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.

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