GREEN INFRASTRUCTURE ON CAMPUS: DOES GREEN INFRASTRUCTURE HELP
Engineering Approach to Green Infrastructure - Iowa … Approach to Green Infrastructure ......
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Engineering Approach to Green Infrastructure T. Andrew Earles, Ph.D., P.E., D.WRE Wright Water Engineers, Inc.
Transcript of Engineering Approach to Green Infrastructure - Iowa … Approach to Green Infrastructure ......
Engineering Approach to Green Infrastructure
T. Andrew Earles, Ph.D., P.E., D.WREWright Water Engineers, Inc.
Why do we care about stormwater quality?
The Regulation of Storm Water by Decade
» 1960s
» 1970s
» 1980s
» 1990s
» 2000s
» 2010s
Phase I and II Storm Water Regulations» Phase I
» Phase II
Four Step Process
Runoff Reduction
Directly Connected Impervious Area
This is what we want to avoid!
Runoff Reduction
» Minimize Directly Connected Impervious Area
Runoff Directed to Landscape
Runoff Reduction
» Reduce Impervious Area
UIA
Conceptual Model
UIA = Unconnected Impervious AreaDCIA = Directly Connected Impervious Area
RPA = Receiving Pervious AreaSPA = Separate Pervious Area
Effective Imperviousness Adjustments
0%
10%
20%
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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Effe
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perv
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Total Imperviousness
Directly Connected 2-year Level 2 10-year Level 2 100-year Level 2
Based on typical development patterns & 4-cover Imperviousness model
Treat the WQv
Treat the Water Quality Volume (WQv)
Equivalent to capturing and treating roughly 90% of all runoff on an annual basis in Iowa
Source: Iowa Stormwater Management Manual
Ames, Iowa Rainfall Summary1960-2006
“Maximized” Water Quality Volume
Volumetric Runoff Coefficients (Rv)
Adjustment Factors for MDCIA
Treat the Water Quality Volume (WQv)--Example
Approximately 4,500 ft3 Wqv required per acre of impervious area.
Recharge Volume (Rev)
The Rev is a part of the WQv and can be achieved by MDCIA or a WQv practice such as bioiretention.
Stabilize Drainageways
Water Quality, Channel Protection & Flooding
Stream Channel Stability
Lane’s Stable Channel Concept
The Channel Protection Storage Volume (Cpv) is the volume required for extended detention release (24-hour) of the 1-year, 24-hour storm
Implement Source Controls
Source Control BMPs
BMP Photo Gallery
Two Key Aspects of Performance: Improving BMP Maintenance and Implementing Maintainable BMPs
When preparing landscaping plans for BMPs, remember that access is necessary.
Swales that are too flat can lead to ponding and nuisance conditions.
Runoff cannot get to BMP because curb is not cut.
Soggy bottom may be due to shallow groundwater, poor draining soils and/or overcompaction.
Hydrology and Impervious Area
Hydrologic Cycle
Source: Sustainable Sites Initiative
Hydrologic Budget Components
GAINS
» Precipitation» Runoff» Groundwater Gains
LOSSES
» Interception and Depression Storage
» Evaporation and Transpiration
» Infiltration» Groundwater Withdrawals» Diversions
Source: Kansas Biological Survey, Native Prairie Hay Meadows
Large Storm
Higher and More Rapid Peak Discharge
Small Storm
More Runoff Volume
Lower and Less Rapid Peak
Higher BaseflowGradual Recession
Pre-developmentPost-development
TIME
STR
EAM
FLO
W R
ATE
IMPACT OF URBANIZATION ON STREAMFLOW
Source: Schuler, T.R. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing BMPs. Washington DC: Metro Council of Governments.
Large Storm Higher and More
Rapid Peak Discharge
More Runoff Volume
Lower and Less Rapid Peak
Higher Baseflow Gradual Recession
Pre-developmentPost-development
Why are Stormwater Management and LID Important?
Source: Federal Interagency Stream Restoration Working Group 1998
How do you quantify impervious area?
Source: UDFCD
Source: UDFCD
Nothing is as effective as site level drainage mapping & analysis
What Do You Need? Why Do You Need It? What Does It
Tell Us?
Typical Design Information Needs»
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Drainage Basin Mapping—Watershed Scale
Land Use and Imperviousness Mapping
Plan for future imperviousness
Regional, Sub-regional and Onsite
Regional Approach»»
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Source: Arapahoe County (Colorado) Stormwater Management Manual
Regional, Sub-regional and Onsite
Sub-regional Approach»
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Source: Arapahoe County (Colorado) Stormwater Management Manual
Regional, Sub-regional and Onsite
Onsite Approach»
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Source: Arapahoe County (Colorado) Stormwater Management Manual
Site-scale Topography and Mapping
Geotechnical Data
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Soil Classification and Characterization
Sieve Size Analysis
Soil Survey Mapping and Data
Soil Testing Parameters for Successful Revegetation
» pH»»»»
» Electrical Conductivity (EC): »»
» Free Lime»
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Soil Testing Parameters for Successful Revegetation» Nitrogen(N) - Phosphorus(P) - Potassium(K)
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» Saturation Percentage»»
»» Organic Matter Content
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Soil Testing Parameters for Successful Revegetation
» Cation Exchange Capacity (CEC)»
» Sodium Absorption Ratio (SAR) »
» Soil Texture by Hydrometer Method»
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