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. NO,ncoincident Flood events or tributary inflows that have peaking times that are ~ synchroni~ed. NOTlllll1.ni,st~i button A normal distribution is a mathematical distribution that is com- tIIOt\ly 't:eferredto as the "bell shaped" curve. A log-Pearson type III curve has a normal distribution when, the skew coefficient is equal to ~lM',O. Overland ,Flow Length An ide.ali~ed estimate of the average length of the overland ;flow distance that run.offwate'r will travel to get ,to a ,stream or channel in a hylh'ologic 1IIOdel ,subarea. Partial Duration Denot-es the type of discharge-frequency analysis. Anannus1 series curve is based on using a single momentary maximum event each year. A partial duration series considers all peaks above a given balle. Peak Dischsrge The maximum instantaneous discharge of a flood at a given loca- tion. It usually occurs at or near the time of the flood crest. In the graphical representation of flow versus time, which is known as a flood hydrograph, the peak discharge occurs between the ascension limb and the recesaion limb. Peaking TilDE! The lag time from the start of a runoff-producing rainfall to the time the flood reaches its maximum discharge. probability The annual chance of occurrence of specific hydrologic event6, such as rainfall, over a specified area or peak discharge at a speci- fied location expressed in percent, e.g., 5 percent representing one chance in 20 of the event occurring in any year. The 10-, 50-, 100-, and 500-year floods are floods having a 10-, 2-, 1-, or .2-percent probability, respectively, of occurrence in any year or an average recurrence interval in the order of once in 10, 50, 100, or 500 years, respectively. It may be based on statistical analyses of streamflow records and/or the analyses of rainfall and runoff characteristics in the general region of the watershed. Rainfall Distribution (See "Hyetograph") A-4 .