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Accurately enter the Percentage Impervious value when determining pipe sizes.
Type:
Tutorial
Length:
2 min.
Tutorial resources
These downloadable resources will be used to complete this tutorial:
Transcript
00:03
the percentage impervious value defines the proportion of
00:06
the catchment that has been developed as roads,
00:08
roofs
00:09
and other hard standing areas.
00:12
This is crucial because it is assumed that only rainfall landing on these
00:16
areas will run off over land and end up in a manhole.
00:20
In a typical housing or urban development,
00:22
roads make up about 30% of a catchment area,
00:26
roofs make up another 30% and the remaining 40% is permeable land,
00:31
such as grassy areas, gardens,
00:33
grass verges
00:35
and open undeveloped land from which there is
00:37
assumed to be no contribution to the runoff.
00:41
If you were designing for structures such as an airport,
00:44
a large parking lot or a large warehouse facility,
00:48
the roads and roofs values could be as high as 100%.
00:53
However, for the example, you see here,
00:55
these average urban development numbers will suffice
00:59
the roads and roofs values together make up
01:02
the percentage impervious value or the pimp value.
01:06
This could be an assumed value or you could
01:08
use digitized data for a more accurate analysis.
01:12
There are G. I. S. Systems that can help you to calculate more accurate pimp values.
Video transcript
00:03
the percentage impervious value defines the proportion of
00:06
the catchment that has been developed as roads,
00:08
roofs
00:09
and other hard standing areas.
00:12
This is crucial because it is assumed that only rainfall landing on these
00:16
areas will run off over land and end up in a manhole.
00:20
In a typical housing or urban development,
00:22
roads make up about 30% of a catchment area,
00:26
roofs make up another 30% and the remaining 40% is permeable land,
00:31
such as grassy areas, gardens,
00:33
grass verges
00:35
and open undeveloped land from which there is
00:37
assumed to be no contribution to the runoff.
00:41
If you were designing for structures such as an airport,
00:44
a large parking lot or a large warehouse facility,
00:48
the roads and roofs values could be as high as 100%.
00:53
However, for the example, you see here,
00:55
these average urban development numbers will suffice
00:59
the roads and roofs values together make up
01:02
the percentage impervious value or the pimp value.
01:06
This could be an assumed value or you could
01:08
use digitized data for a more accurate analysis.
01:12
There are G. I. S. Systems that can help you to calculate more accurate pimp values.
The Percentage Impervious value defines the proportion of the catchment area that has been developed as roads, roofs, and other hard-standing areas. It is assumed that only rainfall landing on these areas will run off overland and end up in a manhole.
Typical housing or urban development catchment areas consist of:
Roads + Roofs = Percentage Impervious (PIMP):
Industry:
Role:
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