WORLD METEOROLOGICAL ORGANIZATION 
HOMS COMPONENT 

Explanation of the criteria for classification and numbering of components  K35.3.13 (DEC 99) 

Explanation of the dates on the component's description  
BRANCHNETWORK DYNAMIC FLOW MODEL (BRANCH) 

1. Purpose and objectives To simulate unsteady flow through reaches and networks of open channels for water resources investigations involving water withdrawal effects, bridge location and design analyses, flood inundation, and tidal flushing. The model is well suited for simulation of regulated, tidal, or wind driven flows in upland or coastal open channel reaches or in a network of channels connected in a dendritic layout or looped pattern. 2. Description The BRANCH model uses a four point, implicit, finite difference approximation of the unsteady flow equations. Flow equations are formulated to account for nonuniform velocity distributions through the momentum Boussinesq coefficient, to accommodate flow storage/conveyance separation, and to include wind shear on the water surface as a forcing function. The model employs a nonlinear, iterative matrix solution method with user specified tolerance controls. The implicit solution technique permits 3. Input Crosssections are defined by piecewise, linear relations that can be
manually prepared or interactively entered, processed, and formatted via the supporting Channel Geometry Analysis Program (CGAP). Initial flow conditions can be prescribed as observed, estimated, assumed, or previously 4. Output Time series of computed flow results can be output for selected locations as tables or graphs. Tables include results at each time step or iteration and daily summaries. Individual terms can be calculated at each time step or iteration, and particle tracks, and cumulative flow volumes
can be listed. Graphs include computed discharge or stage and computed versus measured discharge or stage. 5. Operational requirements and restrictions BRANCH is coded in FORTRAN 77, making the program compatible with mainframe, workstation, and microcomputer systems and a variety of compilers. For microcomputers, a 32 bit processor (386 or higher) is needed. The code is easily dimensioned to allow use of the model for any channel configuration. Graphics output requires either a GKS or CalCOMP
graphics library. The time required (in seconds per day) for simulating the flow and movement of 8 conservative particles in a network of 25 6. Form of presentation Scientific documentation and user guide are available in English (see reference below). Program, examples, and documentation are available on floppy disk and the Internet. The program is provided as executable code, but the source program is available on request. The BRANCH distribution includes the CGAP and TDDS programs, also written in FORTRAN 77. Training is conducted by the USGS. 7. Operational experience BRANCH model use is extensive and worldwide. Currently, the model is
in operational use at nearly 40 sites as conducted by more than 12 USGS offices. The model has been in operational use since 1980. 8. Originator and technical support U.S. Geological Survey, Office of Surface Water. 9. Availability From the HOMS National Reference Centre for USA for 3 1/2" floppy or printed documentation; or electronically on the Internet at
http://water.usgs.gov/software/ or 10. Conditions on use Program is available free of charge; there is a charge for documentation. References: Schaffranek, R.W., Baltzer, R.A., and Goldberg, D.E., 1981, A model for simulation of flow in singular and interconnected channels. U.S. Geological Survey, TWRI, Chapter C3, Book 7, 110pp. Schaffranek, R.W., 1985, Model for simulating floods in rivers.Society for Computer Simulation, Simulation Series v. 15, no.1, pp. 132139. Schaffranek, R.W., 1987, Flow model for openchannel reach or network. U.S. Geological Survey Professional Paper 1384, 12p.


(First entered:01 FEB 93  Last updated: 01 FEB 94) 