Multi-Benefit River and Floodplain Management in the Salinas Valley: Bringing Stakeholders Together with New Technologies and Approaches

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1 Multi-Benefit River and Floodplain Management in the Salinas Valley: Bringing Stakeholders Together with New Technologies and Approaches September 8, 2016 Paul Frank, PE

2 Flood-prone communities ~$6 Billion agricultural economy Crucial steelhead spawning habitat

3 Problem: Flood Risk 1280 acres flooded = $6.5M loss

4 History of the Salinas Stream Maintenance Program Management for flood risk reduction in response to 1995 flood. Administered by MCWRA which held the 404 and 401 permits. Landowners obtained their own 1600 permits for maintenance activities Potential impacts to threatened species and the river system halt the SMP Stakeholders at odds over management approaches, Monterey County-led SMP effort fails

5 Stream Maintenance Limited regional or reach-wide coordination Damaging to riparian corridor No design basis in hydraulics or geomorphology Flood benefits never quantified nor compared against impacts

6 History of the Salinas Stream Maintenance Program Management for flood risk reduction in response to 1995 flood. Administered by MCWRA which held the 404 and 401 permits. Landowners obtained their own 1600 permits for maintenance activities Potential impacts to threatened species and the river system halt the SMP Stakeholders at odds over management approaches, Monterey County-led SMP effort fails

7 History of the Salinas Stream Maintenance Program Management for flood risk reduction in response to 1995 flood. Administered by MCWRA which held the 404 and 401 permits. Landowners obtained their own 1600 permits for maintenance activities Potential impacts to threatened species and the river system halt the SMP Stakeholders at odds over management approaches, Monterey County-led SMP effort fails

8 The Nature Conservancy: Demonstrating a new approach to stream maintenance TNC starts working with stakeholders in 2013, eventually creating open, productive dialog Start back at the drawing board Build the relationships Jointly design a new approach that would provide multiple benefits Science-based approach Sophisticated flood modeling Geomorphology Biological / vegetation surveys and analysis

9 Scientific foundation The 2D hydraulic model

10 Scientific foundation The 2D hydraulic model ~90 river miles long, 2-3 miles wide Modeled multiple flow magnitudes up to 10-year return interval event Modeled bookend management scenarios to understand range of possible benefits and impacts Bookend 1 Current, unmanaged conditions Bookend 2 Total clearing of vegetation in the riparian corridor Understanding of complex flow patterns led to design of flood reduction strategies

11 Scientific foundation Designing the secondary channels Mimic the natural braiding of a sand-based system Rebuild some of the historical structure and function of the river Allowed by regulators to connect to the active channel Coordinate with county-wide arundo removal efforts Meander cutoffs Low-lying areas with natural vegetation Former river alignments

12 Secondary Channels

13 Secondary Channels

14 Scientific foundation Designing the secondary channels

15 Scientific foundation Visualizing the benefits

16 Scientific foundation Visualizing the benefits

17 Scientific foundation Visualizing the benefits

18 Modeling Outcomes Dispel myths: vegetation removal is the solution to flooding problems Targeted vegetation removal offers measurable improvement on both reach and parcel scales with dramatically less impacts Demonstrated to landowners how important a holistic view of the valley is 5-year return interval flood is sweet spot A different strategy is needed to reduce flood damage at >10-year event

19 Detention storage in the future?

20 Keys to Success of Modeling Transparency to stakeholders through regular, open meetings Use visualizations effectively to communicate technical concepts Revise model / validate results with landowner experience to build credibility

21 Demonstrating the approach Implementation Spring 2014 Got permits for 12-mile demonstration reach Fall 2014 Work begins at the demonstration reach (Chualar and Gonzales, RMUs 4 and 5) Fall 2015 Second year of work at demonstration reach Summer 2016 Permits for entire Valley Fall 2016 Fall 2017 Work begins throughout Valley

22 Thank you! Paul Frank, PE Water. Ecosystems. Science. Technology FlowWest.com