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Drone researchers show extent of 'Desmond' floods

Wednesday 20 January 2016

THIS WINTER’s devastating floods were made much worse due the breakdown of the natural symbiosis of rivers and their floodplains, according to researchers from the University of Salford.

Rivers and floodplains “no longer function together” they conclude, and state that floodplains –the environment’s natural ‘sponge’ – are “probably the most degraded natural environment seen in Britain.”

Geographers from the 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.

Major changes

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.”

So-called natural flood risk management is now highly-advisable to reverse the trend and allow for a longer, slower release of flood water than we currently see during heavy rainfall, they said.

1 in 200 year event

The Carlisle flood followed a series of extreme rainfall events in the River Eden catchment, generating a flood peak that exceeded the 1 in 200 year flood event which exceeded the recently enhanced protection for the city. In its aftermath, Neil and George captured high definition footage from the unmanned aerial vehicle (UAV) revealing that the entire floodplain along the main river and tributaries was active during the event along over 60 km of surveyed watercourse.

In such extreme events, they say, even some natural flood management measures downstream would quickly become ineffective, and they called for all data collected by the authorities this winter to be made available to help learn the lessons.

Added Dr Entwistle: “We simply do not know how much land compaction has increased surface runoff, 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.”

The research – funded by School of Environment and Life Sciences, has been reported by BBC News, The Ecologist, The Conversation (link), AboutManchester, BBC Radio Cumbria, BBC Radio Lancashire and elsewhere.

For more information, please contact:

Dr Neil S. Entwistle BSc PhD PGCHE FHEA

Lecturer in Geography | Admissions tutor for Geography & Environmental Management | School of Environment & Life Sciences

Room 326, Peel Building, University of Salford, Salford M5 4WT

t: +44 (0) 161 295 3394 or 44 (0) 7736074485 @salfordhydro

n.s.entwistle@salford.ac.uk | www.salford.ac.uk