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, String) - name of the Catchment
    Avoid names that are too long, or that contain the following characters: '*', '>', '<', '/', '\', '"', ':', ';', '|', '=', '`', '#', ',', '?'
  • Description (Description, String) - description of the Catchment
• Object
  • Style (Style, ObjectID) - name of the style associated with the bowl
• Geometry
  • Contribution Area (ContributionArea, Double) Area of the polygon that delimits the Catchment
  • Vertices (Vertices, GeometryPointList) - list of vertices that define the area polygon
  • Perimeter (Perimeter, Double) - Perimeter of the polygon
• Input Output
  • Network (SolNetwork, ObjectID) - network to which the device belongs
  • Output (OutPart, ObjectID) - device into which the Catchment discharges
• Hydrology
  • Runoff Coefficient (C, Double) - rate of runoff that effectively flows over the surface (C)
  • Delay Coefficient (Cr, Double) - 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 (I, Double) - precipitation evaluated by the rainfall equation for the characteristics of this Catchment (I)
  • Outflow (CatchmentFlow, Double) - Calculated Catchment outflow (QIN)
    
    QIN = CR * C * I * Area Where
    
    I = f (TR, TC)
    
    Where:
    TR = recurrence time. Please note that this value is for informational purposes only. The actual value will be calculated on the devices, as it depends on the network's TR/TRV
• Time of concentration
  • Average Slope (AverageSlope, Double) - average slope of the basin
    When the list of thalweg vertices is entered, it will be calculated by the formula
    AverageSlope = (LT / Sum(deltah/dist2d))^2
    Where:
    deltah = vertex(j).Z - vertex(j+1).Z
    dist2d = vertex(j).Distance2D(vertex(j+1))
    LT = Sum(vertex(j).Distance2D(vertex(j+1)))
  • Time of Concentration (Tc, Double) - time that the longest (distant) particle takes to reach the point of concentration discharge (TC)
  • TC Equation (TcEq, Enum) - 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
    In all equations:
    
    areaKm - Catchment area in square kilometers
    Tc will be given in minutes
    Lkm - length of the thalweg, will be given in kilometers
    H - thalweg unevenness, will be given in meters
    AverageSlope - average slope of the thalweg will be given in (m/m) or dimensionless.
    
    The equations are:
    1. Kerby - Applicable to small bowls TC = 37 * (Lkm * 0.5 / (100.0 * AverageSlope)) ^ 0.47
    2. Kirpch - Originally applicable to catchments smaller than 0.8 km².
       According to the DNIT, it is applicable to small, medium and large catchments. TC = 57 * (Lkm ^ 2 / (1000.0 * AverageSlope)) ^ 0.385
    3. Picking - Applicable to small catchments TC = 60 * 5.3 * (Lkm ^ 2 / AverageSlope) ^ (1.0 / 3.0)
    4. USCE (U.S. Corps of Engineers) Applicable to small catchments TC = 60* 0.3 * (Lkm / ((100.0 * AverageSlope) ^ 0.25)) ^ 0.76
    5. Ven Te Chow - Applicable to small catchments TC = 25.2 * (Lkm / ((100.0 * AverageSlope) ^ 0.5)) ^ 0.64
    6. DNOS - Applicable to any Catchment TC = (1.0 / vk) * (areaKm * 100.0) ^ 0.3 * Lkm ^ 0.2 * (catchment.AverageSlope * 100.0) ^ 0.4
       

       Land	vk
       Sandy clay soil, covered with intense vegetation, high absorption	2.0
       Common land, covered with vegetation, appreciable absorption	3.0
       Clay soil, covered with vegetation, medium absorption	4.0
       Clay soil, average vegetation, little absorption	4.5
       Rocky terrain, sparse vegetation, low absorption	5.0
       Rocky terrain, sparse vegetation, reduced absorption	5.5

