hydromod tools eric stein
TRANSCRIPT
Developing Tools for Hydromodification Management
and Assessment
Eric Stein
S. Ca. Coastal Water Research Project (SCCWRP)
Today’s Presentation
• Project Overview
• General Study Approach
• Tool development
• Expected Products
• Status
Flow Rate
Before Development
After Development
Time
Hydrologic Responses to Development - increased rates of flow - increased flow volumes
After Development Before Development
Increase in: - Imperviousness - Drainage Slope - Direct Runoff
Decrease in: - Evapotranspiration - Recharge - Base Flow
Effect of Increased Impervious Cover
Hydromodification
Effects of Hydromodification
Regional Issue Regional Approach
• Relationship between increased impervious cover and stream stability is a regional concern
• Build on previous work:Stormwater Monitoring Coalition (SMC)Santa Clara CountyContra Costa County
Prior Study Approaches
• Compare historic and contemporary channel shape and size to changes in impervious cover
• Use relationship between changes in channel stability and changes in impervious cover to determine expected responses in S. Ca. streams
• Modeling studies in SF Bay area counties Long-term hydrologic simulations Risk-based modeling
Major Conclusions
• Southern Ca. streams appear to be more sensitive to changes in impervious cover than streams in other areas of the country Estimated threshold of response ≈ 5% TIMP
• All streams studied are adjusting to flow conditions on an annual basis All streams undergo constant change and adjustment Rate of change differs between natural and developed areas
• Management approaches will differ depending on stream type, drainage area and amount of impervious cover
• SCCWRP Technical Reports #450 and #475 – www.sccwrp.org
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Percent Impervious Cover (log)
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Conclusions of Past Studies
Empirical Analysis
(S. Ca.)
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Conclusions of Past Studies
Likelihood of Channel Instability
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Erosion Potential (Ep)- Existing/ Pre-Urban
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Empirical Analysis
(S. Ca.)
Logistic Regression (Modeling)
(S.F. Bay Area)
Current Study
Joint project between SCCWRP and Colorado State Univ. Based on results of 2005 workshop Funded by Proposition 50
1. Which streams are at the greatest risk of effects of hydromodification?
2. What are the anticipated effects in terms of increased erosion, sedimentation, or habitat loss, associated with increases in impervious cover?
3. What are some potential management measures that could be implemented to offset hydromodification effects?
Major Tasks
• Develop protocols for mapping and classificationSusceptibility evaluation
• Develop protocols for monitoring and assessmentAdditional data for model development
• Develop and calibrate predictive models
• Develop management tools
Preliminary Study Sites
Data to support:
- Development of screening tool
- Calibration of predictive models
- Development of standard monitoring protocols
Expected Products
• Screening tool – evaluate whether or not a project is likely to be of concern for hydromodificationChecklists
• Effects tools –evaluate the expected magnitude or intensity of effect Models, decision tree, nomograph or plots
• Mitigation tools –guide recommended mitigation and management measures. fact sheets, design criteria, sizing standards
Screening Tool• Not all streams are the same
• Level of concern & appropriate management strategy will differ based on:Condition of streamCondition of catchmentAnticipated change in land use/runoffExisting control/management measuresProposed management measures
• Tool to help prioritize level of effort/attentionChecklist, decision tree, etc.
Elements of Screening Tool
• Intrinsic Channel Properties
• Catchment Characteristics
• Existing Infrastructure
Different Goals for Different Stages
Protect manage runoff buffer stream
Restore stabilize recontour
Manage for New Condition alternate stream type
Modeling Tool
• Channels are dynamic, vary over multiple time scales
• Goal is to understand long-term “equilibrium” condition after proposed land use changeUltimate target period beyond most typical monitoring
• Need to “translate” model results into simple to use tools for planners & managersNomographs, plots, tables
Working Hypotheses
• Urbanization & increased imperviousness shift the natural delivery of water and sediment to a water course, increasing the risk of incision, widening, and general instability change in channel form
Class IIIClass IIIClass IIClass II
Class IVClass IVClass VClass V
Class IClass I
Class VClass V
Class IIClass IIClass IIIClass III
Class IClass I
Class IaClass Ia
Class IVClass IV
CONTINUOUS HYDROLOGIC MODELING (decadal scale) Magnitude, f requency, duration (flow regime) I ntegrates development style and site-specifi c characteristics (precipita-
tion, soils, topography, etc.)
Long-term hydrology + geomorphic data yields hydrogeomorphic metrics
representing balance of erosive and resisting f orces f or a stream type /
context
Risk- based modeling Logistic regression CART Probability networks Regression
Geomorphic response
Ecologic response
Process Modeling Hydraulics – varied flow Transverse shear stresses Mobile boundary
- aggradation / degradation Channel evolution / response potential
Interaction of Models
Mitigation Tool• Management response will vary based on:
Existing channel conditionProposed change in land use, runoff
• Need to select appropriate management actions:On site runoff controlStream channel bufferingFloodplain restorationStructural controlManage for new “equalibrium” condition
• Decision tools for managers, planners, etcFact sheets, decision trees, tables
What is Appropriate Management Response?
Hasley Canyon Wash
Next Steps
• Site selection completed
• Field data collection – Summer 2007
• Produce draft protocols & monitoring recs. – Fall 2007
• Produce draft screening tools – Spring 2008
• Modeling – 2009
• Final Products – Winter 2010
