Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and animals. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolian) erosion, zoogenic erosion and anthropogenic erosion such as tillage erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes.
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone through lithification.
A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern.
Stormwater, also written storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil (infiltrate) and become groundwater, be stored on depressed land surface in ponds and puddles, evaporate back into the atmosphere, or contribute to surface runoff. Most runoff is conveyed directly as surface water to nearby streams, rivers or other large water bodies without treatment.
A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces.
A ravine is a landform that is narrower than a canyon and is often the product of streambank erosion. Ravines are typically classified as larger in scale than gullies, although smaller than valleys. Ravines may also be called a cleuch, dell, ghout (Nevis), gill or ghyll, glen, gorge, kloof, and chine
The United States Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) is a dynamic rainfall–runoff–subsurface runoff simulation model used for single-event to long-term (continuous) simulation of the surface/subsurface hydrology quantity and quality from primarily urban/suburban areas.
Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites that reduce the flow rate, total quantity, and pollutant load of runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas. Rain gardens rely on plants and natural or engineered soil medium to retain stormwater and increase the lag time of infiltration, while remediating and filtering pollutants carried by urban runoff. Rain gardens provide a method to reuse and optimize any rain that falls, reducing or avoiding the need for additional irrigation. A benefit of planting rain gardens is the consequential decrease in ambient air and water temperature, a mitigation that is especially effective in urban areas containing an abundance of impervious surfaces that absorb heat in a phenomenon known as the heat-island effect.
Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in preventing water pollution, soil loss, wildlife habitat loss and human property loss.
In hillslope geomorphology, a rill is a shallow channel cut into soil by the erosive action of flowing surface water. Similar but smaller incised channels are known as microrills; larger incised channels are known as gullies.
Surface runoff is the unconfined flow of water over the ground surface, in contrast to channel runoff. It occurs when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the soil is saturated by water to its full capacity, and the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because impervious areas do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or human-made processes.
Runoff is the flow of water across the earth, and is a major component in the hydrological cycle. Runoff that flows over land before reaching a watercourse is referred to as surface runoff or overland flow. Once in a watercourse, runoff is referred to as streamflow, channel runoff, or river runoff. Urban runoff is surface runoff created by urbanization.
A buffer strip is an area of land maintained in permanent vegetation that helps to control air quality, soil quality, and water quality, along with other environmental problems, dealing primarily on land that is used in agriculture. Buffer strips trap sediment, and enhance filtration of nutrients and pesticides by slowing down surface runoff that could enter the local surface waters. The root systems of the planted vegetation in these buffers hold soil particles together which alleviate the soil of wind erosion and stabilize stream banks providing protection against substantial erosion and landslides. Farmers can also use buffer strips to square up existing crop fields to provide safety for equipment while also farming more efficiently.
Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces are constructed during land development. During rain, storms, and other precipitation events, these surfaces, along with rooftops, carry polluted stormwater to storm drains, instead of allowing the water to percolate through soil. This causes lowering of the water table and flooding since the amount of water that remains on the surface is greater. Most municipal storm sewer systems discharge untreated stormwater to streams, rivers, and bays. This excess water can also make its way into people's properties through basement backups and seepage through building wall and floors.
A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. Check dams themselves are not a type of new technology; rather, they are an ancient technique dating from the second century AD. Check dams are typically, though not always, implemented in a system of several dams situated at regular intervals across the area of interest.
Batavia Kill is a 21-mile-long (34 km) tributary of Schoharie Creek, that flows across the towns of Windham, Ashland and Prattsville in the U.S. state of New York. Its waters reach the Hudson River via Schoharie Creek and the Mohawk River. Since it drains into the Schoharie upstream of Schoharie Reservoir, it is part of the New York City water supply system. From the source to Maplecrest, Batavia Kill drains the northern slopes of the Blackhead Mountains, which include Thomas Cole Mountain, Black Dome, and Blackhead Mountain, the fourth-, third-, and fifth-highest peaks in the Catskills, respectively.
Nigeria Erosion and Watershed Management Project (NEWMAP) is a World Bank assisted project aimed at addressing the Nigerian gully erosion crisis in Southeastern Nigeria and land degradation in Northern Nigeria on a multi-dimensional scale. This project was born out of the request for assistance made by President Goodluck Ebele Jonathan to World Bank in 2010. He requested for assistance in tackling severe gully erosion in Southern Nigeria, land degradation in Northern Nigeria and environmental insecurity. The project is being monitored by the Federal Ministry of Environment. Some aspects of the project includes erosion and watershed management infrastructure investments, erosion and watershed management institutions and information services and climate change response.
The May Be’ati is a river of the Nile basin. Rising in the mountains of Dogu’a Tembien in northern Ethiopia, it flows southward to empty finally in the Giba and Tekezé River.
Agro-Climatic Resilience in Semi-Arid Landscapes (ACReSAL) is a six-year project funded by the World Bank, aimed at restoring degraded landscapes in Northern Nigeria. The region is marked by significant challenges, including high poverty rates, low literacy levels, and an environment of fragility, conflict, and violence. The degradation of natural resources, poor agricultural productivity, and climate risks like desertification further complicate the situation. Additionally, the area suffers from poor penetration of modern technology and weak institutional capacity.
