The role of different factors related to social impact of heavy rain events: considerations about the intensity thresholds in densely populated areas

ABSTRACT: 

In the assessment of social impact caused by meteorological events, factors of different nature need to be considered. Not only does hazard itself determine the impact that a severe weather event has on society, but also other features related to vulnerability and exposure.

The requests of data related to insurance claims received in Meteorological Services proved to be a good indicator of the social impact that a weather event causes, according to studies carried out by the Social Impact Research Group, created under the frame of the MEDEX project. Taking these requests as proxy data, diverse aspects connected to the impact of heavy rain events have been studied.

The rainfall intensity in conjunction with the population density has demonstrated to be one of the key factors in social impact studies. One of the conclusions we obtained is that various thresholds of rainfall should be applied for differently populated areas. In this study, the role of rainfall intensity has been analysed for a highly populated urban area like Barcelona. A period without significant population changes has been selected for the study to minimise the effects linked to vulnerability and exposure. First, correlations between rainfall recorded in different time intervals and requests have been carried out. Afterwards, a method to include the intensity factor in the social impact index has been suggested, based on return periods given by Intensity-Duration-Frequency (IDF) curves.

Authors: L. Barbería, J. Amaro, M. Aran, and M. C. Llasat

LINK: www.nat-hazards-earth-syst-sci-discuss.net/2/459/2014/nhessd-2-459-2014.html

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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.

Podéis descargar el artículo de forma gratuita hasta el 31 de agosto. LINK:  http://authors.elsevier.com/a/1PLdgcd3RmlUW

Climate change impacts on wildfires in a Mediterranean environment

Nou artícle publicat a Climatic Change sobre els impactes del canvi climàtic als incencis del Mediterrani.

 

Abstract

We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate effects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced.

AUTHORS: Marco Turco, María del Carmen Llasat, Jost von Hardenberg and Antonello Provenzale.

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