Natural flood management - an Ecosystem based Adaptation response for climate change

Abstract

Climate change is one of the most pressing issues facing civil society. Scientific evidence indicates the likelihood of greater variability and more frequent extremes of temperature and precipitation which will result in increased flood risk and corresponding social, economic and environmental impacts. Complementing more traditional structurally-based engineering interventions, an important additional
adaptation strategy is through natural flood management (NFM). NFM seeks to utilise natural processes (i.e. by promoting higher infiltration through land management practices) to attenuate flood peaks. Such measures have wider significance in the context of Ecosystem based Adaptation (EbA), to deliver highly beneficial solutions as they provide important benefits in relation to runoff rates but also in terms of wider environmental aspects (e.g. water quality, biodiversity). The present study used a holistic approach to evaluate the effectiveness of NFM options in reducing the flood risk for the current and future climate with a consideration also for the wider delivery of ecosystem services. Tarland Burn catchment (NE Scotland) was used as a platform to explore individual adaptation options through woodland expansion (distinguishing between coniferous and deciduous) and drainage schemes, together with land use scenarios that explore emergent socio-economic contexts. The distributed hydrological model WaSiM-ETH was utilised for the analysis linking land management options with climate projections obtained from UK Climate Projections (UKCP09). Modelling results showed that the magnitude of extreme weather events is expected to increase up to the end of the century with important implications for climate adaptation strategies. Woodland expansion could help attenuate the high flows, with the benefit for flood protection significantly higher for coniferous woodland compared to deciduous woodland and up to 1.5 more if woodland is located in lowland areas. However, modelling results suggested that there are potential negative impacts of afforestation on low flows (and hence water quality) which could exacerbate existing vulnerabilities. This may become an even greater issue in the future as summers are predicted to be drier and warmer. Improving the efficiency of the drainage network was seen to reduce the high flows, though the results are marginal for the winter when most floods occur. Modelling results suggested that climate change will eventually exceed the capacity of beneficial land use change by itself (through NFM measures) to avoid significant changes on catchment hydrology. This has important implications as other complementary engineered solutions may therefore be required to counteract the adverse impacts of climate change on flood risk. Moreover, the EbA assessments results indicated that NFM options may not always be ‘win-win’ solutions as commonly advertised (McShane et al., 2011). Instead trade-offs between the delivery of different services may be required and decisions should be aimed at maximizing benefits whilst minimizing the disbenefits. This novel approach highlighted that land use change should be carefully managed and the choices about land use and flood risk should always have at their core an enhancement of landscape resilience, particularly at the catchment scale

Date of Award	2015
Original language	English
Sponsors	ClimateXChange
Supervisor	John Rowan (Supervisor), Iain Brown (Supervisor) & Christopher Ellis (Supervisor)