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<br />--.-.-____...._,____~,w__..~_,......_____""',_~"...,.....~._... , ~.~..,..,,~..__',_loiiIlIWlillll_....____ <br /> <br />6.3.3.2 Discharge Frequency Analysis. This method requires streamflow records, usually <br />annual peak discharges. Also required is a general knowledge of the watershed characteristics, such <br />as the presence of dams or urbanization through the basin to ensure stationarity. If a site has a stream <br />gage and an adequate length of dependable gage data, statistical streamflow analysis would be a <br />better method than a deterministic method. <br /> <br />6.3.3.3 Rainfall-Runoff Analysis. This method is the mosl data intensive. Required data <br />include extensive spatial and temporal rainfall data, spatial and temporal infiltration losses, and <br />extensive routing data requirements listed in Table 6.2 (Fread, 1993). <br /> <br />Table 6.2 <br />Data Requirements for Lumped and Distributee! Models <br /> <br />Data Type <br /> <br />Routing models <br />Lumped Distributed <br /> <br />Observed inflow hydrograph, I(t) <br />Observed outflow hydrograph, Q(t) <br />Observed water-surface elevation time series, h(t) <br />Lateral intlow hydrograph, q(t) <br />Surface area - elevation table, Sa(h) <br />Cross-section top width - elevation table, B(h) <br />Friction coefficient-water surface elevation or discharge table <br />Expansion and contraction coefficients, Koc <br />Sinuosity tactors, s, and 8m <br /> <br />a <br />a <br /> <br />c <br />c <br />c <br />d <br /> <br />b <br /> <br />e <br />f <br />g <br />h <br /> <br />a = required tor 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 />6.3.4 Resources. By means of practicality, the choice 01 hydrologic methods depends on both the <br />time and funding available to do the analysis and the available expertise to accomplish the analysis. <br />More complex methods generally require greater expertise in their use and interpretation. Without the <br />required time and expertise, results may be less accurate than simpler methods. <br /> <br />6.3.5 Flowchart. Figure 6-1 shows a flowchart showing the proper steps and decisions that should be <br />used in selecting the appropriate hydrologic method. <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />6.9 <br /> <br />DRAFr <br />