Preparing for the unknown

WFP study on the impact and plan of action for potential earthquakes is the first ever model in Bhutan for humanitarian planning

By Tashi Namgyal

The Himalayan region has amongst the highest earthquake risk globally, with recent moderate-sized events resulting in tens of thousands of casualties.

Despite this, understanding of earthquake risk in the region is limited, particularly in Bhutan, where research on both past and future earthquakes is also limited. While recent work has clearly shown the potential for large earthquakes in the Himalayan region, the impacts from potential future earthquakes in Bhutan is entirely unknown.

The EquIPBhutan project (Bhutan Earthquake Impact Planning) by the World Food Programme (WFP) provides the first ever model of impacts from potential earthquakes in Bhutan, accounting for multiple possible eventualities to inform government and humanitarian planning for a future event.

Using population and housing data from the 2017 Population and Housing Census of Bhutan, the study modeled the number of building collapses, fatalities, serious injuries, and displaced persons.

In total, 110 different earthquake scenarios are considered, and the number of fatalities, serious injuries and displaced people are modeled. The results show that in the worst-case there could be more than 9000 fatalities, 10,000 serious injuries, and 45,000 displaced nationally. There are 5 different scenarios in which more than 5000 fatalities occur nationally, and 3 scenarios with more than 5000 injuries, but at least 13 scenarios with more than 10,000 displaced. Earthquake risk is heavily concentrated in the more populous Western Bhutan where impacts are typically three times larger than in Eastern Bhutan. Wangduephodrang and Punakha Dzongkhags have the highest risk nationally since the majority of damaging scenarios result in more than 500 fatalities and 1000 displaced in each Dzongkhag. The amount of damage an individual Dzongkhag experiences is close to its maximum for M 7.5 earthquakes and stronger earthquakes do not produce significantly more damage within a Dzongkhag. However, nationally, stronger earthquakes impact bigger areas and therefore have much larger total impacts

Of the 110 possible scenarios, 65 are large enough to cause at least one fatality in Bhutan but of these, 15 result in more than 1000 fatalities and five result in more than 5000 fatalities. There are 70 scenarios large enough to cause serious injuries and displaced people, with at least 17 scenarios resulting in more than 1000 serious injuries and more than 5000 displaced. However, there are 13 different scenarios that result in more than 10,000 displaced people. 

Earthquakes that occur in Western Bhutan result in at least three times more damage than if they occurred in Eastern Bhutan. In fact, a moderate earthquake striking Western Bhutan may result in more damage than a much larger earthquake striking Eastern Bhutan. However, large earthquakes in Eastern Bhutan can still result in thousands of fatalities and serious injuries, and tens of thousands of displaced people.  Earthquakes in Western Bhutan are typically found to be causing more fatalities than serious injuries due to the large number of adobe buildings in the region. These structures have extremely large fatality rates meaning most people inside these structures when they collapse would be killed leaving relatively few injured survivors

Dzongkhag-level findings:

Thimphu has the highest worst-case impacts of any Dzongkhag. In the worst-case, there could be at least 1500 fatalities, 1500 serious injuries, and 6500 displaced people. However, there are just 28 scenarios that result in severe damage in Thimphu and the majority result in small numbers of fatalities, injuries, and displaced people.

However, despite not having the largest worst-case, impacts are most consistently high in Punakha and Wangduephodrang, where 45% of all damaging scenarios cause more than 500 fatalities and more than 1000 displaced people. Serious injuries in both are comparatively low however, because the dominant building types have high fatality rates, meaning most exposed people are killed leaving relatively few survivors. Wangduephodrang and Punakha are therefore considered the highest risk Dzongkhags in Bhutan.

Within each Dzongkhag, a nearby M 7.5 earthquake may result in almost as much damage as an M 8.5 earthquake despite being 32 times weaker. Nationally, an M 8.5 earthquake causes far greater total damage because it impacts multiple Dzongkhags simultaneously. However, within each Dzongkhag, the amount of damage sustained does not increase substantially for earthquakes bigger than M 7.5.

Within Bhutan, earthquake risk is most highly concentrated in Wangduephodrang, Punakha, Thimphu, and Paro Dzongkhags where 33 of the most at-risk Gewogs/Thromdes are located, comprising 35% of the national population.

Within these four Dzongkhags, earthquake risk is most heavily concentrated in the urban Gewogs and Thromdes, particularly Thimphu Thromde, Wangduephodrang town, Paro town, and Punakha town. The large populations mean these urban areas typically account for at least 20% of the entire Dzongkhag’s impacts. Thimphu Thromde is at especially high risk, often accounting for more than 70% of the fatalities, more than 85% of the injuries, and more than 80% of the displaced population across Thimphu Dzongkhag. However, Thimphu Thromde accounts for 80% of the population of Thimphu Dzongkhag, highlighting that recent earthquake strengthening efforts in the city are reducing fatalities

Earthquake risk is heavily concentrated in the more populous Western Bhutan where impacts are typically times larger than in Eastern Bhutan. Wangduephodrang and Punakha Dzongkhags have the highest risk nationally since the majority of damaging scenarios result in more than 500 fatalities and 1000 displaced in each Dzongkhag. The amount of damage an individual Dzongkhag experiences is close to its maximum for M 7.5 earthquakes and stronger earthquakes do not produce significantly more damage within a Dzongkhag. However, nationally, stronger earthquakes impact bigger areas and therefore have much larger total impacts.

“Increasing public awareness and understanding of the earthquake risk in Bhutan is expected to be beneficial for both local resilience and preparedness. This could be undertaken via the Desuung who are well placed to engage in community earthquake preparedness activities,” the report suggests.

It mentions that efforts to reduce earthquake risk in Bhutan should prioritise reducing risk in the urban areas of western Bhutan by increasing the resilience of new and existing buildings.

The report calls for investment into researches relating to earthquake-safe construction practices, targeted assessment of the current conditions of all essential buildings, retrofitting those that do not meet standards and training of local masons in ‘build-back-better’ techniques.