Seasonal rainfall and flow trends within three catchments in South-West England

Abstract

Hydrological and hydraulic design and analysis is dependant on the probabilistic, risk and uncertainty analysis of hydrological events. Hydrological variables are traditionally treated as random and stationary with certain probability distributions. If changes in rainfall and flow patterns are evident, they will have significant impact on existing infrastructure, current practice and future strategies in flood defence and water resources management. Recent floods in England have triggered debate on the impact of climate change on floods. In this study, trend analyses were carried out on seasonal rainfall depth, mean flow and peak flow, and return period of peak flows over three distinctive catchments in South West England. It found that there are general trends of increased volume of rainfall and runoff in winter and slightly changed volume (either in decrease or increase) of those in summer, which is in agreement with the current climatic model’s simulation. However, the peak flows (both annual and seasonal) across three catchments appear to move in opposite directions, indicating the change of rainfall patterns or/and anthropogenic activities in the region. This could have significant impact on hydrological design of water engineering structures in the future due to the disparity between the flood volume and peak. The paper also illustrated the change of the return periods of flow in the region and discussed its serious implications in existing and future hydraulic engineering projects.