Acting on disaster warnings: Don't miss the human factor

Sudhir Kumar in SciDev.net: The Great East Japan Earthquake and subsequent tsunami of 11 March 2011 challenged global ideas about responding to disasters. It showed that structural defences alone, such as breakwaters, coastal dykes and tidal barriers, cannot provide protection from tsunamis of such magnitude. The events of that day also emphasised the importance of 'end-to-end' early warning systems (systems spanning all steps from hazard detection through to community response). A Japanese government study, published in the Japan Times in August 2011, has found that only 58 per cent of people in coastal areas of Fukushima, Iwate and Miyagi prefectures heeded tsunamiwarnings immediately after the earthquake and headed for higher ground.

Of those who attempted to evacuate after hearing the warning, just five per cent were caught by the tsunami.  The report's findings raise the question of why some people act on early warnings while others ignore them. 

As climate change alters the risks posed by extreme weather events, how a community responds to early warnings will be a decisive factor in how people fare in hydro-meteorological events, including cyclones, blizzards, heavy snowfall, avalanches, coastal storm surges, floods, drought, heat-waves and cold spells.

There are barriers to action. The first may be the technical language used by warning systems. Individuals and communities may not be able to understand the meaning of obscure terms such as 'Cyclone Category 4', or the significance of a given wind speed.

Even when a community receives a warning, people's perception of risk may discourage them from heading for safety. In 2008, for example, Myanmar's Department of Meteorology and Hydrology detected Cyclone Nargis at an early stage, but people underestimated its intensity and believed that staying indoors would offer protection from winds, floods, and sea surge. 

The early warning system itself may underestimate the risk, as occurred when floods struck Mumbai, India, on 26 and 27 July 2005. A subsequent fact-finding committee found a significant gap between rainfall forecast (between 65 millimetres and 124.9 millimetres) and actual rainfall (944 millimetres — the eighth heaviest rainfall during a 24-hour period on record). Several hundred people lost their lives in the flooding.... 

Glenwood Springs, CO, June 8, 2002 -- The evening sun barely penetrates the smoke and ash as evacuees flee West Glenwood because of the spreading wildfires in Garfield County. Photo by Bryan Dahlberg/FEMA News Photo