In the engineering world we are often met with questions around risk mitigation, especially when it relates to the rising risk of flooding and coastal inundation. This is often met with a large concrete structure or building hardening, all designed to withstand the elements. But we can take a more holistic approach to risk management and reduction.

Hazard, Exposure & Vulnerability

Risk is composed of three distinct elements: Hazard, exposure, and vulnerability. They allows us to understand and reduce risk in different and complementary ways. Each is a critical element, and each demands a specific management approach.

To manage the hazard, we try to hold back the water using levees and sea walls.

To decrease our vulnerability we develop higher buildings, with stronger walls and flexible connections.

But to remove the need for either of these we can shift our exposure. In other words, leave nothing valuable to be flooded.

A holistic approach considers all three elements and finds the appropriate balance of measures dependent on level of risk, cost to mitigate, and socioeconomic benefits of the asset in question.

New Questions are Needed in Flood-Prone Areas

Recent flood events around the world highlight the importance of asking, does it really need to be there?

If we look at the Mississippi River, it has been engineered to such an extreme level that today it barely resembles the natural and changing flow channel it once was. This, coupled with residential and commercial development in its floodplains, left only the inevitable to happen. Three days of rain starting on the 26 December 2015 caused 25 deaths, caused thousands to be evacuated, and resulted in huge rebuild costs (The Economist, 2016). So should we have continued to develop in its floodplains?

Floods over Christmas 2015 in the UK similarly highlighted the need to consider development approvals in flood-prone areas. It’s expected that 20,000 homes will be built in flood-prone areas across the UK (The Telegraph, 2015).

Image of a tweet containing an image of a flood site, and a sign that says "Development site with permission for 39 dwellings". The entire site is underwater.

Spotted on Twitter

Although these new developments may be behind existing protection measures, the ever-changing nature of the hazard, driven by climate change, means the water is only getting higher. The story is no different in Australia with the Productivity Commission last year calling land use planning perhaps the ‘most potent policy lever’ for influencing the level of future natural disaster risk.

Understanding Exposure

The emphasis on land use planning and consideration of exposure in disaster risk reduction often focuses on restricting new development. But it can (and should) be more subtle than that.

When managing the exposure to any natural hazard, considering supply chains, critical infrastructure, essential services and network redundancies are all equally important. When we broaden our thinking and delve into the factors that allow society to evolve, our management approaches equally broaden. This provides decisions makers with many more approaches with which to deal with the hazards societies face, apart from a yes or no development approval.

Modelling Exposure

As we broaden our thinking in terms of risk, to manage and reduce it we need to model all of its components. The modelling of exposure is particularly challenging. It’s a challenge that relates to some of this group’s (iWade’s) work.

Modelling exposure into the future requires an understanding of demographic and economic drivers for new investments and developments. The uncertainty involved in this can also be staggering. Methods need to be developed to ensure risk reduction options are robust or can adapt to future hazards and societal needs.

An approach this research group is taking is to model land use change. This is driven by the need to meet the State’s population and economic projections. We are also overlaying flood modelling (along with other disasters) to understand the changing risk due to climate change, economic development and population changes. These, coupled with developing scenarios for the future of cities, allows the capture of uncertainties and the testing of policies to assess their future effectiveness.

Research Report on Modelling, Understanding Reducing Exposure

Members of this research group are currently developing decision support systems which include the land use change and hazard models for government departments in South Australia, Victoria and Tasmania.

The research includes developing software packages and running workshops to ensure the models are designed to be as relevant as possible to assist decision makers to make better long-term decisions for risk reduction

You can download a short report on our approach to understanding risk and exposure here [PDF].