These examples use the Expected Moments Algorithm (EMA) to fit the Log Pearson Type III distribution to annual maximum flow data sets. The multiple inputs and outputs are provided to illustrate the use of selected options and to assist in verifying the correct execution of the program. The first six examples use the same data sets that are provided with the Bulletin 17C document (England, et al., 2018). As shown in the example data sets, the HEC-SSP software produces the same results as the USGS PeakFQ Software (Veilleux, Cohn, Flynn, Mason, & Hummel, 2013) for these six data sets. The last four examples make use of additional inputs and settings that are not demonstrated within the Bulletin 17C document.
All of these test examples are provided with the software as a single HEC-SSP study labeled "Bulletin_17C_Examples." You can install this study on your computer by selecting the Help | Install Example Data menu option. After opening this study for the first time on your computer, you must compute each example before viewing tabular and graphical results.
A brief description of each example is provided. In most cases, the computed at-site station skew is used in lieu of a weighted skew to more clearly illustrate the effects of EMA and the other procedures outlined within Bulletin 17C. The example problems shown in this section are entitled:
- Systematic Record – Moose River at Victory, VT
- Analysis with Low Outliers – Orestimba Creek near Newman, CA
- Broken Record – Back Creek near Jones Springs, WV
- Historical and Data – Arkansas River at Pueblo, CO
- Crest Stage Gage Censored Data – Bear Creek at Ottumwa, IA
- Historic Data and Low Outliers – Santa Cruz River at Lochiel, AZ
- User Overrides (Low Outliers and Confidence Limits) – Rapid Creek above Canyon Lake near Rapid City, SD
[inf – inf] Perception Threshold – Pembina River at Neche, ND
[0 – value] Perception Threshold – Clark Fork River below Cabinet Gorge Dam, ID
- Systematic and Historical Record with Regional Skew – Schuylkill River at Berne, PA
When the "Bulletin_17C_Examples" study file is open, the screen will appear as shown in Figure 1. The following sections document each of the example data sets.
