Claim: Because of their rather loose nature and absence of controlled spillway, landslide dams, a natural damming of a river by some kind of landslides, such as debris flows and rock avalanches, or by volcanic eruptions, are responsible for two types of flooding: backflooding (upstream flooding) upon creation and downstream flooding upon failure.
Evidence: Because of their rather loose nature and absence of controlled spillway, landslide dams frequently fail catastrophically and lead to downstream flooding, often with high casualties. A landslide dam or barrier lake is a natural damming of a river by some kind of landslides, such as debris flows and rock avalanches, or by volcanic eruptions. Landslide dams are responsible for two types of flooding: backflooding (upstream flooding) upon creation and downstream flooding upon failure.