Types of water erosion
There are seven main types of water erosion that impact landscapes around the world. Each type has distinct causes and effects on the environment. Understanding the various forms of water erosion can help mitigate damage through preventative measures.
Raindrop Erosion Causes Splash and Topsoil Loss
Raindrop erosion, also called splash erosion, occurs when raindrops hitting exposed soil dislodge and propel particles into the air. As the soil particles land, they can plug soil pores and batter plants, damaging root systems and reducing growth. Over time, the impact depletes topsoil nutrients, organic matter, and productivity, especially on slopes.
Factors influencing raindrop erosion include climate, soil properties, slope, and ground cover. Steady rainfall intensity of tropical climates accelerates erosion. Coarse-textured, low-organic soils are most vulnerable. Long, steep slopes increase erosion by concentrating and gathering momentum of fast-moving runoff. Plant roots and litter help protect soil structure from raindrop detachment and splash.
Sheet Erosion Wears Down Topsoil Gradually
Sheet erosion uniformly removes soil in thin layers across wide areas of landscape by way of broad runoff sheets. The shallow, slow-moving water causes little apparent damage alone. But steady loss of rich topsoil reduces soil fertility and depth. Sheet erosion may go unnoticed for years until gullies form or subsoil layers expose poor plant growth conditions.
Controlling factors involve soil, slope, climate patterns, and land management. Fine-textured, low permeability soils are highly erodible. Gentle and moderately steep slopes shed more gradual runoff. High-intensity storms increase erosion risk, as do bare fallow fields versus sustained plant or residue ground cover.
Rill Erosion Carves Many Small Water Channels
Rill erosion occurs as runoff concentrates into numerous small, fast-flowing streams after prolonged rainfall. The streams incise shallow yet steep-sided channels less than one foot deep into the土 surface. Rill erosion quickly moves soil particles downslope and may evolve into more severe gully erosion.
Climate, steepness, soil type, and ground cover affect rill severity. Long durations of intense precipitation on moderately steep hillslopes cause substantial damage. Sandy soils with little cohesion erode more than heavy clay soils. Bare slopes increase erosion versus anchored plant roots and residues dispersing flow energy.
Gully Erosion Cuts Deep Channels Impacting Infrastructure
Gully erosion generates deep channels through unconsolidated materials by concentrated flows after intense rainfall or rapid snowmelt. Gullies may reach over 30 feet deep and compromise roads, fences, pipelines, and buildings. Reclamation requires heavy equipment to regrade and stabilize gullies.
Factors include topography, lithology, soil characteristics, land use, and climate. Gullies often originate from rills and other erosion features channelizing flow. Coarse soils on moderately steep slopes draining large areas are highly susceptible. Gullies grow progressively wider and deeper when unsupported by vegetation. Intense storms trigger gully initiation and enlargement.
Stream Channel Erosion Alters Watercourse Size and Shape
Stream channel erosion, also called fluvial erosion, describes wearing away of river and stream beds and banks. Flowing water naturally shapes channels by sediment transport and scouring actions. But land use affecting runoff and sediment supply can accelerate harmful erosion exceeding replenishment.
Influences involve water flow, sediment load, erosion resistance, and watershed changes. High-velocity flow during floods degrades unprotected banks, while inadequate sediment transport deepens channels. Erodible fine bank materials like sand and silt are vulnerable. Altered land cover and urbanization increase runoff and peak discharges.
Landslides Damage Infrastructure Through Mass Wasting
Landslides or mass wasting refer to downward slides of rock, soil, or debris under gravity. Common landslide triggers include intense rain, snowmelt, seismic shaking, added weight, and erosion undermining support. Sliding debris and velocity pose risks to developed areas below slopes.
Factors include slope material, steepness, structure, water content, and vibration. Bedrock, surficial deposits, or artificial fill can slide on failure planes. Increased slope angle reduces stability, as does water pressure in pores. Clay-rich rock prone to landslides has low permeability and shear strength. Nearby construction or earthquakes induce slides.
Wave Erosion Degrades Coastlines and Cliffs
Wave erosion or coastal erosion involves wearing of shorelines and sea cliffs by wave action. Waves constantly strike the coast, quarrying rock and moving sediments. While beaches naturally shift, excess erosion associated with storms and sea level rise threatens structures.
Erosion risks relate to rock strength, wave energy, sea level, and storms. Weaker rocks like shale erode faster than granite. Large waves attacking tall cliffs intensify undercutting and collapse. Rising oceans elevate and accelerate wave attack. Storm surges coupled with waves cause rapid short-term erosion.
Erosion by Insolation
In hot countries, the surface of rocks becomes very hot during the day because of intense heat and sun. the crust of the earth beneath the rocks consists of different minerals, which expand at different rates because of heat and sun. One mineral expanding more quickly than other, causes the rock to burst. This gives rise to cracks. During night, the rocks get cold, and thus contract. This process is repeated day after day, so that cracks increase in size and gradually the rocks break up into small pieces. The action of sun is called insolation and is important in hot and dry countries.
