Upper Petaluma River Watershed Flood Control Project Kent Gylfe Principal Engineer Kent.Gylfe@scwa.ca.gov

Introduction

2005/06 New Years Day Flooding

Similar Studies in Three Watersheds Napa County Sonoma County Laguna Mark West Sonoma Valley Zone 2A Petaluma River Marin County

Planned Process – Phases of Work Feasibility Gaps Analysis Alternatives Analysis Design/ Construction Predesign/ Permitting Implementation Funding Visioning, Develop Objectives Concept Development Scoping Stakeholder Involvement FUTURE PHASES

Scoping Study Schedule Define project purpose and objectives Apr 2011 Review data and consider problems being addressed, strategies, and issues May 2011 Stakeholder input Develop conceptual alternatives and screening criteria Sept 2011 Identify priority concepts Oct 2011 Review prioritization results Dec 2011 Develop project implementation strategy Dec 2011

Project Participants SOLICITING INPUT FROM… RMC Water and Environment Study Area Residents North Bay Agricultural Alliance Sonoma Mtn.Preservation Grp. City of Petaluma United Anglers Western United Dairymen Son. County Open Space & Ag OWL Foundation River Clean-up Committee Son. County Regional Parks Southern Sonoma County RCD KOA Campground Zone 2A Committee The Bay Institute P.L.A.N. Friends of the Petaluma River Petaluma Wetlands Alliance Regulatory Agencies Petaluma River Council LandPaths North Bay Watershed Assoc. Sonoma Land Trust RMC Water and Environment Sonoma County Water Agency

Project Basis Two core objectives Projects are multi-benefit Provide flood hazard reduction Improve likelihood of outside funding Increase groundwater recharge Provide additional implementation value Seven supporting objectives Broaden support by stakeholders and community Water quality Projects reflect input of partners, stakeholder groups, regulators and study area residents Water supply System Sustainability Ecosystem Multiple workshops Agricultural land Project tour Undeveloped land Consistent with Water Agency mission and initiatives Community benefits

Supporting Project Objectives

Project Concepts- Multi-Benefit Approach

Conceptual Locations General concept location criteria Undeveloped land Relatively flat Relatively close to waterway or floodplain Relative location to geologic formation Individual concepts have unique considerations Preferred project locations to be confirmed during Feasibility Phase based on additional criteria

Recharge Criteria Wilson Grove and Petaluma Formations are most effective for water supply recharge Alluvium above Wilson Grove and Petaluma also considered viable for water supply recharge Other alluvium could provide benefits other than water supply recharge

Concept 1: Managed Floodplain Goal: Maintain flood protection and recharge benefits provided by existing floodplain Continued effectiveness of downstream flood projects depends on avoiding upstream attenuation degradation

Concept 2: Off-stream Detention Goal: Divert high flows to temporary holding ponds for flood reduction and recharge Concept keeps low flows in the channel to maintain environmental conditions and sediment transport characteristics

Concept 3: In-stream Detention Goal: Detain high flows for flood reduction and recharge using the existing stream as a basis Possible to integrate multiple basin uses with waterway.

Concept 4: Floodplain Modification Goal: Create additional storage volume and potential recharge area using existing floodplains as a basis Modified Floodplain Added Floodplain Storage Same concept as Petaluma’s Denman Terracing Project

Concept 5: Levee/Floodwall Goal: Constrain flows to a narrower pathway than the existing floodplain Project impact area directly correlated with benefit area

Concept 6: Channel Modification Goal: Reshape channel section for increased capacity and recharge area Additional Hydraulic Capacity Minimal Impacts to Opposite Bank Project impact area directly correlated with benefit area

Concept 7: Bypass Channel Goal: Divert high flows to parallel channel for flood reduction and potential recharge Existing capacity leads to flooding At-grade bypass can reduce flooding Buried bypass can reduce flooding Concept keeps low flows in the channel to maintain environmental conditions and sediment transport characteristics

Concept 8: Bridge Improvement and Debris Removal Goal: Improvement of bridge areas to reduce potential for flooding due to debris build-up Concept could lead to less emergency operations and maintenance

Concept 9: Low Impact Development Goal: Reduce development-related runoff and provide opportunity for recharge Many LID practices improve runoff water quality

Concept 10: Policy Review and Development Goal: Identify policies that impact flood hazards and groundwater recharge and update as necessary Collaborative concept could be applied at local or county-wide scales.

Concept 11: Direct Recharge Goal: Pump water directly into aquifers Better control of water quality entering aquifers than percolation methods

Concept Screening & Prioritization

Prioritization Process Concept Pool 2 Stages Screening Prioritization No Is the concept suitable for this Project? Yes Does the concept align well with the objectives (compared to the other concepts)? No Yes Concept Recommended for Feasibility Analysis

Screening Process Concept Response 1. Managed Floodplain Yes 2. Off-stream Detention 3. In-stream Detention 4. Floodplain Modification 5. Levee/Floodwall No 6. Channel Modification 7. Bypass Channel 8. Bridge Improvement & Debris Removal 9. Low Impact Development 10. Policy Review and Development 11. Direct Injection Does the Concept Provide Flood Hazard Reduction and Groundwater Recharge (Key Project Purpose)? Yes = Advanced to the prioritization process No = Not advanced to the prioritization process Water Agency could consider participation through other venues

Objectives Support Concept Prioritization Core Objectives Supporting Objectives Screened Concepts Priority Concepts

Additional Project Types Low Impact Development (LID) Ecosystem enhancement Other smaller-scale projects Have the potential to: Bring additional cost-share dollars to the table Significantly increase the attractiveness of a proposed project to funding agencies Generally broaden public support for a project among the community

Next Steps Review worksheet input and comments Update concept descriptions and prioritization Identify focus locations for feasibility study Final public Scoping Study workshop Review prioritization results Dec 2011 Develop project implementation strategy Dec 2011 Phase 2: Feasibility Study

Upper Petaluma River Watershed Flood Control Project Kent Gylfe Principal Engineer Kent.Gylfe@scwa.ca.gov