Published works

This report forms part of the output to a research project titled ‘Cost effective mitigation strategy development for flood prone buildings’ within the Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC, 2015). The motivation for this project arises from the experience and observations during the recent flooding in Australia in 2011, 2013 and 2015, which caused widespread devastation in Queensland. A fundamental reason for this damage was inappropriate development in floodplains and a legacy of high risk building stock in flood prone areas. Although the vulnerability and associated flood risk is being reduced for newer construction by adopting new standards (ABCB, 2012), building controls and land use planning, the vulnerability associated with existing building stock remains. Therefore, the existing vulnerable buildings contribute disproportionally to overall flood risk in many Australian catchments. The BNHCRC project aims to address this issue and is targeted at assessing mitigation strategies to reduce the vulnerability of existing residential building stock in Australian floodplains.

As a first step to achieving this goal within this project a building schema has been developed to categorise the Australian residential building stock (Maqsood et al. 2015). The next step is to conduct a literature review of mitigation strategies developed nationally and internationally and this report presents the findings of this research component. The review will help to evaluate the strategies that suit Australian building types and typical catchment behaviours and hence may be adopted in Australia. Strategies have been developed for different types of floods and the adoption of a particular strategy depends upon the characteristics of flood hazard and building stock along with any mitigation incentives and associated cost benefit analysis. This report discusses the commonly used strategies and summarises the advantages and disadvantages of each of them. The review categorises mitigation strategies into the following categories:

• Elevation
• Relocation
• Dry floodproofing
• Wet floodproofing
• Flood barriers

Elevation is traditionally considered to be an easier and effective strategy and is the one which generally result in incentives such as a reduction in insurance premiums (Bartzis, 2013). However it becomes difficult to execute for slab-on-grade structures. Relocation is the surest way to eliminate flood risk if relocated outside the floodplain but, as in the case of elevation, it becomes more difficult to implement for heavier and larger structures. Dry floodproofing and flood barriers are efficient only in shallow low velocity hazard areas and are generally not recommended in deep fast flowing waters. Wet floodproofing is suitable in low to moderate depths of water with a inundation duration of not more than a day.

In future years (2015-2019) of this project, each mitigation strategy will be evaluated and costed through engagement of professional quantity surveyors. Strength degradation of common building components (materials, structural systems) due to wetting and subsequent drying will be assessed through experimental testing. Cost benefit analyses will be conducted to determine optimum retrofit strategies for selected residential building types within a range of catchment behaviours. The result will be an evidence base to inform decision making by government and property owners on the mitigation of flood risk by providing information on the cost effectiveness of different mitigation strategies and an optimal solution for different cases of building and catchment types.