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Embankment dam breach parameters revisited
Abstract
The extent of flooding and travel time of a flood wave that would result from the failure of a dam need to be predicted to establish needed spillway capacities and to prepare emergency action plans that would be used in the event of an actual dam failure. Data generated from 63 embankment dam failures were assembled to evaluate breach formation model parameters. Basing from these data, empirical models of breach formation were evaluated and prediction methods for the height, average width, side slope ratio, and formation time of the ultimate breach were developed. Results of the study are intended to help improve the accuracy of numerical simulations of dam-break flood waves.
... Empirical equations for dam breach outflow characteristics can be calibrated based on historical dam failures, both simulated and actual. Equations such as the ones presented by Froehlich (1995aFroehlich ( , 1995bFroehlich ( , 2008Froehlich ( , 2016, Xu and Zhang (2009), Thornton et al. (2011), Gupta and Singh (2012), Hooshyaripor et al. (2014), Azimi et al. (2015) and Zhong et al. (2020) can quickly provide values for peak flow of a dam breach, which can be combined with an estimate for a time to failure to form a simple hydrograph and provide the input for a simple flood hazard analysis. Most of these equations rely on only basic information about the dam such as height of water (Hw) and live storage volume (Vw) (i.e. the volume of water that is released upon failure), with a few requiring other characteristics such as erodibility and embankment width. ...
... There are fewer empirical equations available in the literature for predicting time to failure (tf), and there is less uniformity in these equations with regards to which variables are considered. Some equations include the height of the breach (Hb) rather than (or as well as) the height of water (Froehlich 1995b, 2008, Zhong et al. 2020, and others include the height of the dam (Hd) (Xu andZhang 2009, Zhong et al. 2020). Compared to other breach parameters, there are relatively few historical failures with records on the time to failure (e.g. ...
... It was also noted that, unlike Froehlich (1995a), Webby (1996) does not result in high outliers (Froehlich 2016). In yet another paper, Froehlich (2008) used multiple linear regression to develop an empirical equation for time to failure based on data from 23 historical dam failures; of these 23 failures, only one involved a small dam. An analysis of the effect of failure mode on time to failure was also performed, with the conclusion that failure mode has an insignificant effect on time to failure of a breached embankment. ...
To determine the impact of a dam's failure on the surrounding people, infrastructure, and property, sophisticated models are often used when resources are available. However, in the case of small dams, it is often impractical to use these more sophisticated models. Empirical equations for peak flow rate and time to failure based on historical dam failures are a pragmatic and cost-effective way to reasonably estimate these values for a desktop study. However, typical empirical equations are developed for a wide range of dam sizes, and it is not well-known how well they perform for small dams. In this study, various empirical equations from the literature are applied to the same small dams with the goal of evaluating the performance of these equations. For certain ranges of inputs, both the peak flows and the times to failure predicted by these equations differ from one another by more than an order of magnitude. The divergent results from each empirical equation yield different predictions in terms of anticipated impacts on people and infrastructure, leading to inconsistent recommended regulations for a given small dam. The equations are also compared to the historical breaches of two small dams from the literature to determine their accuracy in two specific scenarios, with the results suggesting that many existing equations may underpredict the peak flow of small dams. The variety in results also demonstrates that there is a need for the development of an empirical equation specifically for small dams.
