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SEDIMENTATION IN ENVIRONMENT by Roberta Cunningham. Sedimentation. This is the deposition of sediments from a state of suspension or solution in a fluid . Formation of Sedimentation.
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Sedimentation • This is the deposition of sediments from a state of suspension or solution in a fluid .
Formation of Sedimentation • Rivers carry sediment down their riverbed, allowing for the formation of deposital features such as: river deltas,alluvial fans braided rivers, oxbox lake, levees and coastal shores • . The construction of a dam blocks the flow of sedimentdownstream, leading to downstream erosion of these sedimentary depositional environments, and increased sediment build-up in the reservoir.. • While the rate of sedimentation varies for each dam and each river, eventually all reservoirs develop a reduced water-storage capacity due to the exchange of storage space for sediment
Impacts of Agriculture on the Environment • Eutrophication: is defined as an increase in the rate of supply of organic matter in an ecosystem.” - Nixon, 1995
Biocide Leaching • In agriculture, leaching refers to the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.Leaching may also refer to the practice of applying a small amount of excess irrigation where the water has a high salt content to avoid salts from building up in the soil .Where this is practiced, drainage This is usually employed to carry away the excess water.
Erosion • : Permeability is a physical characteristic of a soil and is a measure of the ability of the soil to pass water, under saturated conditions, through the natural voids that exist in the soil. Permeability is a function of soil texture, mineral and organic composition, etc.. In contrast, "porosity" is the measure of the amount of void space in a soil; however, permeability refers to the extent to which the porosity is made up of interconnecting voids that allow water to pass through the soil. As an example, styrofoam is highly porous but impermeable, whereas a sponge is both porous and permeable.
SEDIMENT AND DESTRUCTION OF CORAL REEFS • : Sediment has been identified as a major cause of decline • and destruction of coral reefs, world wide. Experts (M. Risk, pers. comm., 1995) estimate that percentages of reefs affected by siltation are: • Central America - 100%Polynesia - 10%Asia - nearly 100%Worldwide - 60-70% of fringing reefs • Studies of coral reefs in the Australia indicate that terrestrial particulate organic carbon can be transported off-shore over distances of 110 km to reef locations (Risk et al., 1994). Sediment is largely produced by agricultural activities and from erosion of deforested lands. Sediment production from intensive logging of the island of Madagascar have killed the fringing reefs. Observations from space described the transition of Madagascar from an island of green in a sea of blue, to an island of brown in a sea of red (sediment).
Loss of Biodiversity • Organic chemicals associated with sediment enter into the food chain in a variety of ways. Sediment is directly ingested by fish however, more commonly, fine sediment (especially the carbon fraction) is the food supply for benthic (bottom dwelling) organisms which, in turn, are the food source for high organisms. • Ultimately, toxic compounds bioaccumulate in fish and other top predators. In this way, pesticides that are transported off the land as part of the runoff and erosion process, accumulate in top predators including man.
