Modeling multiple storm events in a single scenario

Product(s): Bentley SewerGEMS, CivilStorm 
Version(s): 08.11.XX.XX, 10.XX.XX.XX
Area: Modeling

Problem

How can I model multiple storms in a single scenario, for example when an area of the model needs to use a different storm event?

Background

In SewerGEMS or CivilStorm it is possible to model a system for more than one storm event in a single scenario. The need to assign multiple storms in a single scenario may be due to following reasons;

a) The area under consideration is large and modeling remote network elements as per local storm conditions is necessary.
b) Network elements (conduits/channels) within the same network should be designed for different durations of storm.

Solution

To assign multiple storm events the following steps must be followed.


For this procedure, we are considering an example consisting of two storm events; 5-year return period user defined Time-Depth curve and 2-year return period user defined Time-Depth curve. The 5-year return period storm is specified as the global storm occurring over the entire model. However, the 2-year storm needs to be applied locally to certain hydraulic elements.


The model is created with all network elements and catchments properly assigned. It is assumed that the storm events are created and global storm event is assigned as 5-year return period Time-Depth curve.


Step 1:


Go to Alternatives > Rainfall Runoff > Base Rainfall Runoff.


Note: Currently for the sake of simplicity we are working with the assumption that there is only a Base Rainfall Runoff alternative. However, the steps will remain the same regardless of number of alternatives.
Double click to open Base Rainfall Runoff alternative.

Here it can be seen that the global storm event for the entire model is set as 5-year return period Time-Depth curve.

Note: you can also assign the storm using the Global Storm Event dialog.


Step 2:


Select the element which should receive the local storm (2-year return period Time-Depth curve).

In this case the local storm shall be applied to Catchment CM-1

Note: If a single storm has to be applied to multiple catchments a selection set can be created for said catchments and then the local storm can be applied to the selection set.

Go to the Catchment tab and check on “Use Local Rainfall?” option. Select the appropriate local storm event from the drop-down menu.

Note: this can also be done from the catchment properties or flextable.

See Also

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