1. Upper Petaluma River Watershed Flood Control Project
Kent Gylfe
Principal Engineer

2. Introduction

3. 2005/06 New Years Day Flooding

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

5. 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

6. 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

7. 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

8. 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

9. Supporting Project Objectives

10. Project Concepts- Multi-Benefit Approach

11. 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

12. 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

13. 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

14. 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

15. 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.

16. 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

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

18. 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

19. 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

20. 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

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

22. 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.

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

24. Concept Screening & Prioritization

25. 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

26. 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

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

28. 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

29. 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

30. Upper Petaluma River Watershed Flood Control Project
Kent Gylfe
Principal Engineer