Application of flow variability analysis to identify impacts of agricultural land-use change on the River Axe, southwest England

Flow variability analysis based on the annual number and duration of pulses above flow thresholds has been used to identify potential impacts of agricultural land-use change on the River Axe catchment (288.5 km²). The analysis shows significant trend and step changes in runoff response which coincide both with changes in land use and management and with changes in rainfall amount and intensity. The effects of climatic variability are taken into account by regression analysis; residuals from regression continue to show a trend which is ascribed to land-use change. Seasonal analysis indicates that the winter season has the greatest change in runoff response but little change in rainfall. In contrast, the summer season shows little change in runoff response but altered rainfall frequency. The success of flow variability methods in identifying trends and the sources of trends in the runoff response on the Axe catchment indicates the potential of the methods for more general application for the development of flood risk management policies based on land-use and management.