Linked Two-dimensional/One-dimensional Flow Modelling Using the Shallow Water Equations

The ability to represent a hydrodynamic system as a combination of 1-D and 2-D models run in unison has numerous benefits relating to cost and accuracy. To address this issue a computer program, codenamed TUFLOW, for simulating depth averaged, 1-D and 2-D unsteady free-surface flows has been developed. Areas of complex flows are computed over a 2-D rectangular grid which may have attached to it any number of 1-D network models. The 2-D solution technique is based on the scheme by Stelling (1984) while coding from the hydrodynamic program ESTRY was utilised for the 1 -D network component. Details of the TUFLOW program development and testing including the 1-D/2-D interface algorithm are presented. Results of the work to date indicate the Stelling scheme to be a major improvement on the well-known RAND Corporation program (Leendertse, 1967) with respect to stability, robustness and boundary representation. Testing and practical application has shown the 1-D/2-D interface algorithm to be accurate, versatile and a powerful feature for modelling complex flow patterns in estuaries and rivers.