Characteristics of Large Low-frequency Debris Flow Hazards and Mitigation Strategies

A low-frequency debris flow took place in the north coastal range of Venezuela on Dec. 16, 1999, and scientists all over the world paid attention to this catastrophe. Four characteristics of low-frequency debris hazard are discussed: long return period and extreme catastrophe, special rare triggering factors, difficulty in distinguishing and a series of small hazards subsequent to the catastrophe. Different measures, such as preventing, forecast — warning, engineering, can be used for mitigating and controlling the catastrophe. In engineering practice, it is a key that large silt-trap dams are used to control rare large debris flow. A kind of low dam with cheap cost can be used to replace high dam in developing countries. A planning for controlling debris flow hazard in Cerro Grande stream of Venezuela is presented at the end of this paper.