the direction of net wave-induced longshore transport and resulted in the 

 extension of the foredune into overwash and spit areas. 



Overwash deposits serve as a source of sand, and these breaches in the 

 barrier dune also act as corridors for eolian transport. The redistribution 

 of storm overwash deposits by wind is important in effecting the vertical 

 growth of a barrier island. (Author) 



Schwartz, R. K. 1975. "Nature and Genesis of Some Storm Washover Deposits," 

 CERC TM-61, US Army Engineer Waterways Experiment Station, Coastal 

 Engineering Research Center, Vicksburg, Miss. 



Under certain conditions large amounts of sediment are moved across the 

 beach during storms and stored subaerially instead of being eroded from the 

 beach and foredune and introduced, or simply returned seaward, into the 

 littoral drift system. Washover occurrence is a function of the degree of 

 storm surge and backshore-f oredune relief. The shape and dimension of a 

 washover sand body are largely controlled by the surrounding topography. The 

 major immediate source of washover sediment during storm-surge flood is the 

 beach and shoreface; the foredune may contribute variable amounts. Subenvi- 

 ronments of the backbarrier supply sediment during storm-surge ebb flow, and 

 eolian processes add variable amounts of sediment during washover deposition 

 depending upon storm wind intensity and duration. In turn, washover deposits 

 serve as a sediment source to the poststorm eolian system or encroaching 

 bodies of water, e.g., a transgressing sea. 



Both structural and textural properties are explained by pulsating 

 (discontinuous) unidirectional flow of sediment-charged water across the 

 washover surface. Velocities imparted by the fluid surge of overwashing 

 storm waves, combined with gravity effects due to a landward-sloping surface, 

 result in the development of flow similar to sediment gravity flow. Each 

 flow event results in initial scouring of the subaerial surface followed by 

 the development of planar (horizontal) stratification, while injection into 

 the more distal subaqueous setting results in the development of delta- 

 foreset structures. Normal and inverse textural grading as well as textural 

 coarsening in the direction of flow are also the products of this flow. 



The observed washover properties and genetic interpretations describe 

 washover response to two particular storm conditions. Although the same 

 basic response is expected for storms of various magnitudes, modifications 

 are expected. In response to a larger storm surge (e.g., hurricane) or a 

 different topographical setting, storm surge-ebb may be an important factor 

 in washover sedimentation. With a storm surge sufficient enough to keep the 

 washover area submerged, flow characteristics will vary; therefore, 

 textural-structural response properties will vary. On a smaller scale, 

 temporal-spatial variations in the local setting (e.g., slope, initial flow 

 velocity, sediment size and sorting, sediment-fluid concentration, and 

 percolation) may also result in process-response variation. 



The occurrence of washover suggests an important relationship to the 

 littoral system in subaerial sediment storage versus permanent offshore 

 sediment loss or temporary offshore storage. Washover contributes to the 

 landward and vertical accretion of coarser detritus (relative to other 

 facies) in the barrier environment. The sediment is stored until later 

 erosion by similar storm processes, wind, incremental encroachment, and 

 erosion by surrounding water bodies or other sediment processes. The 



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