However, if the material forms a levee or dam and is saturated, at least in part, failure may be rapid and extensive and lead to release of impounded water with consequent hazard to life and property. An example is the failure of the lower San Fernando Dam at the time of the San Fernando earthquake (USA). The dam was not completely breached but only 3-4 feet of free- board remained. The lives and property of about 50,000 people in the urban area below the dam were imperilled and immediate evacuation was necessary until the water behind the dam was lowered to a safe level. 6.3 Landslides 6.3.1 Concepts and risk management The term “landslide” is here used in its broad sense to include downward and outward movement of slope-forming materials - either natural rock and soil or artificial fill - by falling, toppling, true sliding along a surface or surfaces of shear failure, or by distributed movements involving lateral spreading or flowing. Although individual slope failures generally are not so spectacular or so costly as some other natural catastrophes, they are more widespread and the total financial loss due to slope failures probably is greater than that for any other single geologic hazard to mankind. More- over, much of the loss of life and damage occurring in conjunction with earthquakes and heavy rainfall are due to landslides triggered by shaking or by water. Risk management requires knowledge of the specific areas which are subject to the hazard and, if possible, the ability to predict the time of occurrence. In this context, landslides are a type of hazard that is susceptible‘ to a considerable degree of rational management. The kinds of geological and topographic environments that lead to high incidence of slope failures and the triggering agents that precipitate failure are relatively well known. Mapping of areas subject to 
**Analysis**
The text primarily discusses natural hazards, such as dam failures and landslides, and their potential consequences on human life and property. It also touches on the importance of risk management and prediction to mitigate these hazards. This suggests that the text is related to the field of natural resources and environment, but also has implications for humanitarian aid and relief, as well as science and technology.

**Category**
Natural resources and environment, Humanitarian aid and relief, Science and technology