The World Bank is warning cities around the world are unprepared for fast-increasing risks from extreme weather and other hazards, which is compounded by population growth and surging migration.
By 2050, 1.3 billion people and US$158 trillion (NZ$232.17 trillion) in assets will be affected by worsening river and coastal floods alone, warns a new report on Monday prepared by the Global Facility for Disaster Reduction and Recovery (GFDRR), managed by the World Bank.
But as cities expand and revamp, there's the opportunity to reduce risk with more resilient infrastructure and preventive policies.
Many city officials have no clear idea of the range of disaster risks they face and how serious they could be.
Argentina, for instance, has no volcanoes but is affected by ash from eruptions in Chile, while Malawi's 2009 earth quake came as a surprise.
A new open-source disaster risk management tool, ThinkHazard!, makes planning for such threats easier by pulling together information on all potential disaster risks in a region.
The tool, aimed at national and city planners, and project developers, also offers advice on what might work to reduce the risks.
The new tool, developed by the GFDRR, brings the information together and simplifies it, alerting developers to risks they may not even be aware of, which can be substantial.
In Indonesia, chances of flooding from overflowing rivers are expected to grow 166 percent over the next 30 years, while coastal flooding risk could rise 445 percent.
Nepal's capital Kathmandu could see a 50 percent rise in earthquake risk by 2045 as more slums and informal buildings go up.
A combination of sea-level rise and sinking of coastal cities, including from excessive extraction of the groundwater, could drive disaster losses in 136 coastal cities from US$6 billion (NZ$8.82 billion) a year in 2010 to US$1 trillion (NZ$1.47 trillion) a year by 2070, the report said.