Breach Parameters Research Articles

Laboratory experiments on failure characteristics of non-cohesive sediment natural dam in progressive failure mode

Natural dam failure may cause disastrous floods in the downstream, especially for dam outbursts in progressive failure mode. Until now researches about the characteristics of progressive failure are still completely unclear. In this paper, a series of flume tests were conducted to investigate the formation mechanism of progressive failure of natural dam, the breaching characteristics and the effect of outburst flood on the channel bed. According to the results, three typical features in the progressive failure process of natural dams were observed: seepage on downstream slope, slide of the downstream slope and overtopping. With phreatic line rising continuously, seepage occurred on the downstream slope, which caused slide of downstream slope of the dam. The breaching discharge hydrographs were asymmetric on both sides of peak discharge, which was similar to the breaching discharge of overtopping. The relationship between breach width and depth was like a shape of “S”, which followed a logistic function. In the breaching process, sediment in the channel bed near the dam was first deposited and then scoured, where the flow velocity was large with strong turbulence; while flow on channel bed far away from the dam showed lower velocity and the flow regime transferred from supercritical flow to subcritical flow. Sediment deposited at first and then scoured gradually on channel bed, but only deposited at a large distance from the dam. The outburst flood eroded the channel bed continuously, the erosion mechanism was from tractive erosion to backward erosion, and returned to tractive erosion finally. In addition, the further away from the dam, the weaker the erosion intensity was. The results of this paper enriched the understanding of the failure mechanism of progressively outburst natural dam, which is helpful to predict breaching parameters in progressive failure mode and to provide some reference about flood prevention.

Studies of dam disaster in India and equations for breach parameter

It has been found that the less care is shown while constructing the water retention structures as compared to the amount of care shown in designing for it. This is more often in earthen embankments, where soil properties need to be controlled within the designed limits. The life and stability of embankments are entirely based on the extent to which the design assumptions are achieved in the field. History shows many failures were due to the lack of quality control during construction. In India every year many water storage structures fail, but very few were reported. Till date, only 37 dam failures in India are reported but not appropriately analyzed. This paper is focused on compiling the Indian dam failure list with relevant data which can be used for developing breach parameters equation. The data are collected from Government reports, articles news reports and magazines. This paper is also focused on developing new empirical equations for breach parameters and peak outflow from the dam failure which suits Indian condition. In developing the regression equation for breach depth, average breach width, peak discharge and failure time, different combinations of control variables is highlighted such as the dam height, reservoir capacity, average dam width, dam type, failure mode and dam erodibility. In this study, we incorporate the dam average thickness as another control variable for finding out the breach parameters and found suitable for breach depth calculation. New equations are proposed to compute the peak outflow rate. Further, these equations are compared with other developed regression equations for breach parameters and peak outflows.

Hydrodynamic moraine-breach modeling and outburst flood routing - A hazard assessment of the South Lhonak lake, Sikkim

The presence of glacial lakes in the Himalaya makes it a potential mountain hazard, as catastrophic failure of such waterbodies may lead to high-magnitude glacial lake outburst flood (GLOF) events that can cause significant damage to the low-lying areas. The present study evaluates the hazard potential of the South Lhonak lake located in the state of Sikkim, using both one and two-dimensional hydrodynamic modeling approaches. Different breach parameters were calculated based on the lake bathymetry and moraine dimensions. The worst-case GLOF scenario is revealed during an overtopping failure of the moraine, producing a peak flood of 6064.6 m3 s−1 and releasing a total water volume of 25.7 × 106 m3. The GLOF hydrograph is routed to calculate peak flood (m3 s−1), inundation depth (m) and flow velocity (ms−1) along the main flow channel. The interaction of the flood wave with a major topographic obstruction located 15.6 km downstream of the lake, shows a significant reduction of the flow energy leading to a minimization of the South Lhonak GLOF impact. The flood wave reaches the nearest town Lachen, located at a distance of 46 km downstream from the lake, at 3 h 38 min after the initiation of the breach, with a peak flood of 3928.16 m3 s−1 and a maximum flow velocity of 13.6 ms−1. At Chungthang town, located at a distance of 62.35 km from South Lhonak lake, the flood wave potentially inundates settlements along the bank of the flow channel, where a peak flood of 3828.08 m3 s−1 is reached after 4 h of the initial dam breach event. The study also incorporates modeling of a framework to propose a potential flood remediation measure of the South Lhonak lake GLOF by demonstrating the effect of a lateral inline structure along the flow channel, to check the flow of the potential flood wave.

