Dossier pedagógico sobre los riesgos de las inundaciones y las tormentas

Podeu consultar la versió catalana a http://hdl.handle.net/2445/8610 i la versió anglesa a http://hdl.handle.net/2445/8611 Este trabajo se ha realizado gracias al apoyo de: "Grupo de Análisis de situaciones Meteorológicas Adversas (GAMA)-Universitat de Barcelona; Proyecto EDRINA-06 (FECYT. Ministerio de Educación y Ciencia); Proyecto europeo FLASH (FP6-2005-Global-4) no. 036852Dosier pedagógico compuesto por fichas sobre inundaciones, tormentas y aspectos de prevención. Partes: Observación de la atmosfera (conceptos generales, meteorología, métodos de pronóstico); Inundaciones y Tormentas; Ecología de las inundacionesEste trabajo se ha realizado gracias al apoyo de: "Grupo de Análisis de situaciones Meteorológicas Adversas (GAMA)-Universitat de Barcelona; Proyecto EDRINA-06 (FECYT. Ministerio de Educación y Ciencia); Proyecto europeo FLASH (FP6-2005-Global-4) no. 03685

Flash-floods in Catalonia: the social perception in a context of changing vulnerability

In assessing a flood event two risk components need to be considered: the intrinsic hazard of the hydrome- teorological event causing the flood and the vulnerability of the area where the precipitation has been registered. In the present study four flood events selected by the FLASH Eu- ropean project have been classified according to the charac- teristics of the meteorological event (classification according to hazard) and according to the physical and economic dam- ages caused (classification according to vulnerability). The social impact of these events is analysed taking into account the growth of the population. An increase in the number of extraordinary flash-floods was detected in the areas with a major growth of the population, as a consequence of an in- creased vulnerability of these areas, both from a physical per- spective (exposure of infrastructures) and from an economic perspective (more goods exposed). In addition, the numer- ous non-native inhabitants of the region are not aware of the meteorological risks characteristic of the area, and this con- tributes to increased social vulnerabilit

Evolving flood patterns in a Mediterranean region (1301-2012) and climatic factors - the case of Catalonia

Data on flood occurrence and flood impacts for the last seven centuries in the northeastern Iberian Peninsula have been analysed in order to characterise long-term trends, anomalous periods and their relationship with different climatic factors such as precipitation, general circulation and solar activity. Catastrophic floods (those that produce complete or partial destruction of infrastructure close to the river, and major damages in the overflowed area, including some zones away from the channels) do not present a statistically significant trend, whereas extraordinary floods (the channel is overflowed and some punctual severe damages can be produced in the infrastructures placed in the rivercourse or near it, but usually damages are slight) have seen a significant rise, especially from 1850 on, and were responsible for the total increase in flooding in the region. This rise can be mainly attributed to small coastal catchments, which have experienced a marked increase in developed land and population, resulting in changes in land use and greater vulnerability. Changes in precipitation alone cannot explain the variation in flood patterns, although a certain increase was shown in late summer-early autumn, when extraordinary floods are most frequently recorded. The relationship between the North Atlantic circulation and floods is not as strong, due to the important role of mesoscale factors in heavy precipitation in the northwest of the Mediterranean region. However, it can explain the variance to some extent, mainly in relation to the catastrophic floods experienced during the autumn. Solar activity has some impact on changes in catastrophic floods, with cycles related to the quasi-biennial oscillation (QBO) and the Gleissberg solar cycle. In addition, anomalous periods of high flood frequency in autumn generally occurred during periods of increased solar activity. The physical influence of the latter in general circulation patterns, the high troposphere and the stratosphere, has been analysed in order to ascertain its role in causing floods

Twitter's messages about hydrometeorological events. A study on the social impact of climate change

This study is based on an interdisciplinary collaboration between scientists from natural and social sciences to create scientific knowledge about how Twitter is valuable to understand the social impact of hydrometeorological events. The capacity of citizens' reaction through Twitter to environmental issues is widely analyzed in the current scientific literature. Previous scientific works, for example, investigated the role of social media in preventing natural disasters. This study gives scientific evidence on the existence of diversity in the intentionality of Twitters' messages related to hydrometeorological events. The methodological design is formed by four experiments implemented in different moments of a temporal axis. The social impact on social media methodology (SISM) is implemented as social media analytics. From the findings obtained, it can be observed that there are different forms of intentionality in Twitter's messages related to hydrometeorological events depending on the contextual circumstances and on the characteristics of Twitter's users' profiles (including the geolocation when this information is available). This content is relevant for future works addressed to define social media communication strategies that can promote specific reactions in vulnerable groups in front the climate change

Characteristics of 2D convective structures in Catalonia (NE Spain): an analysis using radar data and GIS

