Sensitivity analysis of flood damage estimates: A case study in Fredericton, New Brunswick

Abstract

Recently, the U.S. FEMA's standardized best-practice methodology Hazus for estimating potential losses from common natural hazards, including earthquakes, flood, and hurricanes has been adopted for use in Canada. Flood loss estimation relies on the combination of three components: flood level, inventory of the built environment, and pre-selected vulnerability parameters such as depth-damage functions, all of which have large associated uncertainties. Some of these parameters, such as occupancy schemes and vulnerabilities, have been carried over from the U.S. version on the presumption of regional similarities between Canadian provinces and states south of the border. Many of the uncertainties can be reduced by acquiring additional data or by improving the understanding of the physical processes. This paper presents results from a series of flood risk analyses to illustrate the sensitivity that can be associated to the depth-damage function, flood level, and restoration duration and to identify their relative impacts on the resulting losses. The city of Fredericton is chosen as the test case as it was subjected in 2008 to flood water levels breaching 1.86m above flood stage resulting in more than 680 residents evacuated from their homes, and economic costs of more than $23 million. The loss results are expressed by the number of flooded residential buildings which varied between 579 and 623 and the range of replacement cost is $21 million. These results highlight the importance of proper selection of input parameters customized to the study area under consideration.