Risk Analysis of the Maximum Daily Precipitation in the Southwest of the Iberian Peninsula Over the Period 1861–2016

One of the characteristics of the Mediterranean climate is the irregularity of its intra-annual precipitation. Thus, very intense and short rain events can have a serious impact due to the sudden increase of the water level in drainage basins, with the subsequent risk of pluvial and riverine floods. This study analyses the evolution––and the return periods––of maximum daily precipitation in the San Fernando Observatory (SW Iberian Peninsula) for the period of 1861–2016. From this temporal series, we analysed the tendency, the variability, and SQRT-ETmax. These data allowed establishing the return periods associated with daily precipitation and their risk thresholds. The most relevant characteristic of the temporal series analysed, and regarding the length of torrential rain events, is the irregularity in the inter-annual intensity and distribution of precipitation. Of the 156 years analysed, 61 years (39%) reached Moderate Risk, and 22 years (14%) reached High Risk due to daily torrential rainfall.