Studies throw new light on the causes of the devastating December floods in Cumbria

Researchers at the University of Salford said the inundation was made much worse due the breakdown of the natural relationship between rivers and their floodplains; while academics at Lancaster University have warned that as a consequence of floods, losses of soil and nutrients on agricultural land in Cumbria could increase by an average of nine per cent by 2050.

Both research teams analysed the effects of Storm Desmond on Cumbria, with the Salford team sending up a drone over the River Eden valley to assess the floodplain impact.

They concluded that rivers and floodplains in Cumbria 'no longer function together' and the latter - the environment’s natural ‘sponge’ – were 'probably the most degraded natural environment seen in Britain'.

Geographers from Salford's School of Environment and Life Sciences found that unprecedented rainfall was only one of the factors that contributed to flood waves passing down rivers in Cumbria, and said that anthropogenic ‘tinkering’ with the hydrological functioning of river catchments had exacerbated the risk of downstream flooding in every catchment in Britain.

Dr Neil Entwistle and Dr George Heritage filmed in the Eden river catchment, in Cumbria during and after storm Desmond using ‘drones’ to highlight how the technology can quickly assess the potential role of upstream floodplain storage on the Eden and its tributaries.

Dr Entwistle said: “Efforts to drain valley farms and roads, and dredging and embanking of many watercourses helps contain flow within the river preventing floodplain flooding.

“This improved drainage of uplands means that precipitation is often concentrated into channel networks more quickly and flows downstream into main river valleys faster.

“Instead of water naturally inundating valley bottom areas, where it would pond and flow more slowly downstream, it is draining and flowing downstream much quicker on account of the vegetation being largely managed grassland.

“We simply do not know how much land compaction has increased surface run-off, how significant or even how extensive our surface and subsurface land drainage network is in relation to flood wave generation or just how dysfunctional our river-floodplain system is.

“The floods have left a vast amount of evidence and information regarding their generation and operation in the Eden and other catchments impacted by the recent flooding and we must act to capture these data before they are lost.”

In a new paper in the journal Science of the Total Environment, researchers from Lancaster University warned that losses that soil and nutrients could increase by an average of nine per cent by 2050, with some years washing off greater than 20 per cent more soil than the average year.

Professor Phil Haygarth of the Lancaster Environment Centre said: “There always has been, and always will be, large variability in the weather between years, but there is undoubtedly a trend towards warmer, wetter winters which could result in increased water pollution from agricultural land.”

Nutrients, such as phosphorus and nitrogen are essential to plant and animal growth, but too many nutrients cause excessive plant growth and algal blooms in rivers and lakes. These suffocate fish and other organisms and require costly remediation by water supply companies.

Fertilisers and manures washed off in storms are a major source of nutrients, with more than 60 per cent of the nitrogen and 25 per cent of the phosphorus in our rivers coming from agriculture.