Author(s)

H. MAIWALD & J. SCHWARZ

Abstract

The planning and implementation of numerous flood protection measures and the associated cost–benefit studies after the 2002 flood in Germany showed the demand for accurate damage functions. Conventional loss models are limited to the relationship between flood height and the recovery costs for a specific usage class (e.g. private residential buildings). Important parameters on the resistance side such as the building materials and further impact parameters such as flow velocity remain unconsidered. Following the procedure developed in the risk analysis of earthquakes, it is checked whether methodical fundamentals can be transferred or are to be adopted in case of flood impact and which parameters must be derived from data surveys.

On the basis of a large and uniformly elaborated flood damage database (including different data sets collected by the Earthquake Damage Analysis Center (EDAC) after the 2002 flood in Saxony, Germany), an engineered and vulnerability-oriented prognosis tool was developed to determine the structural damage and the losses for any given flood scenario.

Repeatedly observed damage patterns are transformed into a classification scheme of damage grades. With this tool, the structural damage of many different damage cases can be analysed in a systematic way and related to the parameters describing the flood impact. Vulnerability classes for the different building types are defined by using the data for determining characteristic ranges of damage expectation. Basic steps of the procedure are illustrated for a fictitious data set and subsequently applied to the existing database.

Specific vulnerability and damage functions enable the calculation of damage grades and the loss assessment in separate steps of the same procedure, related to the inundation level or additionally the flow velocity (action side), and the predominant building types or the vulnerability classes (resistance side).

The damage distribution caused by the August 2002 flood can be re-interpreted for study areas with close agreement to the observed effects. A similar good prognosis could be achieved for the reported loss in monetary terms by correlating vulnerability and impact parameters using the recently elaborated specific damage functions. First investigations with respect to the location of buildings, the direction of flow and the structural damage are also represented. This paper gives an overview of the background and the basic steps of the developed procedure and illustrates the different fields of its application.

Keywords

damage functions, damage grades, flood damage, flow velocity, loss estimation, specific energy height, vulnerability classes, vulnerability functions