Drainage Design Manual, Hydrology - Flood Control District of ...

Drainage Design Manual for Maricopa County
Hydrology: Indirect Methods
outcome, but clearly note if the variable values are not within the “cloud of common
values.”
4. Calculate the peak discharge estimates using the applicable regression equations for
the flood region within which the project site is located.
5. Plot the 100-year peak discharge estimate on a copy of the appropriate Q 100 data
points and 100-year peak discharge relation graph (Figure 8.8 or Figure 8.9).
D. For all three Indirect Methods:
1. Quantitatively and qualitatively analyze the results of the primary and the secondary
peak discharge estimates. Address watershed characteristics that may explain differences
between the primary and secondary estimates.
2. Prepare a summary of results by all methods and a qualitative evaluation of the
results. The qualitative evaluation should provide a description of the findings from
step D.1 and assess whether the model results make logical sense when compared
with the available indirect method data. If there is reason to doubt the model results
based on the indirect method comparisons, the engineer/hydrologist should reexamine
the model input parameters for reasonableness and adjust them where appropriate.
If there is no reason to doubt the model results based on the indirect method
comparisons, it should be so stated.
August 15, 2013 8-21