Estuaries are unique and complex environments located between oceans and river mouths. As freshwater flows into the sea from land, it dilutes the salty water in a small area around the shore. This relatively small space is the site of sediment build-up resulting from fluvial (stream or river) erosion along the riverbanks. The organic sediments and brackish (slightly salty, but undrinkable) water make a unique environment that supports a diverse community of plants and animals. The sediments themselves also form characteristic types of deposits and bed forms (the appearance of the horizontal layers of sand) that are easily seen in cross-section.

It is well known that rivers often carry tremendous amounts of sediment which, when emptied into the oceans, construct distinctive patterns in the underlying sediments. In an estuary, the deposition of sediments is greatly influenced by tidal currents and ocean waves. Even climate is a factor in...