High rates of weathering, abundant rainfall, and high discharge rates combine to supply large volumes of sediment to the coastal zone of eastern Nicaragua. This terrigenous sediment is confined to a narrow section of the inner shelf (<30 km wide) due to the circulation pattern within a coastal boundary layer. Sediment transport within the inner shelf and shore zone is to the south. This simple transport pattern is considerably modified by variations in wave-energy levels that are a function of

more »

... helf width, bottom friction, and wave sheltering. In northern sections , the shelf is up to 200 km wide but narrows to less than 20 km in the south. A direct result is that wave-energy levels at the shoreline are of the order of three times greater in the south. In the north the Rio Coco delta is prograding seaward in a fluvially dominated environment, whereas the Rio San Juan delta in the south has a wave-dominated morphology characterized by deflected dis-tributaries. Other major accumulation features have developed where wave-shadowing is produced by offshore reefs and cays. Alongshore a spatial variation was recorded, with straight beaches and simple linear bars in the north that change to rhythmic beach topography and crescentic nearshore bars as wave-energy levels increase toward the south.