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<br /> <br /> <br /> <br /> <br /> <br />8. D AM FAILURE <br /> <br /> <br /> <br /> <br />8.1 GENERAL BACKGROUND <br />8.1.1 Definition and Classification of Dams <br />A dam is an artificial barrier that can store water, wastewater, or liquid-borne materials for many reasons—flood <br />control, human water supply, irrigation, livestock water supply, energy generation, containment of mine tailings, <br />recreation, or pollution control. Many dams fulfill a combination of these functions. They are an important <br />resource in the United States. In California, dams are regulated by the State of California Division of Safety of <br />Dams. Additional regulatory oversight of dams is cited in Chapter 5 and described in Appendix C. <br /> <br />The California Water Code (Division 3) defines a dam as any artificial barrier, together with appurtenant works, <br />that does or may impound or divert water, and that either: <br /> Is 25 feet or more in height from the natural bed of the stream or watercourse at the downstream toe of the <br />barrier (or from the lowest elevation of the outside limit of the barrier if it is not across a stream channel <br />or watercourse) to the maximum possible water storage elevation; or <br /> Has an impounding capacity of 50 acre-feet or more. <br />Dams can be classified according to their purpose, the construction material or methods used, their slope or cross - <br />section, the way they resist the force of the water pressure, or the means used for controlling seepage. Materials <br />used to construct dams include earth, rock, tailings from mining or milling, concrete, masonry, steel, timber, <br />plastic, rubber, and combinations of these. <br /> <br />8.1.2 Causes of Dam Failure <br />Partial or full failure of dams has the potential to cause massive destruction to the ecosystems and communities <br />located downstream. Partial or full failure can occur as a result of one or a combination of the following reasons <br />(FEMA, 2015): <br /> Overtopping caused by floods that exceed the dam capacity (inadequate spillway capacity) <br /> Prolonged periods of rainfall and flooding <br /> Deliberate acts of sabotage (terrorism) <br /> Structural failure of materials used in dam construction <br /> Movement and/or failure of the foundation supporting the dam <br /> Settlement and cracking of concrete or embankment dams <br /> <br /> <br /> <br />8-1