8.3: Water Erosion
- Page ID
- 42690
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Processes of Water Erosion
Erosion is the geological process involving the detachment of earth materials, such as soil, rock, and sediment, from the surface. Once detached, these materials are then transported by mobile agents—most commonly water (the most ubiquitous form of erosion), but also wind and ice—to a new location where they are eventually deposited .
Rain splash erosion is the initial stage of water erosion, caused by the direct impact of raindrops striking the surface . The process involves two general steps: first, as precipitation soaks into the ground, it fills the pore spaces, which loosens soil particles and pushes them apart. Second, the energy from subsequent raindrop impacts forcefully splashes these loosened particles away from the point of contact. This action typically gives the soil surface a pitted or dimpled appearance and prepares the soil for transport by later stages of erosion, like sheet flow.
Surface runoff begins when the intensity of rainfall during a storm exceeds the infiltration capacity of the soil, meaning the ground cannot absorb water fast enough. Sheet erosion is then caused by this unconfined, thin film of water flowing evenly across the surface . Because this process removes a very thin, uniform layer of topsoil, its effects are often difficult to detect immediately. Significant land degradation resulting from sheet erosion may only become perceptible after several years of cumulative soil loss.
Rill erosion occurs when surface runoff concentrates into innumerable, closely-spaced, small channels, or rills, which are typically only a few centimeters deep . These rills are formed by the erosive power of concentrated water flow. If left unchecked, the water flow continues to cut both vertically (deepening) and horizontally (widening) these small channels. When multiple rills join together and continue to enlarge, they form the much larger, deeper, and more destructive channels known as gullies.
