Managing Flooding - Hard Engineering
Geography: Cambridge International GCSE (2027 Exams), topic 2.3.2
Flood Defences - Hard Engineering
Hard engineering strategies aim to reduce the effects of flooding by building man-made constructions that control a river's flow. Examples of hard engineering strategies include:
Dams and reservoirs
- A dam is a large earth, stone or concrete wall built across a river in the upper course. Behind the dam, a reservoir (man-made lake) forms.
- Reservoirs can reduce flooding risk by filling up with water when there is a lot of rainfall. This water can either be drunk or used to produce energy (hydroelectric power).
- But, dams are expensive and habitats and towns can be destroyed by the flooding needed to create a reservoir.
- The soil downstream from a reservoir usually loses some of its fertility because minerals are deposited in the reservoir instead of downstream.
Channel straightening
- Bends and meanders are removed by constructing man-made, straight channels connecting the meanders.
- Straight channels reduce flood risk by keeping the water flowing through an area quickly.
- But, downstream areas are more at risk of flooding and erosion because more water flows there more quickly.
Embankments
- Embankments are walls built either side of the river channel to raise the height of the banks.
- Embankments reduce flooding risk by increasing the capacity of the river.
- But, embankments are expensive to build and if the banks do burst, then flooding can still happen.
Flood relief channels
- Flood relief channels are secondary channels built alongside rivers that divert water away from particular areas or take it somewhere else if there is too much rainfall.
- The amount of water flowing through a given point in a river is reduced (river discharge falls).
- But, the river discharge will increase at the junction between the relief channel and the river it links up with.
Test yourself on Managing Flooding - Hard Engineering
What do we call a large wall built across a river in the upper course?
With channel straightening, which areas are more at risk of flooding?