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  Hydrologic & Hydraulic Technical Specifications

  PCSWMM can be applied to a wide variety of stormwater, wastewater and watershed modeling applications. These applications utilize a core set of US EPA SWMM5 hydrologic and hydraulic processes, as outlined below:

  Rainfall-runoff methods

  • Spatially-distributed rainfall (radar-rainfall)
  • Non-linear reservoir routing
    • Interception
    • Detention storage
    • Evaporation
    • Infiltration
      • Horton
      • Green-Ampt
      • SCS curve number
    • Overland sheet flow (Manning's formula)
  • Subcatchment to subcatchment routing (run-on)
  • Triangular unit hydrograph
    • Set of 3 per node
    • Initial abstraction and recovery
  • Groundwater interflow
  • Inflow from other hydrologic models

  Routing methods (3 types)

  • Dynamic wave routing
  • Kinematic wave routing
  • Steady-state routing

  Dynamic flow conditions

  • Open channel flow
  • Surcharged (pressure) flow
  • Reverse flow
  • Backwater effects
  • Looped-pipe networks
  • Force mains
    • Hazen-Williams
    • Darcy-Weisbach

  Continuous and single-event modeling

  • Variable time step
  • Infiltration recovery
  • Pollutant build-up

  Inflows

  • Direct inflow at hydraulic nodes
    • Baseline flow
    • Inflow time series (measured or third party runoff model generation)
  • Dry weather flow (DWF)
    • Hourly, daily, weekend and monthly time patterns
    • Sub-sewershed load allocation
  • Rainfall-dependent inflow and infiltration (RDII)
    • Triangular unit hydrographs (RTK)
    • Initial abstraction and recovery terms
    • Sub-sewershed specific responses
    • Monthly/seasonal variation
  • Groundwater inflow
    • Infiltration of groundwater into drainage system
    • Exfiltration of surface water from the drainage system
    • Aquifer unsaturated and saturated zone modeling
    • Groundwater recharge through subcatchment infiltration
    • Groundwater losses through evapotranspiration, lateral flow and deep percolation

  Hydraulic model elements

  • Manholes / catchbasins / junctions
    • Inflows
    • Flooding and/or local ponding
    • Bolted covers (surcharging)
    • Major/minor system interaction
    • Losses
    • Inlet control
    • Drops and/or sumps
  • Detention/storages
    • Functional (power function relating area to stage)
    • Tabular (stage/area relationship)
    • Inline
    • Offline
    • Detention ponds (wet/dry)
    • Tanks
  • Outfalls
    • Free outfall boundary condition
    • Fixed elevation boundary condition
    • Tidal boundary condition
    • Time-varying boundary condition
    • Normal flow boundary condition
    • Flap-gate
  • Dividers (flow splitters)
    • Overflow
    • Cutoff
    • Tabular (rating curve
    • Weir
  • Conduits (26 types)
    • Open channel (6 types)
      • Rectangular
      • Trapezoidal
      • Triangular
      • Parabolic
      • Power
      • Irregular (with station/elevation cross-section data)
    • Closed conduit (20 types)
      • Circular
      • Force-main
      • Filled-circular (e.g. sediment depth)
      • Rectangular
      • Horizontal ellipse
      • Vertical ellipse
      • Arch (standard)
      • Arch (non-standard)
      • Rectangular with triangular bottom
      • Rectangular with round bottom
      • Basket handle
      • Modified basket handle
      • Egg shaped
      • Horseshoe
      • Gothic
      • Catenary
      • Semi-elliptical
      • Semi-circular
      • Custom conduit shapes (via shape curve)
      • Dummy (inflow = outflow)
    • Entrance, exit and other losses
  • Natural channels (irregular)
    • Transect station-elevation data with overbanks
    • HEC-RAS and HEC-2 data importing
  • Pumps (4 types)
    • Off-line pump with a wet well where flow increases incrementally with available wet well volume
    • In-line pump where flow increases incrementally with inlet node depth
    • In-line pump where flow varies continuously with head difference between the inlet and outlet nodes
    • Variable speed in-line pump where flow varies continuously with inlet node depth
  • Weirs (4+ types)
    • Transverse (incl. multiple end contractions)
    • Side-flow
    • V-notch
    • Trapezoidal (incl. multiple end contractions)
    • Leaping weirs (divider with diversion curve)
    • Reverse flow
    • Optional flap gate
  • Orifices (4 types)
    • Side circular
    • Side rectangular
    • Bottom circular
    • Bottom rectangular
    • Reverse flow
    • Optional flap gate
  • Outlets
    • Tabular (outflow/head relationship)
    • Functional (power function relating outflow to head)
    • Optional flap gate
  • Gates
    • Flap gates for Conduit, Orifice, Weir, Outlet and Outfall entities

  Control rules (real-time control)

  • Passive real time control
  • Global optimal real time control (GO RTC)
  • Modulated controls
  • Proportional Integral Derivative (PID) controllers
  • Pump on/off controls
  • Weir crest elevation controls
  • Orifice size controls
  • Node depth, head or inflow based rules
  • Link flow or depth based rules
  • Simulation time based rules
  • Date/time based rules
  • Boolean logic structure (AND, OR, ELSE, PRIORITY)

• Modeling approach

• In addition, PCSWMM can accommodate a number of modeling approaches, some of which are discussed below.

  Lumped vs. distributed modeling

  Models developed with PCSWMM can embody lumped or distributed ideals, depending on the number of discretized elements. Models can be as simple as a single catchment (lumped), where a single set of parameters define the rainfall-runoff relationship for the project area as a whole, or as complex as 100,000+ discretized subcatchments, accounting for spatial variations in runoff response at a sub-parcel level. While not common, excellent results have been obtained discretizing to a square meter resolution.

  Empirical vs. deterministic modeling

  Models developed with PCSWMM can be based on empirical relationships, deterministic processes, or some combination of both, depending on which functions you choose. For example, detention pond outflow can be represented empirically with a rating curve, or with a parallel set of orifices, weirs, etc. representing the actual physical structures.

• For more information

• If you have any questions about the application of PCSWMM (and the US EPA SWMM5 engine) in your project, please contact us at tel. (519) 767-0197, or email our technical support at support@computationalhydraulics.com (pre-sales questions welcome).

PCSWMM and PCSWMM.NET are trademarks of CHI.