RÉSUMÉ Pour déterminer l'impact de la rupture d'un barrage sur les personnes, les infrastructures et les biens environnants, des modèles sophistiqués sont souvent utilisés lorsque les ressources sont disponibles. Cependant, dans le cas des petits barrages, il n'est n'est souvent pas pratique d'utiliser ces modèles plus sophistiqués. Des équations empiriques pour le débit de pointe et le délai de rupture, basées sur des défaillances historiques de barrages, constituent un moyen pragmatique et rentable d'estimer raisonnablement ces valeurs dans le cadre d'une étude de bureau. Cependant, les équations empiriques typiques sont développées pour une large gamme de tailles de barrages, et leur performance pour les petits barrages n'est pas bien connue. Dans cette étude, diverses équations empiriques tirées de la littérature sont appliquées aux mêmes petits barrages dans le but d'évaluer la performance de ces équations. Pour certaines gammes d'entrées, les débits de pointe et les temps de rupture prédits par ces équations diffèrent les uns des autres de plus d'un ordre de grandeur. Les résultats divergents de chaque équation empirique donnent lieu à des prédictions différentes en termes d'impacts anticipés sur les personnes et les infrastructures, ce qui conduit à des réglementations recommandées incohérentes pour un petit barrage donné. Les équations sont également comparées aux ruptures historiques de deux petits barrages de la littérature afin de déterminer leur précision dans deux scénarios spécifiques, les résultats suggérant que de nombreuses équations existantes peuvent sous-estimer le débit de pointe des petits barrages. La diversité des résultats montre également qu'il est nécessaire de développer une équation empirique spécifique aux petits barrages.
... Looking at the global ability of each equation to characterize all types of dams, Eq. 5 from appears to provide the best results with the lowest RRMSE value. The three equations (3, 4, and 6) from Froehlich (1995aFroehlich ( , 2008Froehlich ( , and 2016a (5) however can adapt to the properties of the material and provides a better estimation. ...
... Indeed, there is a certain lack of representativity of rockfill dams in the literature. Many authors proposed relations focusing on earthen embankment dams (Soil Conservation Service 1981;Evans 1986;Froehlich 1995aFroehlich , 2008Froehlich , 2016aFroehlich , 2016bPierce 2008;) but only one reference focused on rockfill ones (U.S. Bureau of Reclamation 1988). Furthermore, the equations supposed to be representative of embankment dams have been developed with a great majority of earthfill dams rather than rockfill ones. ...
The report provides a summary of research on failure modes in embankment dams during overtopping events. The primary focus is on testing empirical formulas to estimate failure parameters. The report highlights which empirical formulas yield the best results, while also pointing out that these formulas are not particularly well-suited for typical rockfill dams. The empirical formulas do not take into account the erosion protection of the rock on the downstream side, which is common in Norwegian rockfill dams. A simplified erosion model is also tested, yielding good results, although this model requires extensive input data (material parameters, etc.) that are not always available.
... They were calculated using the empirical relationship (Eqs. (2) and (3)) developed by Froehlich [81], as illustrated below: ...
... Amidst several breach parameters, breach formation time (B f ) is one of the critical parameters that govern the peak discharge and outflow hydrograph [11,91], and it was determined using empirical relation given by Froehlich [81] in our case. The downstream Gouli et al. ...
Moraine-dammed glacial lakes in the Himalayas are rapidly expanding due to glacier retreat, significantly increasing the risk of glacial lake outburst floods (GLOFs) to downstream settlements and infrastructure. In this study, we present a comprehensive assessment of GLOF risk in the Poiqu-Bhotekoshi and Gyirong-Trishuli transboundary basins, which span between China and Nepal. We employed Machine Learning (ML) models, initially trained in the Himalayas, to evaluate GLOF susceptibility in these basins. Also, we conducted hydrodynamic modeling of two representative glacial lakes for multi-dam break scenarios (high, medium, and low). These outcomes were intersected with publicly available physical infrastructure data to assess exposure and risk. Our findings identify 28 glacial lakes (= >0.01 km2) as highly susceptible to GLOFs. In extreme scenarios, modeled lakes could release peak discharges ranging from 7,532 to 38,220 m3/s and inundate up to 60 m depth, surpassing seasonal high-flow floods by up to ten times. Our analysis indicates that over 3,000 buildings, about 50 bridges, nine hydropower sites, and around 50 km of the road could be at risk from anticipated GLOFs. Specifically, six sub-districts in Nepal and two counties in China have been identified as high risk. This study is expected to help authorities and policymakers in both countries in developing joint-ventured holistic disaster risk reduction strategies, thereby mitigating the GLOF risk in these vulnerable transboundary basins.
