Green Stormwater: LID with GIS

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http://www.ohm-advisors.com: Stormwater Best Management Practices (BMP) are rapidly evolving and gaining significant popularity as a method to fight non-point source pollution. Knowing where to place …

http://www.ohm-advisors.com: Stormwater Best Management Practices (BMP) are rapidly evolving and gaining significant popularity as a method to fight non-point source pollution. Knowing where to place BMPs in the ground to effectively treat stormwater can be tricky. However, with the use of GIS, you can review several environmental variables such as BMP location, size, and mitigated runoff volume. By analyzing orthoimagery, DEMs, existing infrastructure, soils, and right-of-way, users within organizations can more efficiently and effectively plan and optimize their BMPs.

Often BMP placement is often determined on a site-by-site basis. Using GIS and existing spatial datasets allow users to evaluate many sites and perform large scale planning efforts to get the most out of each BMP location. Effective planning at the local or watershed scale will make it easier to prioritize BMPs.

In this presentation, GIS analyst and Environmental Planner, Scott Kaiser, GISP, CFM, discusses the methods used to plan and choose stormwater BMPs with GIS.

Scott Kaiser is a green stormwater guru. A GIS Analyst and Environmental Planner with OHM: http:www.ohm-advisors.com, Scott has more than eight years experience in GIS, focusing on water protection.

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  • 1. Scott M. Kaiser, GISP, CFM GIS Analyst & Environmental Planner
  • 2. Introduction • Use GIS to evaluate the potential and place stormwater BMPs. • Why use GIS • Free and/or inexpensive, readily available data • Increased efficiency
  • 3. 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
  • 4. What is LID? LID – Low Impact Development Attempting to manage rainfall were it lands - as nature would. Implementing LID with BMPs
  • 5. 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
  • 6. Example BMPs Bioinfiltration Porous Surfaces Rain Barrel Green Roof
  • 7. 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.
  • 8. 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
  • 9. 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
  • 10. Software ArcGIS Desktop and Spatial Analyst Optional (advanced data development and analysis) Image processing – eCognition or Feature Analyst Modeling - SWMM
  • 11. The Process… • The discussion will focus on conceptual BMP placement to help a community or organization fix stormwater problems. • Reactive approach
  • 12. The Process… Step 1. Public Involvement Getting the public input Hold a charrette Bring maps to mark-up based on public comment
  • 13. The Process… Step 2. Find Open Space Opportunities Parks, preserves, riparian corridors, wetlands, floodplains, and/or conservation easements
  • 14. The Process… Step 2. Find Open Space Opportunities
  • 15. 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
  • 16. The Process… Step 3. Determine Potential Public Improvement Projects
  • 17. The Process… Step 4. Pick an Area of Interest Narrow list of areas to focus on LID techniques Can be one to many sites
  • 18. The Process… Step 4. Pick an Area of Interest
  • 19. 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
  • 20. The Process… Step 5. Delineate Watershed and Catchments for Area of Interest
  • 21. 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
  • 22. The Process… Step 6. Calculate Slope
  • 23. 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
  • 24. The Process… Step 7. Evaluate Soils
  • 25. 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
  • 26. The Process… Step 8. Delineate Land Cover
  • 27. 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
  • 28. The Process… Step 9. Mash it all Together
  • 29. 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
  • 30. The Process… Step 10. Determine the Volume Managed and P Removal
  • 31. 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
  • 32. 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.
  • 33. Future Projects • Virtual BMP map • BMP database
  • 34. Summary • GIS data and spatial analysis can be effective for BMP mapping • Harness as much readily available data as possible
  • 35. Want to Know More? Scott Kaiser, GISP, CFM Orchard, Hiltz & McCliment, Inc. ohm-advisors.com scott.kaiser@ohm-advisors.com 734.466.5444