A variety of graphical and tabular results are available after a frequency analysis is computed. The same results are also available for the current analysis, so long as no data used in the analysis has changed. The program tracks all of the data in the frequency analysis and selected basin model and meteorologic model on which it is based. It further tracks all of the data used in the basin model and meteorologic model that is the basis of the frequency analysis. If any of the data have changed, you will need to re-compute the frequency analysis to get up-to-date results.

Once a result is open for viewing it will remain open until it is closed by the user. It is possible that data or model information used by the analysis that produced the result could change while the result is open for viewing. In this case, the open result will immediately show an indication that data has changed and the frequency analysis needs to be recomputed. After the frequency analysis is recomputed the open results are automatically updated with the new results and the indication is updated with the data and time of the most-recent compute.

Frequency Curve Plot

One of the most unique and helpful results output from a frequency analysis compute is the frequency curve plot. In the example below, annual exceedance probability (AEP) is plotted on the x-axis and the peak flow value in units of flow is plotted on the y-axis on log scale. Each point on the frequency curve represents the peak value result from an individual frequency ordinate compute. In this example, there were nine frequency ordinates that made up the frequency analysis which resulted in the nine points on the frequency curve plot. The frequency curve plot is accessed from the Results tab within the Watershed Explorer

Frequency Curve Plot

Frequency Curve Table

The frequency curve table summarizes results for each of the ordinates that make up the frequency analysis. In the below example, there are nine frequency ordinates resulting in nine rows in the table. The analysis point element name and its drainage area should be the same for each ordinate. The AEP and peak value should be different for each ordinate, with peak values increasing as the AEP decreases. The frequency curve table is accessed from the Results tab within the Watershed Explorer

Frequency Curve Table

Individual Elements

In a frequency analysis, a computation will be made for each frequency ordinate. Individual basin element results are available for each of the ordinate computes as seen in the below figure. A frequency analysis compute may not result in all basin elements having results. Only the chosen analysis point for each of the frequency ordinates and the elements upstream of it will have results.

Frequency Analysis Watershed Explorer Results Nodes

A global summary table summarizes the drainage area, peak discharge, time of peak, and total volume for each of the computed basin elements. 

Global Summary Table

The information included in the below element graph varies by element type, but will always include outflow. Optional items such as observed flow, computed stage, and observe stage may also be displayed.

Individual Element Graph

The information included in the summary table seen below also varies by element type but always includes the peak flow, time of peak flow, and outflow volume.

Individual Element Summary Table

The time-series table below includes the same information as the graph but in numerical format. 

Individual Element Time-Series Table