asked Her Majesty's Government:

What action they are taking to promote the (a) cleaning, and (b) dredging of river systems; and [HL679]

What assessment they have made of the effect of reducing, (a) cleaning and (b) dredging of river systems on (i) the water table and (ii) flood risk. [HL680]

Defra has funding and policy responsibilities but does not carry out works to reduce flood risk. The operating authorities (principally the Environment Agency) undertake prioritised programmes of maintenance work on watercourses, including cleaning and dredging where appropriate. Otherwise responsibility for clearance lies with the land owner.

Reducing maintenance on low-risk watercourses releases resources for the Environment Agency to use on high-risk watercourses in accordance with its risk-based approach to asset management.

The effect on low-risk watercourses will probably be increased weed growth and siltation which will reach a natural balance. This may result in an increase in flood risk along these watercourses, which is accepted as it is classified as low risk.

While it is important that all channels for flood water are kept free of debris and at their design profile, there is often a limit to the amount of dredging that can sensibly take place. Main rivers and other larger or more natural watercourses should not need dredging and normally establish stable regimes. On some rivers, too much dredging could cause the river banks or walls to collapse; likewise deepening a tidal river below its natural bed level will not normally reduce flood risks. Dredging can also cause significant disruption to the natural river environment.