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HYDROMODIFICATION: AN INTRODUCTION AND OVERVIEW. Presented by Jeffrey Haltiner, Ph.D., P.E. Philip Williams & Associates, Ltd. San Francisco, CA May2006. Hydromodification: An Integrated Element of Stormwater Management DISCUSSION TOPICS. HISTORICAL PERSPECTIVE HYDROMOD PROCESSES

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HYDROMODIFICATION: AN INTRODUCTION AND OVERVIEW


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hydromodification an introduction and overview
HYDROMODIFICATION: AN INTRODUCTION AND OVERVIEW
  • Presented by
  • Jeffrey Haltiner, Ph.D., P.E.
  • Philip Williams & Associates, Ltd.
  • San Francisco, CA
  • May2006
hydromodification an integrated element of stormwater management discussion topics
Hydromodification: An Integrated Element of Stormwater ManagementDISCUSSION TOPICS
  • HISTORICAL PERSPECTIVE
  • HYDROMOD PROCESSES
  • MANAGEMENT STRATEGIES
  • CONCLUSIONS
historical changes in california streams subtitled whither goest willow creek
HISTORICAL CHANGES IN CALIFORNIA STREAMS:subtitled: “whither goest Willow Creek
  • “How did we get here and whose fault is it anyway?”
an adaptive lifestyle
An “adaptive” lifestyle

Dry Season

Wet Season

slide13
Development sequence:1. Develop the watershed2. Build near the river3. River floods4. Call for help: “somebody do something!”
in the hour of need
In the hour of need…

A hero arose…

our tools
Our tools…

and the scale of our projectsrapidly expanded

regulatory framework
Regulatory Framework
  • Flood management
    • FEMA
    • Local Flood Control Districts
  • Habitat protection
    • US Fish & Wildlife Service (Section 7)
    • CA Department of Fish & Game (Section 1601)
  • Water Quality
    • Federal Clean Water Act (US EPA)
    • Regional Water Quality Control Boards (RWQCBs)
in response to the regulatory requirements we developed methods to address
In response to the regulatory requirements, we developed methods to address:

1. Flood hazard management2. Wildlife habitat3. Urban Runoff Water Quality

despite our flood control and water quality efforts channel problems continued
Despite our flood control and water quality efforts, channel problems continued….

Channel incision

Downstream deposition

discussion topics
DISCUSSION TOPICS
  • HISTORICAL PERSPECTIVE
  • HYDROMOD PROCESSES
  • MANAGEMENT STRATEGIES
  • CONCLUSIONS
urbanization direct hydrologic impacts
Urbanization Direct Hydrologic Impacts
  • Increased runoff volume
  • Increased peak flow rates
  • Reduced time lag to peak flow
  • Increased duration of high flow
  • Increased frequency of flow events
hydrograph modification impacts

Urbanization tends to increase stormwater runoff:

  • peak flows
  • volume
  • frequency

Post-Development

Hydrograph Modification Impacts

Pre-Development

Runoff

Time

slide30
While we understand the basic effects of urbanization, the detailed processes are v. complex
  • We use simple tools to characterize these impacts.
scientific modeling overview rainfall runoff processes modeling
Scientific/modeling overview:Rainfall-runoff processes/modeling
  • Rainfall-runoff: spatial and vertical complexity
scientific modeling overview stream channel processes
Scientific/modeling overview:Stream channel processes
  • Basic concept is that altered hydrology results in channel erosion
  • Very difficult to predict the “threshold” for channel response
urbanization indirect hydrologic impacts
Urbanization Indirect Hydrologic Impacts
  • Increased Channel network complexity
  • Increased channel “efficiency”
historical channel modification associated with development
Historical Channel Modification associated with development

ca 1870

1899

Stevens Creek, ca 1870 and 1899

urbanization hydrologic impacts variability all watersheds and streams are not created equal
Urbanization Hydrologic Impacts: Variability(all watersheds and streams are not created equal)
  • Soil characteristics
  • Cover (vegetation, duff layer etc)
  • Channel characteristics (bed material, slope etc)
  • Sensitivity to hydromod varies greatly
discussion topics39
DISCUSSION TOPICS
  • HISTORICAL PERSPECTIVE
  • HYDROMOD PROCESSES
  • MANAGEMENT STRATEGIES
  • CONCLUSIONS
management strategies
Management Strategies
  • Regulatory compliance/Implementation
  • Integrating hydromod with other hydrologic project elements
  • Development location/footprint
  • Managing site runoff
  • Channel management
regulatory framework41
Regulatory Framework
  • Flood management
  • Habitat protection
  • Water Quality
  • Hydrograph Modification Management
    • New NPDES permit requirements (RWQCBs)
    • How should it be regulated? Who should lead the regulatory side?
    • Which agency should manage this?
in developing hydrologic strategies in urbanizing areas we now need to integrate four key elements
In developing hydrologic strategies in urbanizing areas, we now need to integrate four key elements:

1. Flood hazard management2. Wildlife habitat3. Urban Runoff Water Quality4. Downstream impacts from increased runoff (hydro- modification)

management strategies43
Management Strategies
  • Regulatory compliance
  • Integrating hydromod with other hydrologic project elements
  • Development location/footprint
  • Managing site runoff
  • Channel management
slide44
Much of the urbanization in the state has already occurred
  • Much of the new permitting will be on small infill projects and small to medium developments at the urban fringe.
site design and layout has a major effect on the stormwater runoff effects
Site design and layout has a major effect on the stormwater runoff effects.

Mass site grading and extensive, connected paving lead to large increases in runoff rate and volume.

-Maintain open space-Maintain pervious soils-Disconnect impervious areas-Create pervious zones/buffers

management strategies46
Management Strategies
  • Integrating hydromod with other hydrologic project elements
  • Regulatory compliance
  • Development location/footprint
  • Managing site runoff
  • Channel management
imp gallery
IMP Gallery
  • Infiltration trench/
  • basin
  • Vegetated swale
detention facilities can be modified to include hydromod
Detention facilities can be modified to include hydromod

Park/permanent pond

  • Expanding our flood detention facilities to include hydromod: -they will have to be considerably larger-outlet structures will be more complex-allows regional mgmt

Wetland/wildlife Habitat

water quality management
Water Quality Management
  • Wetland treatment ponds
management strategies52
Management Strategies
  • Integrating hydromod with other hydrologic project elements
  • Regulatory compliance/Implementation
  • Development location/footprint
  • Managing site runoff
  • Channel management
discussion topics56
DISCUSSION TOPICS
  • HISTORICAL PERSPECTIVE
  • HYDROMOD PROCESSES
  • MANAGEMENT STRATEGIES
  • CONCLUSIONS
concluding thoughts
Concluding thoughts
  • We are inheriting watersheds and streams with extensive impacts
  • Hydromod management must be integrated with other management elements
  • Hydromod management must be applicable to different watershed locations
  • The regulatory process is ahead of technology; no long-term experience
  • The regulatory process is ahead of administration
  • Long-term Performance/Maintenance?
in response
In Response:
  • Monitoring is important
  • Flexibility in technology, regulation, administration
  • Expect rapid evolution in the field: “Adaptive Management”
field data collection
Field Data Collection
  • You learn about natural systems by field observation and data collection (NOT just sitting behind a computer screen or a book)
field data collection60
Field Data Collection
  • Ignore the discomforts

The importance of field work: We learn more from observation than from computer models

Bring the kids

Be thorough

project design and implementation
Project Design and Implementation
  • You learn how to build projects by trying things out and learning from your mistakes and successes
  • It is easier to criticize than to do!
  • Be humble; there is a lot to learn