Sedimentary Budget

Sedimentary Budget

Sedimentary budgets are a coastal management tool used to analyse and describe the different sediment inputs (sources) and outputs (sinks) on the coasts, which is used to predict morphological change in any particular coastline over time. Within a coastal environment the rate of change of sediment is dependent on the amount of sediment brought into the system versus the amount of sediment that leaves the system. These inputs and outputs of sediment then equate to the total balance of the system and more than often reflect the amounts of erosion or accretion affecting the morphology of the coast.

To assess the sedimentary budget the coast has to be divided into two separate morphologies, commonly known as littoral cells and compartments. Sediment compartments can usually be defined as two rocky barriers which mark the ends of a beach and have a fixed sediment budget, although usually leaky to some extant. Littoral cells can either be free or fixed and can occupy a hierarchy of scales, from individual rip cells to entire beaches.

There are various types of natural sources and sinks within a coastal system. Sediment sources can include river transport, sea cliff erosion and longshore drift into an area. Sediment sinks can include longshore drift of sediment away from an area and sediment deposition into an estuary.

Anthropogenic activities can also influence sedimentary budgets; in particular damming of a river and in stream gravel mining of a river bed can reduce the sediment source to the coast. In contrast beach nourishment can increase sediment source.

In 1966, Bowen and Inman defined a littoral cell and separated sediment inputs, accretion by longshore drift and outputs.

Sedimentary budgets are used to assist in the management of beach erosion by trying to show the present sediment movement and forecast future sediment movement.