Natural flood management, land use and climate change trade-offs: the case of Tarland catchment, Scotland

A distributed hydrological model (WASIM-ETH) was applied to a meso-scale catchment to investigate natural flood management as a non-structural approach to tackle flooding and climate change. Changes in peak flows were modelled using climate projections (UKCP09) in combination with afforestation-based land use change. Runoff projections showed a significant increase in peak flows from climate change. Afforestation could reduce some of the increased flow, with greatest benefit from coniferous afforestation, especially when replacing lowland farmland. Nevertheless, large-scale woodland expansion was required to maintain peak flows close to present and effects were reduced for more extreme floods. Afforestation was also modelled to increase risks of low flow episodes in summer. Evaluation using land-use scenarios showed catchment-scale trade-offs across multiple objectives were particularly complex when afforestation replaced lowland farmland. Hence, combined structural/non-structural measures may be required here and in similar catchments, with integrated catchment management to synergize across multiple objectives.