Location: Hydraulic Engineering Research
Title: Breach parameter and simulation comparisons Authors
Submitted to: State Dam Safety Officials Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 10, 2008
Publication Date: September 8, 2008
Citation: Hanson, G.J., Tejral, R.D., Temple, D.M. 2008. Breach parameter and simulation comparisons. In: Dam Safety 2008. Proceedings of the Association of State Dam Safety Officials Annual Conference, September 7-11, 2008, Indian Wells, CA. CDROM. Interpretive Summary: Our ability to predict the rate an embankment dam erodes and fails when during flooding is crucial to determining the risk to people and property downstream. Historical cases of dam failures have previously been used to predict dam failure characteristics important for determining risk. There is a significant amount of uncertainty in historical cases which has led engineers, regulators and owners to take conservative approaches to prediction of dam failures for emergency action planning and hazard classification of these structures. Today other tools for predicting and analyzing dam failures are being developed. This paper discusses one model, an embankment failure simulation model SIMBA (Simplified Breach Analysis), that is being developed to provide an additional tool for prediction of dam failure processes and rates.
Technical Abstract: Our ability to predict the rate of breach development and the associated outflow from an overtopped embankment or dam is crucial to characterizing and evaluating the risk due to potential dam failures. Historical databases of dam failures have been used to develop breach parameter prediction equations (i.e., peak breach discharge, breach width, and breach formation time). The small number of well documented historical cases relative to the large number of dams, uncertainties in breach data, and limited information on the properties of the dam embankments has led to large uncertainty in these prediction equations. This uncertainty combined with the perceived risk has historically led engineers, regulators, and owners to take very conservative approaches to prediction of breach parameters for emergency action planning and hazard classification of structures. Today there are several tools available for analyzing dam failures. In addition to the empirical relations developed from the available data, these tools include computational models based on the physical processes. These models continue to evolve and mature as the overall breach process becomes better understood. This paper discusses the physically based breach simulation model SIMBA (Simplified Breach Analysis) that is being developed as a research tool. In this paper SIMBA is used to perform breach simulations representing embankment heights ranging from 5 ft (1.5 m) to 400 ft (120 m) with a range of material properties. The peak discharges predicted by this model are then compared to those predicted by the NRCS peak discharge breach equation. The coherence and reasonableness of the results are discussed along with the impacts of embankment and reservoir properties on these results.