... dengan: FK = faktor keamanan Ic = gradien keluaran kritis Ie = gradien keluaran dari hasil analisis rembesan ′ = berat isi efektif (t/m 3 ) = berat isi air (t/m 3 ) Gs = berat spesifik e = angka pori Data terrain pada RAS-Mapper 2D di HEC-RAS mengunakan DEMNAS yang telah dilakukan pendekatan kalibrasi dengan pengukuran topografi bendungan di lapangan. Metode keruntuhan bendungan berdasarkan rumus Froehlich 2008 [9]. Bendungan Jlantah disimulasikan runtuh dengan skenario piping, sedangkan Bendungan Gajah Mungkur disimulasikan runtuh akibat overtopping ketika masing-masing menerima debit banjir rencana PMF dan terjadi dalam satu waktu. ...
... Pada sepanjang aliran Sungai Bengawan Solo dan Sungai Jlantah breakline dengan ukuran 5 x 5. Untuk pemilihan angka computation point spacing, cell sice, dan breakline dimana semakin kecil angka yang dimasukkan maka semakin detail dan rapat hasil keluaran rambatan banjir.Gambar 7. Pemodelan Bangunan Infrastuktur HilirUntuk membuat skenario keruntuhan bendungan, maka perlu dilakukan analisis rekahan yang terbentuk akibat oevertopping dan piping. Dalam hal ini menggunakan metodeFroehlich (2008). Parameter pada Tabel 3 kemudian dimasukkan pada jendela HEC-RAS pada Gambar 8.Tabel 3. Parameter Keruntuhan BendunganHasil simulasi analisis banjir akibat keruntuhan Bendungan Jlantah dan Bendungan Gajah Mungkur dapat dilihat pada Gambar 10 dengan debit rancangan Q1000 dan Gambar 11 dengan QPMF. ...
... However, this method requires high resolution bed depth/topography, and therefore the spillway model needs to be designed specially, which compromises the requirement for timeliness. In addition, we ignore the uncertainty originated from a complex shape of the breach and the duration of breach progression (Froehlich, 2008). Here, we show that the simple and generalized discharge model suffices in fitting the various remote sensing observations at an overall scale and can generate key information of interest (e.g., breach size, volumetric flow rate, and water spill amount). ...
Fourteen months post the Ukrainian‐Russian war outbreak, the Kakhovka Dam collapsed, leading to weeks of catastrophic flooding. Yet, scant details exist regarding the reservoir draining process. By using a new technique for processing gravimetric satellite orbital observations, this study succeeded in recovering continuous changes in reservoir mass with a temporal resolution of 2–5 days. By integrating these variations with satellite imagery and altimetry data into a hydrodynamic model, we derived the effective width and length of the breach and the subsequent 30‐day evolution of the reservoir discharge. Our model reveals that the initial volumetric flow rate is (5.7±0.8)×104 m³/s, approximately 28 times the average flow of the Dnipro River. After 30 days, the water level in the reservoir had dropped by 12.6±1.1 m and its water volume was almost completely depleted by 20.4±1.4 km³. In addition, this event provides a rare opportunity to examine the discharge coefficient—a key modeling parameter—of giant reservoirs, which we find to be 0.8–1.0, significantly larger than the ∼0.6 value previously measured in the laboratory, indicating that this parameter may be related to the reservoir scale. This study demonstrates a paradigm of utilizing multiple remote sensing techniques to address observational challenges posed by extreme hydrological events.
... Dams globally face increased threats of overtopping due to additional loads exceeding their original design capacity. Overtopping is a major concern to dam safety around the world, particularly for embankment dams, because it is the leading cause of dam collapses, which can have disastrous repercussions such as downstream floods and loss of life [29]. ...
