Storm Sewer Design with DREN-URBA, what you should know

This tutorial is for the interface and features of Version 1.1 of DREN-URBA.

With the release of Version 2.0 in November 2015, some features have been modified, as you will see in the corresponding tutorials.

The definition of the Storm Sewer Network, in a project created with DREN-URBA, begins by defining the properties of each system’s section (sewer pipe) that will be responsible for conveying the flow caught by the drain Inlets in the Superficial Urban Drainage System.

Knowing the location of the stormwater drain inlets, you only need to specify, for each section or sewer pipe, which of those drain inlets are discharging into it. Then, DREN-URBA will perform the respective drainage areas accumulation and the subsequent stormwater peak flow calculation for each sewer so that, together with the geometrical properties entered by the user, the user will determine parameters such as sewer Capacity, Full Flow Velocity, and Real Flow Velocity.

Thus, the Storm Sewer Network Design Engineer may establish compliance (or not) of the normative aspects of these type of systems.

Storm Sewer Design Example with DREN-URBA

Let’s look at the steps to create, from the superficial drainage system already created in DREN-URBA, the respective storm sewer network. We will use the example project that we saw in this tutorial.

In our example, it was established that placing storm drain inlets in four streets of the studied area were left satisfied the design flood spreads required for the stormwater collection system design.

Now, creating the sewer network responsible for driving the caught stormwater to the system’s provided point of discharge is required. The following figure shows the layout of the Storm Sewer Network, indicating the ground elevations (street’s corners) at the places where the system’s manholes are located.


Counting with the network’s layout, it is possible to know not only the ground elevations characteristic to each sewer pipe, but also their lengths and, of course, the drainage inlets associated with each one.

So let’s start creating the Storm Sewer Network on DREN-URBA’S project file generated in the previous tutorial (superficial urban drainage system with stormwater Drainage inlets):

1After opening the aforementioned project file, we’ll verify and modify the default value settings to be used in the creation of each sewer pipe. In this case, we’ve set the values at Default Settings dialog of DREN-URBA, as follows:


Close the dialog by clicking the OK button.

2Changing to the Storm Sewers tab on DREN-URBA’S main window, we’ll begin the sewers creation, preferably from the most downstream (the one that contains the system’s discharge point).

Click the Insert Sewer button to show the Storm Sewers Editor on the screen:


In the specific case of this dialog, you will notice that by selecting an inlet from the list and adding it to the actual sewers assigned inlets, it will be removed from the list of available ones, so as to avoid duplication of drain inlets in the Storm Sewer Network:


Conversely, when removing a drainage inlet from the list of sewer’s assigned inlets (by selecting it and clicking the remove button), that inlet will be added back to the list of available ones so it can be assigned to another sewer pipe, if any.

Thus, having properly entered the information for all the storm sewers of the system, there should be no available drain inlets for assignment. In any case, DREN-URBA will give a warning message to the user if there are still drain inlets unassigned when the calculation is performed.

3Similar to the previous step, we’ll add the following sewers in our example network, bearing in mind appropriately specifying the sewer in which the actual one will discharge.

For example, for sewer E2-E1, the following data must be entered:


4With all storm sewers introduced and after clicking the Start Calculation button, the DREN-URBA’S main window (Storm Sewers tab) would be similar to the following:

Storm Sewer final Design with DREN-URBA

Here it is observed that the criteria of capacity (Qc>=Qr) of every storm sewer, as well as those of minimum velocity at full section (Vc<Vmin), are fulfilled.