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Detailed'- Prepared using mathematical analysis for the fOllowing steps, topographic mapping, hydrologic calculations, and hydraulic calculations, to arrive at precise water surfaceprofiJes and flo()dplain,delineations, Detention -- The slowing, dampening or attenuating of flows by temporarily holding (generally less than 72 hours) the water on a surface area, in a storage basin, or within the storm or combined sewer itselt. All detained water will be returned to the stream after the storm has passed at rates which will not adversely affect downstream occupants and water users. Discharge -- The amount or rate of flow of water through a given stream reach. Duration -- The time that elapses between when water first flows over a stream's banks until floods are again confined to the stream's banks. Dynamic -- (see Hydrodynamic) Embankment -- A mound of earth or stone built to hold back water. Ephemeral Stream (or Stream Reach) -- A stream (or stream reach) that flows only in direct response to precipitaiton; measurable discharge generally occurs less than 10 percent of the time.lt receives no long-continued supply from melting snow or other surface sources. Because an ephemeral stream channel is at all times above the water table, it also receives no water from springs or sustained ground-water seepage. Erodibility -- The tendency of a stream bank or other area near a stream to be worn away during periods of high flow. Feasibility Study-- A study to evaluate the feasibility of a flood control project based on the benefit/cost ratio, the availability of public funding, the likelihood of participation by private entities in funding and so on. Field Survey -- The process of measuring dimensional relationships such as horizontal distances, elevations, directions, and angles on the earth's surface for locating property boundaries, construction layout, and mapmaking. Flood or Flooding -- Temporary inundation of otherwise normally dry land adjacent to a river, stream, lake, etc. Flood Crest.- The elevation or maximum height reached or expected to be reached by the waters of a given flood at a given location. Flood Frequency -- A measure of the likelihood of the ocCurrence of a flood expressed by the period of years during which one would expect such a flood to occur once; the frequency is calculated through a probability dis- tribution analysis. Flood Fringe -- The part of the floodplain located oufside of the floodway but still subject to flooding. Flood Hazard Boundary Maps -- Maps prepared by the Federal Insurance Administration or the Federal Emergency Management Agency showing areas of potential flood hazard as determined through approximate methods. Flood Insurance Emergency Phase -- That phase of the National Flood Insurance Program when limited amounts of flood insurance are available. Communities use Flood Hazard Boundary Maps to identify flood hazard areas and they also adopt general flood resolutions or measures. Subsidized rates are charged regardless of fiood risks since technical flood information has yet to be determ ined. Flood Insurance Rate Maps -- Maps prepared by the Federal Insurance Administration on the Federal Emergency Mangement Agency showing areas that have a 1 % chance of being flooded in any given year (1 DO-year floodpiain) as determined through detailed methods and showing Flood Insurance Rate Zones for determining insurance rates for the National Flood Insurance Program. Flood Insurance Regular Phase -- That phase of the National Flood Insurance Program when communifies approve their Flood Insurance Study (FIS) and adopt a legally enforceable floodplain ordinance that meets FEMA criteria. In Colorado, a floodplain ordinance is legally enforceable only after the Colorado Water Conservation Board approves and designates a community's floodplain study. Actuarial insurance rates are used which reflect the degree of risk. Higher limits of coverage both for structures and their contents are available under the regular program. 54