Green Stormwater: LID with GIS

Scott M. Kaiser, GISP, CFM GIS Analyst & Environmental Planner

Introduction • Use GIS to evaluate the potential and place stormwater BMPs. • Why use GIS • Free and/or inexpensive, readily available data • Increased efficiency

What are BMPs? BMP – Best Management Practice Structural and non-structural methods to manage the adverse impacts of developed land Primarily used to protect water resources through pollutant reduction, volume reduction and/or flow attenuation. LID oriented

What is LID? LID – Low Impact Development Attempting to manage rainfall were it lands - as nature would. Implementing LID with BMPs

Types of BMPs? Bioinfiltration aka rain gardens Porous roadways Hydrodynamic separation Green roofs Rain barrels Riparian buffers Underground detention with infiltration Open space preservation* Floodplain, riparian and wetland preservation* Reduced impervious or compacted surfaces* *No construction necessary

Example BMPs Bioinfiltration Porous Surfaces Rain Barrel Green Roof

Helping Managing Stormwater with GIS Two pronged approach: Proactive Use data to help direct future stormwater management and/or rehabilitation projects. Reactive Typical method Use GIS to guide a response to mitigate an existing problem such as flooding or pollution.

Analytical Goal Sites with… Good Soils Gentle Slopes Open Space or right-of-way } Infiltration BMPs Moderate to low storm flow Open space or right-of-way Proximity to existing infrastructure } Hydrodynamic Separation Wetlands Greenway Floodplain Parks or Preserves } Preservation/Habitat Rehab

Data Considerations Topography and slope Structural BMPs, <5% Existing infrastructure Proximity to storm structures Land ownership Public and private opportunities Hydrography Land cover Determine runoff volume and velocities Orthoimagery

Software ArcGIS Desktop and Spatial Analyst Optional (advanced data development and analysis) Image processing – eCognition or Feature Analyst Modeling - SWMM

The Process… • The discussion will focus on conceptual BMP placement to help a community or organization fix stormwater problems. • Reactive approach

The Process… Step 1. Public Involvement Getting the public input Hold a charrette Bring maps to mark-up based on public comment

The Process… Step 2. Find Open Space Opportunities Parks, preserves, riparian corridors, wetlands, floodplains, and/or conservation easements

The Process… Step 2. Find Open Space Opportunities

The Process… Step 3. Determine Potential Public Improvement Projects • Existing improvements projects are excellent opportunities for stormwater BMP retrofits • Consider road reconstruction and property redevelopment

The Process… Step 3. Determine Potential Public Improvement Projects

The Process… Step 4. Pick an Area of Interest Narrow list of areas to focus on LID techniques Can be one to many sites

The Process… Step 4. Pick an Area of Interest

The Process… Step 5. Delineate Watershed and Catchments for Area of Interest • Several factors to consider: • Start with ArcHydro for DEM based topography • Don’t forget human induced drainage – Storm sewer – Lot and road grading

The Process… Step 5. Delineate Watershed and Catchments for Area of Interest

The Process… Step 6. Calculate Slope BMPs are best used on slopes less than 5% Run DEM through Spatial Analyst 10m or 30m DEM LIDAR is becoming a popular

The Process… Step 6. Calculate Slope

The Process… Step 7. Evaluate Soils Soil hydrologic groups – A, B, C or D A and B – good infiltration C – ok infiltration D – poor infiltration Determines if soil amendments and underdraining will be necessary

The Process… Step 7. Evaluate Soils

The Process… Step 8. Delineate Land Cover • Helps to determine applicable BMP – Commercial/Instructional – green roof – Transportation – porous surfaces or bioinfiltration – Single family homes – rain barrels

The Process… Step 8. Delineate Land Cover

The Process… Step 9. Mash it all Together • Evaluate the landscape – Run iterations of intersected data based on slope, soils, land cover, open space, property ownership and improvements projects • Create BMP feature classes • Conceptually sketch BMPs in proposed locations • Prepare to determine BMP volume and pollutant removal

The Process… Step 9. Mash it all Together

The Process… Step 10. Determine the Volume Managed and P Removal • Delineate the contributing area to each BMP • Calculate the anticipate volume and/or flows • Estimate the potential nutrient (P) removal

The Process… Step 10. Determine the Volume Managed and P Removal

The Process… Step 11. Summarize Findings • Example Contributing Land Cover Contributing Weighte BMP Treatment FF Untreated (sf) C Area (sf) dC FF Volume (cf) (cf) % FF Treated (cf) 251,760 0.95 Bioinfiltration 68,753 0.25 466,006 0.74 14,319 8,244 57.6% 6,074.90 145,493 0.60 681,110 0.95 Porous 39,124 0.60 720,234 0.93 27,939 10,204 36.5% 17,734.70 Sidewalk 1,365,452 0.95 Oversized Pipe 10,585,110 0.60 11,950,562 0.64 318,677 7,530 2.4% 311,146.89 0.45 Total BMP Total FF Volume Total % FF Total FF Volume Treated (cf) Managed Remaining (cf) (cf) 360,935 25,978 7% 334,956

Lessons Learned • It’s only GIS • We’re not building bridges • We can get a good conceptual idea for the improvements to stormwater runoff • The only way to truly measure success is over time with metering and sampling.

Future Projects • Virtual BMP map • BMP database

Summary • GIS data and spatial analysis can be effective for BMP mapping • Harness as much readily available data as possible

Want to Know More? Scott Kaiser, GISP, CFM Orchard, Hiltz & McCliment, Inc. ohm-advisors.com scott.kaiser@ohm-advisors.com 734.466.5444

Green Stormwater: LID with GIS

by OHM Advancing Communities on Jun 08, 2010

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