Carlos Bateira

DISASTER: a GIS database on hydro-geomorphologic disasters in Portugal

AbstractIn the last century, Portugal was affected by several natural disasters of hydro-geomorphologic origin that often caused high levels of destruction. However, data on past events related to floods and landslides were scattered. The Disaster project aims to bridge the gap on the availability of a consistent and validated hydro-geomorphologic database for Portugal, by creating, disseminating and exploiting a GIS database on disastrous floods and landslides for the period 1865–2010, which is available in http://riskam.ul.pt/disaster/en. Data collection is steered by the concept of disaster used within the Disaster project. Therefore, any hydro-geomorphologic case is stored in the database if the occurrence led to casualties or injuries, and missing, evacuated or homeless people, independently of the number of people affected. The sources of information are 16 national, regional and local newspapers that implied the analysis of 145,344 individual newspapers. The hydro-geomorphologic occurrences were stored in a database containing two major parts: the characteristics of the hydro-geomorphologic case and the corresponding damages. In this work, the main results of the Disaster database are presented. A total of 1,621 disastrous floods and 281 disastrous landslides were recorded and registered in the database. These occurrences were responsible for 1,251 dead people. The obtained results do not support the existence of any exponential increase in events in time, thus contrasting with the picture provided to Portugal by the Emergency Events Database. Floods were more frequent during the period 1936–1967 and occurred mostly from November to February. Landslides were more frequent in the period 1947–1969 and occurred mostly from December to March.

Movimentos em massa no norte de Portugal: factores da sua ocorrência

portuguesNeste artigo pretende-se definir e caracterizar os factores de ordem natural e antropica que estao na base da ocorrencia de movimentos em massa no Norte de Portugal. A exposicao dos varios factores de risco e feita com base em quatro casos previamente estudados. EnglishThis article pretends to define and characterize the natural and anthropic factors, which are responsible for mass movements at the North of Portugal. The analysis of risk factors is based on presentation of four study cases.

Assessing the spatial probability of landslides using GIS and informative value model in the Bamenda highlands

Landslides are a major natural hazard in the Bamenda highlands of Cameroon, and their occurrence in this region has most often been studied using qualitative methods. The aim of this research is to quantitatively assess the spatial probability of landslides using GIS and the informative value model. Landslide inventory was done through literature review, aerial photo-interpretation, participatory GIS and field survey. Six geo-environmental factors including slope, curvature, aspect, land use, lithology and geomorphology were used as landslide conditioning (static) factors. The susceptibility of the area to future landslide events was assessed by making a correlation between past landslides and geo-environmental factors using the informative value model. The landslide inventory involving 110 landslides was divided into two equal groups using random division criterion and was used to train and validate the model. The analysis showed that slope and land use are the most important causal factors of landslides in the area. The susceptibility index map predicted most landslides to occur around the steep slopes of the Bamenda escarpment that is being used for multiple anthropic activities. The training model had a success rate of 87%, and the validation model had a prediction rate of 90%. The prediction rate curve shows that 44, 32, 18 and 6% of future landslides will occur on 3, 8, 21 and 68% of the study area. The model correctly classified 89% of unstable areas and 81% of the stable areas with an accuracy rate of 0.90. This quantitative result complement other qualitative assessment results that show the Bamenda escarpment zone as a high-risk area. However, the area susceptible to landslide in this study goes beyond what earlier studies had indicated as houses and other infrastructure were found on old landslide sites whose scars have been eroded by human activities. This new input thus improves the quality of information placed at the disposal of civil protection units and land use managers during decision making.

Baião landscape units: “dashes of nature and culture”

Definido pelas carateristicas da natureza moldadas pelo Homem,o municipio de Baiao insere-se num espaco de transicao, constituindo,portanto, uma area privilegiada para a analise integrada dapaisagem, nomeadamente atraves da conciliacao entre a distribuicaoespacio-temporal do seu vasto patrimonio cultural com a diversidademorfo-estrutural, climatica, distribuicao de recursos naturais e dinâmicasterritoriais distintas. E este jogo de elementos, responsaveispela modelacao dos territorios, que serve de input a definicao dasunidades de paisagem de Baiao, objetivo principal deste estudo.Do cruzamento de aspetos relacionados com a morfologia, geologia,uso do solo, distribuicao da populacao/edificado, acessibilidades e vestigios arqueologicos e historicos, resultou a identificacao de quatrounidades de paisagem, cujas caracteristicas sao o reflexo da formacomo o Homem, ao longo do tempo, (con)viveu neste espaco cujaocupacao remonta a Pre-Historia