Assessing the Impact of Climate Change and Extreme Value Uncertainty to Extreme Flows across Great Britain

Lila Collet, Lindsay Beevers, Christel Prudhomme
2017 Water  
Floods are the most common and widely distributed natural risk, causing over £1 billion of damage per year in the UK as a result of recent events. Climatic projections predict an increase in flood risk; it becomes urgent to assess climate change impact on extreme flows, and evaluate uncertainties related to these projections. This paper aims to assess the changes in extreme runoff for the 1:100 year return period across Great Britain as a result of climate change using the Future Flows
more » ... ture Flows Hydrology database. The Generalised Extreme Value (GEV) and Generalised Pareto (GP) models are automatically fitted for 11-member ensemble flow series available for the baseline and the 2080s. The analysis evaluates the uncertainty related to the Extreme Value (EV) and climate model parameters. Results suggest that GP and GEV give similar runoff estimates and uncertainties. From the baseline to the 2080s, increasing estimate and uncertainties is evident in east England. With the GEV the uncertainty attributed to the climate model parameters is greater than for the GP (around 60% and 40% of the total uncertainty, respectively). This shows that when fitting both EV models, the uncertainty related to their parameters has to be accounted for to assess extreme runoffs. Water 2017, 9, 103 2 of 16 with climate change to future extreme events is therefore of vital economic significance to the UK government, and to governments globally. Floods tend to be controlled by climatic, landscape and geological conditions. Across Great Britain there is a strong northwest-southeast rainfall gradient (Figure 1a) , with the highest 1:100 year return levels in northwest Scotland, England and Wales, and the lowest in south/southeast England [7] . The main aquifers are located in southeast England (Figure 1b) , where important chalk and Jurassic limestone reservoirs exist. These climatic and landscape controls exert variability in catchment conditions and hydrology across Great Britain [8], which thus influence flood exposure across the UK. Water 2017, 9, 103 2 of 16 uncertainty associated with climate change to future extreme events is therefore of vital economic significance to the UK government, and to governments globally. Floods tend to be controlled by climatic, landscape and geological conditions. Across Great Britain there is a strong northwest-southeast rainfall gradient (Figure 1a) , with the highest 1:100 year return levels in northwest Scotland, England and Wales, and the lowest in south/southeast England [7] . The main aquifers are located in southeast England (Figure 1b) , where important chalk and Jurassic limestone reservoirs exist. These climatic and landscape controls exert variability in catchment conditions and hydrology across Great Britain [8] , which thus influence flood exposure across the UK.
doi:10.3390/w9020103 fatcat:4vjzvqhe7fdlnopwybfzsdvu3y