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<br />6,3,3 Data Availabilitv, Data availability 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 Simplified Methods. Simplified methods such as the rational method have <br />relatively small data requirements of: (1) landuse, (2) site specific 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 />stationarity. If a site 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-Runoff Analysis. This method is the most data intensive. <br />Required data include extensive spatial and temporal rainfall data, spatial and temporal <br />infiltration 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 models <br />Lumped Distributed <br /> <br />Observed inflow hydrograph, 1ft) a <br />Observed outflow hydrograph, a(t) a <br />Observed water-surface elevation time series, h(t) <br />Lateral inflow hydrograph, q(t) <br />Surface area - elevation table, 5a(h) b <br />Cross-section top width - elevation table. 8(h) <br />Friction coefficient-water surface elevation or discharge table <br />Expansion and contraction coefficients. K.. <br />Sinuosity factors, So 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 uniform channels <br />h = can be assumed 1.0 for fairly straight channels <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />6.7 <br /> <br />fR'JFT <br />