Predicting Peak Discharge from Gradually Breached Embankment Dam

Froehlich, David C.

doi:10.1061/(asce)he.1943-5584.0001424

Cited by 56 publications

(19 citation statements)

References 23 publications

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“…At the breach, simulated peak discharge (1.73 × 10 5 m 3 /s) exceeds by 32% the discharge (1.25 × 10 5 m 3 /s) estimated using the benchmark predictive equations for natural, constructed, and scale‐model dam failures of O'Connor and Beebee () and Walder and O'Connor (; Figure a). More information about the geometry of the Yigong landslide dam would be needed to apply breaching models using sophisticated predictive equations that involve dam dimensions (e.g., Froehlich, ). The time to peak discharge, t p , can be estimated based on the timescale of natural landslide dam failures, which varies over several orders of magnitude depending on the erodability of landslide material and failure mechanism (e.g., Garcia‐Castellanos & O'Connor, ; O'Connor & Beebee, ; Walder & O'Connor, ).…”

Section: Evaluation Of Flood Simulation Resultsmentioning

confidence: 99%

“…The assumption of instantaneous dam failure, such as we have made here, may be appropriate for examining flood hazard and hydraulics downstream because it represents a worse‐case scenario of breaching and provides maximum estimates for peak discharge and flow depth downstream. However, this treatment of the dam failure could be improved with more sophisticated empirical dam breaching models (e.g., Froehlich, ; Westoby et al, ), particularly if parameters related to the geometry and composition of the dam are known. The precise timescale of the Yigong dam failure is unclear (Delaney & Evans, ; Shang et al, ; Zhu et al, ) and likely <1 hr, but future simulations could investigate the effects of different breaching rates and dam parameters on downstream flow conditions.…”

Section: Insights Into Outburst Flood Hazard and Geomorphic Processesmentioning

confidence: 99%

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The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

2019

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Outburst floods in mountainous landscapes traverse complex topography and interact with the channel and valley walls, producing intense flow hydraulics that drive geomorphic change and impact people and infrastructure. Evidence of modern and ancient outburst floods is scattered around the eastern Himalaya, but hydraulics related to these geomorphic features are uncharacterized, limiting our understanding of the role of large floods in long‐term evolution of the region. Here we combine remote and field observations of the 2000 Yigong River landslide‐dam outburst flood with 2‐D numerical flood simulations using the software GeoClaw. Modeling results agree with field evidence to the extent that we judge the simulated hydraulics to be relevant to flood hazard and geomorphic investigations. Results show that the hydraulics of outburst floods through rugged topography differ from those expected for nonflood flows, in magnitude and in the spatial patterns of flow speed, direction, and shear stress. The flood produced sustained high bed shear stresses capable of plucking meter‐scale blocks immediately downstream of breach, in the steep Tsangpo Gorge, and in isolated locations associated with valley constrictions. Simulated shear stresses suggest that outburst floods deposited numerous kilometer‐scale boulder bars observed along the flood pathway, armoring the bed, increasing channel roughness, and inhibiting incision in locations that would not be predicted for nonflood flows. Our findings highlight the potential for different magnitude flows to promote not only different amounts, but also different patterns of bedrock erosion, with implications for the role of prehistoric megafloods in the topographic evolution of the eastern Himalaya.

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Section: Evaluation Of Flood Simulation Resultsmentioning

confidence: 99%

Section: Insights Into Outburst Flood Hazard and Geomorphic Processesmentioning

confidence: 99%

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

2019

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“…More large scale physical tests should be carried out to progressively improve both simple and more complex models in the future, reducing their uncertainty and improving their effectiveness at predicting embankment breaches. = Variable coefficient dependant on failure mode (Froehlich, 1995a(Froehlich, , 2008(Froehlich, , 2016a = Embankment height factor (Froehlich, 2016b) = Peak outflow from breach (…”

Section: Discussionmentioning

confidence: 99%

A Guide to Breach Prediction

West

Morris

Hassan

2018

Dams and Reservoirs

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Executive summaryEarthen embankments that are categorised as large (15m or greater in height) number in the tens of thousands globally. Embankment dam risk assessment is a vital measure that has been adopted throughout the industry to assess the potential impact that catastrophic dam failures can carry. A critical part of this assessment is the prediction of the breach process, which will determine the reservoir outflow hydrograph. This is crucial for the following stage of flood routing, which aids in flood risk assessment, evacuation planning and land-use planning.This report provides details of the breach prediction methods available to users, ranging from simple parametric equations to complex multi-dimensional erosion models. These are commonly divided into three categories; parametric models, semi-physically based models and physically based models.

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“…Currently, regression relations obtained from each type of dams are still frequently used method for calculating and forecasting the peak discharge (Q). The regression methods can give no better than order-of-magnitude estimation of probable peak discharge and allow for a tradeoff between the prediction accuracy and the difficulty of complex parameter acquisition, even they do not reflect the effect of breach-formation rate on the peak discharge (Walder and O'Connor, 1997;Cenderelli, 2000;O'Connor et al, 2013;Froehlich, 2016). The Q is estimated based on the dam factor (Vh) (drained volume (V) times depth of breach (h)), which represents potential energy of the dammed lake, and usually produce the low average stand error (Costa, 1985;Costa and Schuster, 1988).…”

Section: Methodsmentioning

confidence: 99%

Outburst floods in China: A review

Liu

Carling

et al. 2019

Earth-Science Reviews

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Outburst floods can have disastrous impacts on people, and are an important driving force in landscape change and have been studied widely on Earth. In China, although outburst floods have occurred frequently, they have been relatively little systematic studied. Here, we review outburst floods in China in terms of the characteristics, distribution, causes of dams and outburst floods. In terms of natural dams, landslides accounted for the majority (287 cases), followed by moraine dams (33 cases), which are mainly found on and around the Tibetan Plateau, and although other types (such as glacier and volcanic dams) were historically rare, many examples may be preserved in the geologic record. In addition, there have been thousands of outburst floods from artificial-constructed dams, the majority of which were from small earth dams. The largest reliably recorded peak discharge for an outburst flood was 1.24×10 5 m 3 /s, which occurred in Yigong, Tibet. The peak discharge of the 1975 Banqiao collapse was 7.9×10 4 m 3 /s, was the largest outburst flood of man-made dam. Our recent investigations on the Yarlung Tsangpo in Southeast Tibet have identified gravel deposits that probably record megafloods and offer great potential for paleoflood analysis.

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Predicting Peak Discharge from Gradually Breached Embankment Dam

Cited by 56 publications

References 23 publications

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

A Guide to Breach Prediction

Outburst floods in China: A review

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