River Engineering A Great Step for River Conservation -Zannatul Mouwa Naz

Engineering works are often required where roads, railways, tracks, pipelines, cables and buildings such as rivers and their floodplains communicate with infrastructure flood wall embankments, bank protection, dams and wires, channel retainment’s, dredging, bridges, culverts and low flow disconnections. Flood risk reduction, swarming or erosion mitigation, water release, general management of fisheries, large scale infrastructure projects, land management and ecological recovery or habitat enhancement.

While such works can certainly provide effective results, there is a growing need that they be sustainable in the long run and sensitive to the natural environment. These objectives are best achieved by working with natural river processes, looking for solutions aimed at reproducing or restoring the natural form and function of stable channel-floodplain systems. Regulatory bodies place this approach at the center of decision-making.
River mechanics and engineering: It has a thorough background in the basic principles of river mechanics by understanding the natural processes that manage water or sediment in river systems and complex river systems. Planning and design application for various river engineering structures to improve natural river conditions including training work, stabilization, bank recognition, dredging, diversions, cofferdams, channelization, and flood control works. To rehabilitation projects and river and wetland management, geological science bridges the gap between hydraulic engineering and ecosystem management. Considering the physical processes that naturally shape channels and wetlands in natural tidal and non-tidal environments.
Our expertise in river engineering includes:
l Watercourse rehabilitation and naturalization
l River bank protection
l Hydraulic control structures
l Hydro-generation
l River walls and quays
l Navigation and canal engineering
l Ecological enhancement
l Geomorphology and water quality
l Assessments in accordance with Water Framework Directive (WFD)
l Consents, licenses and approvals
River control by hard engineering: Multi-purpose dams are often built across the channel to conserve water and control river discharge. The reservoir upstream of the dam is conserved and released in a controlled manner. This protects the climate from potential flooding. Large dam projects are used for clean hydroelectric power, for large-scale irrigation projects, and for strategies that open up the interior of countries for transportation and trade.
Channelization is a deliberate attempt to change the natural geometry of a river. Channelization can be achieved in a variety of ways. The river can be deepened and widened to increase the capacity of the channel. This increases its hydraulic efficiency and allows for greater discharge to be included in the channel. This will help prevent floods. The channel can be further straightened by the use of artificial cut-off. The channel can be implemented to artificially increase the long profile gradient so that the velocity increases and flood water is removed more quickly, which speeds up the flow and aids in navigation. Channelization is often achieved by banks and beds through concrete lining. It prevents bed or bank erosion.

Dredging: River excavation is the process by which the bed load is removed from the river channel. This is achieved through heavy industrial pumps and excavators or through the eyelids at the foot of the river which encourages the flow of the river. The purpose of the river is to increase cross-sectional area and increase capacity and hydraulic efficiency to reduce channel roughness. The advantage of using dredging is that it maintains the natural aesthetics of the river bank. However, it is an expensive and time-consuming process that is only suitable for a small part of the river, for example, near or within the city environment. Also, the process has a high environmental impact on natural ecology.

Soft engineering or bank protection: The purpose of bank protection is to help prevent bank losses. This can be achieved through the provision of bank assistance. There are different methods. Stone wire cages allow gabions to look soft. If used in the right way, they can also encourage deposition near banks, which produce deposition and coastal vegetation over time. The fine is made towards the title of the grain. Over time, riparian plants will develop. Even a softer approach is to plant bank trees or allow the plant to grow. This is achieved simply by not cutting it back. It will have different consequences according to the goal. Planting trees along the edges provides greater durability and can reduce erosion. However, allowing the plant to recover in a controlled manner may actually encourage greater channel roughness and reduced migration. Combined with floodplain drainage breakage will increase the water table and increase the likelihood of flooding. In contrast plant clearance reduces channel roughness, discourages bank surveys, and increases river hydraulic efficiency.

Floodplain restoration: Increasingly, sewage basin managers are realizing the importance of floodplains for water conservation, discharge reduction, and efficient agricultural recycling efficiency. The process of river engineering for flood transfer and restoration of natural flood patterns is floodplain recovery. Floodplain recovery can be made in two main ways. First, both by removing river control controls as previously explained by breaking down floodplain drainage and encouraging shore vegetation. Second, and more generally it can be achieved through engineering.

River engineering method to managing saltwater intrusion: One of the keys to controlling saltwater intrusion is to maintain a proper balance between the amount of water pumped from the aquifer and the amount of recharging water. Continuous monitoring of the salt-water interface is required to determine proper management strategies. In the past, many communities that have had the problem of saltwater infiltration have simply installed new production wells inside new ones. In all these cases hydrological surveys and monitoring of water quality are necessary to better understand the movement and interaction of groundwater and salt water and to determine the best method of managing saline water infiltration. Potential groundwater mapping can provide important information by determining the direction of groundwater flow in a limited watershed. Plotting the water level height on a map and contouring the results determines this. The thin surface is known as the pentametric surface, which is actually the map of the hydraulic head in the aquifer.

Engineering works to increase the navigability of rivers can only be conveniently managed with moderate falls in the larger rivers and a suitable discharge at their lowest level, as the current flow with a large fall presents a great obstacle to up-stream navigation and there is usually great difference in water level and dryness. During the season when the discharge becomes very low. It is impossible to maintain sufficient depth of water in low-water channels.

The possibility of maintaining uniformity in the depths of a river by reducing the shoals that obstruct the channel depends on the nature of the shoals. A soft shoal in a river bed is produced by a decrease in the velocity of the flow, a decrease in the fall, and a decrease in the width of the channel, or by the decay of the density of the main stream, from one concave bank to the other. Reducing this type of shoal by submerging it depends only on the temporary depth, as soon it is recreated from its causes. However, the removal of rocky barriers on the rapids, although increasing the depth and equalizing the flow in these places, creates a river bed above the rapids to facilitate flow, resulting in the presence of fresh shawls at the bottom of the river bed. And the bed of the river can be improved permanently by enabling their removal by obstructing the erosion by the currents of soft material above and below, deepening its bed by the natural rush of the river.
The writer is an Executive Editor, The Environment Review.