Landslide dam is formed by hillside landslides, rain, earthfall caused by earthquakes, landslides, debris flows and other circumstances. At times, it is also formed by a massive outwash from a main river to a tributary river.
When a landslide dam is formed, it yields an extreme amount of sediment, potentially causing extensive damage.
Therefore, if a landslide dam is formed, the first priority is to calculate the scale and kind of possible damage and establish proper countermeasures.
Generally speaking, the cause of a failure of a landslide dam is thought to be an overflow or piping. Emergency measures include founding a diversion tunnel, draining by pump, installing a cutoff, installing groundsill (a block, etc.) and other bed wall(s) to prevent downstream scouring, levee heightening in lower reach, and clearing debris from the sabo dam in the lower reaches.
- Translated from Journal of Japan Sabo Association, Sabou to Chisui, Vol.163, pp.85, 2005