Hydro-Meteorological Characterization of Major Floods in Spanish Mountain Rivers

Abstract

Spain, one of the most mountainous countries in Europe, suffers from frequent river flooding due to specific climatic and topographic features. Many headwaters of the largest rivers in Spain are located in mountainous areas of mid-to-high elevation. These include the Pyrenees, the Central System, and the Cantabrian mountains, that have a sustained snowpack during the winter months. Most previous research on flood generation in Spain has focused on intense rainfall events, and the role of snowmelt has been ignored or considered marginal. In this paper we present a regional-scale study to quantify the relative importance of rainfall versus snowmelt in the largest floods recorded in mountain rivers in Spain during the last decades (1980–2014). We further analyzed whether catchments characteristics and weather types may favor the occurrence of rainfall or snowmelt induced floods. Results show that in 53% of the 250 analyzed floods the contribution of rainfall was larger than 90%, and in the rest of events snowmelt contribution was larger than 10%. Floods where snowmelt was the main contributor represented only 5% of the total events. The average contribution of snowmelt represents 18% of total runoff in floods that were analyzed. The role of snowmelt in floods, rather than triggering the event, was usually amplifying the duration of the event, especially after the peak flow was reached. In general, the importance of snowmelt in floods is greater in catchments with characteristics that favor snow accumulation. However, this does not apply to floods where contribution of snowmelt was larger than 90%, which tend to occur at catchments at mid-elevations that accumulate unusual amounts of snow that melt rapidly. Floods were more frequent under both cyclonic and anticyclonic synoptic situations over the Iberian Peninsula, as well as under advection of western and eastern flows. Our results contribute to the ongoing improvement of knowledge about the role of snow in the hydrology of Spanish rivers and on the importance of mountain processes on the hydrology of downstream areas.

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

“…Contrarily, the A (anticyclonic) type has very little spatial and seasonal influence. These observations are in agreement with the results obtained by Morán-Tejeda et al [87] that analyzed the hydro-meteorological response of major floods in Spanish mountain rivers, and concluded that the floods were more frequent under cyclonic (26%), as well as under advection of westerly flows (26% of total floods) and easterly flows (22% of total floods).…”

“…The predominance of the A type is strongly related to the migration of the Azores anticyclone towards the Iberian Peninsula [90]. However, in summer, under anticyclone situations, high values of runoff and sediment production can be recorded locally in high mountain areas due to the capacity of mountain ranges for triggering convective activity at the local scale because of high isolated radiation [87]. These local processes cannot be detected in this study due to the coarse spatial resolution of the applied reanalysis grid.…”

“…Summer events are associated with short, intense, and localized rainfalls, often associates to thermal convective lows and high rainfall intensity. Morán-Tejeda et al [87] suggested that large rainfall amounts in the western Mediterranean basin are more intense and concentrated in events of a few hours, and have usually a convective origin due to the occurrence of cold depressions in the middle troposphere (cut-off-low) with advection of warm flows from the Mediterranean. Similar results were found in different areas of the Mediterranean basin by Ramos et al (2014).…”

A Decrease in the Regulatory Effect of Snow-Related Phenomena in Spanish Mountain Areas Due to Climate Change

“…In the last decades various studies have been carried out to analyze the phenomenon of snow in Spain and its contribution to flooding [10][11][12][13][14].…”

The significance of monitoring high mountain environments to detect heavy precipitation hotspots: a case study in Gredos, Central Spain

“…Heavy precipitation events associated to orographic uplift together with steep topography involve potential risks on the mountain slopes or in downstream areas where population often concentrates. Numerous damaging processes have been reported in mountain areas associated with heavy precipitation, including floods (Morán-Tejeda et al 2019;Ruiz-Villanueva et al 2013;Weingartner et al 2003), landslides and rockfalls (Melillo et al 2020;Stanley et al 2020;Valenzuela et al 2018), or snow avalanches (Abermann et al 2019;Stimberis and Rubin 2011).…”