Nashe Dam Fail and Risk Analysis

Nashe earth fill dam was constructed for the aim multi-purpose use (hydroelectric power and irrigation). While the construction of this dam many peoples around Dam were immigrated from their residential to another places including to the town. This research focused on the dam fail analysis by considering overtopping and piping failure mode. The input data were collected from Min. of Water and Energy, Federal Democratic Republic of Ethiopia (FDRE). The dam breach parameters were determined by applying the principle with Von Thun and Gillette. In dam break analysis the first step is model setup by using three dimensions (x, y and Z) of the downstream. By applying overtopping model, the peak discharge 8761.23m3/sec was obtained, which was more than 7.33 times the probable maximum flood and by applying piping mode, the peak discharge was obtained is 8620.85 m3/sec which was more than 7.21 times the probable maximum food at the nearby location of the dam. This indicates that, the peak outflow development during raining season was greater than inflow discharge flood (IDF) used as upper boundary condition for breach parameters. So it was summarized that high peak outflow and risk were developed to downstream by overtopping mode as compare by piping mode during occurrence of dam breach. As from the sensitivity analysis it was concluded, the effect of breach time on discharge is more sounded than the water level increase. This Dam Break modeling results obtained by studies could be used as flood mappings to assist the societies/communities for future planning developments in the flood prone areas/zones in advance.

Modelling Chorabari Lake outburst flood, Kedarnath, India

In this study, the Glacier Lake Outburst Flood (GLOF) that occurred over Kedarnath in June 2013 was modeled using integrated observations from the field and Remote Sensing (RS). The lake breach parameters such as area, depth, breach, and height have been estimated from the field observations and Remote Sensing (RS) data. A number of modelling approaches, including Snow Melt Runoff Model (SRM), Modified Single Flow model (MSF), Watershed Management System (WMS), Simplified Dam Breach Model (SMPDBK) and BREACH were used to model the GLOF. Estimations from SRM produced a runoff of about 22.7 m3 during 16–17, June 2013 over Chorabari Lake. Bathymetry data reported that the lake got filled to its maximum capacity (3822.7 m3) due to excess discharge. Hydrograph obtained from the BREACH model revealed a peak discharge of about 1699 m3/s during an intense water flow episode that lasted for 10–15 minutes on 17th June 2013. Excess discharge from heavy rainfall and snowmelt into the lake increased its hydrostatic pressure and the lake breached cataclysmically.

Assessment of embankment dams breaching using large scale physical modeling and statistical methods

Understanding the failure mechanisms of embankment dams due to overtopping is essential for the design of flood mitigation, flood mapping, and flood warning systems. The breach process in embankment dams can be characterized using breach parameters such as breach opening dimensions, time of breach formation, and peak breach outflow. The main objective of this study is to derive new set of statistical equations to predict the target breach parameters. A database of 126 events of embankment failure was collected and then multiple nonlinear regression analysis is used to derive the new set of equations and the uncertainty in the computed parameters was quantified. Finally, five large-scale overtopping failure tests were conducted on cohesive and non-cohesive soils embankments. The derived breach parameters equations showed good agreement with the results of the physical models for non-cohesive soil embankments, while the failure of cohesive soil embankments varied significantly with soil properties; indicating that breach parameters in cohesive soil embankment should be computed based on not only embankment dimensions but soil properties as well.

Experimental investigation of p-section concrete beams under contact explosion and close-in explosion conditions

Abstract This paper presents the results of an experimental investigation on explosive breaching of p-section concrete beams. Twenty three p-section concrete beams with a 100 cm length were tested. TNT charges were placed at three positions: contact detonation in the center, contact detonation above the web and close-in detonation in the center. The external and internal breach parameters of the panels were evaluated by measuring the diameter of the ejection crater, spalling crater and breach hole created by the charge detonation. The experimental results were compared to predict values obtained by the analytical models proposed by McVay, Morishita and Remennikov. A modified breach with crater limit line and breach without crater limit line were put forward based on the experimental results. The maximum cross-sectional destruction area ratio (MCDAR) values were used to evaluate the damage degree. The maximum value of MCDAR reached 0.331 corresponding to the C5 experimental condition, of which explosion occurred above the web.

Experimental study of embankment breach based on its soil properties

ABSTRACT Understanding of the phenomenon of embankment breach via overtopping is complex but essential for forecasting the flood inundation map and developing an emergency action plan. Case studies of embankment failures caused by overtopping indicate that apart from hydraulic forces, the influence of the soil properties also plays a crucial role in the formation of the breach. The influence of the soil properties on the breaching process was investigated by performing 13 experiments in the hydraulic engineering laboratory of National Institute of Technology, Rourkela, India. The data obtained from the overtopping failure of these embankments are analyzed and presented in this article. Further, a multivariable regression was performed using the test data of 25 embankments to obtain the relationship between the breach parameters and the soil properties (control variables). New nondimensional control variables, such as embankment soil factors, relative compaction effort, relative particle size, and erodibility, were proposed for developing the relationships. An attempt is made here to understand the influence of these control variables on the dam breach that is not reported so far.

