Spatial scan statistics in vulnerability assessment: an application to mountain hazards

Abstract

In the European Alps, the concept of risk has increasingly been applied in order to reduce the susceptibility of society to mountain hazards. Risk is defined as a function of the magnitude and frequency of a hazard process times consequences; the latter being quantified by the value of elements at risk exposed and their vulnerability. Vulnerability is defined by the degree of loss to a given element at risk resulting from the impact of a natural hazard. Recent empirical studies suggested a dependency of the degree of loss on the hazard impact, and respective vulnerability (or damage-loss) functions were developed. However, until now, only little information is available on the spatial characteristics of vulnerability on a local scale; considerable ranges in the loss ratio for medium process intensities only provide a hint that there might be mutual reasons for lower or higher loss rates. In this paper, we therefore focus on the spatial dimension of vulnerability by searching for spatial clusters in the damage ratio of elements at risk exposed. By using the software SaTScan, we applied an ordinal data model and a normal data model in order to detect spatial distribution patterns of five individual torrent events in Austria. For both models, we detected some significant clusters of high damage ratios, and consequently high vulnerability. Moreover, secondary clusters of high and low values were found. Based on our results, the assumption that lower process intensities result in lower damage ratios, and therefore in lower vulnerability, and vice versa, has to be partly rejected. The spatial distribution of vulnerability is not only dependent on the process intensities but also on the overall land use pattern and the individual constructive characteristics of the buildings exposed. Generally, we suggest the use of a normal data model for test sites exceeding a minimum of 30 elements at risk exposed. As such, the study enhanced our understanding of spatial vulnerability patterns on a local scale.

Micro-sized enterprises: vulnerability to flash floods

“…Totschnig et al (2011) On the other hand, as reported by Karagiorgos et al (2016a), the low vulnerability values in the area are also a result of local building construction techniques as well as construction materials used. This is in line with conclusions drawn in Fuchs et al (2012c) and Highfield et al (2014) showing that building codes and standards are an important factor to reduce physical vulnerability. Studies presented by Totschnig et al (2011), Totschnig andFuchs (2013) and Papathoma-Köhle et al (2015) were focusing on fluvial sediment transport and debris flow processes in mountain torrents with considerably higher impact pressure than the flash flood events analysed in East Attica.…”

Damage assessment in Braunsbach 2016: data collection and analysis for an improved understanding of damaging processes during flash floods

“…In this regard, the relevance of building characteristics and location for vulnerability estimations were highlighted. Similarly, Fuchs et al (2012) conducted a study which describes the vulnerability of elements at risk, based on clusters of similar damage ratios caused by flood events. This spatial approach revealed that higher damage ratios are not only a result of stronger floods, debris flows or hyperconcentrated flows, but are also dependent on land-use patterns and the characteristics of the elements at risk, such as the type and year of construction.…”

A physical approach on flood risk vulnerability of buildings

“…Moreover, previous studies have shown that spatial patterns in vulnerability of buildings exposed to torrent processes exist (Fuchs et al, 2012b) which cannot be satisfactorily explained only by the spatial and temporal process dynamics on the torrential fans. Therefore, a deeper insight into the mechanisms causing losses is necessary as a basis of any subsequent engineering design of feasible and economically efficient risk mitigation strategies (Mazzorana et al, 2012a, b;Mazzorana and Fuchs, 2010).…”