicit Discharge Elimination

13 Non-Structural Measures - Runoff Reduction Impervious disconnection Downspout disconnection Sheetflow to buffer Permeable pavement Green roofs Pervious area management BayScaping Tree planting Rain gardens Rainwater harvesting Rain barrels Cisterns

14 Case Studies Cabin John Creek Kirwan Creek Mill Creek

15 Kirwan Creek Characteristics Location: Kent Island MD Area: 1,488 acres Use 14% Urban 20% Water / Wetlands 66% Rural Modeling: Spreadsheet Baltimore Harbor Cheseapeake Bay Kent Island

16 Kirwan Creek Retrofits Structural Urban Swales Shoreline buffers Non-Structural Urban Downspout disconnection Lawn care education Street sweeping (Spring) Other Septic system upgrades Rural Low-till techniques Riparian buffers Cover crops Sediment traps

17 Kirwan Creek Results Prior to Retrofits Disconnection has more benefits than structural controls Retrofits Non-structural has about 2/3 the TN reduction as structural Other Notes Septic system upgrades were the most effective TN retrofit in this watershed Future / Proposed URBAN RUNOFF TN TP TSS UNTREATED LOAD 3, ,590 Residential IA Disconnection ,694 Existing Tree Canopy Structural Controls ,836 NET BASELINE 2, ,060 RUNOFF REDUCTION Tree planting not modeled Res downspout disconnection (to 80%) ,869 SOURCE CONTROLS Lawn care outreach Street sweeping STRUCTURAL SWM retrofits ,907 Filter strips / buffers ,353 OTHER Stream restoration Septic System upgrades 2,158

18 Mill Creek Characteristics Location: Tidewater VA Area: 3,603 acres Use 63% Urban 7% Water / Wetlands 30% Rural Modeling: Spreadsheet York River Williamsburg James River Yorktown

19 Mill Creek Retrofits Structural Urban Swales Dry pond to wetlands Culvert retrofit Bioretention Non-Structural Urban Downspout disconnection Reforestation Lawn care education Other Septic system upgrades

20 Mill Creek Results Prior to Retrofits Existing disconnection has more benefits than structural controls Retrofits Non-structural has about the same TN reduction as structural Structural retrofits are more effective for sediment Mill Creek Existing / Proposed URBAN RUNOFF TN TP TSS UNTREATED LOAD 10,367 1, ,221 Residential IA Disconnection 1, ,985 Existing Tree Canopy Structural Controls ,026 NET BASELINE 7, ,210 RUNOFF REDUCTION Tree planting not modeled Res downspout disconnection (to 80%) ,748 Rain gardens Rain barrels SOURCE CONTROLS Lawn care outreach Street sweeping not modeled STRUCTURAL SWM retrofits ,072 Filter strips / buffers OTHER Stream restoration Septic System upgrades

21 Cabin John Creek Characteristics Location: Suburban Washington DC Area: 2,280 acres (within City of Rockville) Use 65% Urban 1% Water / Wetlands 34% Forest / Turf / Golf Modeling: WTM (Beta) Fairfax Rockville Washington Potomac River Columbia

22 Cabin John Creek Retrofits Structural Urban Dry pond retrofits Non-Structural Urban Rain gardens Reforestation Lawn care education Street sweeping Storm drain marking Other Stream restoration Regenerative storm conveyance

23 Cabin John Creek Results Prior to Retrofits Existing tree canopy has more benefits than structural controls Retrofits Non-structural has more pollutant reductions than SWM retrofits Stream restoration is most effective for sediment Cabin John Creek Existing / Propose URBAN RUNOFF TN TP TSS UNTREATED LOAD 14,467 2, ,344 Residential IA Disconnection ,378 Existing Tree Canopy 2, ,470 Structural Controls 1, ,544 NET BASELINE 10,002 1, ,952 RUNOFF REDUCTION Tree planting 1, ,102 Res downspout disconnection (to 80%) ,344 SOURCE CONTROLS Lawn care outreach 12 1 Street sweeping ,572 STRUCTURAL SWM retrofits ,253 Filter strips / buffers OTHER Stream restoration ,161 Septic System upgrades

24 Summary - Water Quality Toolbox Preservation Rural Measures Point Sources Non-Stormwater Discharges Urban Non-structural SWM Facilities Stream Restoration conservation, better site design Crop management Fertilizer management Manure management Reforestation WWTP, CSO SSO Septic systems Illicit discharges Source controls Runoff reduction Ponds, wetlands, infiltration, filtration, swales Stream restoration Wetland restoration Regenerative stormwater conveyance

25 Questions?