Running individual storms with ARR data

As well as running DRAINS models with ARR storm ensembles, models can be run with selected storms from these ensembles. This can be done in two ways.

The first way allows you to run trial and error calculations easily based on the median or mean storms for a component of interest, varying drainage system components between runs.

This can be done by separately performing an Analysis run with major and minor ensembles, and after each run, right clicking on an object of interest to select Select Median Storms for Next Run, as is shown below for a detention basin.  The outputs shown below are for major storms, but similar outputs will be provided for minor storms.

If you choose this, the following message will appear.

When you click on Yes, the selected storms for the various durations will be stored.

After performing this action for both major and minor storms you then need to go to Project → Options and select the Individual Storms option,

You will then be able to do major and minor storm analysis that will utilise the selected storms for each duration. It will be possible to see information that is not available with the full ensemble runs, such as inflow/outflow hydrographs from detention basins. After you inspect this, you can go back to Project → Options and re-select the Ensembles of Storms option. You can then make changes to your components and repeat the process. This trial-and-error process can be used to initially speed up the process to determine the dimensions of outlets and storage volumes required in detention basins, or the sizes of pipes needed to convey flows. Once design is complete, final safety checks should be performed using the Ensembles of Storms.

Running storms provided by a user, such as historical (real) storms and probable maximum precipitation (PMP) storms, can still be done by un-ticking the box labelled Use ARR procedures in the Project → Options property sheet. This then allows you to enter storms in the way that was done prior to the introduction of the ARR procedures, entering and running 1987 storms, probable maximum precipitation storms or any other storms that you require.

 

The second way is for the user to manually specify which individual storms to include in an analysis for both major and minor storms by initially selecting the Individual Storms option from Project → Options

If you then select Project → Select major/minor storms, the following property sheet will appear:

You can enter individual storms from the ensembles, specifying its AEP, burst duration and storm number, and then pressing the Add Storm button.  The name of the storm will appear in the panel below. Additional storms can be added in the same way. In the Storm box, you will find an All 10 storms option that can be used to input all the ensemble storms of a particular AEP and duration.

Once storms are entered into the Select Major Storms sheet, and the OK button is clicked, a similar Select Minor Storms sheet appears, and this can be filled in the same way.

These storms can be used to run sets of data and inspect results. For example, the following set allows you to explore results from the median storms from a number of durations. 

The results of running these 10 major storms are shown below:

Another example is where we may want to examine the results for a full ensemble of storms with a given duration and AEP:



This can be done by individual entries to produce the results shown below:

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