The impact of floodplain degradation on flooding in the UK

A review of floodplain functioning in the north of England following the winter storms of 2015 was conducted \nusing high resolution aerial imagery of the events captured using drone and helicopter survey during and \nimmediately after the flooding. This revealed that for the most part 100% of the floodplain area was inundated. \nSediment left across floodplains from the 2015 flood events areas suggest high floodplain velocities (> 1.5 \nm/s). GIS analysis of land use mapping for valley bottom areas across England reveal part of the cause for \nthese unnaturally high velocities is the near complete loss of natural rough floodplain surfaces, having been \nreplaced by a hydraulically smoother managed arable/grassland mix. The review has revealed extensive and severe degradation of floodplain systems in England and it is highly likely that similar results would be found \nfor floodplains across the rest of the UK, both upland and lowland areas are equally impacted and the result is \nan almost complete loss of natural floodplain functioning. River restoration remains concentrated on in-channel \nactivity, however, the push for natural flood management offers an opportunity to restore our floodplains with an associated improvement in ecological value and flood driven functionality. The research presented here suggests that it is not lack of floodplain storage space in the upper catchment, rather the decreased efficiency of floodplain areas to retard flow which is leading to increased downstream flood risk. \nFloodplain reconnection, vegetative naturalization and selective grazing reduction are required to begin to \nrestore upstream floodplain flood function helping alleviate flooding pressure downstream.