St. Johns County San Sebastian Study

Jones Edmunds assisted St. Johns County with evaluating and developing a coastal resiliency vulnerability assessment for infrastructure and structures within the San Sebastian drainage basin. The assessment assisted the County in both assessing risk and in developing drainage improvements.

The project consisted of four primary tasks. The first task identified potential future flooding risks based on the following inputs:

2017 NOAA sea level rise (SLR) projections to characterize coastal flooding risks.

Regional stormwater models (West Augustine and/or North Augustine Regional Models) previously developed for the County by Jones Edmunds. We updated the models to characterize potential future inland flooding risks. Our updates reflected changes in boundary conditions and soil storage due to SLR.

Using a regional ADCIRC Model to characterize surge levels and wind speeds occurring at typical planning frequencies (i.e., the 25-, 50-, 100-, and 500-year storms).

The second task used the results from the first task to identify impacted infrastructure and structures. The third task identified adaptation strategies for five priority infrastructure projects. The strategies included options and conceptual approaches for adaptation along with a time horizon for implementation. The final task provided guidance for future infrastructure planning in areas of increased SLR risk.

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