A Comparison of Factors Driving Flood Losses in Households Affected by Different Flood Types

Abstract

Flood loss data collection and modeling are not standardized, and previous work has indicated that losses from different flood types (e.g., riverine and groundwater) may follow different driving forces. However, different flood types may occur within a single flood event, which is known as a compound flood event. Therefore, we aimed to identify statistical similarities between loss-driving factors across flood types and test whether the corresponding losses should be modeled separately. In this study, we used empirical data from 4,418 respondents from four survey campaigns studying households in Germany that experienced flooding. These surveys sought to investigate several features of the impact process (hazard, socioeconomic, preparedness, and building characteristics, as well as flood type). While the level of most of these features differed across flood type subsamples (e.g., degree of preparedness), they did so in a nonregular pattern. A variable selection process indicates that besides hazard and building characteristics, information on property-level preparedness was also selected as a relevant predictor of the loss ratio. These variables represent information, which is rarely adopted in loss modeling. Models shall be refined with further data collection and other statistical methods. To save costs, data collection efforts should be steered toward the most relevant predictors to enhance data availability and increase the statistical power of results. Understanding that losses from different flood types are driven by different factors is a crucial step toward targeted data collection and model development and will finally clarify conditions that allow us to transfer loss models in space and time.

Compound flood events: different pathways–different impacts–different coping options?

“…This supports the hypothesis that the overall (hydraulic) severity of a flood pathway is more important for the perceived psychological burden than the general flood type (see Laudan et al, 2020). The results further support studies that suggest developing pathway-specific loss models (Vogel et al, 2018;Mohor et al, 2020). 350 At this point, the question arises whether and to which degree flood pathways also govern coping options.…”

Residential flood loss estimated from Bayesian multilevel models

“…Yet loss estimation remains challenging, even for direct losses that can be more easily determined than indirect losses (Figueiredo et al, 2018;Vogel et al, 2018;Amadio et al, 2019;Meyer et al, 2013). Numerous methods of inferring flood damage from field or survey data have been tested, if not validated, with varying degrees of success (Gerl et al, 2016;Molinari et al, 2020).…”

“…floods from levee breaches, riverine floods, surface water floods, or rising groundwater floods). Mohor et al (2020) used this database to explore the most relevant factors for estimating relative loss of residential buildings with a regression model. From a larger pool of candidate variables, the authors selected 13 predictors of the flood hazard, building characteristics, and preparedness, including flood type as an indicator, and suggested that the influencing factors contribute with different magnitudes across flood types.…”

“…Here we expand on the model of Mohor et al (2020) by acknowledging structure in the dataset and explore whether a single regression model can apply not only to different flood types but also to regions or flooding events. Single flood events can affect cities differently across regions, likely reflecting socioeconomic and geographic conditions and building codes, for example.…”

The object-specific flood damage database HOWAS 21

“…The Austrian Federal Railways (ÖBB) holds an objectspecific flood damage database for railway infrastructure and operation in Austria (Moran et al, 2010;Kellermann et al, 2016). This database incorporates information about the affected infrastructure object and resulting service disruptions, the structural damage and corresponding repair costs, the hazard characteristics, and possible mitigation measures.…”