Dam break threshold value and risk probability assessment for an earth dam

Abstract. The instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed significant differences in the timing and extent of inundation. A GLUE-based methodology for constructing probabilistic maps of inundation extent, flow depth, and hazard is presented and provides a useful tool for communicating uncertainty in GLOF hazard assessment.

show abstract

Section: Uncertainty and Equifinality In Numerical Modellingmentioning

confidence: 99%

Numerical modelling of glacial lake outburst floods using physically based dam-breach models

et al. 2015

View full text Add to dashboard Cite

show abstract

“…One of the complexities in quantifying the uncertainty of the breach outflow hydrograph is that the outflow is affected by multiple uncertain variables, in which the nature and range of their uncertainties are not independent (Zhong et al, 2011). There have been few studies that analyzed the uncertainties of breach parameters.…”

Section: Introductionmentioning

confidence: 99%

A probabilistic framework for comparison of dam breach parameters and outflow hydrograph generated by different empirical prediction methods

Ahmadisharaf

Kalyanapu

Thames

et al. 2016

Environmental Modelling & Software

View full text Add to dashboard Cite

This study presents a probabilistic framework to simulate dam breach and evaluates the impact of using four empirical dam breach prediction methods on breach parameters (i.e., geometry and timing) and outflow hydrograph attributes (i.e., time to peak, hydrograph duration and peak). The methods that are assessed here include MacDonald and Langridge-Monopolis (1984), Von Thun and Gillete (1990), Froehlich (1995) and Froehlich (2008). Mean values and percentiles of breach parameters and outflow hydrograph attributes are compared for hypothetical overtopping failure of Burnett Dam in the state of North Carolina, USA. Furthermore, utilizing the probabilistic framework, the least and most uncertain methods alongside those giving the most critical value are identified for these parameters. The multivariate analysis also indicates that lone use of breach parameters is not necessarily sufficient to characterize outflow hydrograph attributes. However, timing characteristic of the breach is generally a more important driver than its geometric features.

show abstract

“…Recent studies have undertaken various forms of sensitivity analyses and uncertainty estimation to quantify the effects of uncertainty on numerical dam-breach model output (e.g. IM-PACT, 2004;Xin et al, 2008;Dewals et al, 2011;Zhong et al, 2011;Worni et al, 2012). The uncertainties surrounding model parameterisation are likely to translate into varying characteristics of the breachoutflow hydrograph, specifically peak discharge, time to peak, and the hydrograph form.…”

Section: Uncertainty and Equifinality In Numerical Modellingmentioning

confidence: 99%

Numerical modelling of Glacial Lake Outburst Floods using physically based dam-breach models

Westoby¹,

Brasington²,

Glasser³

et al. 2014

Preprint

View full text Add to dashboard Cite

Abstract. The rapid development and instability of moraine-dammed proglacial lakes is increasing the potential for the occurrence of catastrophic Glacial Lake Outburst Floods (GLOFs) in high-mountain regions. Advanced, physically-based numerical dam-breach models represent an improvement over existing methods for the derivation of breach outflow hydrographs. However, significant uncertainty surrounds the initial parameterisation of such models, and remains largely unexplored. We use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed with a Generalised Likelihood Uncertainty Estimation (GLUE) framework to quantify the degree of equifinality in dam-breach model output for the reconstruction of the failure of Dig Tsho, Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Equifinal breach morphologies were produced by parameter ensembles associated with differing breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was discovered to exert a dominant influence over model performance. Percentile breach hydrographs derived from cumulative distribution function hydrograph data under- or overestimated total hydrograph volume and were deemed to be inappropriate for input to hydrodynamic modelling. Our results support the use of a Total Variation Diminishing solver for outburst flood modelling, which was found to be largely free of numerical instability and flow oscillation. Routing of scenario-specific optimal breach hydrographs revealed prominent differences in the timing and extent of inundation. A GLUE-based method for constructing likelihood-weighted maps of GLOF inundation extent, flow depth, and hazard is presented, and represents an effective tool for communicating uncertainty and equifinality in GLOF hazard assessment. However, future research should focus on the utility of the approach for predictive, as opposed to reconstructive GLOF modelling.

show abstract

Dam break threshold value and risk probability assessment for an earth dam

Cited by 35 publications

References 12 publications

Numerical modelling of glacial lake outburst floods using physically based dam-breach models

Numerical modelling of glacial lake outburst floods using physically based dam-breach models

A probabilistic framework for comparison of dam breach parameters and outflow hydrograph generated by different empirical prediction methods

Numerical modelling of Glacial Lake Outburst Floods using physically based dam-breach models

Contact Info

Product

Resources

About