Disaster preparedness, combined with updated risk information and database and timely assessments of damages and needs, were critical for Tonga’s response to the undersea volcanic eruption.
On 15 January 2022, the underwater HungaTonga-Hunga Ha’apai volcano near Tonga erupted with a force that NASA scientists estimated to be hundreds of times more powerful than the Hiroshima bomb. The eruption obliterated an uninhabited island and unleashed a series of tsunami waves.
On Tonga’s main island, Tongatapu, the western coast was devastated, while the shoreline of Tonga’s capital, Nuku’alofa, also suffered damages. The tsunami tragically killed three people and forced the evacuation of thousands more to higher ground. In addition to the tsunami, the eruption triggered a massive plume of ash, steam, and gas reaching above the stratosphere and covering Tongatapu in a heavy blanket of ash.
Disasters of this scale are unsettling for everybody and pose a particular challenge to local disaster managers and decision-makers who must overcome the initial disorientation and a lack of information. Tonga’s situation was no different and aggravated by damage to the undersea cables that disrupted Tonga’s domestic and international communication, including the internet.
Tonga’s national emergency management organization and operations center were able to kick into action swiftly, but communication challenges hampered the ability to assess the overall situation both in terms of immediate humanitarian needs, and damage to housing, livelihoods, and infrastructure.
While Tongan officials, volunteers, and communities battled these challenges on the ground and demonstrated ingenuity and a strong sense of collective care to reach the most vulnerable, Pacific neighbours and development partners were figuring out how to best assist the response and recovery efforts, as the COVID-19 pandemic and related travel restrictions excluded the deployment of international response and assessment teams.
In this situation, the best way to establish an understanding of the disaster and its impact was to use pre-existing geographic and statistical information on population and assets, combine it with information on both the ashfall and tsunami and complement the analysis with data derived from satellite and aerial imagery taken during and following the volcanic eruption.
Just seven months before the disaster, in June 2021, the Government of Tonga, with support from ADB, completed a multi-hazard disaster risk assessment of Tongatapu. This assessment and an associated geo-referenced database covered population, land use, and 28,000 residential and non-residential buildings, the latter classified by sector and use. It also covered 500 water and 26,000 power assets, and 1,200 kilometers of roads in Tongatapu.
Associated data included the elevation, footprint, height, construction types, design qualities, and replacement costs of each asset. Following the eruption, the Government of Tonga shared this data with interested researchers, as well as bilateral, regional, and multilateral organizations which informed several assessments and information products focused on helping the government and people to address the eruption impacts.
By 17 January, less than two days after the eruption, volcanologists at the University of Canterbury and the National Institute of Water and Atmospheric Research in New Zealand had produced estimates of the thickness of ashfall deposits for the entire island of Tongatapu, including detailed maps for the energy, water, road, and agricultural sectors using data from the initial assessment.
This covered preliminary predictions of damage and an advisory to the government on cleanup operations, both of which provided time-sensitive information to focus the response on the areas and sectors particularly affected and to mitigate the impact of the disaster. In the weeks following the eruption, this information was refined in cooperation with Tonga’s Geological Survey.
Following a request from the Tongan government, the World Bank also produced a Global Rapid Post-Disaster Damage Estimation, using a methodology developed to provide specific information on direct disaster losses in the weeks following the eruption.
These losses were estimated in relation to residential and non-residential buildings, infrastructure and agriculture, forestry, and fishing and amounted to more than $90 million, equivalent to 18.5% of the country’s Gross Domestic Product.
The results were further broken down to highlight the significant impact on the tourism sector; direct losses in the communications, energy, water, transport and social sectors; and the costs of the ashfall cleanup operation. The damage assessment results were available just three weeks after the tsunami to inform the government’s financing needs and recovery plan.
The experience of the volcanic eruption highlighted several lessons for generating, managing, and using geospatial risk data and further localizing risk information:
- While the multi-hazard disaster risk assessment was primarily designed to inform longer-term adaptation plans and risk reduction investments, the disaster underlined its value in providing a faster understanding of response and recovery needs.
- Disaster risk information and databases require redundancy and need to be publicly accessible. As Tonga was cut off from communication, ADB needed to step in to disseminate data with relevant parties. Without the Government of Tonga undertaking the risk assessment and its agreement in 2021 to share the results publicly, that sharing would have been significantly delayed.
- Remote impact and damage assessments that provide estimates using statistical tools need to be complemented by detailed local analysis on the ground. This kind of local data would provide references for future risk assessments.
Disaster preparedness, combined with updated risk information, and timely assessments of damages and needs, were critical for Tonga’s response to the devastating volcanic eruption.
This blog was written by Alexandra Galperin, Senior Disaster Risk Management Specialist, Asian Development Bank (ADB), originally published at ADB on 28 March 2022, reposted via PACNEWS.