Title: Observed trends in daily data and maximum hourly intensity of rainfall events in Asturias (NW Spain)
Authors: Elena Fernandez Iglesias - University of Oviedo, INDUROT (Spain)
Gil Gonzalez-Rodriguez - University of Oviedo (Spain)
Ana Belen Ramos-Guajardo - University of Oviedo (Spain) [presenting]
Abstract: Extreme rainstorms in headwater catchments imply flash floods and landslides, the most serious geomorphological hazards in Asturias mountain region, located in the Cantabrian Range (NW of Spain). Brief episodes (less than 24 hours) of heavy rainfall are recognized as one of the most important triggers of these natural hazards, but the studies developed until now only include daily precipitation data. Due to climate change, the frequency and magnitude of these events are being altered. The main goal is to analyse long-term trends selecting hourly precipitation data from meteorological gauges. We have identified rainfall storm events by considering a 0.9995 quantile in the hourly precipitation series. For each rain gauge, a Bootstrap isotonic test in the strict sense has been applied to check whether the corresponding trend is constant or, otherwise, there is an effective increment. The obtained p-values at the usual significance levels have shown opposite behaviour between the inland and the coastal area. We identify an effective increment in expected total rainfall, total time and the number of storm events per year in the inland area. In contrast, an effective decrease is clear in the mean length and number of storm events in the coastal area. Although there is an important variability in Asturias, the rainy trends in central/inner areas are more representative, where there is the highest activity of geomorphological hazards.