Author(s): Kevin Spence; Ian Rotherham

Linked Author(s): Kevin Spence

Keywords: Flood storage; Infiltration basin; Leaky dams; Landscape sensitivity; Local communities

Abstract: Climate change projections indicate an increasing frequency and severity of flooding. The City of Sheffield (UK) has a history of flooding which is exacerbated in some areas by the canalisation and culverting of long stretches of watercourses. As there is limited opportunity for engineering intervention in urban rivers, the utility of introducing natural flood management in upland urban-fringe catchments is therefore being considered citywide. This approach is being explored by assessing changes in the hydrological response of the Limb Brook sub-catchment of the Rivers Sheaf and Don. This is necessary since the efficacy of upland spatially distributed intervention measures are still subject to a high degree of uncertainty. The review will be undertaken over an extended time-period, with the support of the Environment Agency, Sheffield City Council, and the Sheffield and Rotherham Wildlife Trust. The watershed includes upland moor, coniferous and mixed woodland, grazing pasture, amenity grassland, and a small proportion of suburban housing. The study area has high amenity value and significant associated biodiversity and landscape heritage. Rain gauges and flowmeters (Lady Canning’s plantation, Whirlow Bridge & Limb Bridge) are being installed and the following interventions are planned from December 2021: •Interception of run off in Lady Canning’s Plantation (commercially managed coniferous woodland) which frequently erodes the public paths. Suspended soil and overland flow are to be diverted to a series of small infiltration basins aligned with the contours. These will be created using logs from selective tree felling. Increased carbon capture will be an additional benefit as vegetation growth is promoted and erosion of organic sediment is reduced. •A sequence of circa 30 to 40 leaky log dams along the Limb Valley to attenuate the flow through temporary reservoir storage. Floodplain storage will be promoted on the lower more level areas of landscape. There will be capture of sediment from soil erosion in the lower Ecclesall Woods, again in the more level zones, and potentially from a currently actively eroding Planted Ancient Woodland on very steeply sloping land in the Limb Valley. •Diversion of extensive field drainage in Whirlow Playing Fields from an outfall pipe to a series of attenuation ponds, swales, and with created wildflower meadows and tree planting. •Assessment of intervention sites with respect to landscape heritage sensitivity and ecology conservation value. Where appropriate there will be carefully planned seeding, planting and management regimes. •Promotion of public information and citizen science with the engagement of local communities such as the Friends of Whirlow Park and the Friends of Ecclesall Woods. The designs of the Natural Flood Management interventions and initial monitoring results will be discussed at the conference.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221834

Year: 2022