Abstract. Flow velocity is generally presumed to influence flood damage. However, this influence is hardly quantified and virtually no damage models take it into account. Therefore, the influences of flow velocity, water depth and combinations of these two impact parameters on various types of flood damage were investigated in five communities affected by the Elbe catchment flood in Germany in 2002. 2-D hydraulic models with high to medium spatial resolutions were used to calculate the impact parameters at the sites in which damage occurred. A significant influence of flow velocity on structural damage, particularly on roads, could be shown in contrast to a minor influence on monetary losses and business interruption. Forecasts of structural damage to road infrastructure should be based on flow velocity alone. The energy head is suggested as a suitable flood impact parameter for reliable forecasting of structural damage to residential buildings above a critical impact level of 2 m of energy head or water depth. However, general consideration of flow velocity in flood damage modelling, particularly for estimating monetary loss, cannot be recommended.

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.

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Die Quantifizierung der Schadenspotentiale infolge Hochwasser setzt realistische Zusammenhänge zwischen Einwirkungs‐ und Verlustkenngrößen voraus. Da sich herkömmliche Schadensfunktionen auf den Zusammenhag zwischen Fluthöhe und den versicherungsseitig nachvollziehbaren Kosten für eine bestimmte Nutzungsklasse (wie. z. B. private Wohngebäude) beschränken, fehlt zum einen die notwendige Differenzierung nach den für die Widerstandsseite relevanten Merkmalen, zum anderen bleiben weitere Einwirkungsgrößen wie die Fließgeschwindigkeit unberücksichtigt.Auf der Grundlage einer einheitlichen Datenerhebung wurde ein System entwickelt, mit dem die strukturelle Schädigung eines Bauwerks oder eines betroffenen Bauwerksbestands für konkrete Hochwasserszenarien bestimmt werden kann.Dieses Instrumentarium wird erweitert, so dass der Zusammenhang zwischen den Einwirkungskenngrößen Überflutungshöhe und Fließgeschwindigkeit und dem strukturellen Schaden hergestellt werden kann.Die Studie stützt sich auf dabei zwei Datensätze, die nach dem Hochwasser 2002 erhoben wurden:– Datensatz 1 bezieht sich auf eine schriftliche Befragung, welche zwischen 2002 und 2004 in Sachsen durchgeführt wurde.– Datensatz 2 stellt dabei das Ergebnis einer Auswertung von Schadensgutachten im Auftrag der Landestalsperrenverwaltung Sachsen dar.Im Ergebnis kann ein neuartiger Typ von Verletzbarkeitsfunktionen bereitgestellt werden, der den Zusammenhang zwischen Überflutungshöhe, Fließgeschwindigkeit und den Schadensgraden Di in Abhängigkeit von der konkreten Bauwerksverletzbarkeit beschreibt.Mit Hilfe ebenfalls neu entwickelter Schadensfunktionen werden die so berechneten Schadensgrade in konkrete Verlustaussagen überführt.Wie an drei Testgebieten im Freistaat Sachsen nachgewiesen werden kann, gelingt es mit diesen Funktionen, die gemeldeten Verluste infolge des Hochwassers 2002 in guter Übereinstimmung nachzuvollziehen.Im Weiteren werden erste Untersuchungen zum Einfluss der städtebaulichen Einbindung und der Anströmrichtung auf die strukturellen Schäden vorgestellt.Consideration of flow velocity in flood damage models.Reliable prognoses of building damage caused by flood impact require realistic relationships between action and damage or loss describing parameters. Due to the fact that commonly applied damage functions are related to the different usage classes (i.e. private housing), the required differentiation according to the parameters on the resistance side is still missing and further impact parameters like flow velocity remain unconsidered.On the basis of the August 2002 Saxony flood data base, a method to determine the structural damage for any given flood scenario was developed.This method is improved to consider the correlation between inundation level and flow velocity and structural damage. The study is based on two different datasets collected after the flood 2002 in Saxony:– Dataset 1 is related to the outcome of a questionnaire survey performed by the authors between 2002 and 2004.– Dataset 2 is the outcome of an evaluation of damage expertises by order of the “Landestalsperrenverwaltung Sachsen”.A set of new Specific Vulnerability Functions (SVF) for calculation of damage grades is derived considering the inundation level and the flow velocity depending on the vulnerability of the predominant building types.Based on new developed Specific Damage Functions (SDF) the calculated damage grades are transferred into loss estimates.The developed tools are applied to the reinterpretation of the August 2002 flood damage. Results of the approach are presented for three different study areas in the free state of Saxony. In all cases a remarkable good agreement between the predicted and the reported loss can be stated.First investigations with respect to the location of buildings, the direction of inflow and the structural damage are represented.

Within the framework of recent research projects, basic tools for GIS-based seismic risk assessment technologies were developed and applied to the building stock and regional particularities of German earthquake regions. Two study areas are investigated, being comparable by the level of seismic hazard and the hazard-consistent scenario events (related to mean return periods of 475, 2475 and 10000 years). Significant differences exist with respect to the number of inhabitants, the grade and extent of urbanisation, the quality and quantity of building inventory: the case study of Schmo¨lln in Eastern Thuringia seems to be representative for the majority of smaller towns in Germany, the case study of Cologne (Ko¨ln) stands for larger cities. Due to the similarities of hazard and scenario intensities, the considerable differences do not only require proper decisions concerning the appropriate methods and acceptable efforts, they enable conclusions about future research strategies and needs for disaster reduction management. Not least important, results can sharpen the focus of public interest. Seismic risk maps are prepared for different scenario intensities recognising the scatter and uncertainties of site-dependent ground motion and also of the applied vulnerability functions.The paper illustrates the impact of model assumptions and the step-wise refinements of input variables like site conditions, building stock or vulnerability functions on the distribution of expected building damage within the study areas. Furthermore, and in contrast to common research strategies, results support the conclusion that in the case of stronger earthquakes the damage will be of higher concentration within smaller cities like Schmo¨lln due to the site-amplification potential and/or the increased vulnerability of the building stock. The extent of damage will be pronounced by the large number of masonry buildings for which lower vulnerability classes have to be assigned. Due to the effect of deep sedimentary layers and the composition of building types, the urban centre of Cologne will be less affected by an earthquake of comparable intensity.