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Hydrograph Help
	Menu Bar    File    Edit    Plot    Report    Window    Help   User Input    Unit Hydrograph    Rainfall Distribution    Interpolation Method    Peak Factor    Storm Duration    Rainfall Depth    Initial Abstraction Ratio    Basin Area    Curve Number    Time of Concentration    Output Time Increment   Program Output    Peak Runoff    Time to Peak    Runoff Volume    Unit Hydrograph Volume   Run Exit
Error Messages Convolution Tutorial References   Peak Factor Unit hydrograph peak factor; filled automatically if Unit Hydrograph filename ends with three digits.   The peak factor K is a unit conversion and shape factor derived from a triangular unit hydrograph with base Tb and height qp.  Expressing the area under the hydrograph, or volume of runoff, in inches
where A = basin area.  Solving for qp and introducing the unit hydrograph time to peak Tp   qp = K A Q / Tp     where     K = 3872 / (3Tb/Tp).   When Tb/Tp = 8/3, K = 484.  Other ratios Tb/Tp yield other peak factors K.   Storm Duration Duration of design storm (hr); filled automatically if Rainfall Distribution filename ends with three digits.   Rainfall Depth Cumulative rainfall depth (in | mm).   Initial Abstraction Ratio Dimensionless ratio of initial abstraction Ia and potential maximum retention s   λ = Ia / s.   The initial abstraction ratio corresponding to published SCS curve numbers is λ = 0.2.   Basin Area Drainage basin area (ac | km2).   Curve Number Composite SCS curve number corresponding to Initial Abstraction Ratio.   Time of Concentration Longest basin travel time (min).   The rain burst duration d and unit hydrograph time to peak Tp are functions of the time of concentration Tc.  The equations   Tp = 0.5 d + 0.6 Tc Tc + d = 1.7 Tp   are solved simultaneously to obtain d = Tc / 7.5 and Tp = 5 d = 2 Tc / 3.   Output Time Increment Time increment (min) for Detail Report.   Peak Runoff Maximum runoff flow rate (cfs | cms).   Time to Peak Time (hr) at which the Peak Runoff occurs.   Runoff Volume Areal depth (in | mm) for Runoff Hydrograph.   Unit Hydrograph Volume Areal depth (in | mm) for Unit Hydrograph.   Run Updates program output, generates checked Plot and Report items, and returns the following column vectors to the current workspace.   tq runoff hydrograph time (hr) q runoff hydrograph flow rate (cfs | cms) tu unit hydrograph time (hr) u unit hydrograph flow rate (cfs | cms) t rainfall-runoff time (hr) p cumulative rainfall (in | mm) Q cumulative runoff (in | mm)   Exit Closes GUI and Plot windows.