High-resolution ensemble flood forecasting: a case study in Höje Å, Sweden / Högupplösta ensembleprognoser för översvämningar: en fallstudie i Höje Å
The number and impacts of pluvial floods are likely to increase with the growth of our cities and as extreme weather is anticipated to intensify with climate change. Improved preparedness is needed which may be attained owing to recent development of high-resolution hydro-meteorological observations and forecasts as well as geographical data. This paper investigates the capacity of the HYPE model for rainfall-runoff modelling and ensemble forecasting at hourly resolution. The analysis includes evaluation and application of several new highresolution data sources: radar-based precipitation (HIPRAD), urban land-use data (EEA Urban Atlas) and high-resolution ensemble forecasts (MEPS). These components are finally integrated in a forecasting prototype for a catchment in southern Sweden. The results showed that HYPE, forced with HIPRAD and with land-use from Urban Atlas, performed well with a long-term Nash-Sutcliffe Efficiency > 0.8 at hourly level. Analysis of selected pluvial-type high-flow events close to an urban area indicated a good representation of fast runoff. The application of MEPS forecasts has been demonstrated for a few single events with promising results. Overall, it is concluded that the 1-hour forecasts provide added value compared with the 1-day time step and that an increased resolution in time and space is important to accurately forecast pluvial-type events.