You can use the Catchment Properties tab to change the Reference Pipe Network Structure, the Runoff Coefficient, the Time Of Concentration Method, and the Time Of Concentration (if the method is user-defined). The Catchment Properties tab also displays several read-only properties for the catchment.
Catchment
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2D Area of Catchment
- Displays the calculated area of the catchment.
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Discharge Point
- Displays the specified discharge point of the catchment. If you defined the flow path from a polyline, this is the downhill end point of the selected flow path polyline. If you defined the flow path from a surface, this is the discharge point you selected in the drawing.
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Exclusionary
- Specifies whether a catchment will exclude other catchments.
Exclusionary catchments exclude any other catchments within the same Catchment Group whether the other catchments are exclusionary or not. If a catchment is exclusionary, its boundary (and flow path) can be modified either by existing catchments as it is being created or by new catchments as they are being created.
As a catchment is created, it will check all other catchments within the same Catchment Group for two situations:
- If another catchment is exclusionary, and if the new catchment has some (or all) of its boundary within it, the other exclusionary catchment will exclude the new catchment from itself.
- If the new catchment is exclusionary, and if the other catchment has some (or all) of its boundary within it, the new catchment will exclude the other catchment from itself.
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Reference Pipe Network
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Displays the name of the pipe network that contains the pipe network structure you select in the Reference Pipe Network Structure list.
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Reference Pipe Network Structure
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Optionally specifies the pipe network structure to use as a reference for the catchment.
Note: Catchments can be associated with a single pipe network structure. The reason for making this association is to enable catchment data to be exported to Storm and Sanitary Analysis. When catchments are associated with a structure, they can be exported and converted into a Storm and Sanitary Analysis subbasin. With no association, however, catchment data cannot be exported.
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Catchment Group Name
- Displays the group in which the catchment was created. To change the catchment group, you can use the Move To Catchment Group command.
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Reference Surface
- Displays the surface upon which the catchment area was calculated. If the catchment was creating using the Create Catchment From Object command, this value is <none>.
Important: The surface associated with a catchment cannot be changed after the catchment is created. The catchment does not update dynamically if the surface changes after the catchment is created. However, you may select another surface to use for calculating flow paths when using the Edit Flow Segments command.
Hydrological Properties
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Runoff Coefficient
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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; 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.
Flow Segment Settings
The following notes apply to the Sheet Flow, Shallow Concentrated Flow, and Drainage Channel Flow sections.
- If the Time Of Concentration Method is set to User-Defined, then the Sheet Flow, Shallow Concentrated Flow, and Drainage Channel Flow sections are not shown in this dialog box.
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So that all flow segment data can be transferred to Storm and Sanitary Analysis in the STM file, the number of flow segments per flow type is limited to three. A maximum of three Sheet Flow, three Shallow Concentrated Flow, and three Drainage Channel Flow segments are allowed for any given flow path.
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By default, flow paths are created with the number of segments as specified in the catchment feature settings. You can use the Edit Flow Segments command to add additional segments of any of the three types to a flow path after creation.
Sheet Flow
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Sheet Flow Segments
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Displays the number of sheet flow segments defined within the flow path.
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Total Sheet Flow Travel Time
- Displays the travel time for all sheet flow segments.
Shallow Concentrated Flow
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Shallow Concentrated Flow Segments
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Displays the number of shallow concentrated flow segments defined within the flow path.
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Total Shallow Concentrated Flow Travel Time
- Displays the travel time for all shallow concentrated flow segments.
Drainage Channel Flow
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Drainage Channel Flow Segments
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Displays the number of drainage channel flow segments defined within the flow path.
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Total Drainage Channel Flow Travel Time
- Displays the travel time for all drainage channel flow segments.
Time Of Concentration
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Time Of Concentration Method
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Specifies which method to use for calculating the Time Of Concentration, TR-55 or User-Defined.
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Time Of Concentration
- Displays the sum of the calculated travel time values if the Time Of Concentration Method is set to TR-55. This field is editable if the Time Of Concentration Method is User-Defined.
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Hydraulically Most Distant Point
- Displays the coordinates of the selected or calculated point that is the upstream end of the flow path.
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Hydraulically Most Distant Length
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Displays the distance between the specified discharge point and hydraulically most distant point.
This length may not be the longest measurable distance between any two points within a catchment; it can be shorter.
Water moves through a watershed as sheet flow, shallow concentrated flow, swales, open drainage channels, street channels, storm sewers, or some combination of these. The hydraulically most distant length represents these flows along a path where "distant" relates to time rather than length.