Auapaau, F.R.; Craig, H.M.; Williams, J.G.; Stewart, C.; Hayes, J.L.; Vaiomounga, R.; Kula, T.; Tukuafu, P. ; Manu, M.; Fa‘oliu, S.; Maea, A.; Latu‘ila, F. ; Bowbrick, Z.; Tuiafitu, T. ; Ika, T.; Matahau, K.; Chandegra, V. ; Williams, S.; Weir, A; Leonard, G.S.; Scheele, F.R. 2025 Impacts of the January 2022 eruption of Hunga volcano, Tonga, on Tongatapu. Lower Hutt, N.Z.: GNS Science. GNS Science report 2025/05. 45 p.; doi: 10.21420/TQ6A-E207
Abstract
The 15 January 2022 eruption of the Hunga volcano, Tonga, generated a tsunami, atmospheric shockwaves and volcanic ashfall that had widespread impacts across Puleʻanga Fakatuʻi ʻo Tonga the Kingdom of Tonga (Tonga). Currently, there is little detailed knowledge of the impacts from volcanic ashfall in the South Pacific. This report presents findings from two field studies investigating the impacts of the eruption on public health, buildings, agriculture and infrastructure, focusing primarily on the Tongatapu island group. These studies were undertaken in June and August 2023 in collaboration with Tonga Geological Services (TGS). The response to the eruption was complicated by the global outbreak of COVID-19. At the time of the eruption, precautions to keep COVID-19 out of Tonga included strict requirements for the contactless delivery of aid supplies, closing of international borders, rolling lockdowns, curfews, school closures and restrictions on events such as kava parties, church services, funerals and weddings. Relief organisations required a special order granted by the Government of Tonga to continue critical response activities. Initial public messaging focused on encouraging people to wear masks when outside in the ashfall. Messaging about masking was sent out through radio channels due to power and internet outages. Among the public, the main health concern was the safety of drinking water. Bottled water demand increased rapidly in the days after the eruption, and government intervention was needed to stop retailers from raising prices. Although root crops made up the largest proportion of cultivated crops on Tongatapu, these were largely unaffected by ashfall. Immediate losses were reported mainly for crops where the edible part was above ground, such as breadfruit, tree fruits, leafy vegetables and coffee. These losses were attributed to ashfall abrasion, loading and leaf death. Impacts on cash crops, such as vanilla, were reported, with varying severity impacts depending on the location. Limited mitigation methods or recovery strategies were employed, with most farmers waiting for rain to wash ash from the crops. For fisheries and aquaculture, the tsunami following the eruption caused more damage than the ashfall, with a lack of funding provision slowing recovery. Ash initially coated coral reefs and deprived fish of feeding and spawning areas. The tsunami also destroyed aquaculture structures, damaged vessels in-port and damaged or destroyed 300 small-scale fishing vessels. At the time of field visits, fisheries staff estimated they had recovered to 40–50% of pre-eruption capacity with assistance from the government and non-governmental organisations. Buildings on Tongatapu are predominantly constructed from modern materials. As expected for ashfalls of approximately 20–50 mm, there were no reports of roof collapse. However, there were numerous reports of gutter collapse, as well as increased rates of corrosion damage to roofing materials, although roof conditions prior to the eruption are unknown. Immediate and extended impacts on the Tongatapu and Nuku‘alofa (the capital city) power network were reported by Tonga Power Ltd following the eruption. This was despite upgrades to the power network assets across rural Tongatapu and 80% of urban Nuku‘alofa between 2015 and 2018. Immediate efforts were focused on switching off electricity, clearing solar panels and closing wind turbines to reduce potential impacts. Ash on transformers and insulators caused some flashover, shorting and outages, requiring extensive clean-up activities. Restoration of electricity occurred quickly (days to weeks), with coastal areas taking much longer due to tsunami-related safety concerns. In addition to ongoing clean-up efforts concentrated on insulators and transformers, delayed impacts were observed due to damaged electrical cables where solidified ash had increased the friction between the cabling, corroding the rubber and increasing short circuiting.Nuku‘alofa is served by a treated, reticulated water-supply system utilising groundwater extraction. The system is completely enclosed from source to customer, and no issues were reported with ash contamination. However, intermittent power outages during the first 2–3 weeks after the eruption interfered with the operation of the electric water-abstraction pumps. It was a constant challenge for the Tonga Water Board to maintain water production to meet demand during this time, especially as water consumption was high during the clean-up operations. Water-service disruptions were also experienced in coastal parts of Nuku‘alofa due to tsunami damage to distribution pipes. The road network on Tongatapu remained operational after the ashfall; however, a reduction in traction was reported. Despite this, no increase in traffic accidents was reported. Some communities created informal ‘speed bumps’ out of ash piles or thick ropes to slow down motorists and reduce airborne re mobilisation of ash deposits. The Ministry of Infrastructure cleared ash from the main roads, while communities cleared the rest. An increase in road-surface flooding occurred during rainfall events, likely due to ash material blocking stormwater drainage systems. Ashfall impacts to the marine environment were relatively minor compared to those caused by the tsunami. Port infrastructure was not damaged by ashfall, limited issues were reported to boats and ferries and some navigational aids were damaged, albeit with no effect on local boat operators due to their familiarity with sea routes. The only impact caused by ash and debris was on the ocean surface, which disrupted ship filtration systems. As a result, Tongan naval ships were delayed in conducting relief missions to the outer islands to provide aid and re-locate affected populations. The experiences of the responding agencies were recorded during an all-stakeholder-agencies workshop, with key lessons identified. Much of the feedback from participants of the workshop acknowledged the role of infrastructure agencies in the swift re-instatement of water- and power-supply systems following the eruption. There were also successes noted at an operational level, including activities undertaken before, during and after the eruption. Many key lessons identified had a focus on multi-agency and public communication. These ranged from improving public understandings and perceptions of risk to the coordination of expert advice and the importance of good working relationships, reflected in the collaborative approach to hazard response. (auths)
