CHAPTER 8: FLUVIAL PROCESSES, PATTERNS AND LANDFORMS
Fig. 12 Radial drainage pattern in County Donegal
8.3 Fluvial processes Rivers shape the landscape by the processes of erosion, transport and deposition. Erosion breaks down the landscape, transport moves it and deposition drops the eroded river material. The sediment carried by a river is called its load. The load is created by erosion and the addition of sediment by mass movement (soil moved downhill by rain and gravity) from the valley sides. Much of the river’s energy is used in transporting the load. These processes of erosion, transport and deposition continually reshape the landscape over which the river flows. River processes are also known as fluvial processes.
Factors affecting fluvial processes
The ability of a river to shape and reshape the landscape depends upon the following factors: • River volume • River speed/velocity • Slope/gradient • Channel width and depth • Load Each of these factors influence the river’s energy (its ability to do itswork). Themore energy a river has, the more erosion it is capable of doing.
River volume and velocity/speed
The energy of a river depends on the volume of water and speed of flow (velocity). Large fast-flowing rivers are very powerful. Rivers in flood do so much damage