Laserfiche WebLink
<br />from the sample or observed discharge values, <br /> <br />Advantaaes <br /> <br />Disadvantaaes <br /> <br />1, Generally provides most accurate <br />means of discharge-frequency analysis, <br /> <br />1, Usually not a stream gage exactly at <br />s~e of interest. <br /> <br />2, Well documented, standardized <br />procedures (Bulletin 17B), <br /> <br />2, Assumes probability distribution <br />model Ins population, <br /> <br />3, Assumes sample data is <br />representative of population. <br /> <br />4, Assumes parameters of population <br />can be detennined from sample data, <br /> <br />6.1,3 Rainfall-Runoff Modellina, For s~uations where historic streamflow data are <br />inadequate or nonexistent, a rainfall-runoff model is commonly used for flood-runoff <br />estimates, Generally, a rainfall-runoff modElI must be used if ~ is intendeclto evaluate the <br />effects of e~her landuse changes or structural modification in the watershed, Rainfall- <br />runoff models are generally divided into two classes: single event and continuous <br />streamflow modelling, Single-event modelling involves simulating the runoff response of <br />the hydrOlogic system to precipitation for a single unique stonn event. Continuous <br />streamflow modelling involves continuously accounting for sustained periods of precip~ation <br />over a basin w~h special emphasis on adjusting the soil moisture, evaportranspiration, and <br />subsurface flows during periods of no precip~ation, The primary interest in flood hydrology <br />is the flood hydrograph, so consequently, Single-event modelling is usually the procedure <br />used for analysis. <br /> <br />Single-event modelling usually follows the steps listed below, <br />(1) Determination of subbasin average precip~ation <br /> <br />(2) Determination of precipitation excess from infinration losses <br /> <br />(3) Transformation of precipitation excess into a runoff t1ydrograph <br /> <br />(4) Routing of stream flows <br /> <br />(5) Reservoir routing <br /> <br />(6) Combination of hydrographs <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />6,2 <br /> <br />fRlJFr <br />