Hydrograph Help - Dimensionless Unit Hydrograph

Hydrograph Help

Dimensionless Unit Hydrograph All dimensionless unit hydrographs should begin with (0,0), include the coordinates (1,1), and end with (Tb/Tp, 0).  SCS unit hydrograph convolution requires that the dimensionless hydrograph be sampled at time ratio intervals of 0.2.  Time ratios are multiplied by Tp and flow ratios are multiplied by qp = K A / Tp to obtain an appropriately scaled unit hydrograph.  Filenames without the required '.duh' extension are ignored.   Tabular Any filename that includes neither the word 'triangle' nor the word 'gamma' will be loaded as a dimensionless unit hydrograph table.  The first column is time ratio T/Tp, and the second column is flow ratio q/qp.  The required ordinates are interpolated using Method.   Triangular Any filename that includes the word 'triangle' will generate a triangular dimensionless unit hydrograph with coordinates (0,0), (1,1), and (Tb/Tp, 0) where Tb/Tp = 3872 / (3K).  The required ordinates are linearly interpolated.  The contents of filename are not used.   Gamma Distribution Any filename that includes the word 'gamma' (but does not include the word 'triangle') will generate a gamma distribution dimensionless unit hydrograph with ordinates   q/qp = tα eα ( 1 – t )    where    t = T/Tp  and  Tb/Tp = 2500 / K.   The parameter α is given by the solution of   Γ(α) (e/α)α = 1 / f   with initial estimate   α0 = 0.045 + 0.5 f + 5.6 f 2+ 0.3 f 3    where    f = 3K / 1936.  The required ordinates are computed directly.  The contents of filename are not used.