www.sonomacountywater.org

Upper Petaluma River Watershed Flood Control Project

Kent GylfePrincipal Engineer

Kent.Gylfe@scwa.ca.gov

Introduction

www.sonomacountywater.org

2005/06 New Years Day Flooding

Similar Studies in Three Watersheds

Sonoma County

Marin County

Napa County

Laguna Mark West

Sonoma Valley

Petaluma RiverZone 2A

Planned Process – Phases of Work

Feasibility

Gaps Analysis

Alternatives Analysis

Design/ Constructio

n

Predesign/ Permitting

Implementation

Funding

Visioning,Develop

Objectives

Concept Development

Scoping

Stakeholder

Involvement

FUTURE PHASES

Scoping Study Schedule

Stakeholder input

Stakeholder input

May 2011May 2011

Sept 2011Sept 2011

Dec 2011Dec 2011

Oct 2011Oct 2011

Define project purpose and objectivesDefine project purpose and objectives

Review data and consider problems being addressed, strategies, and issues

Review data and consider problems being addressed, strategies, and issues

Develop conceptual alternatives and screening criteria

Develop conceptual alternatives and screening criteria

Identify priority conceptsIdentify priority concepts

Review prioritization resultsReview prioritization results

Apr 2011Apr 2011

Dec 2011Dec 2011Develop project implementation

strategyDevelop project implementation

strategy

Project Participants

SOLICITING INPUT FROM…

Sonoma County Water Agency

RMC Water and Environment

Project Basis

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

Concept 1: Managed FloodplainGoal: 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 DetentionGoal: 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

Same concept as Petaluma’s Denman Terracing Project

Modified Floodplain

Added Floodplain

Storage

Concept 5: Levee/FloodwallGoal: Constrain flows to a narrower pathway than the existing floodplain

Project impact area directly correlated with benefit area

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

Concept 7: Bypass ChannelGoal: Divert high flows to parallel channel for flood reduction and potential recharge

Concept keeps low flows in the channel to maintain environmental conditions and sediment transport characteristics

Existing capacity leads to flooding

At-grade bypass can reduce flooding

Buried bypass can reduce flooding

Concept 8: Bridge Improvement and Debris RemovalGoal: 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 RechargeGoal: Pump water directly into aquifers

Better control of water quality entering aquifers than percolation methods

Concept Screening & Prioritization

Prioritization Process

• 2 Stages– Screening

– Prioritization

Is the concept suitable for this Project?

Does the concept align well with the objectives (compared to the

other concepts)?

No

No

Yes

Yes

Concept Recommended for Feasibility Analysis

Concept Pool

Screening Process

• Yes = Advanced to the prioritization process

• No = Not advanced to the prioritization process– Water Agency could

consider participation through other venues

Does the Concept Provide Flood

Hazard Reduction and Groundwater

Recharge (Key Project Purpose)?

Objectives Support Concept Prioritization

Core Objectives

Screened Concepts

Supporting Objectives

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

Dec 2011Dec 2011Review prioritization resultsReview prioritization results

Dec 2011Dec 2011Develop project implementation

strategyDevelop project implementation

strategy

• Review worksheet input and comments

• Update concept descriptions and prioritization

• Identify focus locations for feasibility study

• Final public Scoping Study workshop

Phase 2: Feasibility StudyPhase 2: Feasibility Study

www.sonomacountywater.org

Upper Petaluma River Watershed Flood Control Project

Kent GylfePrincipal Engineer

Kent.Gylfe@scwa.ca.gov