About This Item
Share This Item
Five surveys of painted sand plugs were made between 1982 and 1983 at 7 washover sites on Assateague Island to observe sedimentologic and geomorphologic changes during overwash. The stormy 1982-83 period included a large extratropical storm in October 1982 that produced waves exceeded only by the March 1982 Ash Wednesday storm, 7 northeasters of moderate intensity, and a significant tropical storm.
Our surveys suggest that eolian and washover processes are equally important in net sediment dynamics and morphology of washover fans. Strong storm winds caused erosion of fan surfaces and adjacent dunes. Eolian activity sealed the throats of 2 fans early in the October storm, preventing subsequent washover. Erosion dominated the early phases of washover events and was followed by accretion. For all storms studied, the net effect was accretion.
The occurrence of storms of various magnitudes and frequency permits a comparison of their relative effectiveness in transporting sediment and causing geomorphologic change. The October storm deposited between 20 and 40 cm (8 and 16 in.) of horizontally bedded coarse sand and shell fragments on fans located along northeasterly trending shorelines. Fans along easterly trending shorelines were shielded from direct wave attack and experienced little change. The net effect of 7 subsequent northeasters of moderate intensity also resulted in net accretion, but their total sediment movement averaged less than the amount deposited by the October storm. Surfaces of recently overwashed fans exhibited upper flow regime bedforms and lacked relief. Eolian processes altered fan surfaces between was over events and established partially vegetated dunes on their surfaces in less than 6 months.
End_of_Article - Last_Page 496------------