Use of soil data in a grid-based hydrological model to estimate spatial variation in changing flood risk across the UK

摘要

A grid-based flow routing and runoff-production model, configured to employ as input either observed orudRegional Climate Model (RCM) estimates of precipitation and potential evaporation (PE), has previouslyudbeen used to assess how climate change may impact river flows across the UK. The slope-based Gridto-udGrid (G2G) model adequately simulated observed river flows under current climate conditions for highudrelief catchments, but was less successful when applied to lower-relief and/or groundwater-dominatedudareas. The model has now been enhanced to employ a soil dataset to configure the probability-distributedudstore controlling soil-moisture and runoff generation within each grid-cell. A comparison is made of theudability of both models to simulate gauged river flows across a range of British catchments using observationsudof rainfall and PE as input. Superior performance from the enhanced G2G formulation incorporatingudthe soil dataset is demonstrated.udFollowing the model assessment, the observed precipitation and PE data used as input to both hydrologicaludmodels were replaced by RCM estimates on a 25 km grid for a Current (1961–1990) and a Futureud(2071–2100) time-slice. Flood frequency curves derived from the flow simulations for the two time-slicesudare used to estimate, for the first time, maps of changes in flood magnitude for all river points on a 1 kmudgrid across the UK. A high degree of spatial variability is seen in the estimated change in river flows,udreflecting both projected climate change and the influences of landscape and climate variability. Theseudmaps also highlight large differences between the climate impact projections arising from the two models.udThe improved structure and performance of the soil-based G2G model adds confidence to its projectionsudof flow changes being realistic consequences of the climate change scenario applied. A resamplingudmethod is used to identify regions where these projections may be considered robust. However, with theudclimate change scenario used representing only one plausible evolution of the future climate, no clearudmessage can be drawn here about projected river flow changes.