Sedimentation Problems in Rivers
Sediments are said to be solid organic or mineral materials suspended in bodies of water and are transported or moved from its original site or location on the surface of the earth. Oftentimes, sediments are referred to as soil material. However, it can also take the form of other materials, such as by-products from different manufacturing processes (Robertson and Pierce 1997). Although sediments are being carried away by different agents, such as water, wind, ice, and gravity, the main agent for the transport of sediments to different bodies of water, is through water erosion. In relation to this, this particular essay regards water erosion, through river current and movement as the primary agent of sedimentation, leading to different problems.
It has been reported that rivers are arteries for the transport and storage of physically and chemically weathered material from continents, through estuaries, and ultimately to oceans, thus, playing major roles in the Earth’s biogeochemical cycling of materials, and influence the climate of the Earth. River forms river systems that are not country-selective, thus cross international boundaries. This then raises important issues in relation to sediment transport and deposition in rivers, particularly with respect to contamination, erosion and flooding (Perry and Taylor 2007). One of the problems that sedimentation causes rivers to experience is the change in its current or flow, due to the change in soil deposition at the bottom of the river. It has been indicated that both coarse and fine material is being transported downstream and eventually deposited as bars or over bank units on lower elevation terraces, thus, can result in sediment transport that largely affects river channel geometry (Perry and Taylor 2007). The change in the river channel geometry changes the current and the flow of the river, which may affect the differences in the depth of rivers over time. In this regard, the change in the depth and the flow or current of the water in the river may contribute to flooding of banks and low-lands, leading to devastation, massive flooding, landslides, and erosion.
Increase in the sedimentation of rivers also leads to changes in the pH, temperature, colour, sunlight penetration, mineral content, and oxygen content of the water in the river. The changes in such factors may deliberately and drastically affect the biological systems of the different organisms living in the river, such as fishes, micro organisms, and plants. Because such factors are important to the growth of such organisms, the increase in the sedimentation of rivers due to natural and man-made activities may significantly affect the flora and fauna living in the water system. In addition, the increase in the turbidity and water quality can be affected by the increased loads of nutrients and toxic substances attached to the different sediment particles (Parks Flora and Fauna Division 2001). As such, the death of the organisms may be the result. In relation to this, the change in water quality in the river due to increase in sedimentation has significant physical, physiological, and behavioural effects on fishes. Sediments are harmful to the gills of fishes, clogging gill mucus and causing asphyxiation. Fishes can also swallow and take in large quantities of sediments, thus, causing them to get ill, reduce growth, and eventually die. Increase in sediments also reduces the visibility of fishes to see prey in the water, thus, preventing them to hunt and feed. It also changes the habitat diversity in the river, smothering whole stream beds and reduces its variation of habitats and flows. Aside from fishes, invertebrates and other micro organisms are also affected with the increase in sediments in the river. Some invertebrates obtain their food through filtering the silt from the environment. The increase in sediments may clog their filtering mechanisms with more silt, thus, leading to its ineffectiveness. While some invertebrates use hooks for attachment to surfaces under the river, such mechanisms will be ineffective with the increase in sediments found in river surfaces. Plants are also affected with the increase in sediments in rivers. This is because the increase in the turbidity in the water affects the growth of aquatic plants. Silt in the water lessens light penetration for aquatic plants to use for photosynthesis and growth, while deposited sediments can smother plants living at the bottom of the river. Moreover, the increase of sediments, such as from agricultural, sewage and some industrial processes runoff can also lead to increased amounts of nitrates and phosphates in the water. This leads to changes in the pH and temperature of the water, thus, resulting to algae and weed blooms that affects the growth of aquatic plants in the river (Parks Flora and Fauna Division 2001).
Furthermore, larger organisms that live and drink water from the rivers are also affected. Larger animals, such as bears, wolves, foxes, and other four-legged creatures that drink water from the river may also get infected by the sediments in the water. Thus, this may cause fatal illnesses and other medical conditions that would lead to abnormalities, changes in behaviour, and changes in biological, physical, and psychological compositions. In this sense, the species of such larger animals may be significantly affected and decreased. Aside from such animals, humans can be possibly infected by the increase in sediments in rivers. As mentioned, the increase in sediments in rivers contributes to the changes in depth and current of the river. In this sense, during strong rains or storms, humans can be affected, as changes in flow and depth of rivers may lead to increase in flood flows to low-lands, thus, submerging cities and towns. In addition to this is the possibility of increased water pollution, which mobilizes and contaminates the sediments from the river to the water resources used by humans for consumption. Because some cities and towns do not have advanced and developed technologies for processing their water resources, their susceptibility for increased risk for infections may be higher than individuals having more sophisticated water systems. This endangers the lives of such communities, particularly children and infants drinking contaminated water.
In this sense, it can be understood that the increase in sediments in the river and other water systems does not only affect the river itself, but all the organisms in and out of it. As such, the problems mentioned in this essay, and other problems that have not been identified must be provided with immediate solutions and actions in order not to produce more complicated and hard-to-solve problems in the future.
References
Parks Flora and Fauna Division 2001, ‘Freshwater Ecosystems Biodiversity Management Issues: Sedimentation of Rivers and Streams’, Flora and Fauna Statewide Programs, pp. 1-4.
Perry, C and Taylor, K 2007, Environmental Sedimentology, Blackwell Publishing Ltd, Oxford, UK.
Robertson, LS and Pierce, FJ 1997, ‘Understanding sediments: problems and solutions’, Michigan State University Extension, viewed 13 May 2008, <http://web1.msue.msu.edu/waterqual/docs/wq08p1.html>.
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