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theses

This thesis combines the study of geomorphic effects of beach topography, sediment characteristics, and transport with physical processes of waves, swash, and reflected energies to evaluate the effects of bulkheads on estuarine beaches. I hypothesize that the truncation of a beach by a bulkhead will (1) concentrate and increase turbulence directly seaward of the structure increasing sediment activation depth; (2) create interference and patterns of swash/wave and reflected energy interactions, increasing the topographic variability of the foreshore; and (3) increase turbulent energies enough to remove finer grained sand. Measurements of topographic variability, sediment activation depth, and net change were made over 21 tidal cycles on the foreshore at two wooden sheet pile bulkheads and a control site 45 m south of the bulkheads at Fortescue, New Jersey. Sediment cores were taken seaward of the bulkhead and at equivalent elevations on the control site to the depth of sediment activation. A video record was taken of swash and waves interacting with the bulkhead. The main conclusions are that since the swash and waves are precluded from migrating higher up the foreshore with the tide, the increased concentration of incident and reflected energies at bulkheads more than doubles the depth of sediment activation directly seaward, increasing the potential for sediment transport under higher energy conditions. Though no significant net surface change occurred seaward of the bulkheads, there are more frequent erosional/depositional cycles. The bulkheaded beaches have a more undulatory profile and a steeper slope within 0.5 to 1.5 m of the structure. The surface sediment on the bulkheaded beaches have a smaller amount of coarse sand and granules, although this may be an artifact of horseshoe crab burrowing on the control site. The type of bulkhead construction influences processes and beach response. One bulkhead that has buttress pilings on the bayward side has a steeper beach out to a greater distance (1.5 m) and smaller depth of sediment activation than the planar bulkhead due to sediment accumulation between the buttresses, which broke up the reflected energy. The 8.58 m long beach enclave between the two bulkheads has characteristics similar to bulkhead sites.

M.S.

Includes bibliographical references (p. 87-91).

http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17376

ETD_851

doi:10.7282/T3M61KKS

ETD graduate

The author owns the copyright to this work.

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