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 MANAGEMENT STRATEGIES CONCLUSIONS

HISTORICAL CHANGES IN CALIFORNIA STREAMS: subtitled: “whither goest Willow Creek “How did we get here and whose fault is it anyway?”

Native American Life in California

An “adaptive” lifestyle Dry Season Wet Season

Arrival of the Spanish… and their cows

All of this occurred before the invention of the modern “low impact” cow

California in the 20 th Century

California in the 20 th Century: Urban and suburban growth

Development sequence: 1. Develop the watershed 2. Build near the river 3. River floods 4. Call for help: “somebody do something!”

A hero arose… In the hour of need…

Our tools… and the scale of our projects rapidly expanded

But along the way, our vision of rivers and streams

Began to get lost

As did our natural connection with streams

We began to get some bad press

And our image changed for the worse

The era of multi- objective watershed mgmt In response to these problems, the regulatory climate has changed dramatically, and we have entered

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: 1. Flood hazard management 2. Wildlife habitat 3. Urban Runoff Water Quality

Despite our flood control and water quality efforts, channel problems continued…. Channel incision Downstream deposition

DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

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

runoff infiltration precipitation Runoff Processes

Hydrograph Modification Impacts Runoff Time Pre-Development Urbanization tends to increase stormwater runoff: peak flows volume frequency Post-Development

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 Rainfall-runoff: spatial and vertical complexity

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 Increased Channel network complexity Increased channel “efficiency”

Historical Channel Modification associated with development Stevens Creek, ca 1870 and 1899 ca

Expansion of channel incision: creation of new first order channels

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

Watershed sensitivity to flow: Central coast example

Stream Channel sensitivity to flow changes: Stream response depends on morphology

DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

Management Strategies Regulatory compliance/Implementation Integrating hydromod with other hydrologic project elements Development location/footprint Managing site runoff Channel management

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: 1. Flood hazard management 2. Wildlife habitat 3. Urban Runoff Water Quality 4. Downstream impacts from increased runoff (hydro- modification)

Management Strategies Regulatory compliance Integrating hydromod with other hydrologic project elements Development location/footprint Managing site runoff Channel management

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. 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 Strategies Integrating hydromod with other hydrologic project elements Regulatory compliance Development location/footprint Managing site runoff Channel management

Designing a ‘storage’ vs. ‘conveyance’ approach to runoff management

On-site/individual unit mgmt: Planter Box

IMP Gallery Infiltration trench/ basin Vegetated swale

Detention facilities can be modified to include hydromod Park/permanent pond Wetland/wildlife Habitat Expanding our flood detention facilities to include hydromod: -they will have to be considerably larger -outlet structures will be more complex -allows regional mgmt

Water Quality Management Wetland treatment ponds

Management Strategies Integrating hydromod with other hydrologic project elements Regulatory compliance/Implementation Development location/footprint Managing site runoff Channel management

DOUGHERTY VALLEY: ALAMO CREEK RESTORATION

EXCAVATION OF A NEW FLOODPLAIN TERRACE

ALAMO CREEK AND RESTORED FLOODPLAIN: POST CONTSTRUCTION

DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

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: Monitoring is important Flexibility in technology, regulation, administration Expect rapid evolution in the field: “Adaptive Management”

You learn about natural systems by field observation and data collection (NOT just sitting behind a computer screen or a book) Field Data Collection

Ignore the discomforts Bring the kids Be thorough The importance of field work: We learn more from observation than from computer models

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

Hydro mod means urban: Get involved in the community

Build Education into your projects

Share what you’ve learned

Teach the next generation too… (they’ll be paying for your social security)

Hydromod management is poised at the crossroads of Technology and Innovation