To the experts, Calderdale is known as a rapid response catchment.
To the layman, that means the area can have very quick flood events, as epitomised by the 2015 Boxing Day floods that caused such catastrophic damage along the Calder Valley.
But from bad came good, with residents, engineers, landscape artists and hydrologists joining forces to form Slow the Flow Calderdale to examine the catchment in the hope of finding a solution.
And they claim their efforts can augment the massive £33m scheme earmarked for Hebden Bridge, Mytholmroyd and Todmorden as well as reducing the flood impact downstream by as much as 10%.
Their work has been captured on video by filmmaker Mark Wharton. The seven-minute film makes for a remarkable chronicle of grit and determination.
Investigating natural flood management, the team looked at projects in Gloucestershire and North Yorkshire and whether natural techniques could be “imported” into places such as Hardcastle Crags near Hebden Bridge.
Volunteers spent a year carrying out river surveys along the main stretches of water in the Calder Valley as well as feeder tributaries. The data was fed into river modelling undertaken by the Environment Agency.
“Hardcastle Crags was the obvious choice,” says technical officer Stuart Bradshaw. “Since the start of this year we’ve been installing leaky woody dams on some of the streams here to try and slow some of the flow.”
Among the techniques employed was the use of Shire horses to move logs through woodland into their desired positions to create a leaky woody dam – a random arrangement of logs in a stream course that pushes water out and onto the woodland floor.
That means there is more permeability available for water to be absorbed by the ground, which means it arrives at the main river channel much slower. The risk of flooding is therefore lessened.
Gullies are also stuffed with wooden detritus to raise the level of water in a peak flow – a big rainstorm – onto the bank, rather than finding its way into the main channel further downstream.
The dams also prevent sediment going into main watercourses. Trimming trees allows more light onto the forest floor, growing more ground flora, which also helps slow the flow. The benefits are multitudinous.
“Fifty per cent of the properties affected in Calderdale were flooded because of surface water,” says research officer Robin Gray.
The spread of ages among volunteers has been from ten-year-olds to septuagenarians.