Date: Wed, 23 Jun 2021 10:12:51 -0700 (PDT) Message-ID: <1014307905.61675.1624468371617@HILLINCONF.xps.xpsolutions.com> Subject: Exported From Confluence MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_Part_61674_445041032.1624468371617" ------=_Part_61674_445041032.1624468371617 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Content-Location: file:///C:/exported.html Time of Concentration

# Time of Concentration

The amount of time that it w= ill take for water landing on the roof area to enter the system. The inflow= s from the area will then  be evenly spread over this time when the ar= ea is analysed.

This amount of time can be calculated with the Time Of Concentration Calcu= lator. The Percent Impervious is defined as = the pervious portion of the Inflows area.

This option may not be available or different for your region. For more inf= ormation, refer to the=20 Regionalisation=  topic.

### Analysis

The analysis is the same as the Time Area Diagram method with the time area diagram b= eing built with an even spread of the area over the time of concentration.&= nbsp;

Eg. Time of Concentration =3D 3 mins, Area =3D 0.75ha

If the timestep is 1 minute, A1 =3D 0.25, A2 =3D 0.25, A3 =3D 0.25.

The rainfall profile and the time area diagram are combined with the vol= umetric runoff coefficient in the following way:

Q1 =3D (I1 x A1) x 2.78 x Cv

Q2 =3D (I1 x A2 + I= 2 x A1) x 2.78 x Cv

Q3 =3D (I1 x A3 + I= 2 x A2 + I3 x A1) x 2.78 x Cv

And so on.

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