Slow The Flow have applied via Source Partnership for a grant from the Environment Agency to install small structures at up to sixty identified sites in watercourses in Hardcastle Crags. Our engineers have been out looking at the rivers and the surrounding banks to determine the best places to install interventions in the Crags, National Trust owned land. The structures will either be small wooden plate weirs or small leaky woody dams made from logs, their purpose to “Slow the Flow”, our maxim and one that is hoped will reduce the flood peak and help prevent catastrophic flooding to our downstream towns and villages.
Phase 1 of the project will be for small interventions on brooks and ditches with some study work in preparation for Phase 2. Phase 2 programmed for 2017 is for larger leaky woody dams on Hebden Water itself, along with attenuation ponds.
Slow The Flow have also applied for additional grant aid again from the EA for further studies into similar interventions in Crimsworth Dean on Crimsworth Dean Beck, this is rather more complicated and expected to take longer to come to fruition due to land ownership issues and the fact that the river bed is designated a Site of Special Scientific Interest by Natural England.
It is hoped this project will be a pilot that will shine a spotlight on the Calder Valley and the steps we are taking to help ourselves, at least some of the work will be carried out by volunteers, so if you want to help yourself or your neighbours here is your opportunity, it is hoped work will commence in the Autumn.
In order to secure funding one of the stumbling blocks we have to get over relates to the way the EA is funded and a requirement to demonstrate the benefits of the proposed interventions. This is no easy task, however it is not insurmountable as our colleagues at Pickering can vouch for. We believe we can make a case for these works by a combination of river level monitoring and river (computer) modelling. Currently the EA have only one river gauge on Hebden Water, below Valley Road bridge, a much better picture of the river in flood would be attained by introducing further gauges on structures upstream of Valley Road. This can be done relatively cheaply using these types of gauges which cost around £300 each.
River modelling was one of the first objectives of Slow The Flow and for good reason. The Pickering project came about by effective river modelling to substantiate the benefits of introducing interventions into stream flows, they were lucky in some respects because the Pickering Beck was the subject of a Defra funded project so their modelling (or at least the initial phases) was funded and it was relatively straightforward to use these models to make an adequate case . At the present juncture we are being asked to substantiate benefits without any funding in place, a classic chicken and egg situation.
We will have to apply some pressure if we are to make any headway, this is ongoing but in the meantime, the data that we will eventually need for this exercise still needs to be collated. We have a small team of river surveyors but we need more hands on deck if we are to obtain the geometric data in timely fashion that is needed to compile the river models. So here again we return to the “Helping ourselves” principle that I wrote about in Part 1 of this blog.
Why have the EA not surveyed the rivers sufficiently, surely they must have done this for their current river models?
The EA’s remit is for the main river, the Calder, the tributaries fall under the responsibility of the Lead Local Flood Authority, Calderdale MBC. The EA have geometric survey data only for the Calder and for a short stretch of each tributary. The modelling we are proposing introduces out of channel flow caused by introducing interventions in the stream flow, so the channel depths, widths and the channel roughness play a significant role in the modelling process. A rougher channel with say cobbles and boulders in the stream bed slows the water as opposed for example to a concrete lined channel. It is this data which can only be obtained by fieldwork that is central to our case.
If you can help the cause then please get in touch via our website.
Stuart Bradshaw C.Eng.