Flood defences are only part of the answer. Design and drainage play their part, too.
What can be done to prevent floods causing such extensive damage next time there is heavy rain? Richard Gamble, the head of flood risk management at engineer Mott MacDonald, says protecting against recent levels of rainfall would be “very difficult and expensive”.
Deciding which communities get flood defences is based on an economic appraisal and the risk of flooding. Solutions include building walls along rivers. But Gamble believes these “tend to push the water elsewhere where it causes problems. If the walls break or it goes over the top it can be worse than having no defences at all”.
A better solution is to identify poor quality agricultural land upstream and allow this to act as a giant retention pond which should reduce the water level further downstream.
Dealing with flood risk in new developments is easier as this can be designed in. Designers must follow the planning policy PPS 25 – development and flood risk. This states that developments should only be built on flood plains if there is no alternative. Ideally buildings on flood plains should be raised up, or ground floors should be used for non-residential uses. They should also have sustainable drainage to prevent rainwater run-off affecting buildings downstream.
Thomas Lane is Building’s technical editor