Erosion is the process by which soil and rock are removed from the Earth's surface by exogenic processes such as

wind or water flow, and then transported and deposited in other locations.

Sheet and channel erosion refer notes

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, and/or by the force of gravity acting on the particle

itself.

Blowouts are sandy depressions in a sand dune ecosystem (psammosere) caused by the removal of sediments

by wind. Blowouts occur in partially vegetated dune fields or sand hills. A blowout forms when a patch of protective

vegetation is lost, allowing strong winds to "blow out" sand and form a depression. Although they generally remain

small, blowouts can expand to kilometers in size and up to around 70m in depth

Gully erosion occurs when runoff water accumulates and rapidly flows in narrow channels during or immediately

after heavy rains or melting snow, removing soil to a considerable depth.

Aeolian processes, also spelled, eolian or æolian, pertain to wind activity in the study of geology and weather, and

specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and

deposit materials, and are effective agents in regions with sparse vegetation and a large supply of

unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are

important in arid environments such as deserts.

Wind erosion is the detachment, transportation, and deposition of loose topsoil or sand by the action wind. Wind

erodes the Earth's surface by deflation, turbulent eddy action and by abrasion. Wind erosion occurs mainly in desert

regions.

Sand blow from the crest of dunes in deserts,

Dust Storm

Case Study

Asian Dust (also yellow dust, yellow sand, yellow wind or China dust storms) is a seasonal meteorological

phenomenon which affects much of East Asia sporadically during the springtime months. The dust originates in the

deserts of Mongolia, northern China and Kazakhstan where high-speed surface winds and intense dust storms kick

up dense clouds of fine, dry soil particles. These clouds are then carried eastward by prevailing winds and pass over

China, North and South Korea, and Japan, as well as parts of the Russian Far East. Sometimes, the airborne

particulates are carried much further, in significant concentrations which affect air quality as far east as the United

States.

Sulfur (an acid rain component), soot, ash, carbon monoxide, and other toxic pollutants including heavy metals

(such as mercury, cadmium, chromium, arsenic, lead, zinc, copper) and other carcinogens, often accompany the dust

storms, as well as viruses, bacteria, fungi, pesticides, antibiotics, asbestos, herbicides, plastic ingredients,

combustion products as well as hormone mimicking phthalates. Though scientists have known that intercontinental

dust plumes can ferry bacteria and viruses.

Areas affected by the dust experience decreased visibility and the dust is known to cause a variety of health

problems, not limited to sore throat and asthma in otherwise healthy people

Although sand itself is not necessarily harmful to soil, due to sulphur emissions and the resulting acid rain, the

storms also destroy farmland by degrading the soil, and deposits of ash and soot and heavy metals as well as

potentially dangerous bio matter blanket the ground with contaminants including croplands, surface water, etc. The

dust storms also affect wildlife particularly hard, destroying crops, habitat, and toxic metals interfering

with reproduction.

An analysis of Asian Dust clouds conducted in China in 2001 showed them to contain high concentrations

of silicon (24–32%), aluminum (5.9–7.4%), calcium (6.2–12%), and iron, numerous toxic substances were also

present, although it is thought that heavier materials (such as poisonous mercury and cadmium from coal burning)

settle out of the clouds closer to the origin.

Sediment yield

The sediment produced by sheet erosion from a catchment may not always reach the point of measurement; ie. The

site of dam reservoir. Some part of the sediment may be deposited en-route. The ratio between the yield of sediment

at the measuring site and the gross erosion in the catchment is called the sediment delivery ratio.

Thus the sediment yield is the gross sediment yield minus the quantity of sediment deposited en – route. The

sediment yield, in fact, is important, since it is this sediment which will get deposited in the reservoir, affecting the

useful life.

Sediment yield of a reservoir can be estimated either by using appropriate empirical equation or by developing a

rational appropriate relation between inflow and sediment, on the basis of actual measurements of sediment load at

the site of the reservoir.

Sediment delivery ratio

Percentage between the sediment transported by a river and the total quantity of erosion material in movement, both

relative to the drainage area at one particular section. Accounts for deposition along the path from the sediment

source to the watershed outlet:

Buffers

Waterways

Ponds/Lakes/Wetlands

Fencerows

Water Sediment Control Basins

Terraces

Dry mass of sediment

Sediment load in ppm = ------------------------------------------------------------------------------------------- X 106

Total mass of original sample including the mass of sediment and water

Refer mathematical equation for sediment rating in the following images and also practice the example from both

image and notes.