Damage and loss prognosis tools correlating flood action and building’s resistance-type parameters

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.

Damage assessment in Braunsbach 2016: data collection and analysis for an improved understanding of damaging processes during flash floods

“…Since the construction year is related to the overall preservation and the building's state of the art in terms of technology, it can still be assumed that newer buildings or buildings in a better condition have a higher resistance to structural damage. This is in line with Maiwald and Schwarz (2015), who consider the building age and condition to have an influence on the expected structural damage.…”

“…The building material, condition (before the event) and age are especially important factors that are related to a building's resistance potential. Factors such as inundation level, flow velocity, fluid density, specific energy and contamination relate to "action" parameters and describe external forces (Maiwald and Schwarz, 2015;Milanesi et al, 2015). Thus, in our study, the inundation depth measured at the building and the building's exposition in flow direction were combined to create a local impact value, which can be seen as a proxy for local flood-related impact and hydrostatical forces at the building.…”

“…The inherent calculations are based on artificial neural networks (Ripley, 1996;Venables and Ripley, 2002) which again do not require any model-specific assumptions such as linearity. Maiwald and Schwarz (2015) give an up-to-date overview of factors which influence structural damage to buildings in cases of flooding. The building material, condition (before the event) and age are especially important factors that are related to a building's resistance potential.…”

“…if the near surrounding is sealed or if an outbuilding or shop window is present) and the existing literature. Here, Thieken et al (2005), Merz et al (2010) and Maiwald and Schwarz (2015) give an overview of important damage-influencing factors in cases of (river) flooding, including building characteristics, precaution measures and contamination.…”

Konzeptionelle Grundlagen und Tools zur Bewertung der Multi‐Hazard‐Verletzbarkeit von Bestandsbauten

“…This takes into account experience of building surveying for seismic risk mapping [3,14,15] or for the validation of the EDAC flood damage model [16][17][18][19][20]. 1.…”