Date of Award

Spring 2007

Project Type

Thesis

Program or Major

Ocean Engineering

Degree Name

Master of Science

First Advisor

M Robinson Swift

Abstract

The Hampton/Seabrook estuary is located at the southern end of the New Hampshire Seacoast area. As it is a dynamic system, tidally dominated, and continually changing, two major changes have become issues in recent years: erosion of a sandbar (threatening waterfront homes), and sediment deposition in Seabrook Harbor. Flow between the Blackwater River and the harbor carved a channel between waterfront homes on River Street and the sandbar referred to as "middle ground," and there was concern about further coastal erosion in this area. Additionally, while Seabrook Harbor has previously been dredged yearly to provide temporary relief for boat traffic, the dredging served to increase velocity differences between the River Street breach (high) and the harbor (low), which promoted sediment deposition. During the winter of 2005, as part of the ACOE National Shoreline Erosion Control Development and Demonstration Program, a channel was dredged through the northern part of middle ground, and the material was deposited in the River Street breach area.

As part of the post-construction modeling effort, the ACOE-developed finite element hydrodynamic model RMA2 was applied to the post-dredge Hampton/Seabrook Estuary. RMA2 is a two-dimensional, vertically averaged hydrodynamic model capable of calculating water surface elevations and velocities, for both steady-state and dynamic analyses, and generates a solution based on existing physical conditions and boundary conditions.

Field data were organized, including bathymetry from several surveys, tide station data, and acoustic Doppler current profile (ADCP) velocity measurements. Post-dredge bathymetry was used to develop the computer finite element mesh, and ocean forcing boundary conditions were generated using tidal prediction techniques and tidal constituents from nearby stations outside the harbor. Model predictions were compared with both tidal elevation and tidal current observation data in the calibration process.

Observations of model predictions as well as field observations were made, and recommendations for improvement and further work were presented.

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