Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, what recent discussions his Department has had with the Environment Agency on trends in the level of (a) dredging and (b) desilting as a means of flood prevention.

Ministers and Defra officials regularly meet with the Environment Agency to discuss flood and water management issues, including dredging.

The Environment Agency assesses each situation individually and dredge when it is the right solution, and it provides long-term value for money. Understanding where it will, and will not, reduce flood risk is key.

Where there is evidence that dredging will reduce flood risk to local properties or agricultural land without increasing flooding downstream, it meets government criteria, and is cost effective, the Environment Agency will do it.

Dredging can contribute to reducing flooding in some locations, but in others dredging would be an extremely inefficient and ineffective way to manage flood risk, as the natural processes in many rivers can cause the silt to return and accumulate in the same places very quickly. We also know from historic records and modelling that dredging in some locations can increase erosion and flood risk for communities downstream.

In extreme flooding events, the relatively small increases in width and depth achievable by dredging the channel do not provide anywhere near enough capacity to contain the excess flood water, since the channel may already be full of water, and therefore does not prevent flooding.

Any structures encroaching in the river such as bridges, weirs and natural features need to be considered, as these could be damaged or may be pinch points with hard foundations which can make dredging ineffective. Deepening can in some instances also cause destabilising of natural riverbanks leading to soil erosion and damage to riverside flood defences.