Soil Erosion by Water and Wind

Soil erosion is the detachment and transport of soil particles by water and wind, a natural process greatly accelerated by land use that strips fertile topsoil and degrades land.

Definition

Soil erosion is the process by which soil particles are detached from the soil mass and transported away by the energy of moving water or wind, encompassing detachment, transport, and eventual deposition of the eroded material.

Scope

This topic covers the mechanics of water erosion, including raindrop impact, sheet, rill, and gully erosion, and of wind erosion through saltation, suspension, and surface creep, the factors that govern erosion rates, and the distinction between natural geologic and accelerated human-induced erosion. It is the problem that soil conservation seeks to control.

Core questions

• How do raindrop impact and runoff detach and carry soil in water erosion?
• How does wind detach and transport soil by saltation, suspension, and creep?
• What factors control the rate of water and wind erosion?
• How does accelerated erosion differ from natural geologic erosion?

Key concepts

• Raindrop impact and splash erosion
• Sheet, rill, and gully erosion
• Wind erosion: saltation, suspension, creep
• Rainfall erosivity and soil erodibility
• Accelerated versus geologic erosion
• Sediment transport and deposition

Key theories

Erosion factors of the Universal Soil Loss Equation

Long-term water erosion is modelled as the product of rainfall erosivity, soil erodibility, slope length and steepness, cover and management, and support practices, identifying the controllable factors that determine soil loss.

Detachment and transport stages

Erosion proceeds through detachment of particles by raindrop impact or wind shear, transport by overland flow or moving air, and deposition where energy declines, so erosion intensity depends on both detaching and transporting capacity.

Mechanisms

In water erosion, raindrops striking bare soil detach particles and seal the surface, reducing infiltration and generating runoff that concentrates into rills and gullies, carrying detached soil downslope. In wind erosion, wind shear lifts fine particles into suspension and bounces sand-sized grains in saltation, which dislodge further particles and roll coarse grains by surface creep. Cover, surface roughness, soil structure, and moisture all reduce detachment and transport, while steep slopes, intense rain, strong wind, and bare, weakly aggregated soils increase them.

Clinical relevance

Accelerated erosion removes the fertile topsoil that took millennia to form far faster than it is replaced, lowering productivity and threatening agricultural sustainability, while the eroded sediment and attached nutrients and pollutants degrade rivers, reservoirs, and air quality.

History

The catastrophic wind erosion of the 1930s Dust Bowl in North America made soil erosion a recognized national problem and spurred the creation of soil conservation institutions. Mid-century research quantified water erosion through the Universal Soil Loss Equation, and later syntheses placed accelerated erosion in the context of long-term agricultural sustainability.

Key figures

• Hugh Hammond Bennett
• Walter H. Wischmeier
• David R. Montgomery

Seminal works

• wischmeier1978
• montgomery2007
• brady2016

Frequently asked questions

What is the difference between sheet, rill, and gully erosion?

Sheet erosion is the fairly uniform removal of a thin layer of soil by overland flow, rill erosion occurs when runoff concentrates into small channels that can be erased by tillage, and gully erosion forms larger, permanent channels too deep to cross with normal equipment; they represent increasing concentration of erosive runoff.

Why is erosion called a slow-motion disaster?

Because soil forms extremely slowly, often taking centuries to millennia to build a few centimetres, while accelerated erosion can remove it within years to decades; the loss is gradual and easy to overlook yet effectively permanent on human timescales.