ENVIRONMENT chiefs have revealed details of how they plan to tackle growing flood risks along York’s River Foss during the 21st century.

As climate change threatens to bring even heavier rain and worse flooding than in the disaster of December 2015, the Environment Agency has been working out how to slow the flow of the river before it reaches York.

The ideas in its ‘Slowing the Flow’ study follow the pioneering lead set on the moors above Pickering to reduce flood risk in the town from the beck.

The ideas include:

*New flood storage areas

*Tree planting alongside rivers

*’Leaky dams’ of woody debris behind which water can back up

*Blocking of moorland grips (drainage ditches)

*Grassy ‘buffer banks’ to slow water draining in to rivers from land

*New land management techniques

At one location, Strensall Common, the agency says there is potential for moorlands grip blocking, new land management and a flood storage pond.

In the upper Foss catchment, officers are considering new land use techniques, flood storage areas, tree planting and woody debris dams.

Project director Ben Hughes stressed that no decisions had been taken and the agency was seeking to work with landowners, internal drainage boards and local authorities in drawing up plans.

He also said the measures would have very long term rather than instant benefits, for example trees taking many years to grow.

York Press:

He said records showed that on average, the peak river level in the centre of York had been increasing annually over the last century.

“This increase means that the level of protection offered by York’s flood defences is decreasing over time. With current land usages and climate change, predictions show that this trend will continue.

“Unless we can slow the flow upstream, it is predicted that in 100 years’ time the flood defences in York will need to be 90cm higher just to offer the same standard of protection as they do now.”

He said engineered storage areas could hold back and slowly release huge volumes of water, altering large areas of farmland. “We already have a number of storage areas upstream of York, and we will look into how best to optimise their effect during floods.”

He said natural flood management measures usually involved fairly subtle changes to land management or drainage and small watercourses, which could be cumulatively effective.

“We have looked first at the Foss catchment as this is the smallest catchment that flows through York, and therefore the simplest to model.” He said it had been calculated that, if natural flood management measures were introduced in every location identified through this project, it would reduce peak flood flows on the Foss in York by a maximum of 10 per cent.

“This is a valuable difference, but it will be difficult to attract conventional flood risk funding for such diverse and widespread work that provides a relatively small benefit. For this reason, we will work with landowners, our partner organisations and community groups to look for opportunities to fund and introduce these measures.”

He said such measures could improve water quality, create habitat, improve biodiversity, and in some cases can help make farms more productive and sustainable, adding: “We are making links with academic programmes to see if new research into crops and land use could help us find joint benefits between agricultural businesses and flood risk management.”

THE map pictured shows some of the Environment Agency's ideas for slowing down the flow of the River Foss before it reaches York.

At a series of locations along the course of the river and its tributaries, a raft of measures will be examined in conjunction with landowners and internal drainage boards.

New flood storage areas could be created and existing ones modified to make best use of them during floods, woody debris such as tree trunks could be used to partially dam water courses and land management could be changed.

Moorland grips, or drainage ditches, could be blocked, trees planted, old river channels reconnected and grassy buffer banks created alongside water courses to slow down the drainage of water into the river from farmland.