How the Bradshaw Model Can Be Used to Model the Fluvial Characteristics of a River

Discuss how the Bradshaw model can be used to model the fluvial characteristics of a river (10 marks)

The Bradshaw model is a geographical model which describes how a river’s characteristics vary between upper course and lower course of a river (Online Geography Resources, 2012). A geographical model is designed to simplify nature which is highly complex in order to understand this complexity (Waugh, 2009). The Bradshaw model differentiates factors which increase and decrease from the upper to lower region, such as discharge, load quantity, load particle size and channel bed roughness. These are just four of the eight characteristics acknowledged by the Bradshaw model. In this essay I will address three fluvial characteristics I have mentioned; discharge, load quantity and load particle size. I will describe and explain how each change with distance downstream.

Discharge is defined as the volume of water that passes through a cross sectional area (meters) per unit of time (seconds) (Online Geography Resources, 2012). In accordance to the Bradshaw model discharge is the most dramatically changing characteristic of all in terms of its change from upstream to downstream. The discharge increases significantly as the river flows downstream, meaning the volume of water passing through the river bed per time increases.

The reason for the significant increase in discharge from source to mouth is due to tributaries meeting the main river acting as secondary sources, called second or third order segments. This process is continuous due to gravity pulling water down into a valley through tributaries within the basin where the river bed lies. Surface runoff, throughflow and baseflow also add to the river. Therefore the flowing volume of water increases as it precedes downstream hence the increase in discharge.

Load quantity is the overall amount of sediment load picked up throughout the course of the river. This is another example of a fluvial characteristic which increases greatly as the river travels downstream. The amount of sediment within the discharge of the river from source to mouth is much greater, which could be in the form of small particles like silt and clay or large cobbles and boulders.

Increase in load quantity downstream is caused by other fluvial characteristics like velocity which also increases downstream. This increase in the speed at which the water is travelling means more sediment can be transported towards the mouth because the force of current allows heavier particles to join the flow. The increasing discharge also plays its part by the constant edition of tributaries which carry their own particles, all adding to the load quantity. Erosion