Larsbreen Proglacial Lake: Assessing a GLOF Hazard
The Larsbreen valley has a glacier that has retreated 1.4 km since 1990. A proglacial lake now covers 2.1 km² and is 38 m deep, dammed by a moraine ridge. Downstream are a village of 900 people, a campsite with 400 beds, and a hydropower intake 6 km below the lake. Permafrost in the valley walls is thawing; rockfall frequency has increased; the lake level is rising about 0.3 m per year. Seismic sensors record about 12 small earthquakes each month. In summer 2023, a meltwater pulse raised the lake by 0.9 m in 10 days. A consultant proposes an early-warning system, an artificial drainage tunnel, relocation of the campsite, and seasonal access restrictions. The regional government has limited funds and wants a single priority.
1. Assess why glacial lake outburst flood (GLOF) risk is increasing in the Larsbreen valley, using glacier and permafrost processes.
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GLOF risk rises because glacier retreat leaves a moraine-dammed lake whose dam is weak and whose volume grows. The lake is already 2.1 km² and 38 m deep, and the 2023 meltwater pulse of 0.9 m in 10 days shows how quickly inflow can raise levels. Thawing permafrost reduces the strength of valley walls and the moraine, increasing rockfall and the chance of an impact wave or dam breach. More frequent rockfall can also create a displacement wave. Small earthquakes may further destabilise the moraine. So the hazard is not just more water; it is a less stable dam and more frequent triggers. Downstream exposure-900 residents, 400 campsite beds and a hydropower intake-makes the risk socially significant.
2. Evaluate the four proposals and recommend a priority with justification.
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Early warning is relatively cheap and protects everyone, but only if people can respond; it does not reduce the physical hazard. The drainage tunnel lowers lake level and reduces breach probability, but is expensive and technically difficult in a moraine. Campsite relocation removes the most exposed population but is contested and does not protect the village. Access restrictions are cheap but hard to enforce. Priority should be the drainage tunnel if engineering is feasible and funded, combined with early warning, because it addresses the source of the hazard; relocation is a secondary measure for the campsite. If funds are very limited, early warning plus seasonal restrictions is the minimum, but it leaves the dam problem unresolved.
3. Explain why relocation of the campsite may be contested.
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Relocation is contested because the campsite is a livelihood for its owners and an economic asset for the village; residents may see it as the government externalising risk onto them. If compensation is inadequate or the new site is less accessible to tourists, resistance is rational. There is also an equity issue: the campsite may serve outside visitors while the village bears the risk. A defensible plan would co-design relocation with operators, phase it, and pair it with warning and insurance; otherwise restrictions may be ignored.