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Optimize Critical Duration

Description​

Simulates overland flow across each hillslope using analytical solution, calculates dcrit (critical duration, or duration of storm that produces peak discharge), tc (time that the entire hillslope contributes to flow at the outlet), Qmax (peak flow for the return interval at dcrit), Amax (maximum contributing area for the return interval), C_calc (calculated runoff coefficient at Qmax and dcrit), Qtc (flow corresponding to tc), and ratio dcrit of to tc ("dc_tc"). In cases where tc is never reached, the ratio dc_tc will be NA, and dcrit will by definition be less than tc. When dcrit is less than tc, the field "dc_lt_tc" is YES, otherwise it is NO. This tool modifies the input hillslopes feature with the newly calculated fields added.

Usage​

Simulates overland flow across each hillslope using analytical solution, calculates dcrit (critical duration, or duration of storm that produces peak discharge), tc (time that the entire hillslope contributes to flow at the outlet), Qmax (peak flow for the return interval at dcrit), Amax (maximum contributing area for the return interval), C_calc (calculated runoff coefficient at Qmax and dcrit), Qtc (flow corresponding to tc), ratio dcrit of to tc ("dc_tc"), and binary field indicating if dcrit is less than tc ("dc_lt_tc").

Parameters​

Parameter NameTypeDirectionData TypeDialog Reference
Input Alpha HillslopesRequiredInputFeature LayerPartitioned hillslopes with alpha calculated using Hillslope Roughness tool.
Input K Parameter for Rainfall Intensity-Duration-Frequency curve [m/s]RequiredInputDoubleInput K from intensity-duration-frequency curve function of the form: I = K/(D^b) (typical values range from 0.0001 to 0.001 m/s).
Input b Parameter for Rainfall Intensity-Duration-Frequency curve [ - ]RequiredInputDoubleInput b from intensity-duration-frequency curve function of the form: I = K/(D^b) (typical values range from 0.4 to 0.65).
Input Saturated Hydraulic Conductivity Ks [mm/s]RequiredInputDoubleInput approximate for saturated hydraulic conductivity in mm/s. For refence, sandy loam soil Ks ~ 0.008 mm/s, loamy soil Ks ~ 0.0009 mm/s, and clay soil Ks ~ 0.00008 mm/s (Rawls et al. 1983).