Adaptability and transferability of flood loss functions in residential areas

Abstract

Abstract. Flood loss modeling is an important component within flood risk assessments. Traditionally, stage-damage functions are used for the estimation of direct monetary damage to buildings. Although it is known that such functions are governed by large uncertainties, they are commonly applied -even in different geographical regions -without further validation, mainly due to the lack of real damage data. Until now, little research has been done to investigate the applicability and transferability of such damage models to other regions. In this study, the last severe flood event in the Austrian Lech Valley in 2005 was simulated to test the performance of various damage functions from different geographical regions in Central Europe for the residential sector. In addition to common stage-damage curves, new functions were derived from empirical flood loss data collected in the aftermath of recent flood events in neighboring Germany. Furthermore, a multi-parameter flood loss model for the residential sector was adapted to the study area and also evaluated with official damage data. The analysis reveals that flood loss functions derived from related and more similar regions perform considerably better than those from more heterogeneous data sets of different regions and flood events. While former loss functions estimate the observed damage well, the latter overestimate the reported loss clearly. To illustrate the effect of model choice on the resulting uncertainty of damage estimates, the current flood risk for residential areas was calculated. In the case of extreme events like the 300 yr flood, for example, the range of losses to residential buildings between the highest and the lowest estimates amounts to a factor of 18, in contrast to properly validated models with a factor of 2.3. Even if the risk analysis is only performed for residential areas, our results reveal evidently that a carefree model transfer in other geographical regions might be critical. Therefore, we conclude that loss models should at least be selected or derived from related regions with similar flood and building characteristics, as far as no model validation is possible. To further increase the general reliability of flood loss assessment in the future, more loss data and more comprehensive loss data for model development and validation are needed.

Uncertainty in flood damage estimates and its potential effect on investment decisions

“…These models differ for good reasons. Each model is specifically derived for a specific country, region and/or flood type and tailored to characteristics of the flooding and objects in the considered region (Cammerer et al, 2013).…”

Modelling flood damages under climate change conditions – a case study for Germany

“…Despite the vast uncertainties, transferability is tacitly (and incorrectly) taken for granted without further validation, mainly due to the lack of real damage data. Cammerer et al (2013) found that flood-loss functions derived from related and similar regions estimate the observed damage quite well indeed, while careful thoughts are needed when transferring loss functions to other geographical regions.…”

“…However, the issue of Cammerer et al (2013) examined adaptability and transferability of stage-damage functions for the estimation of direct flood damage to buildings. Despite the vast uncertainties, transferability is tacitly (and incorrectly) taken for granted without further validation, mainly due to the lack of real damage data.…”

Assessment of Flood Losses with Household Responses: Agent-Based Simulation in an Urban Catchment Area

“…Since regions with similar flood and building characteristics could approximately represent each other [55], the model derived the specific mathematical equations of the depthdamage curves based on the study of Shi et al [56]. Their flood depth-damage curves were drawn from post-flood surveys and interviews of 134 residences in 2008 in Shenzhen and Dongguan.…”