Geography Depositional Processes Within a River Basin

Geography Essay

Rivers are complicated systems with many human and physical variables. Fluvial landforms tend to be formed by either erosional or depositional processes. These vary depending on which course of the river is examined. Deposition occurs when material is laid down due to a number of both physical and human factors. The landforms that are created are usually found in the middle or lower course of a river system.

  The Mississippi river which runs through North America, and continues 4,070km from source to mouth. Here the river deposits much of its load forming a river delta. This type of feature is located in the lower course of the river, where it enters the sea. Deltas are usually composed of fine sediment which is deposited when a river loses energy. This occurs when it flows into an area of slow moving water such as a lake or the sea. The finest materials such as clay are carried furthest by the process of suspension and form the bottomset beds, which are then covered by a layer of coarser materials usually silts and clays. These are deposited to form a slope and create to foreset beds. Lastly the upper layers nearest to the land, are made of even coarser materials such as sand and silt. There are typically 3 formations of river deltas:
Arcuate – a rounded outer margin. e.g Nile
Cuspate – material spread out evenly. e.g Tiber
Bird's foot – many distributaries inbetween sediment islands. e.g Mississippi
One factor responsible for the formation of river deltas is flocculation. This is when fresh water from the river meets salt water from the sea. Here the combination of different water produces an electric charge which causes particles such as clay to change to a solid or semi-solid state and settle on the sea bed. This can be found in the Mississippi river delta.
Secondly, natural levees can be found in the lower course of the river. One example can be found in the Mississippi river. These are formed when a river overflows its banks,...