Document Type

Report

Department/Program

Virginia Institute of Marine Science

Publication Date

9-1-1976

Series

Special Reports in Applied Marine Science and Ocean Engineering (SRAMSOE) No. 110

Abstract

ABSTRACT The effect of storm surge on wave refraction patterns along 320 km of shoreline in the Virginian Sea (Mid-Atlantic Shelf) has been investigated using an analytical model. Two types of storm surge patterns based on Bodine (1971) and Jelesnianski (1972 and 1974) are used to alter the ocean surface of the Virginian Sea Wave Climate Model (Goldsmith, et al., 1974). The first pattern, based on Bodine's (1971) Bathystrophic Storm Surge Model, is of circular shape (with the maximum sea level rise in the center) and in real situations results mostly from the inverted barometric pressure effect associated with intense low-pressure storm systems, wind setup and the astronomic tide. The center of these surge was located at two places in 30 m water depths on the shelf in order to determine if a general wave response pattern could be established, and to delineate a sequence of wave responses. The second type of surge model, based on the general pattern shown by Jelesnianski (1972 and 1974), develops as the storm moves towards shore, and the effects of shoaling, wind stress, and inertia change the shape and height of the surge. At landfall the surge is a long, narrow strip impinging against the shore with a seawardly exponential decay, and with a higher surge height to the right of center. Based on a comparison of two sets of wave ray diagrams, and shoreline wave energy and wave height distributions • • • • • • • • • • computed for (a) the two surge types and (b) no-surge conditions, using similar initial wave input parameters, the characteristics of the general wave response models are briefly sununarized for both surge types as follows: Shelf Surge: Changing wave refraction patterns result in: (a) maximum increases in shoreline wave energy located to the north and south of that point of land downwave of the storm; and (b) decreases in shoreline wave energy in a shadow zone directly downwave from the storm surge. Shoreline Surge: An increase in longshore drift caused by lesser wave refraction. The deeper water close to shore results in a greater shoreline breaker angle than that observed during no-surge conditions. Thus irrespective of the wave height, any type of surge will cause significant changes in the shoreline wave refraction patterns resulting in local increases in longshore drift. The tendency for increases in longshore transport, and concomitant decreases in offshore-onshore transport, is thus promoted by water surges, irrespective of wave size and direction and results in permanent local losses of sediment .

Keywords

Modeling, Storm Surge, Virginia

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