Natural flood management
NFM work included the creation of wetland features such as new pools and reedbeds, floodplain bunds to slow the flow within the floodplain, and in-channel features such as leaky dams and woody barriers. These green engineering options hold back water flow and spread it onto the floodplain when river levels are high. The overrall aim of the NFM solutions implemented at all three sites below was to mitigate flood risk, while simultaneously creating biodiversity-rich green spaces to support wildlife and help local communities connect with wild nature.
Work here was undertaken within the SSSI of Narborough Bog, which regularly floods with heavy rainfall. The aim was to slow the River Soar as it passes through the woodland. A large tree was felled across the river, while leaky dams were created by lying brash and cord logs across the site’s withy bed system, together with a number of large trees. An Oxbow pool was also bunded with a leaky dam structure constructed with trees and brash. All dam structures were secured using natural materials such as chestnut or other hardwood stakes and jute rope (the stakes were treated to increase their life expectancy in a wet woodland habitat).
Work undertaken included the establishment of a site compound, installation of 400 metres of aluminium trackway, and the excavation and removal from the site of 1000m3 of top and subsoils. This was a challenging site, with the river rising and flooding the work area on multiple occasions, necessitating the constant pumping of water to aid excavations. Work also had to respect the archaeology of the area, with an ancient bridge crossing the old river course and the possibility of finds during excavation.
Work here included the excavation of 1100m3 of top and subsoils to form a pond and bund area and the planting of 440 wetland trees, including three species of willow and alder. As per Enderby, work also had to respect the archaeology of the area, due to the close proximity of an iron age fort and other archaeological concerns. The site was also located within 250 metres of a great crested newt (GCN) pond – the topsoil strip was undertaken under a Natural England GCN licence, which saw the use of a sniffer dog and watching brief to hand search the excavation area before any work began.
The construction of the bund used mostly compacted topsoil. This was covered with compacted subsoil, then a natural jute geotextile, and then topped with more subsoil. It was then seeded with a wildflower mixture which had already started to germinate. Much like Enderby, the site suffered from regular flooding, as well as landowner and access issues. Work was also halted between March and August 2020 due to Covid-19.
Exemplified by NFM, nature-based solutions can help us address some of society’s greatest challenges, from climate change and coastal erosion through to crop stabilisation and wildfire mitigation. Much of our work at Ecosulis already focuses on the restoration of landscapes and wild nature, which brings a range of sustainable benefits for both clients and wider society.