    7. Modified Kirpch - Applicable to any Catchment TC = 85.2 * (Lkm ^ 2 / (1000.0 * AverageSlope)) ^ 0.385
    8. George Ribeiro - Applicable to any Catchment TC = 16 * Lkm / ((1.05 - 0.2 * PR) * (100.0 * catchment.AverageSlope) ^ 0.04)
       PR (PR, Double) - is the portion of the watershed covered by vegetation (0% to 100%)
    9. Passini - Applicable to any Catchment TC = 60 * (0.107 * (areaKm * Lkm) ^ (1.0 / 3.0) * catchment.AverageSlope ^ -0.5)
    10. Ventura - Applicable to any Catchment TC = 60 * 0.127 * (areaKm / catchment.AverageSlope) ^ 0.5
    11. Rossi - Contraindicated in any Catchment TC = 46.2 * (Lkm() / (100.0 * Catchment.AverageSlope) ^ 0.5) ^ 0.295
    12. Giandotti - Applicable to medium and large bowls TC = 60 * (4 * areaKm() ^ 0.5 + 1.5 * Lkm()) / (0.8 * H ^ 0.5)
        H = AverageSlope * Lkm * 1000
    13. Lag TC = 16 * Kn * (Lkm() ^ 2.5 / H ^ 0.5) ^ 0.33
        H = AverageSlope * Lkm * 1000
        Kn (Kn, Double) - is the average of the Manning coefficients along the most important watercourses of the Catchment (varies from 0.01 to 0.3)
        Lc (Lc, Double) - length, in km, along the same watercourse from the gauging station to the point closest to the center of gravity of the drainage basin
    14. John Collins TC = 44 * (Lkm / dm) * (areaKm ^ 2 / (AverageSlope * 100)) ^ 0.2
        dm = (4 * areaKm / PI) ^ 0.5
        Where:
        PI - mathematical constant pi
    15. CN TC = 60 * (1.08 * Lkm ^ 1.3 * (1000 / (CN - 9)) ^ 0.7 / H ^ 0.5)
        H = AverageSlope * Lkm * 1000
        Curve Number (CN, Integer) - Curve number recommended by the U.S. Soil Conservation Service for the Mockus rainfall-runoff relationship, based on the soil-vegetation cover complex
    16. Dodge - Applicable to big catchments TC = 21.88 * areaKm ^ 0.41 / AverageSlope ^ 0.17
    17. Bransby Willians TC = 60 * (14.6 * Lkm / (AverageSlope ^ 0.2 * areaKm ^ 0.1))
    18. Arbitrated - Allows the tc value to be arbitrated in the Catchments
  • Minimum Area (MinArea, Double) - minimum area to which the equation applies
  • Maximum Area (MaxArea, Double) - maximum area to which the equation applies
  • Thalweg Length (LT, Double) - 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
  • Surface (RefSurf, ObjectId) - Specifies the name of the surface from which the program will extract the elevation of the device's insertion point. If not provided, the elevation must be entered manually, and in this case, the superelevation will have no effect on the device
  • Talweg unevenness (Htalv, Double) - difference in height between the beginning and end of the thalweg. If a list of vertices is provided for the thalweg during the SCATCHMENT command, it will be calculated using these vertices. Otherwise, the user must enter this value
  • Thalweg (Thalweg, GeometryPointList) - Basin Thaweg Coordinates
    Note: If you entered the thalweg coordinates, don't forget to define the reference surface so that SOLIDOS can obtain the elevations at the thalweg vertices. If you don't, the TC calculation will result in an incorrect value, displaying the Critical icon in the TC value. If you don't enter the thalweg coordinates, manually enter Htalv, LT, and AverageSlope for SOLIDOS to calculate the TC, if you selected an equation to calculate it
• Calculations - Applicable to point catchments when the network is to be simulated in SWMM
  • SWMM (Swmm, SwmmCatchment) - Contains the properties required to simulate the network in SWMM, as well as the results once the simulation is run

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"