Conclusions and Discussion

For the dambreak hydrographs considered and the range of channel slopes modeled, the simple diffusion dambreak model of equation 12 provides estimates of flood depths and outflow hydrographs which compare favorably to the results determined by the wellknown K634 onedimensional dambreak model. Generally speaking, the difference between the two modeling approaches is found to be less than a 3 percent variation in predicted flood depths.
The presented diffusion dambreak model is based upon a straightforward explicit timestepping method which allows the model to operate upon the nodal points without the need to use large matrix systems. Consequently, the model can be implemented on most currently available microcomputers. However, as compared to implicit solution methods, time steps for DHM use are extremely small. Thus, relatively short simulation times must be used.
The diffusion model of equation 22 can be directly extended to a twodimensional model by adding the ydirection terms which are computed in a similar fashion as the xdirection terms. The resulting twodimensional diffusion model is texted by modeling the considered test problems in the xdirection, the ydirection, and along a 45degree trajectory across a twodimensional grid aligned with the xy coordinate axis. Using a similar twodimensional model, Xanthopoulos and Koutitas (1976) conceptually verify the diffusion modeling technique by considering the evolution of a twodimensional flood plain which propagates radially from the dambreak site.

