Sediment budget analysis
Summary of key issues:
|Description||Concept of overall sediment mass continuity within estuary system.|
|Links with other tools||Always useful as an aid to conceptual understanding.|
|Necessary software tools / skills||
|Limitations||It can be necessary to consider the mathematics of the method in detail to understand whether a particular analytical method can reliably be applied to a given estuary system.|
A sediment budget is a balance of the sediment volume entering and exiting a particular section of the coast or an estuary. Sediment budget analysis consists of the evaluation of sediment fluxes, sources and sinks from different processes that give rise to additions and subtractions within a control volume (e.g. a section of coast or an estuary) in order to gain a better understanding of the estuary system. Control volumes on open coasts pertain to sections of a coast which form sediment cells and are controlled by cell boundaries which either inhibit or limit the amount of transport across the cell boundary. A source increases the quantity of material within the control volume and a sink reduces it and within the cell there may be point sources and sinks, such as tidal inlets, and line sources and sinks, such as movements on and off the beach.
An estuary provides a readily defined control volume, where point sources and sinks exist in the form of rivers, other terrestrial outfalls and the open sea. Line sources and sinks may be defined in terms of erosion from cliffs and transfers to or from saltmarshes, wetlands or other intertidal areas. The subtidal beds also needs consideration as an important source/sink as does material stored in suspension within the volume of water that moves back and forth under tidal action within the estuary.