Breach diameter analysis of concrete panels subjected to contact charge detonations

This paper presents the results of an experimental study on the explosive breaching of concrete panels subjected to contact charge detonations. Three square double-reinforced concrete panels having side dimensions of 500 mm and thickness of 100 mm were designed and tested. The concrete panels were cast with two different compressive strengths of concrete which were normal strength and high strength concrete. The contact charges were cylindrical in shape and utilised Composition B explosive. The mass of the contact charges for the three concrete panels were estimated to result in a breaching failure mode of the tested panels. The external and internal breach parameters of the concrete panels were evaluated by measuring the diameter and depth of the ejection crater, spalling crater as well as the diameter of the breached hole created by the contact charge detonation. Along with the experimental results of this study, a test database of the explosive breaching of concrete panels is compiled from data published in the literature. The data is used to validate analytical models for predicting the characteristics of contact charges required to produce a wall breach of the required shape and size.

EROSION CHARACTERISTICS OF A MEDIUM SAND BREACHED EMBANKMENT

Embankment breaching dam studies have been carried out since 1980s and researchers who carried out physical experiments have contributed the understanding in the breaching process. This includes lacking in data and understanding in upgrading the breach models. Therefore, this study is to analyse erosion characteristics of a medium sand of embankment breaching due to overtopping and to produce the breached outflow hydrographs for different inflow rates. Parameters such as sediment sizes, embankment slope and inflow rates were applied to examine the effects of breach parameters towards the breaching process. Experimental works on the breaching embankment were conducted to collect data needed and a dimensional analysis was proposed to get relationship of the dominant parameters that affect the failure of the embankment. The result obtained was presented in hydrographs analysis and a combination of dimensionless group of breached erosion. The finding concluded that the finer sediment produces higher peak outflow compared to a medium sediment size and controlling parameters such as particle diameter, d50, velocity, ub, and water density, ρw are the significant parameters that affect the process of embankment breached. It also observed that the velocity after the breaching process increases once the water flow through an embankment dam and it started to decrease after passing through the middle of embankment due to the large surface area.

Dam Break Analysis and Inundation Mapping, Case Study of Fincha’a Dam in Horro Guduru Wollega Zone, Oromia Region, Ethiopia

Fincha’a Dam was constructed in 1973 for the purpose of electricity generation, irrigation, fishery and truism with 22.2m height and 340m crest length. Fincha’a dam is rock fill dam with uncontrolled over flow spillway. There are different economic developments downstream of the Fincha’a dam including hydropower pant, irrigation project, residential house and sugar factory. These economic developments are affected either dam break by overtopping or piping mode of failure. The calculated breach parameters by Von Thun and Gillette Regression equation are selected as input data into the HEC-RAS model for dam break analysis. The general objective of the study is to analyze Dam break by using hydraulic models (Hydraulic Engineering Center’s River Analysis system). For this study the failure location is assumed to be at the center of the dam due to presence of high hydrostatic pressure and develop equally in both sides. From the result of Fincha’a dam break simulation the peak discharge formed by overtopping mode of failure is more devastating than the piping mode of failure. The effect of dam breach parameters on discharge is more pronounced than that of the water level. Dam break has greater impact on the downstream location where is closer to the dam in accordance with the hydrograph at downstream locations. The created Fincha’a river network was exported to HEC-RAS model for further dam break analysis by addition of different geometric data including dam information, calculated breach parameters, initial condition, upstream and downstream unsteady boundary condition. After full computation the model result were exported to integrated Arc-GIS and HEC- GeoRAS model for mapping flood inundation. Developed inundation map guides the dam owners and emergency management authority to give emergency action plan for the highly affected area by flooding and used for planning future economic development activities.

An evaluation of existent methods for estimation of embankment dam breach parameters

The study of dam-break analysis is considered important to predict the peak discharge during dam failure. This is essential to assess economic, social and environmental impacts downstream and to prepare the emergency response plan. Dam breach parameters such as breach width, breach height and breach formation time are the key variables to estimate the peak discharge during dam break. This study presents the evaluation of existing methods for estimation of dam breach parameters. Since all of these methods adopt regression analysis, uncertainty analysis of these methods becomes necessary to assess their performance. Uncertainty was performed using the data of more than 140 case studies of past recorded failures of dams, collected from different sources in the literature. The accuracy of the existing methods was tested, and the values of mean absolute relative error were found to be ranging from 0.39 to 1.05 for dam breach width estimation and from 0.6 to 0.8 for dam failure time estimation. In this study, artificial neural network (ANN) was recommended as an alternate method for estimation of dam breach parameters. The ANN method is proposed due to its accurate prediction when it was applied to similar other cases in water resources.

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

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 Gillette (1990), Froehlich (1995), 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.

