The management of the flood hazard of the River Derwent

Within weeks of the floods in November 2009, the Environment Agency had published an updated Flood Management Plan for the River Derwent. Although it outlined the need for some small scale hard engineering strategies, the overall preference was for soft engineering approaches to flood defence in the area. Some of these are outlined in this presentation. Use it to make notes onto your diagram in your handout. C. Hard & soft engineering strategies to reduce the impact of flooding

i. Hard Engineering Where there already are existing properties close to the river, it is recognised that small scale hard engineering defences are required, for example at Cockermouth: Maintain the existing flood walls & flood gate – without these a further 119 properties would be at risk. In total, the Derwent has over 49km of flood walls. Cockermouth North

A section of the flood wall at Cockermouth. If the discharge were to rise, the flood wall could act to keep the water in the channel and away from the buildings.

The flood gate at the footbridge in Cockermouth. This gate can be closed during very high discharge to keep the water in the channel and prevent flooding.

i. Hard Engineering Where there already are existing properties close to the river, it is recognised that small scale hard engineering defences are required, for example at Cockermouth: Maintain the existing flood walls & flood gate – without these a further 119 properties would be at risk. In total, the Derwent has over 49km of flood walls. Cockermouth North Continue to dredge the channel in Cockermouth itself to keep it clear and free-flowing.

ii. Soft Engineering The preference will be for soft engineering strategies, however, as these are more sustainable. Use land use zoning to ensure new development does not occur in areas of high flood risk, for example to the west of the hospital. Cockermouth North

Building should be restricted in the area to the west of the hospital. This is a map produced by the Environment Agency showing areas at risk of flooding.

ii. Soft Engineering Use land use zoning to ensure new development does not occur in areas of high flood risk. Cockermouth North In the upper course, near Bassenthwaite Lake , flood defences for farmland should be removed to create safe flood zones on the floodplain around the Lake. Bassenthwaite Lake This will also help reduce the pollutants reaching Bassenthwaite, which is an SSSI.

The rapid overland flow from the Cumbrian Mountains can be allowed to be stored on the floodplain around Bassenthwaite Lake, reducing the discharge moving downstream towards Cockermouth.

The management of the flood hazard of the River Derwent

by A Hamill

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The management of the flood hazard of the River Derwent Presentation Transcript