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Rivers and lakes carry volcanic materials
Volcanic hazards posed by the dynamic combination of water, sediment, and gravity can be persistent, costly, and deadly. Monitoring hydrologic hazards helps understand and help mitigate the risks due to destructive lahars and excess sediment in volcanic river channels.
Monitoring volcanic rivers and lakes helps alleviate lahar and flood hazards
Many volcanoes are covered with vegetation and composed of fine ash and loose, fragmented rock. In these landscapes, rain falls on the vegetation and seeps into the soil and flows freely over the land. This water easily erodes volcanic ash and rocky debris from the hillsides, rapidly carving out large channels and carrying huge amounts of sediment to areas tens of kilometres downstream. This excess sediment can fill channels further away from the volcano, raising river beds, holding back lakes and causing more frequent flooding. Water flowing vigorously under these conditions has the strength to flow through the reservoirs to release lahar-generating floods.
Monitoring the evolution of sediment dispersal helps in resilience management
Since the eruption of Mount St Helens in 1980, rivers flowing from the volcano have acted as redistribution channels for large volumes of volcanic sediment. As part of a long-term strategy to address excessive sedimentation and prevent flooding, a sediment retention structure was built in 1987 to hold back sediment before it could be transported downstream causing economic losses to the region.
Sediment retention dam on the North Fork Toutle River is designed to help stop downstream movement of sediment near where it begins on Mount St. Helens’ debris avalanche deposit.
Monitoring channel erosion and aggradation, Mount St. Helens (North Fork Toutle (left) joins Carbonate Springs Creek (right). Direct observations upstream inform downstream sediment transport effects.
Since 2021 VOLCANO ACTIVE FOUNDATION has been committed to the UN Global Compact corporate responsibility initiative and its principles in the areas of human rights, labour, the environment and anti-corruption.
