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Calculate runoff amounts that help determine the size of stormwater control objects, such as ponds.
Type:
Tutorial
Length:
5 min.
Tutorial resources
These downloadable resources will be used to complete this tutorial:
Transcript
00:04
in a typical suburban design catchment.
00:06
The goal in the design process is to
00:08
determine how much area of a catchment is impermeable
00:12
and how much runoff is caused by those impermeable areas.
00:16
First, you must calculate the pimp value,
00:19
which is the percentage of the catchment that is covered with tarmac,
00:23
concrete or other materials rain cannot penetrate
00:27
info drainage only accounts for runoff from those impermeable areas.
00:32
To start on the ribbon,
00:34
build tab data panel,
00:37
click tables
00:40
in the tables, dialogue, expand the inflows node,
00:44
then expand the time of concentration node,
00:48
enable the percentage impervious and preliminary percentage impervious boxes.
00:53
Along with the summer and winter volumetric runoff coefficients.
00:58
The two Impervious columns should all be set to 60%,
01:02
but if they aren't changed them now,
01:06
It is therefore assumed that 60% of each catchment is hard standing, impermeable,
01:11
such as roads or roof areas.
01:14
Now you can calculate how much runoff is produced by impermeable surfaces.
01:18
In your model,
01:20
note that info works. I. Cm.
01:22
Has more sophisticated methods for calculating runoff amounts
01:26
and offers a variety of models that can
01:28
incorporate variables like ground saturation and soil type
01:33
info drainage makes a simple assumption
01:36
that there is a fixed amount of runoff caused by impermeable surfaces.
01:41
This is reflected in the summer and winter volumetric runoff coefficient columns
01:47
A value of 0.750 or 75% assumes the ground is drier during the summer season.
01:56
That means during a rainfall event,
02:03
The next column assumes a value of 84% during the winter season.
02:08
Keep in mind that these values work for the purposes of this exercise,
02:13
but that in certain situations they may need to be increased or decreased.
02:18
These values are critical because they influence how
02:21
much rainfall enters a drainage system in a model
02:24
and therefore dictate design elements like pipe and storage sizes.
02:30
Close the tables dialog by pressing OK, and save any changes you made.
Video transcript
00:04
in a typical suburban design catchment.
00:06
The goal in the design process is to
00:08
determine how much area of a catchment is impermeable
00:12
and how much runoff is caused by those impermeable areas.
00:16
First, you must calculate the pimp value,
00:19
which is the percentage of the catchment that is covered with tarmac,
00:23
concrete or other materials rain cannot penetrate
00:27
info drainage only accounts for runoff from those impermeable areas.
00:32
To start on the ribbon,
00:34
build tab data panel,
00:37
click tables
00:40
in the tables, dialogue, expand the inflows node,
00:44
then expand the time of concentration node,
00:48
enable the percentage impervious and preliminary percentage impervious boxes.
00:53
Along with the summer and winter volumetric runoff coefficients.
00:58
The two Impervious columns should all be set to 60%,
01:02
but if they aren't changed them now,
01:06
It is therefore assumed that 60% of each catchment is hard standing, impermeable,
01:11
such as roads or roof areas.
01:14
Now you can calculate how much runoff is produced by impermeable surfaces.
01:18
In your model,
01:20
note that info works. I. Cm.
01:22
Has more sophisticated methods for calculating runoff amounts
01:26
and offers a variety of models that can
01:28
incorporate variables like ground saturation and soil type
01:33
info drainage makes a simple assumption
01:36
that there is a fixed amount of runoff caused by impermeable surfaces.
01:41
This is reflected in the summer and winter volumetric runoff coefficient columns
01:47
A value of 0.750 or 75% assumes the ground is drier during the summer season.
01:56
That means during a rainfall event,
02:03
The next column assumes a value of 84% during the winter season.
02:08
Keep in mind that these values work for the purposes of this exercise,
02:13
but that in certain situations they may need to be increased or decreased.
02:18
These values are critical because they influence how
02:21
much rainfall enters a drainage system in a model
02:24
and therefore dictate design elements like pipe and storage sizes.
02:30
Close the tables dialog by pressing OK, and save any changes you made.
The goal in the catchment design process is to determine how much surface area of a catchment is impermeable, and how much runoff is caused by those impermeable areas. To do so, you must calculate the percentage impervious value, or “PIMP value,” which is the percentage of the catchment that is covered with tarmac, concrete, or other materials that rain cannot penetrate. InfoDrainage only accounts for runoff from those impermeable areas.
InfoDrainage assumes:
Keep in mind that these values work for this exercise, but they may need to be increased or decreased for other situations. These values are critical because they influence how much rainfall enters a drainage system in a model, and therefore dictate design elements like pipe and storage sizes.
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