Task 3. Use Bulletin 17C Procedures to Fit an LPIII Distribution to the Short Record

Now that you have imported data, fit a Log Pearson Type III (LPIII) distribution to the Oregon City record.  The results from this analysis will be compared against those obtained after extending the short record using the Estacada data set. 

Create a New Bulletin 17 Analysis

• Click Analysis | New | Bulletin 17 to create a new Bulletin 17 analysis.
• Name the analysis "OregonCity_base".
• Select the Oregon City peak flow data set within the Flow Data Set drop down menu.

The data set will be named "CLACKAMAS RIVER-OREGON CITY, OR-FLOW-ANNUAL PEAK".

• On the General tab, ensure the "17C EMA" radio button is selected within the Method for Computing Statistics and Confidence Limits panel. Leave all other options unchanged.
• Move to the EMA Data tab. This is where perception thresholds and flow ranges are entered which are then used within the Bulletin 17C procedures.

Compute and Visualize the Results

• Click the Compute button at the bottom of the Bulletin 17 editor. A window informing you that the computations are complete should appear. Click OK to close this window.
• Click Plot Curve at the bottom of the Bulletin 17 editor to view the results. A window similar to the figure below should appear.
  
• Close the plot and move to the Tabular Results tab.
• Take note of the tabular information that is contained within this tab including the compute curve, confidence limits, distribution parameters, and details of the selected data set.

Question: What is the calculated 1% AEP peak flow rate for this analysis?

Question: How wide is the 90% confidence interval at the 1% AEP?

Question: Using the rating curve shown below and located here, estimate the corresponding stage for the 1% AEP discharge.

• Click OK to close the Bulletin 17 editor.
• Click the Save button (  ) to save the study.

Continue to Task 4. Perform the Record Extension.