Yesterday I went to the National Trust’s Holnicote Estate near Porlock on Exmoor in north Somerset and was shown the widely acclaimed natural flood management project there by the Project Manager Nigel Hester.
In light of the recent floods natural flood management is widely discussed as an option for solving flooding problems in the future . Yet the Holnicote project was started in 2009. The project have been funded by DEFRA, the Environment Agency and the National Trust. It has been run as a demonstration project so it involves a great deal of modelling and monitoring to show what has worked and the effects have been.
A report has been published by the National Trust which gives a detailed account of what has been done and what the results have been – you can download the report here.
The project is a catchment wide approach to ‘slowing the flow’ of the local rivers using low key and natural interventions in an attempt to reduce / stop flooding in the local villages downstream.
Allerford – one of the local villages at risk from flooding
Perhaps the most obvious feature of the project has been the subtle re-engineering of the flood plain on the Estate which enables the river to flood onto the land – slowing the flow and greatly increasing the flood water storage capacity. The Trust has worked with its tenant farmers who have all bought into and supported the project.
A number of non intrusive bunds have been produced to create water storage areas
A simple woody dam has been installed which in periods of high flow diverts the flood water from the river into the storage areas on the flood plain
In the streams higher up in the catchment a number of simple woody dams have been created to provide ‘hydraulic roughness’ and slow the flow
Up on the high moor ancient features such as this track have tended to funnel water and increase its flow down to the villages below – here small dams and pools have been created to slow the flow
In this lovely coombe scrub is beginning to form which again increases the hydraulic roughness
As well as playing a major part in reducing flooding these small measures also provide new and interesting habitats for wildlife – given a bit of time the coombe above might become attractive to breeding ring ouzels (which are now extinct on Exmoor) and maybe, could even be suitable habitat if a black grouse re-introduction project was ever considered. The little scrubby trees will certainly be useful to cuckoos who need such features so they scan perch and survey the landscape for food and meadow pipit nests.
It is early days for the project but to date despite some heavy rain episodes the villages down stream have not flooded since the natural flood management features were created.
This is a very brief summary of a multi-objective project – read the full report to gain a fuller picture. Really pleased to have seen it for myself – thanks Nigel for showing me around.
The National Trust should be very proud of this pioneering work – very important now to ensure that the House of Commons Select Committees working on solutions to the recent floods see and hear about this project.
This is not complicated or expensive and the approach can be adapted and used across the country to play an important role in reducing flooding.