Rivers disconnected from their floodplains could be having serious consequences for fish and other river life according to a new Environment Agency report.

Using state-of-the-art telemetric tagging systems the Environment Agency has investigated what happens to coarse fish like roach, chub and dace in floods and high river flows and found that the disconnection of rivers from their natural floodplains has serious consequences for aquatic life.

Dr Graeme Peirson, a senior fisheries scientist at the Environment Agency, said:

“Many lowland rivers in England and Wales have been physically separated from their natural floodplains by the construction of floodbanks to prevent flooding and enable development in agriculture and housing. Our research found that when extreme flooding, like that of summer 2007, occurs and floodbanks overtop, fish and other river life enter the nearby floodplain but can become stranded there when river water recedes.”

“The research also shows that this disconnection of river and floodplain can reduce the overall quality of river habitats, causing problems for spawning fish and juveniles.” 

The research team carried out field studies at three locations across England:

Work on the River Ouse in Yorkshire involved collecting young fish from the main river channel, backwaters and areas of water isolated from the main river channel behind floodbanks and using high definition sonar imaging to track their movements. In the summer many of the fish had become trapped in waterbodies created when floodbanks overtopped, and were unable to return to the main river channel.

In the River Roding in Essex, which has been re-stocked following a major pollution in 2003, researchers found that floodplains (both natural and man-made) were being used by a wide range of newly-stocked, hatchery-reared coarse fish as a safe refuge from floods and high river flows.

In the River Trent in Nottinghamshire a number of man-made floodplains showed very similar communities of fish to those found in natural floodplain systems – indicating the benefits of re-creating floodplains that are connected to the river system.
Dr Peirson continued: “The research shows that reconnection of rivers to their natural floodplains or to semi-natural floodplain waterbodies, and re-stocking in appropriate circumstances with farm-reared fish, are both important techniques in achieving a healthy ecosystem.”

“Reconnection of rivers to floodplains is not only good for fish and river life, but can also play a part in reducing flood risk. By allowing high flows from rivers to spill safely into what is a natural part of the river channel, it can help reduce the potential risk of river banks bursting further up stream.”

For more information about the Environment Agency’s fisheries work, visit www.environment-agency.gov.uk/fishing.