BETHANY LOOP CANAL FLOOD MITIGATION

BETHANY BEACH, DE

DESIGN , COMMUNITY, INFRASTRUCTURE, WATER

THE CHALLENGE

The Town of Bethany Beach is frequently affected by sunny day and storm-based tidal flooding due to its elevation as well as tidal influences on the storm drain networks and the canals to which they discharge. The Town has been exploring concepts to reduce the frequency of tidal-related flooding for several years, including the use of a bladder-actuated steel dam at the confluence of the Assawoman Canal and the Loop Canal in concert with tidal one-way flap gates to the north.

HOW WE HELPED

McCormick Taylor was contracted by the Town with completing an extensive hydrologic and hydraulic analysis of the study area and the impacts of the proposed improvements on water surface elevations surrounding the community. The study includes a detailed hydraulic analysis to evaluate the baseline flooding conditions as a point of comparison against the improvements and impacts of the proposed flood mitigation structures utilizing 2-dimensional flood modeling (HEC-RAS 2D). The model simulates various scenarios including high-tide events on sunny days as well as high-tide events coupled with 1-, 2-, and 5-year rainfall events to examine available storage when the canal is blocked from releasing runoff. It was calibrated based on field reconnaissance, data from several tidal gauges, and anecdotal evidence from prior flooding events. Initial water surface elevations within the terrain were adjusted to simulate the deployment of the dam at different points during multiple storm or tidal events, and multiple dam heights were modeled in order to determine the most effective solution for the Town and the surrounding communities. Each adjacent community was analyzed to determine their impact by the project.

RESULTS

McCormick Taylor prepared a report and presented the results of the study in several meetings to Town Council, flood committees, and adjacent communities. Communications materials included slide decks on the project background, animated video simulations, inundation maps for each of the modeled scenarios, and profiles through the canals to demonstrate the effect of the proposed mitigation options on hydraulic conditions for the Town and surrounding communities. Staff also conducted Q&A sessions on the project. McCormick Taylor has completed the preliminary design phase of the dam project and assisted the Town with Benefit-Cost Analyses (BCA) and federal grant applications to fund final design and construction.

Read our Q&A Project Update with Chris Brooks here.