With reference to examples where appropriate, what is a sediment budget and how does this have both positive and adverse effects within drainage basins?
With reference to examples where appropriate, what is a sediment budget and how does this have both positive and adverse effects within drainage basins?
What is a Sediment Budget?
Although it is a difficult task to perform, if the storage time and amount of sediment is calculated, it is possible to work out a balance between erosion and deposition of the sediment in a catchment specific area. This is called the sediment budget. These are used by scientists, which can present the situation of the catchment area, and whether any human activity needs to take place there, for example, removing deposited sediment to reduce the risks of the river over-flowing, resulting in possible flooding of the area. Another situation could be where too much erosion is taking place in a specific area, and the area around the river needs to be protected by some sort of defence.
What the sediment budget shows is the amount of sediment which leaves a catchment area, and how much of it stays and is stored there. Most of the sediment is stored at the floodplain, though there will always be some others along the river’s course. By looking at an example we can see this more clearly.
The sediment budget for the River Start, South Devon, shows, firstly, all of the 107 tonnes/km squared/year of sediment is transported to its first catchment area, and 15% of the sediment is deposited here at Hedgerow. The remaining 85% of the sediment is carried further down the river’s course, to Lower Start Valley, where 58% of the sediment is deposited onto the floodplain. The remaining sediment is then transported to Slapton Ley. (Figure 1.40, P.20)