Flash flood evolution in North-Western Mediterranean

Abstract

The present paper shows an in-depth analysis of the evolution of floods and precipitation in Catalonia for the period 1981–2010. In order to have homogeneous information, and having in mind that not gauge data was available for all the events, neither for all the rivers and stream flows, daily press from a specific newspaper has been systematically analysed for this period. Furthermore a comparison with a longer period starting in 1900 has been done. 219 flood events (mainly flash flood events) have been identified for the period of 30 years (375 starting in 1900), 79 of them were ordinary, 117 of them were extraordinary and 23 of them were catastrophic, being autumn and summer the seasons with the maxima values. 19% of the events caused a total of 110 casualties. 60% of them died when they tried to cross the street or the stream. Factors like the evolution of precipitation, population density and other socio-economical aspects have been considered. The trend analysis shows an increase of 1 flood/decade that probably has been mainly due to inter-annual and intra-annual changes in population density and in land-use and land-cover.

Authors: Maria Carmen Llasat, Raül Marcos, Montserrat Llasat-Botijaa, Joan Gilabert, Marco Turco i Pere Quintana-Seguí.

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The snow storm of 8 March 2010 in Catalonia (Spain): a paradigmatic wet-snow event with a high societal impact

Authors.  M. C. Llasat, M. Turco, P. Quintana-Seguí and M. Llasat-Botija

Abstract. 

A heavy precipitation event swept over Catalonia (NE Spain) on 8 March 2010, with a total amount that exceeded 100 mm locally and snowfall of more than 60 cm near the coast. Unusual for this region and at this time of the year, this snowfall event affected mainly the coastal region and was accompanied by thunderstorms and strong wind gusts in some areas. Most of the damage was due to «wet snow», a kind of snow that favours accretion on power lines and causes line-breaking and subsequent interruption of the electricity supply. This paper conducts an interdisciplinary analysis of the event to show its great societal impact and the role played by the recently developed social networks (it has been called the first «Snowfall 2.0»), as well to analyse the meteorological factors associated with the major damage, and to propose an indicator that could summarise them. With this aim, the paper introduces the event and its societal impact and compares it with other important snowfalls that have affected the Catalan coast, using the PRESSGAMA database. The second part of the paper shows the event’s main meteorological features and analyses the near-surface atmospheric variables responsible for the major damage through the application of the SAFRAN (Système d’analyse fournissant des renseignements atmosphériques à la neige) mesoscale analysis, which, together with the proposed «wind, wet-snow index» (WWSI), allows to estimate the severity of the event. This snow storm provides further evidence of our vulnerability to natural hazards and highlights the importance of a multidisciplinary approach in analysing societal impact and the meteorological factors responsible for this kind of event.

Full article HERE.

 

Floods in the north-western Mediterranean region: presentation of the HYMEX database and comparison with pre-existing global databases

ABSTRACT

The contribution presents the database on floods (1981-2010) that is being developed in the framework of HYMEX project and the preliminary results obtained for the NW sector of Mediterranean region. This database contains data on damages and the main hydrometeorological features of each reported event. The study is included in one of the objectives of the Working Group 5, which is a transversal group of the HYMEX project dealing with all the aspects related to societal and ecological impacts of hydrometeorological extremes, as well as their perception and communication processes. One of the main points of the WG5 is the creation of a common database on floods and their societal impact, for the Mediterranean region, as well as its analysis. Although some databases already exist and are frequently consulted, they are mainly focused on “major” catastrophic events. But the Mediterranean region experiences every year a high number of minor flash-floods that, considered in their totality, produce important losses and disruptions of the everyday life. This contribution is focused on North-Eastern Spain, South of Italy and South-East of France and the objective is to include all the floods that have produced damages, although they are not considered as “major” disasters.