www.sonomacountywater.org
Upper Petaluma River Watershed Flood Control Project
Kent GylfePrincipal Engineer
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