 Eutrophication may lead to excessive nutrients from sewage and animal wastes; pollutants including heavy metals, polychlorinated biphenyls, radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion.The word "estuary" is derived from the Latin word "aestuarium" meaning tidal inlet of the sea, which in itself is derived from the term "aestus", meaning tide.There have been many definitions proposed to describe an estuary.