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APPENDIX A. ACRONYMS AND DEFINITIONS <br />A-5 <br />Drainage Basin: A basin is the area within which all surface water- whether from rainfall, snowmelt, <br />springs or other sources- flows to a single water body or watercourse. The boundary of a river basin is <br />defined by natural topography, such as hills, mountains and ridges. Drainage basins are also referred to as <br />watersheds or basins. <br />Drought: Drought is a period of time without substantial rainfall or snowfall from one year to the next. <br />Drought can also be defined as the cumulative impacts of several dry years or a deficiency of precipitation <br />over an extended period of time, which in turn results in water shortages for some activity, group, or <br />environmental function. A hydrological drought is caused by deficiencies in surface and subsurface water <br />supplies. A socioeconomic drought impacts the health, well-being, and quality of life or starts to have an <br />adverse impact on a region. Drought is a normal, recurrent feature of climate and occurs almost everywhere. <br />Earthquake: An earthquake is defined as a sudden slip on a fault, volcanic or magmatic activity, and <br />sudden stress changes in the earth that result in ground shaking and radiated seismic energy. Earthquakes <br />can last from a few seconds to over 5 minutes, and have been known to occur as a series of tremors over a <br />period of several days. The actual movement of the ground in an earthquake is seldom the direct cause of <br />injury or death. Casualties may result from falling objects and debris as shocks shake, damage, or demolish <br />buildings and other structures. <br />Exposure: Exposure is defined as the number and dollar value of assets considered to be at risk during the <br />occurrence of a specific hazard. <br />Extent: The extent is the size of an area affected by a hazard. <br />Fire Behavior: Fire behavior refers to the physical characteristics of a fire and is a function of the <br />interaction between the fuel characteristics (such as type of vegetation and structures that could burn), <br />topography, and weather. Variables that affect fire behavior include the rate of spread, intensity, fuel <br />consumption, and fire type (such as underbrush versus crown fire). <br />Fire Frequency: Fire frequency is the broad measure of the rate of fire occurrence in a particular area. An <br />estimate of the areas most likely to burn is based on past fire history or fire rotation in the area, fuel <br />conditions, weather, ignition sources (such as human or lightning), fire suppression response, and other <br />factors. <br />Flash Flood: A flash flood occurs with little or no warning when water levels rise at an extremely fast rate <br />Flood Insurance Rate Map (FIRM): FIRMs are the official maps on which the Federal Emergency <br />Management Agency (FEMA) has delineated the Special Flood Hazard Area (SFHA). <br />Flood Insurance Study: A report published by the Federal Insurance and Mitigation Administration for a <br />community in conjunction with the community’s Flood Insurance rate Map. The study contains such <br />background data as the base flood discharges and water surface elevations that were u sed to prepare the <br />FIRM. In most cases, a community FIRM with detailed mapping will have a corresponding flood insurance <br />study. <br />Floodplain: Any land area susceptible to being inundated by flood waters from any source. A flood <br />insurance rate map identifies most, but not necessarily all, of a community’s floodplain as the Special Flood <br />Hazard Area (SFHA).