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Barrier islands are situated along the Atlantic and Gulf coasts of the United States, and act as buffers to open ocean hydrodynamic energy. Different wave conditions produce either erosion or deposition. The retrograding Barrier islands are composed of coalescing washover fans, and terraces and migrate constantly landward. The prograding islands consist of multiple beach ridges and migrate seaward.

Eight years after the Exxon Valdez spill, oil residues in Prince William Sound, Alaska ranged from moderately to extremely weathered. Theleast weathered residues were found in samples collected from gravelbeaches with well-established armor. There had been little to no change in weathering stage for the oil from these sites since 1994. There was evidence of some physical erosion, but little chemical change for this deeply penetrated oil. In contrast, most other oil residues have increased in weathering, compared to 1994. Only one asphalt pavement was at a moderate weathering stage. All other samples contained hydrocarbons which were at advanced or extreme weathering stages. [ABSTRACT FROM AUTHOR]

The largest amounts of, and the least weathered, oil found eight years after the Exxon Valdez oil spill occurred at depths of 25-50+ cm under the protective cover of a well-sorted cobble/boulder armor on intermittently exposed, coarse-grained gravel beaches within Prince William Sound, Alaska. In addition to the armoring, other factors enhancing the retention of the oil include flat slopes of the middle beach and a thick sediment veneer over a bedrock platform. Natural cleaningof the subsurface sediments was accomplished within three years on the finer-grained gravel beaches that have steeper slopes, a thin sediment veneer over the rock platform, and no surface armoring. Minor berm relocation was an effective technique for removing subsurface oil from the finer-grained gravel berms at the high-tide line. Extensive storm berm relocation caused disruptions to beach morphology and sediment distribution which lasted for up to six years. [ABSTRACT FROM AUTHOR]

Wave action is the most effective natural cleaning agent of oiled shorelines. Therefore, the degree of exposure of a shoreline to wave action dictates how quickly that shoreline will be cleaned by natural processes. In the absence of recorded wave data, a simplified exposureindex, tested on the shorelines of Prince William Sound, Alaska oiled during the Exxon Valdez oil spill, can be used to predict potentialcleansing by wave action. Wind gauge data correlated with three effective fetch distances measured perpendicular to and at 45 deg. to theshoreline are used to calculate the exposure index. In Prince William Sound, both biological and geomorphological criteria for exposure to waves agreed with the readings calculated for the index. Surface oil on the exposed shorelines was removed quickly during the first storm season. Sheltered coasts were cleaned more slowly. This technique should also work well for other partially enclosed water bodies. [ABSTRACT FROM AUTHOR]