Modelling the effectiveness of land-based natural flood management in a large, permeable catchment
In this study, the authors investigate the impact of two natural flood management (NFM) measures, tree planting and herbal ley–crop rotations, on peak flows to address their effectiveness for low-probability flood events and in groundwater-dominated lowland catchments. The authors use a case study catchment in the southern United Kingdom, where the upscaling of NFM measures is being actively considered within schemes to manage downstream flood risk to large urban centres. They do this by coupling a process-based soil–water–vegetation model with a groundwater model. We also analyse impacts of NFM on low flows.
A process-based soil–water–vegetation model was coupled with a semi-distributed groundwater model to explore the impact of tree planting and crop–herbal ley rotations on peak and low flows in a large, groundwater-dominated catchment in the southern United Kingdom. Crop–herbal ley rotations, representing regenerative agriculture (RA), were found to have limited potential to reduce flooding in this setting. Spruce and broadleaved woodland planting at levels judged to be the absolute maximum of what could be realistically achieved also showed very limited potential to reduce flooding. The only scenario that produced significant reductions in peak flow was broadscale spruce planting; however, this was also found to reduce low flows, with potential implications for water security and river ecology. Therefore, while RA practices and woodland have significant environmental and leisure benefits, their effect on flooding in groundwater-dominated catchments should not be overstated.
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