Evolution of flood episodes in the Community of Madrid: territorial and synoptic factors

Abstract

Although the Community of Madrid does not have a high risk of flooding, it has had a certain recurrence in the past and currently has occasional events that generate high costs. An exhaustive inventory is carried out based on documentary sources, compiling information on 138 floods between 1836 and 2021. These data explain the causality of the spatial distribution of cases, both in terms of some of their physical and anthropic components. It highlights the enormous weight between the relation of the slope and the hydrographic network with the urban occupation, in which the density of buildings per hectare is taken as an indicator. It is shown that the most vulnerable areas have historically been Aranjuez and Madrid city, while at present the municipalities of the south and east of the Community are incorporated. The study of the synoptic causes of floods has revealed a change between historical and current floods. In the historical floods, the zonal weather types, and Atlantic advections typical of winter, lasting several days, dominated until the mid-fifties of the 20th century, responsible for high rainfall in a still unregulated Tagus basin. In recent decades, the improvements in hydraulic infrastructures and intense urban expansion limit floods preferably to occasional high rainfall associated with DANAs at any time of the year and to barometric swamps, characteristic of the summer season.