FACTORS INFLUENCING ESTUARY SEDIMENT DISTRIBUTION

Abstract

Many factors combine to determine the way in which sediments are distributed throughout an estuary. Most fundamental are those which produce the natural rhythm of diurnal (or semi-diurnal), bi-monthly and seasonal fluctuations due to predictable variations in tide and weather. This group includes tidal discharge, fresh river flow and the resultant distribution of saline water. When considered together with such factors as the availability and properties of sediments within and beyond the landward and seaward limits of an estuary, they determine how the available material shall be eroded, transported and deposited during the course of the natural cycle. Superimposed on these regular fluctuations are the effects of other factors which may or may not be predictable, are not necessarily regular in occurrence and may be either natural or man-made. These include secular trends, such as long-term adjustments in land/sea levels or climatic conditions, which have a small but continuing effect on some of the factors in the first group. They also include sudden, short-term events like earthquakes or hurricanes which impose a shock to the system that may involve the movement of large quantities of material during the subsequent period of readjustment.