Hydraulics & Waterways

Oral

398023 - Ecosystem Restoration through Removal of Tidal Flow Restrictions: Impact on Upstream Flooding under Combined Influence of Rainfall and Tide

Wednesday, June 6
10:30 AM - 12:00 PM
Location: Regency Room

In tidal creeks where flow restriction from undersized culverts is severe, the interactions between tide and upstream salt marshes are altered with deleterious effects on the salt marshes. The significant changes that occur due to tidal restrictions during each tidal cycle are reduction in the available tidal volume into salt marshes and reduction in upstream tidal range. Less available upstream tidal volume implies reductions in the amount of nutrients and salt supplied to salt marshes resulting in impaired salt marsh viability. Lowered upstream surface elevation implies that the marsh surface will receive little or no tidal inundation also resulting in impaired salt marshes. Removal of tidal flow restriction will over time improve the viability of the salt marshes. However, in some watersheds the lowered surface elevations allowed for development of low lying areas, which could become flood prone after removal of the flow restrictions. A hydrological/hydraulic model was established, calibrated, and used to determine the appropriate amount of conveyance required to balance between providing salt marsh benefits and minimizing flooding vulnerability in the Marshes Creek watershed located in Linden, New Jersey. Modeling results show that under a proposed scenario with restrictions removed, during spring tide, the tidal volume available to the upstream marshes increased by 146% and the high water surface elevation increased by 0.26 meters. Also, under the proposed scenario with rainfall added, modeling results show slightly higher water surface elevations up to the 25-year return rainfall event and lower water surface elevations for less frequent rainfall events. In conclusion, removal of the existing tidal flow constrictions from Marshes Creek will improve the viability of its upstream salt marshes while reducing peak water surface elevation during rainfall events with a return period of 25 years or greater under spring tide conditions.

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398023 - Ecosystem Restoration through Removal of Tidal Flow Restrictions: Impact on Upstream Flooding under Combined Influence of Rainfall and Tide



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