Use this dialog box to view and change catchment-related settings
This topic documents settings in all catchment-related Edit Settings dialog boxes (drawing-level, feature-level, and command-level).
- Drawing-level ambient settings are identified by the
drawing icon. - Catchment feature settings are listed near the top of this dialog box, after the General property group, and are identified by the
catchment icon. - Catchment command settings are identified by the
command icon.
- Catchment Name Template
-
Specifies the default name format for new catchments. For more information, see Naming Objects.
- Default Catchment Style
- Runoff Coefficient
-
Specifies the runoff coefficent for the catchment. Acceptable values are between 0.01 and 1.00. A runoff coefficient is used when calculating runoff with the Rational methods. This value is not used by AutoCAD Civil 3D; however, when you use the Edit in Storm and Sanitary Analysis command, it is exported as part of the catchment data so it can be used in Storm and Sanitary Analysis.
TR-55 Sheet Flow, Shallow Concentrated Flow, and Channel Flow Settings
The Sheet Flow, Shallow Concentrated Flow, and Channel Flow settings are all used when TR-55 is used as the Time Of Concentration (Tc) calculation method. If you specify a user-defined Time Of Concentration, these flow values are not used. These settings can be modified in the Catchment Properties.
Sheet flow is a very shallow flow over plane surfaces. It is the first component of Tc and starts at the hydraulically most distant watershed point. Sheet flow normally occurs at a depth of 0.1 ft. or less, and the length of sheet flow rarely exceeds a few hundred feet. The maximum length of sheet flow is 300 ft. Data used to compute the sheet flow are the length of flow, the slope, the 2-year 24-hour rainfall amount, and the ground roughness as measured by Manning's n.
- Sheet Flow Segments
- Sheet Flow Length
-
Specifies the default length of sheet flow segments.Note
AutoCAD Civil 3D creates all specified sheet flow segments first, then shallow concentrated flow segments, then channel flow segments. If one Sheet Flow Segment is specified and one Shallow Concentrated Flow Segment is specified, and the flow path is longer than the specified Sheet Flow Segment length, then the remainder of the flow path is created as Shallow Concentrated Flow.
You can edit flow paths using the Edit Flow Segments command.
- Sheet Flow Manning's Coefficient
- Sheet Flow Rain Intensity
Shallow concentrated flow type normally occurs after a maximum of 300 feet of sheet flow. The average velocity of shallow concentrated flow is determined by watershed slope and channel material (paved or unpaved). Typical areas where shallow flow occurs are in swales between houses and the gutter section of a roadway.