Excel File

Download an Excel file to visualize results here: 

SayersDam_frequency_curves.xlsb

Plot the Multiple Bulletin 17 Analyses and Mixed Population Analysis Results

Statistical analyses can be used to provide estimates of flow (or volume, stage, precipitation, etc.) for extremely rare annual chances of exceedance (ACE), such as 1/10,000.  This is common within dam and levee safety studies where a hydrologic hazard curve must be developed that encompasses a wide range of possible hydrologic or hydraulic scenarios.  Using the previously created Bulletin 17 and Mixed Population Analyses, you will infer and compare results for very rare ACE.  We will visualize the results from each of the analyses frequency curves using the spreadsheet provided at the top of this page.

  • Open the spreadsheet named "SayersDam_frequency_curves.xlsb"
  • On the Curves sheet, enter the computed frequency curves from the all-season, mixed-snow, rain-only, TC/TSR, and Mixed Population analyses.
  • The Curves sheet should resemble the following:

  • Review the frequency curve plots on the B17C_comparison, MPA_results, and MPA_B17C_comparison sheets.

Question. Compare the Mixed Population and All-Season B17C results on the MPA_B17C_comparison sheet.  Which frequency curve is most appropriate for use when extrapolating to very rare AEP (< 1/100)?

The all-season B17C results violate the IID assumption within flood frequency analyses by mixing and matching disparate flood mechanisms.

The Mixed Population analysis results were derived by separating the available information into truly IID samples.  The individual IID samples were then used to infer flood mechanism-specific flow-frequency curves and combined using the probability of union concept.  The resultant combined frequency curve is more appropriate for use when extrapolating to rare AEP when compared against the all-season B17C results. 


Final Project Files

Download the final project files here:

SayersDam_MixedPopulationAnalysis_finish.zip

SayersDam_frequency_curves_finish.xlsb