Discussion of "Enhanced Predictions for Peak Outflow from Breached Embankment
Discussion of "Enhanced Predictions for Peak Outflow from Breached Embankment
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DOI:
10.1061/(asce)he.1943-5584.0000470
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发表时间:
2012-03
期刊:
影响因子:
--
通讯作者:
C. Thornton;Michael W. Pierce;S. Abt;V. Singh
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文献类型:
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作者:
C. Thornton;Michael W. Pierce;S. Abt;V. Singh
By using multivariate regression analysis of data from 87 dambreach cases, the authors of the paper under discussion proposed new equations for improved prediction of peak discharge through breached dam embankments. They tabulated 16 expressions, including five attributed to Pierce et al. (2010) that involved height of water in the dam reservoir at the time offailure (hw), or storage (V), or both as independent variables to predict peak discharge through breached embankments.Although these equationsare based ona large amount of data, the weaknesses inherent in the database undermine the confidence in their application. For example, the nonavailability of data for various geometric elements, as presented in Table 2 of the original paper, alludesto the inconsistency in the databasethatarises from the weakness of dam-failure forensics methodology, as reported by the authors. It is recognized that the collection of data under circumstances of breached dam embankments is a risky operation; and therefore, whatever data is collected is of high value. Further, although the data collected from the various breach case studies present statistically chaotic conditions, every piece of data may reveal information of high relevance. Therefore, the utilization of each available piece of data seems logical for improved prediction of peak discharge through breached dam embankments. Hence, the equations in the paper are, indeed, a step ahead, for they incorporate the height of water level (h), volume of water at the time of failure (V), and average embankment length (L )o r width (W )a s three independent variables. However, it would have been better to utilize the data of all pertinent variables, if they existed. Therefore, multivariate analysis incorporating the height of water behind the dam embankment, volume of water, and a composite variable that includes both the average width and length of the embankment as three independent variables in a single equation was carried out, as opposed to the double equations of the paper under discussion, consisting of only three variables at a time. The availability of average width and length of embankment varies from one case study to another. Thus, a composite variable combining these geometric variables was used to derive a regression equation. The summation of two geometric variables, average width and length of embankment, was used to conceive a composite variable (W þ L). This allowed to obviate the problem of singularity that might arise with the multiplication operation. Thus, the newly proposed equation incorporates the unified effectofall four variables,which adequately deals with the nonavailability of any of the two geometric variables by putting that variable value equal to zero. Further, to eliminate the difficulty while selecting an equation from a group of correlations on the basis of single and double independent variables, i.e., height of water, volume of water, or both together for predicting peak outflow through breached embankments, a single expression for each case is also proposed. Predictive Equations Eq. (1) of the original paper reflects the importance of the length of embankment, and Figs. 2 and 3 (of the paper under