Informal building expansion heightens quake risk in Capital

  • A new report warns the world is ill-prepared for an increasing rise in disasters

Kathmandu, May 17

Earthquake risk in Kathmandu is expected to double to 50 per cent by 2045 due to informal building expansion. This is the finding of a new report that is a warning that the world is ill-prepared for an increasing rise in disasters, spurred by climate change, rising populations and increasing vulnerability of people in large cities and unregulated housing.

The report titled ‘The Making of a Riskier Future: How Our Decisions are Shaping the Future of Disaster Risk’ calls for a radical new approach to assessing risk, which takes into account extremely rapid changes in global disaster risk.

Using vulnerability curves developed through incremental dynamic structural analysis for each possible building configuration, a stochastic building expansion model was presented to simulate possible expansion sequences over the lifetime of a building. The model was then used to simulate an entire neighbourhood in the Kathmandu Valley area, and analysed to understand neighbourhood-level risk over time, based on a reproduction of the 1934 Nepal-Bihar earthquake that destroyed the city.

The researchers found that there is a significant earthquake risk linked with informal building expansion. While the risk is easy to overlook for a single building or short timeframe, given enough time and scaled to entire neighbourhoods, the study revealed that the incremental expansion process can profoundly shift earthquake risk.

“Governments should consider policies to control the most dangerous expansions and/or should develop design guidelines for expanding safely,” says the report, adding, “Both of these steps would have significant impact on reducing the future risk of cities.”

It has further said the disaster risk of rapidly changing cities is predictable, even if it has significant uncertainty. Probabilistic hazard models can be combined with modern structural analysis tools, simulated building expansion, and other models to gain an understanding of the main trends in the disaster risk of cities.

“As part of efforts to ensure that cities are resilient to future disasters, these tools can serve as the basis for risk-informed urban planning and policy analyses that place urban environments on a trajectory to minimise future risk.”

Annual total damages from disasters have been increasing for decades and models show that population growth and rapid urbanisation could put 1.3 billion people and $158 trillion in assets at risk from river and coastal floods by 2050, as per the report.

“With climate change and rising numbers of people in urban areas rapidly driving up future risks, there’s a real danger the world is woefully unprepared for what lies ahead,” John Roome, World Bank Group’s senior director for climate change, has been quoted as saying in the media release issued today. “Unless we change our approach to future planning for cities and coastal areas that takes into account potential disasters, we run real risk of locking in decisions that will lead to drastic rises in future losses.”

In examining literature and case studies from around the globe, the report cites studies showing that densely populated coastal cities are sinking and when coupled with rising sea levels, annual losses in 136 coastal cities could increase from $6 billion in 2010 to $1,000 billion in 2070.

It also cites research warning that in Indonesia, river flood risk may increase 166 per cent over the next 30 years due to rapid expansion of urban areas, while the country’s coastal flood risk could rise by 445 per cent.

This month, over 700 experts and thought leaders will gather in Venice to examine the critical role of technological advances in disaster risk management. The 2016 Understanding Risk Forum, hosted by   Global Facility for Disaster Reduction and Recovery (GFDRR), will showcase the latest innovations, exchange ideas and form partnerships on risk identification and assessment.