Tutta Beck Natural Flood Risk Management project

The potential for using natural flood management & SuDS techniques at the landscape scale: an application to the Tutta Beck catchment, County Durham

This post provides an overview of the research being undertaken by Mr Alex Fraser, Dr Sim Reaney and Dr Richard Hardy at Durham University to understand the opportunities to mitigate flood risk using natural flood management (NFM), Sustainable Drainage Systems (SuDS) and land management changes. This work is focused on the Tutta Beck catchment which has suffered flooding as recently as 2012. The research is based on two complementary approaches: 1: rapid connectivity and risk mapping assessment (SCIMAP-Flood) and 2: detailed physically based, fully spatially distributed, simulation of water flow within the catchment (CRUM3). These methods combine to provide a powerful toolkit to effectively target mitigation measures within the catchment and to predict the potential reduction in the flood peak from actions.

Key Project Investigations

• Investigate the most efficient and effective ways to reduce flood magnitude
  • Change in land management practices treatment for soil erosion (linking with Catchment Sensitive Farming)
  • Effectiveness of change in land use (such as grassland to woodland transition)
  • Use of SuDs features in a rural setting within the catchment (attenuation basins)
  • Use of NFM based in channel mitigation measures (debris dams)
• SCIMAP can be used to target and inform initiatives to reduce the formation of runoff and sediment transport within the catchment.
  • Therefore there is the potential to generate multiple benefits from the flood risk reduction actions including water quality improvements.
• CRUM3 can be used to quantify the potential changes in flow and flood peaks.
• Evaluation of the suitability of the different assessment tools for different stakeholder’s needs.
  • Community groups value the spatial detail of the SCIMAP-Flood results
  • Environment Agency and the local authority require detailed prediction of flows pre and post mitigation from flow summations (CRUM3).

Methodology The project methodology was developed to produce a suite of measures that could be applied to similar catchments across the country and in a format accessible to flood risk management authorities. There are two components to this approach:

SCIMAP-Flood: risk mapping framework that enables analysis on a sub-field scale but across the catchment’s extent using limited data inputs. It identifies key sources and flow routes through analysis of topography and land use, to give an understanding of the surface runoff regime at a catchment scale (www.scimap.org.uk)

CRUM3: a fully distributed hydrological simulation model operating at the catchment scale, predicting time series of river flows. CRUM3 has been used for a variety of academic and industry research relevant to this project. More information on CRUM3 is available in Lane et al. (2009)

The Tutta Beck Catchment The project appraised the effectiveness of the modelled scenarios on reducing peak discharge at Greta Bridge. Flooding was suffered in 2012, anecdotal records show that levels reached close to the properties on a number of occasions. This appraisal was achieved through a comparison of maximum modelled discharge using existing catchment characteristics against the maximum modelled discharge using the flood mitigation scenarios.

Key flood risk reduction scenarios tested using CRUM3 include large scale and spatially targeted land cover change and soil aeration, other measures investigated included woody debris dams, and spatially targeted attenuation & interception of overland flows.

Recommendations It is widely accepted that changes in land management can have some effect on flood magnitude, however in many cases there needs to be a complementary hard engineering scheme. A key aim of this research is to deliver catchment management in more palatable way for flood risk management authorities, it is to this end that the range of mitigation features are being investigated.

Further Information The thesis associated with this Masters project, which contains a full breakdown of the methodology employed, results attained and suggestions for areas of further research is available at http://etheses.dur.ac.uk/

Any questions can be directed to sim.reaney@durham.ac.uk

Lane, S.N., Reaney, S.M. & Heathwaite, A.L., 2009. Representation of landscape hydrological connectivity using a topographically driven surface flow index. Water Resources Research, 45(8). Available at: http://doi.wiley.com/10.1029/2008WR007336.