Structural and Ice Effects on Salt Water Marsh Hydrology

by Thomas P. Ballestero, Univ of New Hampshire, Durham, United States,
Joseph P. Marrone, Univ of New Hampshire, Durham, United States,
Deborah M. Trottier, Univ of New Hampshire, Durham, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract: This study focussed on a New England salt water marsh in which the construction of two drainage structures (culverts) have significantly affected the marsh hydraulics. The result is the loss of approximately 20% of the salt water marsh vegetation to invading fresh water species at the marsh borders. The USCOE TABS model was calibrated and verified for the existing marsh. Simulations of pre-development (natural) flow conditions were compared to existing flows. The two structures limit the salt water inflow to the marsh to 40% of the natural condition. If the USEPA estimates of sea level rise are used as boundary conditions in the hydraulic model, with the two structures left in place the inflow to the marsh in the year 2100 will exceed that of the natural conditions by twofold. Lastly, the effects of winter ice cover on marsh hydraulics was also investigated. Salt water inflow hydrographs during ice-free periods were compared to those during ice cover periods. The data shows that winter ice cover significantly reduces the salt water inflow to the marsh. This then results with (a) the increased ability for ice growth, and (b) less saline ground water conditions at the start of the growing season compared to other times of the year.

Subject Headings: Ice | Salt water intrusion | Salt water | Hydrology | Hydrologic models | Aquatic habitats | Inflow | Hydraulic structures | Flow simulation | North America | United States | New England

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