AIR Worldwide Launches Inland Flood Model for Germany

November 8, 2011

Catastrophe risk modeling firm AIR Worldwide has released an inland flood model for Germany, which it said “offers a fully probabilistic approach for determining the likelihood of flood losses from all types of storms. The model provides insurers and reinsurers with a robust tool for managing inland flood risk — allowing companies to make informed underwriting decisions, to monitor and quantify aggregate concentrations of flood risk across their portfolios, and to assess the potential impact of less frequent but large loss events.”

Dr. Jayanta Guin, senior vice president of research and modeling at AIR Worldwide, explained that the new model is designed to “meet the challenge of capturing both large-scale and small-scale precipitation patterns.” He explained that it “has adopted the innovative approach of coupling a state-of-the-art Global Climate Model (GCM) with a detailed Numerical Weather Prediction (NWP) model. The result is a sophisticated model that simulates realistic and robust storm patterns over space and time, allowing companies to manage their risk from flooding both on and off the floodplain.”

The AIR Inland Flood Model for Germany includes on-floodplain flooding, which covers a river network extending more than 160,000 kilometers and comprising more than 30,000 stream links, and off-floodplain flooding, which is modeled according to the specifics of more than 35,000 small catchments (drainage areas) in Germany.

The announcement noted that “flooding is a regular occurrence in Germany — and not limited to the coast or low-lying river valleys – but nearly ubiquitous due to off-floodplain flash flooding. With a significant percentage of losses from the 2002 floods occurring off-floodplain and much of that loss occurring in highly exposed urban areas. As a result AIR said it “has developed an explicit module for off-floodplain loss estimation. The off-floodplain model accounts for elevation, runoff, drainage backups, and facility aging at each modeled location.

“Furthermore, the NWP model provides all the necessary input — liquid and frozen precipitation, surface wind, surface temperature, and solar radiation — to account for the impact of snowmelt and soil moisture conditions, both important contributors to flood risk.”

A number of factors influence the extent of property damage from flooding. AIR said these include “building characteristics such as construction material, building height, and basements. The model can also account for site-specific flood defense systems often deployed by large industrial facilities. Based on engineering analyses, findings from published research, damage surveys conducted by AIR, and insurance loss data, AIR engineers have developed flood-specific damage functions, or relationships between flood depth and the amount of damage caused to a given building/property, for 34 different construction classes and 50 occupancy classes in Germany.”

Other highlights of the model include the following:
• A state-of-the-art approach accounts for the impact of topography and terrain on regional precipitation fields at high resolution for improved risk selection and better assessment of portfolio risk.
• Topography, soil type, geology, urbanization, and other local factors are used in calculating precipitation runoff throughout the river network.
• A physically based hydraulic model transforms river discharge to water level, or elevation. This step is critical for assessing inundation depth at each location of interest for each event and ultimately for determining loss.
• A component-based approach — one that divides a building into building fabric, fixture and fittings, and services — helps estimate the vulnerability of commercial buildings and their contents.
• Flood defenses play a critical role in protecting properties within Germany’s floodplains. The AIR flood model accounts for flood defense structures such as levees, dikes, and flood walls using a probabilistic approach that incorporates the most prominently used standards of flood protection. The model also supports custom flood defenses, which is particularly useful for accurately assessing the risk to high-value properties such as industrial facilities.
• The model supports the evaluation of reinsurance contracts incorporating a 504-hours clause as well as other durations.
• Extensive analyses of detailed loss experience data, including that from the 2002 Elbe floods, provide validation.

Dr. Guin added: “Limited historical experience and company claims data are not sufficient to estimate potential losses from the most extreme events because the exposure continues to change in number, value, and location. “The average annual insured loss today from inland floods in Germany is estimated around €300 million [$413 million], and this figure will only grow as more homes and businesses are constructed in flood-prone locations.”

The AIR Inland Flood Model for Germany is currently available in Version 13.0 of the CLASIC/2™ and CATRADER® catastrophe risk management systems.

Source: AIR Worldwide

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