CREATE MORE RESILIENT COMMUNITIES ANTICIPATING IMPACTS OF CLIMATE CHANGE

A.Desai, S. Bassan, J. Alvarez De Lugo, P. Wadan (Woods)

ABSTRACT

With continued urban expansion, the effects of climate change have become even more evident. Climate change is projected to increase the frequency and severity of extreme weather events which implies increase in flooding. Floods create hazardous conditions to which humans are particularly vulnerable. It is essential for communities to be able to assess the flood risk they face and to understand the potential impact of these hazards on the built environment. Flood fragility curves and flood hazard definitions, such as those provided in the Australia Rainfall Runoff Guidelines 2016 (ARR2016) and in the RiskScape methodology detailed in NIWA’s technical report ‘RiskScape: Flood fragility methodology’, August 2010 (NIWA, 2010), are critical for assessing flood hazards and understanding the potential impacts these hazards have on communities.

The impacts of climate change, such as sea level rise, changes in precipitation patterns, and increased frequency and severity of extreme weather events, are expected to increase the flood hazards faced by communities. Flood fragility curves are graphical representations of the relationship between flood depth and the likelihood of damage to a building. Flood fragility relates to the likely damage or disruption that a community may suffer from flood events. Fragility functions are typically developed based on expert opinion or historic flood and damage survey data. Flood fragility curves can be used to define the flood hazard faced by a building. Flood hazard definitions classify the different levels of flood hazard for people, vehicles and structures.

The process of assessing flood hazards using flood fragility curves and flood hazard definitions can provide valuable information to quantify flood hazard risk and help communities understand the potential impacts of flooding on their buildings, infrastructure, and residents. Fragility curves set thresholds and assign classes with different levels of associated expected damage. This information can be used to prioritize the buildings that are most at risk, to identify the most effective flood protection measures, and to inform the development of flood emergency response plans. Using flood fragility curves and flood hazard definitions to assess flood hazards involves several critical steps including an assessment which commences with review of topography around the area of interest, developing a hydrodynamic model to be simulated for various storm events and tools for post processing of model results. Once the flood scenarios have been simulated, the results are used to quantify the flood hazard by determining the flood extents, peak flood depths, peak velocities as well as the peak depth * velocity (d * v). The flood hazard definitions are also used to classify the flood hazard faced by each building, based on the relevant criteria.

This paper outlines the process of assessing flood hazards using flood fragility curves and flood hazard definitions, with a focus on the importance of this type of assessment given the impacts of climate change and the need for more resilient communities. A series of examples including recent storms events, with varying levels of risk, will be presented to illustrate these effects.