Influences on the Drainage Basin

Influences on the drainage basin

• Vegetation

Vegetation and land use affect the amount of water reaching the river channel and its estuaries. Transpiration, which is the movement and take up of water from a plant, and evaporation, where the water turns into steam and rises into the atmosphere play a big role in the amount of water that reaches the river. This is also called evapotranspiration, which can be defined as the return of moisture to the air. Plants which have anchored themselves into the soil and the river banks also intercepts, slows, or even almost stops surface run off, and, as the water has been slowed down by the plants, erosion levels also decrease. Plants such as trees and bushes take in a lot of moisture from the rain and air due to their wide, leave packed branches, while grass land can also hold a lot of it due to its surface area and many roots.[pic 1]

• land uses

forests[pic 2]

Land uses play a major role in where the water travels when it rains and how it gets to the river. Rivers that flow through woodlands may not get as much water, as trees, bushes and glass land catch some of the rain that falls, while more is soaked up by the soil, with only a small amount being allowed to get to the main river body. Surface runoff is also extremely low, as most of the ground in a forest is permeable, allowing water to go through it and into the ground water, or travel to the river via through flow.

Urban areas[pic 3]

Urban areas have different issues, as there are a lot of buildings, roads, and not much actual soil ground, meaning there is hardly any through flow. This means there is far more surface run off here than in the countryside, making the risk of flooding go up. The lack of trees, which reduces evapotranspiration and increases the water which hits the ground, and the high amounts of surface run off mean the water gets to the river much faster, and so making the risk of flash flooding higher.