Catchments

Catchments are the polygons that delimit the area where the rain falls and where the flow flows by gravity to the point of discharge.

In the program, the catchments are in the Catchment Groups node and can be of two types:

• Point catchments - applicable to point gravity devices (drains for example)
• Longitudinal catchments - applicable to longitudinal gravity devices (cut/fill protection ditches for example)

To create a Catchment, use the command SCATCHMENT.

A catchment will have the following properties:

• Identification
  • Name - name of the Catchment
    Avoid names that are too long, or that contain the following characters: '*', '>', '<', '/', '\', '"', ':', ';', '|', '=', '`', '#', ',', '?'
  • Description - description of the Catchment
• Object
  • Style - name of the style associated with the bowl
• Geometry
  • Contribution Area Area of the polygon that delimits the Catchment
  • Average slope average slope of the Catchment
• Input Output
  • Network - network to which the device belongs
  • Output - device into which the Catchment discharges
• Hydrology
  • Runoff Coefficient - rate of runoff that effectively flows over the surface (C)
  • Delay Coefficient - depending on the distribution coefficient (n):
    
    CR = Area ^ ( - n)
    
    Where:
    Area is the Catchment area in hectares for large catchments, it softens the final flow (that's what transforms the rational method into modified rational (CR)). See more at Toolspace / Settings / Options / drainage / Distribution Coefficient
  • Precipitation - precipitation evaluated by the rainfall equation for the characteristics of this Catchment (I)
  • Outflow - Calculated Catchment outflow (QIN)
    
    QIN = CR * C * I * Area Where
    
    I = f (TR, TC)
    
    Where:
    TR = recurrence time
• Time of concentration
  • Time of Concentration - time that the longest (distant) particle takes to reach the point of concentration discharge (TC)
  • TC Equation - equation used to evaluate Catchment concentration time. In the case of being arbitrated, the properties below will not apply. For the other options, they appear according to the equation chosen to calculate the TC
  • Minimum Area - minimum area to which the equation applies
  • Maximum Area - maximum area to which the equation applies
  • Thalweg Length - in case a list of vertices for the thalweg is provided during the command SCATCHMENT, will be calculated by these vertices. Otherwise, the user must inform this value
  • Talweg unevenness - difference in height between the beginning and end of the thalweg

The commands for editing catchments are:

• SCATCHMENT - to create catchments
• SPROPS - to edit Catchment properties
• SCATCHMENTSTYLES - to edit the catchment styles
• SEDITSTYLE - to edit the Catchment style
• SDISCONNECT - to disconnect devices or catchments
• SCONNECT - to connect devices or catchments
• SADDVERTEX - to add vertex to Catchment
• SDELVERTEX - to remove vertex from Catchment
• SADDVERTEXTALV - to add vertex to thalweg
• SDELVERTEXTALV - to remove thalweg vertex
• SADDLABELS - to add label to catchment
• SMOVETOGROUP - Move selected basins to another basin group"