Scott M. Kaiser, GISP, CFMScott M. Kaiser, GISP, CFM
GIS Analyst GIS Analyst && Environmental PlannerEnvironmental Planner
Introduction
• Use GIS to evaluate the potential and place stormwaterBMPs.
• 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 roadwaysHydrodynamic separationGreen roofsRain barrelsRiparian buffersUnderground detention with infiltrationOpen space preservation*Floodplain, riparian and wetland preservation*Reduced impervious or compacted surfaces*
*No construction necessary
Example BMPs
Gre
en R
oof
Bioinfiltration
Rain Barrel
Porous Surfaces
Helping Managing Stormwater with GIS
Two pronged approach:Proactive
Use data to help direct future stormwatermanagement and/or rehabilitation projects.
ReactiveTypical methodUse GIS to guide a response to mitigate an existing problem such as flooding or pollution.
Analytical Goal
Sites with…Good SoilsGentle SlopesOpen Space or right-of-way
Moderate to low storm flowOpen space or right-of-wayProximity to existing infrastructure
WetlandsFloodplainParks or Preserves
Infiltration BMPs
Hydrodynamic Separation
Greenway Preservation/Habitat Rehab
}
}
}
Data ConsiderationsTopography and slope
Structural BMPs, <5%
Existing infrastructureProximity to storm structures
Land ownershipPublic and private opportunities
Hydrography
Land coverDetermine runoff volume and velocities
Orthoimagery
Software
ArcGIS Desktop and Spatial Analyst
Optional (advanced data development and analysis)
Image processing – eCognition or Feature AnalystModeling - SWMM
The Process…
• The discussion will focus on conceptual BMP placement to help a community or organization fix stormwater problems.
• Reactive approach
The Process…
Getting the public input
Hold a charrette
Bring maps to mark-up based on public comment
Step 1. Public Involvement
The Process…
Parks, preserves, riparian corridors, wetlands, floodplains, and/or conservation easements
Step 2. Find Open Space Opportunities
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…
Narrow list of areas to focus on LID techniques
Can be one to many sites
Step 4. Pick an Area of Interest
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…
BMPs are best used on slopes less than 5%
Run DEM through Spatial Analyst10m or 30m DEMLIDAR is becoming a popular
Step 6. Calculate Slope
The Process…Step 6. Calculate Slope
The Process…
Soil hydrologic groups – A, B, C or DA and B – good infiltrationC – ok infiltrationD – poor infiltration
Determines if soil amendments and underdraining will be necessary
Step 7. Evaluate Soils
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…
• Example
Step 11. Summarize Findings
Contributing Land Cover
(sf) CContributing
Area (sf)Weighte
d C FF Volume (cf)BMP Treatment
(cf) % FF TreatedFF Untreated
(cf)
Bioinfiltration
251,760 0.95
466,006 0.74 14,319 8,244 57.6% 6,074.9068,753 0.25
145,493 0.60
Porous Sidewalk
681,110 0.95
720,234 0.93 27,939 10,204 36.5% 17,734.7039,124 0.60
Oversized Pipe
1,365,452 0.95
11,950,562 0.64 318,677 7,530 2.4% 311,146.8910,585,110 0.60
0.45
Total FF Volume (cf)
Total BMP Volume Treated
(cf)
Total % FF Managed
Total FF Remaining (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
Recommended
