Plan, design and construct a suite of NFM interventions on farmland within upstream catchments of communities at risk in Poynton & Kettlshulme.
Both of the projects ‘target communities’ have long since suffered from periodic flooding during storm events. However, the flood events of the 31st July 2019 wreaked havoc like never before, on both communities. Following this event, the Environment Agency (EA) responded by committing funds to deliver a programme of flood defence work, aimed at delivering innovative Natural Flood Management (NFM) across catchments in Greater Manchester, Cheshire and Merseyside.
Delivery commenced during the summer of 2020, with the Trust’s operations team leading on engaging local landowners in an attempt to foster support for the scheme and identify opportunities for work on the ground. In the case of Kettleshulme, this proved particularly challenging due to the small size of the catchment area where we needed to work, which extended across only a handful of small farm holdings.
Additionally, we were faced with tightening national covid lockdown measures in the autumn, which presented challenges around engaging safely with landowners. Despite this, the team successfully developed a wide range of projects throughout both catchments, enabling ground work to commence in late January 2021.
Our work aimed to reduce flood risk by tackling it on two levels. Firstly, we wanted to intercept overland flow pathways to increase the time it takes for water to reach the river channel. This was particularly important in Kettleshulme, where tightly grazed swards and compacted soils reduce infiltration rates. To address this, a combination of woodland planting, creating buffer strips along watercourses and planting hedgerows across slopes were implemented. Secondly, we wanted to provide additional storage areas for flood water to reduce peak flows and help flatten the hydrograph. This was done by either providing online storage, in the form of dams that attenuate water in-channel, or providing offline storage through the creation of scrapes and ponds, capable of holding additional water during storm events.
Whilst the primary remit was to provide additional flood attenuation capacity, where possible, we sought opportunities that achieved multiple objectives for the environment, with an emphasis on creating new habitat. Most notably, this included planting new woodlands, creating attenuations ponds, which would hold some permanent water to the benefit of amphibians, and installing large woody debris into channels to diversify flow regimes and provide niches for freshwater invertebrates.
An estimated 2277 cubic metres of additional flood water storage capacity