Slowing the Flow scheme reduced river flow by 15-20% during December

Slowing the Flow, a natural flood risk management scheme reduced river flow by 15-20% during the December floods.

A briefing note published yesterday (13 April) has revealed river peak flow was reduced by around 15-20% during the December floods, due to a pioneering natural flood risk management scheme.

The Slowing the Flow scheme protected the town of Pickering in Yorkshire, when a total of 50mm of rainfall fell over a 36-hour period over Christmas 2015.

The scheme, which uses methods that work with nature to hold water on the land and slow the speed at which it enters the river system, was set up after a series of floods hit Pickering over ten years, with floods in 2007 estimated to have caused damage of around £7M of damage.

Slowing the Flow combines conventional upstream flood storage with a wide range of measures including a flood storage reservoir, the planting of 40,000 trees, the restoration of the local heather moorland and over 300 leaky dams built in forest and moorland draining and streams in the upper catchment.

The new analysis, conducted by Slowing the Flow Partnership, concluded that the measures taken prevented the flooding of a number of homes and the town’s museum, by deducing the flood water between 15-20%.Based on the extent of inflows to the flood storage area, it is estimated that around half of the reduction was due to the upstream land management measures and half due to the flood storage area.

The investigation involved quantifying the volume of rain than fell during the Boxing Day event by analysing the records from local rain gauges, and determining if the amount of rainfall was sufficient to generate a flood by comparing this with other events in previous years.

John Curtin, Environment Agency Executive Director of Flood Risk Management, said: “Natural flood risk management measures when used alongside more traditional flood defences can make an effective contribution to reducing flood risk, as demonstrated in Pickering. They can also deliver more benefits than just reducing flood risk – such as improving water quality, preventing erosion and in some cases storing carbon.”

Jeremy Walker, ‘Slowing the Flow’ Partnership Chairman, said: “This is good news for the town, although we need to remember that the measures installed have their limits and would not be enough to prevent flooding in the event of rainfall on the scale experienced for example in 2007.”

 

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