Flood simulation studies use spatial-temporal rainfall data input into distributed hydrological models. A correct description of rainfall in space and in time contributes to improvements on hydrological modelling and design. This work is focused on the analysis of 2-D convective structures (rain cells), whose contribution is especially significant in most flood events. The objective of this paper is to provide statistical descriptors and distribution functions for convective structure characteristics of precipitation systems producing floods in Catalonia (NE Spain). To achieve this purpose heavy rainfall events recorded between 1996 and 2000 have been analysed. By means of weather radar, and applying 2-D radar algorithms a distinction between convective and stratiform precipitation is made. These data are introduced and analyzed with a GIS. In a first step different groups of connected pixels with convective precipitation are identified. Only convective structures with an area greater than 32 km2 are selected. Then, geometric characteristics (area, perimeter, orientation and dimensions of the ellipse), and rainfall statistics (maximum, mean, minimum, range, standard deviation, and sum) of these structures are obtained and stored in a database. Finally, descriptive statistics for selected characteristics are calculated and statistical distributions are fitted to the observed frequency distributions. Statistical analyses reveal that the Generalized Pareto distribution for the area and the Generalized Extreme Value distribution for the perimeter, dimensions, orientation and mean areal precipitation are the statistical distributions that best fit the observed ones of these parameters. The statistical descriptors and the probability distribution functions obtained are of direct use as an input in spatial rainfall generators

Trends in flash flood events versus convective precipitation in the Mediterranean region: the case of Catalonia

The aim of this paper is to analyse the potential relationship between flash flood events and convective precipitation in Catalonia, as well as any related trends. The paper starts with an overview of flash floods and their trends in the Mediterranean region, along with their associated factors, followed by the definition of, identification of, and trends in convective precipitation. After this introduction the paper focuses on the north-eastern Iberian Peninsula, for which there is a long-term precipitation series (since 1928) of 1-min precipitation from the Fabra Observatory, as well as a shorter (1996-2011) but more extensive precipitation series (43 rain gauges) of 5-min precipitation. Both series have been used to characterise the degree of convective contribution to rainfall, introducing the β parameter as the ratio between convective precipitation versus total precipitation in any period. Information about flood events was obtained from the INUNGAMA database, with the aim of finding any potential links to convective precipitation. This flood data was gathered using information on damage where flood is treated to as a multifactorial risk, and where any trend or anomaly might have been caused by one or more factors affecting hazard, vulnerability or exposure. Trend analysis has shown an increase in flash flood events. The fact that no trends were detected in terms of extreme values of precipitation on a daily scale, nor on the associated ETCCDI (Expert Team on Climate Change Detection and Indices) extreme index, could point to an increase in vulnerability, an increase in exposure, or changes in land use. However, the summer increase in convective precipitation was concentrated in less torrential events, which could partially explain this positive trend in flash flood events. The β parameter has been also used to characterize the type of flood event according to the features of the precipitation. The highest values correspond to short and local events, usually with daily β values above 0.5, while the minimum threshold of daily β for catastrophic flash floods is 0.31

The Results of Applying Different Methodologies to 10 Years of Quantitative Precipitation Estimation in Catalonia Using Weather Radar

The single polarization C-Band weather radar network of the Meteorological Service of Catalonia covers the entire region (32,000 km2), which allows it to apply a series of corrections that improve preliminary estimations of the rainfall field (hourly and daily). In addition, an automatic re-processing using automatic weather stations helps to incorporate ground-based information. The last process of the quantitative precipitation estimation (QPE) is running the end-product again eight days later, when the data have been reviewed and corrected in the case of detecting anomalies in the radar or gauge data. These corrections are applied operationally, with the fields generated and stored automatically. The QPE fields are generated in the GeoTIFF format, allowing easy use with multiple applications and simplifying processes such as quality control. In this way, the analysis of a 10 year period of GeoTIFF QPE daily data compared with ground rainfall values is introduced. The results help to understand different points regarding the functioning of the network such as the dependance on the type of precipitation and the seasonality. In addition, the description of a heavy rainfall episode (22 October 2019) shows the variations and improvements in the different products. The main conclusions refer to how using GeoTIFF combined with point data (rain gauges), it is possible to ensure simple but effective quality control of an operational radar network

Policy and systems of flood risk management: a comparative study between Japan and Spain

This paper shows a comparison from the perspective of flood risk management between two regions of different countries: Tokyo Metropolis (Japan) and Catalonia (Spain). The comparison is based on flood damage data for a 30-year period (1981-2010), legislation, disaster management plans, recovering measures, and communication strategies. A total of 219 flood events and 110 deaths were recorded in Catalonia during 1981-2010, while there were 191 floods in Tokyo, during the same period, giving place to 27 deaths and missing people. In both countries, most of the deaths occurred outdoors and the majority as a consequence of imprudent behavior. Nearly 10% of flood victims in Catalonia were foreign citizens. Regarding the institutions from the state and the communities involved in flood risk management, we have found a similar structure between the two countries. In accordance with the European Floods Directive, all the Spanish regions susceptible of having floods have flood hazard maps for different return periods, including 500 years while in the case of Japan the return periods are usually shorter. Recently, flood risk maps have been built for Catalonia, but none is available in a foreign language. Although all the maps are available in Internet, in Spain it is not mandatory to distribute maps to the public neither evacuation maps in flood-prone areas. On the contrary, evacuation and hazard maps in Japan have some parts written in different languages. In both countries, flood hazard maps are not compulsorily linked to other countermeasures such as land-use regulation (the municipality has the last decision) or flood insurance. Thresholds of heavy rain warnings are similar in both countries, using rain amounts over both short and long periods. Although the Japanese method appears more sophisticated using humidity and runoff indexes, it is too complicated for people to understand it. In contrast, only Catalonia has forecast thresholds considering probability levels. On flood insurance, only Spain has governmental aid to the flood insurance system. The level of flood risk perception is low among the population in both countries, and social communication for flood risk is insufficient, mainly in Catalonia. Thus, it is very important that individuals recognize the flood risk in the area to reduce the number of victims