River management: the pros and cons of hard engineering

 In order to control the hazard of flooding that rivers can create, some people decide to build artificial structures that usually require machinery, to prevent a river from flooding. These structures belong to a technique called hard engineering.

Dams

This type of hard engineering involves a large barrier being built across a river at a certain point to block the rivers flow down stream. this causes water to build up behind the dam creating an artificial lake or a reservoir. this stops the majority of the river’s discharge from flowing downstream and allows the river’s discharge to be managed and monitored.

The Avon dam in South Dartmoor (photo credit belongs to Wikimedia.org)

Dams are very effective in terms of preventing flooding. also, some dams can be used to create hydroelectric power. this creates a renewable energy source for the local area, attracting businesses, creating jobs and reducing energy prices for local residents. dams create a source of water which can provide for the surrounding area’s needs. The reservoir also attracts tourists interested in leisure activities such as fishing, sailing and walking.

There are also some huge problems with dams though. they are one of the most expensive hard engineering techniques, they can cost anything between £50 and £800 million. also, they can have a large impact on the natural landscape and the environment as a whole catchment of a river is destroyed, resulting in the loss of habitats for many natural species and will also force people out of their homes and jobs as the are to be flooded often includes small rural communities and farms. Dams can also trap sediment which can change the chemical composition of the water killing some aquatic species upstream. Also we mustn’t forget that dams are holding back thousands of litres of water and if they were to fail then they would cause massive amounts of devastation and death.

Artificial Levees

these are similar to natural levees but are built of concrete which reduces the risk of erosion. these increase the height of the river channel, allowing the river to have a larger discharge, therefore reducing the chances of flooding.

Levees allow construction on a floodplain and protect important agricultural areas from flooding. they are also cheap to build.

However, levees can increase the damage caused by flooding as they encourage building on floodplains. also, if the levee is breached then the damage to property and lives can be greater than flooding that occurs without a levee in place.

channel straightening

This involves cutting off meanders in rivers , making the river straighter and increasing the velocity of the river. A river with a faster flow will not be as likely to flood as the water will move through the channel quicker and will not build up in areas of a slower velocity, reducing the risk of flooding.

This technique therefore can reduce flooding in the area around the straightened channel. It can also make a river more navigable.

However, channel straightening can cause more flooding downstream because more water will reach a meander downstream, due to the faster velocity, and this will cause the water to back up and lead to flooding.

Source

• information on hard engineering technique of flood prevention sourced from: http://geographyas.info/rivers/flood-management/