Exploring opportunity sites for implementing nature-based solutions against flooding in urban vacant and derelict land : case study area-Glasgow City

Abstract

Rapid urban expansion and changing climate are continuously modifying the natural hydrological cycle. Thus, extreme precipitation-related urban surface water flooding is occurring frequently, with disastrous consequences for both human life and infrastructure. On the other hand, the accumulation of urban vacant and derelict land (VDL) has resulted in many flood affected metropolitan areas being more environmentally and socially fragmented. Though redevelopment is the primary objective, a balance between developing land uses and nature-based solutions (NbS) for VDL regeneration might assist flood mitigation, where implementing NbS is difficult due to space constraints. The umbrella concept of NbS can help to tackle flood risks, water security, and water quality issues by emulating natural processes, which also can provide multi-dimensional ecosystem services through interconnecting fragmented ecosystems. However, the success and effectiveness of these solutions heavily depend on the specific characteristics of the site. This paper aims to explore the suitable site for NbS implementation by considering the interrelationship or dependency of NbS on different environmental criteria in the context of managing surface runoff in the Glasgow City region. The case study area was taken based on both excessive VDL and surface flood issues and the NbS were divided into three categories based on key functions; 1) Retention based, 2) Storage based, and 3) Conveyance based NbS. Seven environmental criteria were considered for this analysis and the relative importance of those criteria was carried out through the multi-criteria AHP analysis based on experts' opinion. To map the identified possible opportunity sites, Geographic Information System (GIS) software was used. Among the selected environmental criteria, surface slope and proximity to flood-prone areas had the most significant impact on the final suitability maps for NbS. Glasgow city showed maximum optimal suitability for retention based NbS (27% of VDL; 1% of total city territory) rather than conveyance-based NbS and storage based NbS (5% of VDL; 0.1% of total city territory). For all the NbS, the maximum portion of the 9.38 km2 VDL was found as moderately suitable, which were 68% (1% of Glasgow city territory), 90% (2% of Glasgow city territory), and 89% (2% of Glasgow city territory) for retention-based, storage-based, and conveyance based NbS respectively. Lastly, this study can contribute to planners, leaders, and decision makers with a better understanding of surface flooding, NbS in surface run-off management, and site suitability analysis to pick the right places for these solutions while making the city more flood-resistant.