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Simulation of Surface-Water Integrated Flow and Transport in Two Dimensions:
SWIFT2D User’s Manual


U.S. Geological Survey Techniques and Methods 6 B-1


By Raymond W. Schaffranek


A numerical model for simulation of surface-water integrated flow and transport in two (horizontal-space) dimensions is documented. The model solves vertically integrated forms of the equations of mass and momentum conservation and solute transport equations for heat, salt, and constituent fluxes. An equation of state for salt balance directly couples solution of the hydrodynamic and transport equations to account for the horizontal density gradient effects of salt concentrations on flow. The model can be used to simulate the hydrodynamics, transport, and water quality of well-mixed bodies of water, such as estuaries, coastal seas, harbors, lakes, rivers, and inland waterways. The finite-difference model can be applied to geographical areas bounded by any combination of closed land or open water boundaries. The simulation program accounts for sources of internal discharges (such as tributary rivers or hydraulic outfalls), tidal flats, islands, dams, and movable flow barriers or sluices. Water-quality computations can treat reactive and (or) conservative constituents simultaneously. Input requirements include bathymetric and topographic data defining land-surface elevations, time-varying water level or flow conditions at open boundaries, and hydraulic coefficients. Optional input includes the geometry of hydraulic barriers and constituent concentrations at open boundaries. Time-dependent water level, flow, and constituent-concentration data are required for model calibration and verification. Model output consists of printed reports and digital files of numerical results in forms suitable for postprocessing by graphical software programs and (or) scientific visualization packages. The model is compatible with most mainframe, workstation, mini- and micro-computer operating systems and FORTRAN compilers. This report defines the mathematical formulation and computational features of the model, explains the solution technique and related model constraints, describes the model framework, documents the type and format of inputs required, and identifies the type and format of output available.




Model Applications

Purpose and Scope

SWIFT2D Model Overview

Governing Equations

Finite-Difference Approximations

Solution Technique

Special Computational Features

Model Implementation Process

Simulation Data Requirements

Model Limitations and Program Considerations

SWIFT2D Simulation Process

SWIFT2D Program Structure

Simulation Setup

Interactive File-Designation Procedure

SWIFT_IDP Execution

SWIFT2D Execution

Run Log File

Restart File

Emergency Restart Files

Hardware and Software Requirements

Computer Memory

Run Time


In-Stream Input

Simulation Input File

Part 1 Input

Part 2 Input

Part 3 Input

Part 4 Input

SWIFT2D Numerical Aspects and Computational Features

Sequence of Operations

Rectangular Grid Layout

Cell Size

Location of Variables

Computational Grid Enclosure

Default Enclosure

Complex Enclosure

Boundary Openings

Time Step

Time and Space Interpolation

Integration Options

Time Smoothing

Drying and Flooding

Permanently Dry Points or Dams

Chezy Coefficients

Marginal Depth Values

Functions of Salinity Gradient

Forcing Functions

Fourier Tide Openings

Space-Varying Wind and Pressure

Constituent Concentrations at Open Boundaries


Condition 0

Condition 1

Condition 2

Condition 3

Condition 4

Conditions 5 and 6

Condition 7

Condition 8

Particle Tracking

Transport and Water-Quality Simulation


Printed Output

Error, Warning, and Run Messages

Override Messages

Dimension Messages

Restart Messages

Emergency Restart Messages

History File Messages

Run Messages

Data Messages

Final Messages

History File

Map File

Coarse-Grid File



References Cited

Appendix 1. SWIFT2D In-Stream-Input Record Format

Appendix 2. SWIFT_IDP Program and Input Description

Appendix 3. Sample SWIFT2D In-Stream-Input (*.ctl) and SWIFT_IDP Input (*.idp) Files


1–3. Flowcharts showing:

1. The processing of data and files associated with SWIFT2D

2. The preprocessing of data and files associated with SWIFT_IDP

3. Files associated with SWIFT2D execution

4. Computational procedure in SWIFT2D

5. Location of variables on SWIFT2D staggered grid

6. Default computational grid with arbitrary openings

7. Computational grid enclosure angles

8. Computational grid enclosure lines

9. Computational grid enclosure polygons

10. KBO codes defining type, location, and orientation of boundary opening

11. Typical barrier between two dam points

12. Barrier in two flow directions at a single grid point

13. Five basic flow conditions for a barrier

14. Sample plot of SWIFT2D simulated particle excursions in the Potomac Estuary


1. Typical contents of the SWIFT2D.MTR file

2. Typical contents of the SWIFT_IDP.MTR file

3. Typical contents of the IDPRUN.LOG file

4. SWIFT2D files

5. Typical contents of the SWIFTRUN.LOG file

6. Relative speed of various computers executing SWIFT2D

7. In-stream-input record order

8. Part 1 variables that cannot be overridden

9. Part 1 variables that produce a warning message if overridden

10. Part 1 variables input order and override checklist

11. Part 1 input record order

12. Definition of Part 1 input variables

13. Part 2 input record order

14. Part 3 input record order

15. Primary computational routines in SWIFT2D

16. Important arrays in SWIFT2D

17. Time step of variable computation

18. Relation of variables in integration options

19. Variable definitions common to equations 11–15

20. Criteria for Chezy coefficient computation, drying, and flooding

21. KBO codes for defining boundary conditions

22. Flow direction of concentration computations at open boundaries

23. Symbols used in barrier history printout



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Printable tabloid cover (5.7 MB)--1 page

Left inside cover (35 KB)--1 page

Report (606 KB)--124 pages


The citation for this report, in USGS format, is as follows:

Schaffranek, R.W., 2004, Simulation of surface-water integrated flow and transport in two dimensions: SWIFT2D user's manual: U.S. Geological Survey Techniques and Methods, 6 B-1, 115 p.

U.S. Department of the Interior, U.S. Geological Survey
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Last modified: Friday, December 02 2016, 03:43:45 PM
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