Introduction to River EngineeringArticles > Introduction to River Engineering
The action of Rivers:
The flow of a river brings many positive as well as negative changes to the landscape. The rivers or streams transport sediments and gravels from one location to another. We should also need to know that as a river flows and erodes sediment, gravels, and silt, which changes the shape of the course of the river. The process of erosion always has been and still is, a natural part of the rock cycle. Without erosion, the existence of sediments and the formation of sedimentary rocks will be impossible. Erosion detaches the loose, unconsolidated soil and sediment from over the bedrock.
Streams and rivers weather, erode, and transport sediment coming across their course of flow. They erode bedrock and sediment from one part of the landscape and deposit these sediments and particles at another place. The flowing water in rivers and streams is one of the major agents in eroding the surface of the bedrock and sediments from over the bottom of the river/stream. As a result of erosion, the rivers and streams reshape their course of flow. These changes can be positive and beneficial for mankind, as well as negative. The negative change includes flooding, land-sliding, excessive erosion, excessive deposition, and wearing and tearing of the adjacent landscapes, and geological features. Rivers and streams create many practical challenges for civil engineers, some of which are as follows.
The need for River Engineering:
- Construction of bridges is the need for carrying the rail-tracks and road across the rivers.
- Hydroelectricity can be generated by utilizing the hydropower of flowing water.
- In order to meet the need the irrigation and protection from floods, dams on the river are inevitable. One of the prime objectives of the construction of the dams is to control the floods.
- By regulating the river channels the objective of navigation and flood control can be achieved.
- Sand, sediments, and gravels are deposited by the rivers in depositional landform, which are used as a fundamental construction material for roads, buildings, and other types of infrastructure.
- River deposits reduce the storing capacity and life of the artificial reservoirs, which is a point of concern for the engineers.
River Engineering is the process of deliberate human interference in the course, action, or flow of a river with an objective to bring some change in the action of the river and get benefits from it. Man has intervened in the natural flow and action of rivers since long before the recorded history in order to manage and utilize the water resources, to protect him against flooding, or to make passage along or across the rivers easier. From ancient Roman times, rivers and streams have been used as a big source of hydropower. Although at the time people were unaware of electricity and its generation, however, hydropower of the flowing water of the rivers and streams was used to run turbines to grind the flour, pump up the water, and lift other masses. Since the end of the 20th century, river engineering has had more environmental problems than immediate human benefit and some river engineering projects have been concerned only with the restoration or protection of natural features and habitats. There are two major concerns of engineers associated with the behavior and action of the rivers. (i) Flood Control, and (ii) River Training.
(1). Flood Control:
During floods, the rivers cause the destruction of life and property, and therefore, flood control is a very important problem for a civil engineer. The various methods which are used to control floods are as follows:
- Construction of Levees. The levees are longitudinal embankments that are built along the river banks to check the overflow of the excess water during floods. The levees not only confine the river water into its channel but they also increase bed erosion and keep the channel clean.
- Dredging: It is the process of removing the sediment deposited at the bottom of the river channel. Dredging is a costly affair as it has to be carried out all the time.
- Construction of Check Dams: The Construction of check dams for controlling floods is a very useful method. The check dams are usually built on small tributary streams that regulate the flow of the main river.
- Diversion of River Water: During floods, a part of the river water is diverted and made to flow through a newly constructed channel. Thus the river water gets divided and the effect of flood reduces.
- Shortening Course of Meandering Rivers: In meandering rivers, artificial cut-offs are made to straighten the course of the river/ stream. This tool increases the efficiency of the river.
(2). River Training:
The river training is mainly connected with the improvement of the river channel for navigation. The various river training measures are as follows.
- Dredging is done to remove sand, mud, and silt from the bottom of the river. Another objective of the dredging is to deepen the deck of the river to accommodate much water. The large deck of the river will prevent the overflow of the water beyond the banks of the river. Dredging also saves the cost of levees. The dredged material can be deposited along the river banks.
- Training walls are constructed which restrict the flow of the water to a given channel. It enhances the scouring effect of the water currents and keeps the channel clean.
- Low groyens are constructed in the course of the river in order to check the erosion caused by the flow of the river at a steep surface.
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