This NBS focuses on the delivery additional ecological components within a hard/built engineering approach to water management. They aid the reduction in pluvial flood risk in urban areas and improve the quality of water within sewerage systems.
The main approaches and benefits of hard drainage flood prevention are:
- Hard-drainage flood prevention includes river engineering and dam construction to control the amount of discharge.
- Dams can be built to hold water back and release it in a controlled way. Water is held in a reservoir behind the dam, and can provide an additional use, such as hydroelectric power or recreation.
- The river channel may be widened or deepened allowing it to carry more water. A river channel may be straightened so that water can travel faster along the course. The channel course of the river can also be altered,diverting flood waters away from settlements.
Considerations in designing hard drainage flood prevention: the dam specifications need to consider sediment trapping behind the dam wall, which can lead to erosion downstream. In addition, altering the river channel may lead to a greater risk of flooding downstream, as the water is carried there faster.