4 minute read
Stroud Rural Sustainable Drainage Systems
Stroud, Gloucestershire, England, United Kingdom
Stroud and nearby communities have historically suffered from flooding. Following a report published by the Environment Agency of England (EA) on potential opportunities for Natural Flood Management (NFM) in the Frome catchment and resulting benefits, a formal partnership was set up between Gloucestershire County Council, the EA, the Regional Flood and Coastal Committee, and Stroud District Council to implement the Stroud Rural Sustainable Drainage (RSuDs) project. Work began in 2014 in an effort to implement a wide range of measures designed to reduce flood risk by slowing peak flows and attenuating high flows while simultaneously improving water quality and restoring biodiversity. By 2017, the project had worked with 16 land managers—12 private and 4 non-governmental organizations—to construct or implement over 300 various NFM interventions, including 162 large woody debris dams installed in four tributaries; 50 minor deflectors; 9 culverts and soakaways; 1 dry stone wall deflector; 3 spring-fed and 3 solar-fed cattle-drinking troughs; 5 large earth berms; 7 small earth berms or check dams; 1.2 kilometers of streamside fencing; and 1 large, dry pond.
Article cover: Slad Brook in flood on Stroud Slad Farm 2016; attenuation behind large woody leaky dam. (Photo by Chris Uttley, Stroud District Council)
Producing Efficiencies
An area of 52.5 square kilometers, or 21 percent of the Stroud Frome catchment, now drains through numerous NFM structures. Comparing EA river gauge data for a rain event in 2016 (36 millimeters in 12 hours) with a rainfall event similar in magnitude and intensity in 2012 suggests that these measures reduced peak river levels in the Stroud Valley by up to 1 meter. Some 53 properties were at 20 percent annual probability of flooding but did not do so in this event.
Using Natural Processes
The primary driver from the local community was to see measures in place on the ground and not a period of protracted planning and evaluation. The project officer therefore focused on working with the National Trust and Gloucestershire Wildlife Trust in the Frome catchment, developing and implementing a wide range of measures working with natural processes, from woody structures in streams to soakaways on forest road culverts. Natural processes were enlarged and improved; systems that occur by chance in nature were mimicked.
Broadening Benefits
All measures are designed to work with natural processes and have multiple benefits: large woody debris improved in-stream habitat by cleaning downstream reaches of silt and impeding the progress of silt downstream; woody debris itself created habitat for invertebrates, fungi, and lower plants; targeted defoliation allowed light to reach riparian areas, increasing plant diversity; erecting fences kept stock out of watercourses, thereby decreasing silt pollution; and measures to reduce soil erosion also reduced silt loads reaching watercourses.
Promoting Collaboration
Following extensive community consultations on contemporary schemes, it was widely accepted that protection against major flood events was not viable and would have an unacceptable impact on the local environment and landscape. The local community proposed that NFM options be investigated. Working with the community through a local action group, Water 21, the EA undertook a series of catchment walkovers and informal discussions with landowners to establish the scope and potential locations of NFM measures. The partners, organizations, and stakeholders involved in this project include Severn and Wye Regional Flood and Coastal Committee, EA, Gloucestershire County Council, National Trust, Gloucestershire Wildlife Trust, University of Gloucestershire, Butterfly Conservation, Woodland Trust, and Severn Rivers Trust.