Climate change poses an escalating threat to the safety of high-hazard embankment dams, increases flood discharge impacting dam overtopping risk by altering the hydrological load of the original dam designed capacity. This paper’s primary aims are to evaluate climate change’s influence on extreme rainfall events and their impact on dam safety and to assess the overtopping risk of Batu Dam under various climate scenarios. This study focusses on assessing the overtopping risk of Batu Dam in Malaysia, utilizing regional climate model projections from the Coupled Model Intercomparison Project 5 (CMIP5) spanning 2020 to 2100. Three Representative Concentration Pathways (RCPs)—RCP4.5, RCP6.0, and RCP8.5 as the scenario and divide into 3 period of study: early century (2020–2046), mid (2047–2073) and late-century (2074–2100) evaluated with hydrological analysis to access the dam safety. Using the Linear Scaling Method (LSM), we corrected the bias projection rainfall data from three Regional Climate Models (RCMs) for the RCPs. Future Probable Maximum Precipitation (PMP) was estimated using statistical analysis techniques developed by the National Hydraulic Research Institute of Malaysia (NAHRIM). Additionally, Rainfall Intensity-Duration-Frequency (IDF) curves were updated based on climate scenarios outlined in the Hydrological Procedure 2021 and the associated Climate Change Factors. The HEC-HMS hydrological model was employed to simulate PMF and IDF for ARIs ranging from 1 to 100,000 years, providing a comprehensive analysis of risks under future climatic conditions. Across all future climate scenarios, inflow events were projected to exceed the dam design inflow, with RCP8.5 indicating the highest inflow values, particularly later in the century, highlighting probability of overtopping risks. Late-century projections show inflow for ARI 50 under RCP8.5 exceeding PMF by 20%, while mid-century RCP6.0 results indicate a 15% higher inflow for ARI 50000. Early-century RCP4.5 shows a 10% increase for ARI 100000 compared to PMF. The study advocates adaptive dam safety management and flood protection measures. This research provides crucial insights for embankment dam owners, stressing the urgent need to address Batu Dam’s vulnerability to extreme flooding amidst climate change and emphasizing proactive measures to fortify critical infrastructure and protect downstream communities.
... The HEC-RAS hydraulic model uses a Digital Terrain Model (DTM) of 1 m, based on the York 2019 survey sourced from National Resource Canada [23]. We used Froehlich empirical equations to estimate the final width of the breach, the slope, and time of breach opening to parameterize the breach model [24]. ...
Forecasting flood characteristics (e.g., water levels and velocity) is a growing concern due to climate change. It is therefore necessary to consider the stability conditions of earthen levees used to mitigate floods during a flood risk assessment. This technical note presents a method to assess probabilistic flood hazard that takes into account levee failures, for a levee located along Etobicoke Creek in Toronto, Canada. We compute flood scenario probabilities resulting from multiple flood scenarios that accounts for both the levee failures across the length of the levee, and different levee-failure mechanisms (e.g., backward erosion and overtopping). Then, for each location of the flooded area, we compute a cumulative flood exceedance probability curve for flood depth and velocity. This method provides a flood-hazard map (depth and velocity) for a given probability and probabilistic maps for given values of depth or velocity.
Recent climate change has resulted in the shrinkage of glaciers and the expansion of the glacial lakes in the Himalayas, thereby increasing the risk of Glacial Lake Outburst Floods (GLOFs). GLOFs from moraine-dammed glacial lakes are often liable to many casualties and colossal devastation of the downstream settlements and infrastructure. Nevertheless, these hazards have been largely overlooked in the Manaslu Region of the Nepal Himalaya, which witnessed a small GLOF from Birendra glacial lake on April 21, 2024, due to a snow-ice avalanche. Here, we used an integrated approach to study the evolution of Birendra Lake and its parent glaciers. We then conducted its GLOF hazard assessment in multi-scenarios by employing remote sensing, geographic information system (GIS), and hydrodynamic model. The results show that the parent glacier shrunk from 25.842 ± 1.21 to 21.56 ± 1.26 km2 between 1988 and 2024, and subsequently, the glacial lake expanded from 0.09 ± 0.02 km2 to 0.22 ± 0.03 km2. Three anticipated multi-scenario GLOF simulations were run using a two-dimensional (2D) dam break model, and the resulting flow was routed approximately 45 km downstream from the dam site. The results showed that the peak dam break flow ranges between 909 and 3,768 m3/s in 10, 15, and 20 m breach height scenarios, and approximately 110 buildings on the downstream side will be submerged in the worst scenario. This study provides insights into the possible consequences of GLOFs in the Himalayan headwaters and contributes to planning and formulating disaster risk reduction and mitigation programs, particularly in the Manaslu region.
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