Tip: How to summarise impervious area and inhabitants per subcatchment

As part of a general drainage master plan, very often we need the following key figures per combined server overflow (CSO):
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[li] total area and total impervious area of all catchments connected to each CSO, and[/li]
[li] total number of inhabitants within the same subcatchments.[/li]
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[img width=200 height=178]http://wiki.mikebydhi.com/_media/mikeurban:anleitungen:gebietseinteilung:lageplan-kategorisiert.png?cache=[/img]

The article [url=http://wiki.mikebydhi.com/mikeurban:anleitungen:ermitteln_von_kennwerten_in_teileinzugsgebieten]Ermitteln von Kennwerten in Teileinzugsgebieten[/url] describes step by step how to derive those key figures. The text is in German, but with Google translate or similar you should be able to get the message. On the way you'll get familiar with the following techniques:
[list]
[li]adding user defined fields to the database[/li]
[li]using SQL commands in order to copy values between tables[/li]
[li]backward flow tracing[/li]
[li]creating tables with summarised values[/li]
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I hope the tip is helpful!