Introduction
Multiple stream gages are operated by the U.S. Army Corps of Engineers Baltimore District (NAB) and United States Geologic Survey (USGS) in and around Foster Joseph Sayers Dam. These gages include Spring Creek at Milesburg, PA (Spring Creek), Bald Eagle Creek Bl Spring Creek at Milesburg, PA (Milesburg), and Bald Eagle Creek at Blanchard, PA (Blanchard) gages, as shown below.
Normally, stream gage records are relatively short (i.e. less than 100 years). However, within dam and levee safety studies, estimates of extremely rare flow rates are needed to adequately assess the risk associated with the structure(s) in question. Analytical frequency curves (e.g. Log Pearson Type III) are used to estimate these extremely rare flow rates. Data recorded at these gage locations can be used to fit analytical curves using various routines.
Objectives
In this workshop you will gain experience creating representative inflow data sets for Sayers Dam. Then, you will fit a Log Pearson Type III (LPIII) analytical distribution to the inflow data set and infer results at rare exceedance probabilities.
The following major tasks will serve as an outline for the workshop:
- Investigate inflow records for Sayers Dam.
- Create a new HEC-SSP project and import data sets.
- Use the Record Extension analysis to extend the 3-day duration inflows.
- Create a Bulletin 17 analysis for the 3-day duration inflows and compute LPIII parameters using Bulletin 17C methodology.
Two additional tasks are included at the end of the workshop, if time allows.
- Incorporate paleoflood information, compute new LPIII parameters, and compare the results.
- Create a Volume Frequency analysis and develop a family of volume-frequency curves.
Spend approximately 15 minutes per task to accomplish Tasks 1 - 4.
Continue to Task 1. Investigate Inflow Records for Sayers Dam and Nearby Gages.