Cascading disasters are causing extreme weather to pack an even bigger punch

In November 2007, strong winds and heavy rain from Cyclone Sidr tore through the southern coast of Bangladesh. Soon, the coastal districts became a wasteland. Houses destroyed, tin shacks flattened and schools blown away. However, the destruction wrought by the deadly cyclone was only the beginning.

As the aftermath saw water and sanitation infrastructures heavily damaged and human waste left untreated, an outbreak of waterborne diseases added to the struggle of the recovery effort. In many communities, drinking-water sources such as tube wells and ponds were also contaminated with saltwater and debris. Tens of thousands of disaster victims contracted respiratory and diarrheal diseases as a result.

What Bangladesh experienced was not just a single disaster, but a phenomenon known as cascading disasters.

Best understood like a row of toppling dominoes, one disaster causes another in a series that leads to worse impacts over a wider area than is expected. Unlike dominoes, the path and impacts can be difficult to predict. In a world that is increasingly reliant on technological networks and interconnected essential infrastructure—power, internet, global food chains, sophisticated waste treatment—one flood or earthquake can cause many different problems.

“Cascading disasters are difficult to mitigate and to respond to,” explains Lisa Guppy, UN Environment Programme’s Regional Coordinator for Disaster and Conflicts in Asia and the Pacific.

Guppy points to the Great East Japan Earthquake in 2011 as another example. “The initial earthquake caused a tsunami which led to a nuclear accident. These incidents show that even well-prepared countries can be caught off guard. The Japanese example also shows that the unexpected effects of cascading disasters on the environment can be felt for many years. Contaminated water and soil management is still a problem in Fukushima in 2019, and it was not until 2015 that radiocesium levels in all fish sampled in the accident zone reached zero.

“As human dependence on technology and critical infrastructure increases, so too does the threat.”

Despite this, most risk assessments, risk reduction initiatives, response plans, policies and recovery strategies across the world fail to take cascading disasters into account. When a cascading disaster does strike, it is likely that emergency responders and governments will be poorly equipped to adequately deal with the cascading consequences, particularly as they must also respond to the primary disaster at the same time.

Cyclone Sidr is now seen as a textbook example of the huge value of preparedness and disaster risk reduction, in that a new network of shelters, an unprecedented evacuation effort and strengthened early warning and alert systems helped keep the death toll below 4,000—a fraction of the human toll of the 1991 cyclone of similar intensity that left over 140,000 dead. But it’s also an example of how risk reduction and preparedness work needs to look beyond minimizing the initial death toll and foresee cascading impacts on our environment.

This is why the UN Environment Programme (UNEP), through its resilience to disaster and conflicts subprogramme, is assisting countries and organizations to understand and prepare for cascading disasters

Guppy underlines that Asia and the Pacific is especially at risk. “Almost 45 per cent of all disasters occur in the region, making it the most disaster-prone in the world,” she says. “The region is home to more than 75 per cent of the global disaster-affected population.

“Alongside this, industry in Asia continues to grow, with environmental safety regulations often struggling to incorporate disaster risks. All these factors combined create distinct vulnerabilities which could lead to significant and unexpected impacts on people and businesses.”

Gianluca Pescaroli is a lecturer at the Institute for Risk and Disaster Reduction at the University College London and a leading researcher in cascading effects. “Vulnerabilities overlap and interact. Eventually, they reach an escalation point, which can therein create secondary effects which have greater impacts than the original triggering event,” he says.

Climate change is amplifying risk. Natural hazards are increasing in frequency and intensity and creating further vulnerabilities in Asia and the Pacific.

“We need a greater understanding of cascading disasters if we are to be prepared,” says Guppy. “Governments, UN agencies, private industry and community groups need to work together to identify and mitigate environmental safety risks and minimize potential impacts on human health.

“The bottom line is that even though cascading disasters are very difficult to predict, we simply can’t afford to ignore them.”