Gravel beaches are the most difficult of all the beach types to clean and restore after an oil spill. Thus, they rank the highest of beaches on the environmental sensitivity index scale (ESI = 6). Problems posed by gravel beaches include: high porosity and permeability that allow deep penetration from the surface; potential for deep and rapid burial by clean sediments; presence of localized, sheltered areas where oil can persist for years; complex patterns of sediment reworking during storms; and slow rates of natural replenishment. Cleanup techniques currently employed on such beaches are usually disruptive to the environment, expensive, and logistically complex. Furthermore, gravel beaches are highly variable in terms of their geomorphol-ogy, sediment grain size, and degree of exposure to waves that can rework the sediments to remove oil and restore the sediments to their original distribution. Thus, cleanup decisions must be site-specific and based on an understanding of how each beach will respond to potential cleanup options. To assist cleanup decision makers, a primer on gravel beaches has been prepared. The primer consists of the following sections: ? Brief introduction to the problems gravel beaches pose to cleanup decision makers ? Description of four classes of gravel beaches, in terms of their detailed geomorphology and sedimentation processes ? "Tools " to be used to predict the rate for natural removal of stranded oil or how long it will take for physical recovery to occur after disruption from cleanup activities.
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