There are a few things that I feel I need to clarify. We will never stop all flooding, particularly under extreme
conditions such as we have seen recently, and we must expect to make changes to adapt should these weather patterns persist. Also a great deal of expertise is used to ensure that decisions are made that have the least impact on local people and businesses, and that also meet the requirements of the range of current legislation, much of which acknowledges the importance of river health for provision of clean drinking water and other human benefits. I think it is time we had some faith in the experts we employ, and accept the fact that these conditions are unprecedented.
In some places man made defences are the only solution to local flood issues, but we need to think about the wider landscape when we consider flooding. It is the speed of water flowing across saturated ground to the river that is helping to cause the deluge, and by the time it gets to the river channel it is often too late to sufficiently reduce the speed of flow. It seems intuitive that increasing the capacity of the channel through dredging will allow more water to pass through it, and in some cases this may well be the best approach. Under extreme events however these deep linear channels can help to speed up the flow of water, and on reaching flatter areas, or pinch points along the river it spills out onto the floodplain. This is characterised by rivers that react very quickly under rainfall showing a rapid rise and fall in water levels. Added to this dredging can reduce natural riverside vegetation and trees and help to increase erosion. Bare and steep banks increase erosion and banks are easily scoured by the river, which carries soil downstream to lower lying land where it accumulates increasing issues with flooding. Indeed that is how these wide floodplains are created, through gradual deposition of silt over time, creating deep and fertile soils which is why they are used for farming. Soil is also picked up from the land and taken downstream via surface water flow. Dredging also reduces the amount of river habitats present - a healthy river should have a range of
different habitats along the banks and in the channel alive with insects, birds and fish, not a uniform and steep sided cutting. A useful document about dredging has been produced by the Chartered Institution of Water and Environmental Management - click HERE.
There are many ways that we can naturally reduce the amount of sediment that travels downstream, and in the Ouse (of which the Uck is part) South East Water are investigating ways that we can practically do this through their Ouse Upstream Thinking project. Like TrUck this project uses a natural approach to reduce these issues.
Trees also have an important role to play in reducing soil erosion. Traditionally bankside trees were pollarded or coppiced to extend their lifespan, and their ability to hold riverbanks together and reduce soil erosion. We have witnessed a rapid decline in riverside trees in the Uck catchment, as now mature and weighty unmanaged coppice stools fall into the river, with their roots unable to take the weight of the tree, particularly under a constant rise and fall in water levels. We are planting new bankside trees all over the catchment to restock for these losses, and are promoting pollarding and coppicing where possible. Widespread application of this approach would help to reduce bank erosion and siltation throughout the river network. Woodlands and hedgerows also prevent movement of soil across the land in surface water flow, especially downhill from areas of arable crops or pasture.
Hopefully we will soon see the waters recede, and things return to normal. As I write problems with ground water flooding (the likes of which I have never seen) are still creating problems, in spite of a break in the relentless wet weather.
We will continue to work towards our natural approach, and implement changes where possible. Time is of the essence with projects such as TrUck, particularly as the woodlands, trees and hedgerows we plant now will take some time to grow and significantly slow the flow. Our funding period is also coming to end, so fingers crossed this increased media interest will encourage further investment in projects such as ours. Slowing water travelling across the land can be easily and cheaply achieved, with benefits for soils and wildlife. There is now a broad base of research that shows us how, and it is time for us to get planting.
Please contact us if you would like further information about our project or approach.