Developing structural-financial flood damage curves for residential buildings

The documentation and quantification of flood impacts is required by multiple actors, such as public administrators, insurers and scientists, for multiple reasons, such as planning, mitigating, projecting or even forecasting. Collecting and analysing impact data is however not systematically undertaken. Direct flood impacts can be documented as structural (or physical) or financial damage. Structural damage is described as an ordered classification with five grades, from moist and dirt, to wall cracking, up to complete collapse. The financial damage is rather documented as absolute or relative damage, i.e. the ratio between repair costs and the building value, which allows for an easier comparability. Both structural and financial damage are at times documented and numerical models have been developed for both types. Models are frequently used to estimate damage of undocumented cases and make projections. Yet, large uncertainties remain and each model has different data requirements, making them sometimes inapplicable for a certain area or after a certain flooding event. In a joint work, we have shown that the documentation of structural damage need not be undertaken on site, but can be accomplished for large areas through remote sensing, when quality aerial data is available. Here, we also explore the relationship between the two impact types, structural and financial damage, to allow for a conversion from structural to financial damage, complementing the data gathering obviating the labour- and time-intensive on-site surveys. The work is based on survey data gathered after eight flood events in Germany. The data can be regarded representative and transferable to Europe as most buildings are of masonry and have a cellar.