Optimising NFM in headwater catchments to protect downstream communities

Natural flood risk management (NFM) describes methods of modifying hillslope and catchment runoff through the modification of landscapes to restore natural hydrological behaviour which limits downstream flood risk. This proposal is for a focussed study of NFM benefits associated with wider ecosystem restoration work which is under way across the uplands of the UK. Headwaters comprise 60-80% of the length of most river systems and high slopes and high rainfall mean that they are important areas of hillslope runoff production. Across the UK there are communities which are prone to flash flooding from steep upland catchments. These headwater catchments are relatively small catchments and are areas where extensive upland restoration is occurring and so they are locations where positive impacts of NFM measures are likely to be observed. Vulnerable communities in headwaters are often small and dispersed with land values that rarely justify hard engineering flood defences through standard cost-benefit approaches. If relatively low cost upland restoration approaches can mitigate risk to communities such as this then it will be possible to provide some protection to communities where funding precludes hard engineering approaches.
This project will work with project partners Moors for the Future and Greater Manchester, Merseyside and Cheshire Environment Agency who have existing funded NFM work in the southern Pennines to undertake a series of field experiments. These will assess the potential impact of various forms of gully blocking, restoration of Sphagnum cover on moorlands, and establishment of upland woodlands on hillslope runoff production and channel flow. It will also assess the longer term evolution of woodland and gully blocking approaches through the study of mature woodland and well established gully blocked systems. This is an important consideration since investment in NFM works requires confidence in the long term impact of the restoration on runoff and knowledge of any ongoing maintenance costs for the interventions.

Installation of NFM schemes to mitigate flood risk requires careful planning and prediction of potential impacts. This project will develop conceptually sophisticated but computationally simple models which can run multiple scenarios in order to assess the catchment wide impacts on runoff of NFM measures implemented to a variety of designs and in a variety of spatial configurations.
The model will be developed (with input from project partner CH2M and input from potential users such as EA) and validated using data from the Glossop Brook catchment in Derbyshire which has a history of major flash flooding impacting households in the town of Glossop. The modelling approach will then be used to assess possible NFM interventions in the upland catchments draining to 21 communities at risk on the eastern edge of Greater Manchester. In each of these catchments we will model the optimum configuration of upland restoration measures for NFM benefit.

The project will also work with partners (Environment Agency, Natural Resources Wales, Scottish Environmental Protection Agency, International Union the Conservation for Nature) to identify existing headwater flow records across the UK which relate to areas of significant upland restoration. At these sites we will model expected impacts and interrogate the available flow data for evidence of these effects on runoff.

The project will work with its range of project partners which span England, Wales and Scotland and which comprise regulators, land managers and industry to develop guidelines to optimise future implementation of NFM measures in headwater catchments across upland Britain.

Increasing frequency of floods with devastating impact on communities has meant that there is widespread interest in approaches to mitigating the impacts of heavy rainfall on downstream settlements. The efficacy of natural flood risk management (NFM) is therefore a pressing area of concern for a wide range of stakeholders including those charged with flood defence and policy (e.g. Environment Agency, Scottish Environmental Protection Agency, Natural Resources Wales and local councils), land managers, environmental consultancies, and communities at risk.
Successful completion of this project will provide a major advance in the understanding of the impact of upland landscape restoration (such as woodland planting and peatland restoration) on downstream flood risk. The project will also develop models to allow optimisation of NFM benefits at the planning stage of restoration works. The project will develop open source modelling approaches which will allow rapid assessment of multiple scenarios of NFM implementation for headwater catchments. These models, developed with input from project partners CH2M and the EA, will be freely available. They will be designed to support and supplement existing industry standard approaches, and could become a part of the standard toolkit for rapid assessment of projects by regulators and consultants. These advances will be of direct use to policy makers in terms of planning new flood defence works, and assessing the catchment scale impact of NFM measures in headwater catchments.
The project will develop guidelines for the optimum implementation of NFM works. We will work with project partners to co-produce these guidelines, and disseminate these to the widest possible range of stakeholders on completion of the project. The guidelines will cover both the design of NFM features and the spatial planning of these approaches. These planning principles will support land managers in the development of upland restoration schemes which will maximise NFM benefits alongside other ecosystem service benefits.
Quantification and prediction of NFM benefits will allow implementation of flood protection schemes based on NFM approaches in areas where hard engineering approaches are too costly, and will also provide the basis for assessing mixed schemes where NFM benefits are able to minimise the degree of hard engineering required for a given protection level. Therefore, there is potential for the implementation of low cost headwater NFM measures that will allow a greater degree of flood protection within limited budgets.
Ultimately, the aim of this work is to positively impact communities at risk of headwater flooding. Demonstration and quantification of NFM benefits associated with upland land restoration may allow the implementation of meaningful flood defence in communities where largescale hard engineering solutions will not be supported. This would empower communities to take local action to protect their homes. The project will produce a travelling exhibition of project findings which will be displayed in local settings to communicate the project's work to communities at risk.