This is done by restricting the progress of water through a catchment and relies on one, or a combination of four key mechanisms which work with the environment to provide a sustainable solution to the problem:
- Storing water such as ponds, ditches and field attenuation bunds.
- Increasing soil infiltration through the creation of ‘infiltration zones’ to help water get into the soil at certain locations, for example tree belts.
- Slowing water by increasing resistance to its flow, for example planting in the floodplain or riverside woodland.
- Redirecting the water by channelling it away from the main flow into temporary water storage areas or buffer zones to hold the water back until the flood peak drops or restoring river meanders. This increases the length of the river and decreases its slope, slowing down the flow.
Recently used in Pickering in 2015, it is estimated that the slow the flow measures coupled with an attenuation reservoir reduced the flood peak by around 15-20%.
Calder Valley Flood Studies Network
A very interesting website focusing on flood alleviation in the Calder Valley, West Yorkshire. This approach would help such places as Keswick & Derwent Catchment as well as other catchments in Cumbria, etc. 'Slowing the flow' measures are proven to be part of the mix of measures to help in flood alleviation, see also 'Pickering Project' & others similar