Monitoring for the Making Space for Water Project
Tim Allott (Reader in Physical Geography, University of Manchester) Hydrological monitoring on Kinder Plateau and the wider area; current scientific evidence for the efficacy of restoration in reducing flood risk downstream
An example of the effects of flooding was the 2002 event in Glossop, when rainwater from a summer storm surged down streams coming off the Bleaklow plateau causing widespread flooding in the Glossop area. This and other such events highlight the potential value of measures which can slow down the flow of water from upland areas and reduce downstream flood risk, but there is a need for good scientific evidence for the most appropriate way of doing so.
Currently there is clear evidence that re-vegetation of upland areas does slow down the flow of surface water from upland areas by increasing surface roughness and micro-topographical storage. The recent installation of thousands of gully-blocks on the Making Space for Water site on Kinder Scout plateau should produce a similar increase in storage capacity, and data is now being gathered to evaluate this address effect.
The effect of blocking gullies is likely to be different to the effect of blocking grips, a technique commonly used in upland areas affected by drainage. This is because grips extend drainage time and distance by running parallel to contours. Moreover, the effect of gully-blocking may be complex, including short term temporary ’adjustment’ effects as well as long term responses. For instance, the initial increase in storage capacity produced by gully blocks will be reduced through time by the accumulation of sediments, but in the long term gully re-vegetation will slow flows by increasing channel roughness. Long term monitoring is needed to assess these effects.
The Making Space for Water project aims to provide strong scientific evidence for the beneficial effects of different restoration practices on reducing flood risk. We have mapped and measured 5 similar sized mini-catchments that have had different restoration scenarios imposed on them. One has been left damaged, with extensive areas of bare peat and deep gullies remaining. Two more have recently been restored (in the spring of 2012); both with re-vegetation and one with additional gully-blocking. Another mini-catchment was restored approximately 10 years ago, and a final mini-catchment is considered to be undamaged and “intact”. This layout should provide exciting new information.