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<br />6,3,3 Data Availability, Data availabilijy also affects which hydrologic method to use, In <br />general, more complex methods require a greater amount of data, The general data <br />requirements for the various hydrologic: methods are shown below. <br /> <br />6,3,3,1 Simplilied Methods, Sirnplilied methods such as the rational method have <br />relatively small data requirements of: (1) landuse, (2) site specilic rainfall intensity _ <br />duration curve, and (3) drainage area, <br /> <br />6,3.3,2 Discharge Frequency Analysis, This method requires streamflow records, <br />usually annual peak discharges, Also required is a general knowledge of the watershed <br />characteristics, such as the presence of dams or urbanization through the basin to ensure <br />stationarny, If a sne has a stream gage and an adequate length of dependable gage data, <br />statistical streamflow analysis would be a better method than a deterministic method, <br /> <br />6,3,3,3 Rainfall-Runofl Analysis, This method is the most data intensive. <br />Required data include extensive spatial and temporal rainfall data, spatial and temporal <br />infiRration losses, and extensive routing data requirements listed in Table 6,2 (Fread, <br />1993), <br /> <br />'Table 6.2 <br />Data Requirements for Lumped and DIstributed Models <br /> <br />Data Type <br /> <br />Routing lTlodels <br />Lumped Distributed <br /> <br />Observed inflow hydrograph, I(t} a <br />Observed outflow hydrograph, Q(t} a <br />Observed water-surface elevation timo series, h(t} <br />Lateral inflow hydrograph, q(t} <br />Surface area - elevation table, sa(h} b <br />Cross-section top width - elevation table, B(h} <br />Friction coefficient-water surface elevation or discharge table <br />Expansion and contraction coefficients, ,1("" <br />Sinuosity factors, Sc and sm <br /> <br />c <br />c <br />c <br />d <br /> <br />e <br />f <br />g <br />h <br /> <br />a = required for calibration of storage and linear systems models <br />b = required for level-pool mOdel <br />c = required for calibration <br />d = not always required <br />e = always required <br />f = can be obtained via calibration <br />g = can be assumed 0,0 for fairly unilorm channels <br />h = can be assumed 1,0 for fairly straight channels <br /> <br />^ <br /> <br />6,3.4 Resources, By means of practicality, the choice of hydrologic methods depends on <br />both the time and funding availiilble to do the analysis and the available expertise to <br />accomplish the analysis, More complex methods generally require greater expertise in <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />E' 7 <br />)" <br /> <br />fFIJFT <br />