Author(s): Christopher R. Goodel; Brian Wahlin
Linked Author(s): Christopher Goodell, Brian T. Wahlin
Keywords: Dam Breach; Hydraulic Modeling; HEC-RAS; HEC-HMS; ReservoirRouting; Dynamic Routing
Abstract: A key component to dam breach modeling is the reservoir drawdown. This has a significant impact on the magnitude and shape of the breach outflow hydrograph, and ultimately the extent of flood inundation in the downstream reach. Drawdown of the reservoir can be modeled with the precise and physically correct dynamic routing method, which uses the full St. Venant equations of Conservation of Mass and Conservation of Momentum. However, this requires detailed bathymetric data for the reservoir, which is frequently very difficult and expensive to obtain for existing reservoirs. Furthermore, dynamic routing is complex and prone to numeric instabilities. A level pool drawdown is a more simplistic, numerically stable approach that can be used successfully under certain circumstances and requires only a simple stage-storage curve for the reservoir. This paper addresses the differences between the two reservoir drawdown methods and presents a practical method for determining whether or not level pool reservoir routing would be appropriate, given some basic characteristic parameters for the reservoir and breach formation. Both methods are compared for a wide variety of reservoir shapes and sizes and breach widths and formation times. The results are compiled on an envelope curve, yielding a very easy and practical method for the hydraulic modeler to decide whether the easier and more practical level pool routing method can be used.
Year: 2009