A one-dimensional dam-break flood routing model is verified by
using observed data on the flash flood resulting from the failure of
Laurel Run Reservoir Dam near Johnstown, Pennsylvania. The model has
been developed on the basis of an explicit scheme of the characteristics
method with specified time intervals. The model combines one of the characteristic
equations with the Rankine-Hugoniot shock equations to trace the
corresponding characteristic backward to the known state for solving the
depth and velocity of flow at the wave front. The previous version of
the model has called for a modification of the method of solution to
overcome the computational difficulty at the narrow breach and at any
geomorphological constraints where channel geometry changes rapidly.
The large reduction in the computational inaccuracies and oscillations
was achieved by introducing the actual "storage width" in the equation of
continuity and the imaginary "conveyance width" in the equation of motion.
Close agreement between observed and computed peak stages at several stations
downstream of the dam strongly suggests the validity and applicability of
the model. However, small numerical noise appearing in the computed stage
and discharge hydrographs at the dam site as well as discrepancy of attenuated
peaks in the discharge hydrographs indicate the need for further model
improvement.