One-dimensional hydrodynamic modeling of GLOF and impact on hydropower projects in Dhauliganga River using remote sensing and GIS applications

This study presents the one-dimensional hydrodynamic modeling for the Glacier Lake Outburst Flood (GLOF) simulation for the six hydroelectric (HE) power projects in Dhauliganga River of Alaknanda Basin. ArcGIS and HEC-GeoRAS extension is used for the whole river GIS database creation. Elevation values and cross-sections were taken from digital elevation models. The initial flow hydrographs were used as upstream boundary condition in MIKE11. The land use/land cover map and Manning’s N values for roughness were prepared using LANDSAT TM and CARTOSAT-1 and verified by the field observation. Cross-sections were also modified after identifying the actual cross-sections width and depth. Subsequently, simulation has been carried out by using MIKE11 HD model at different sections of the river stretch. Calibration is done for the period of June 1, 2001, to May 31, 2002, and validated for the year of 2005 with about 95 % accuracy of observed data. In this study, results have been carried out by 100-year flood ordinates and considering the redistribution of lateral flow from five catchments of Alaknanda Basin. The GLOF peaks for the breach parameters are 1394.28, 1552.04 and 1898.04 m3/s for breach width 40, 60 and 80 m, respectively, just the downstream of the lake site. It is inferred from the study that the GLOF for 80 m breach width gives the peak flood of 1575 m3/s at the project site 1 for first scenario and 3500 m3/s at the site 6 for second scenario. The maximum simulated water levels and depth for the Central Water Commission gauging site at Joshimath are 1381.49 and 4.329 m, respectively, for 100-year-plus GLOF event. This information is critical for the project design discharge calculations.

A case study of the Tangjiashan landslide dam-break

The Tangjiashan landslide dam failed on June 10, 2008, which was the largest one formed during the Wenchuan earthquake in China. No human lives were lost in this dam failure. This paper presents a description of the dam, including the dam geometry, the hydrograph and the reservoir capacity, the diversion channel and the drainage from the lake. Several empirical models are applied to predict the breach parameters, the peak outflows and the reservoir volumes during this breach event. The main objective of the study is to compare various prediction models and to make recommendation of the best model for the prediction of the breach width, the failure time, and the peak outflow. The breach widths predicted by the Froehlich methods with considerations of the reservoir storages and the effect of failure mode are considered to be more reasonable. All prediction methods discussed in this paper are found to underestimate the breach formation time due to the complex material and the large thickness of the dam. The results from the soil conservation services (SCS) method compare well with the observed peak outflow. The Marone method in combination with the coefficient expressions proposed by Macchione gives excellent results in the simulation of the reservoir volume-level curve.

The Washout Mechanism of the Niedów Dam and its Impact on the Parameters of the Flood Wave

On 07 August 2010 a disaster occurred at the barrage Niedów located on the river Witka as a result of unprecedented rainfall in the Nysa Luzycka catchment area. The flood wave swept through the dam crest destroying almost the whole structure within a few dozen minutes. The only element that did not vanish was the concrete structure of the spillway and water-power station. The process of dam breach is not so far completely resolved and reliable predictive models of dam breaching are still challenging problem. Modelling of the process requires an evaluation of parameters affecting this phenomenon, namely, the breach size and the timescales for the breach formation. The latter is particularly important for characterizing the outflow hydrograph and, consequently, for the assessment of the damage risk of areas below the dam. The paper presents a mechanism of breaching of the Niedów dam which consists of three stages: the downstream slope wash out, the breaking down of the dam crest and the damaging of upstream slope revetments. The comparison of breach parameters with that evaluated based on several empirical formulas and numerical modelling is also presented.

Gene expression models for prediction of dam breach parameters

Data from a large database of 140 dam failure cases are used with gene expression programming (GEP) to develop new empirical formulae of physical meaning for prediction of non-dimensional key dam breach parameters. The GEP models are trained on 75% of the data set and validated on the remaining 25%. Parametric and error analyses are conducted to confirm the robustness of the developed relations. Moreover, uncertainty analyses using the Monte Carlo technique is performed to check for the output uncertainty of key dam breach parameters and the contribution of various input parameters to the overall output uncertainty. It is found that uncertainties of 20 to 40% are calculated for the developed GEP models with reservoir shape factor and dam erodibility being main influential predictors.

Simulation of Breach Outflow for Earthfill Dam

Dams have been built for many reasons such as irrigation, hydropower, flood mitigation, and water supply to support development for the benefit of human. However, the huge amount of water stored behind the dam can seriously pose adverse impacts to the downstream community should it be released due to unwanted dam break event. To minimise the potential loss of lives and property damages, a workable Emergency Response Plan is required to be developed. As part of a responsible dam owner and operator, TNB initiated a study on dam breach modelling for Cameron Highlands Hydroelectric Scheme to simulate the potential dam breach for Jor Dam. Prediction of dam breach parameters using the empirical equations of Froehlich and Macdonal-Langridge-Monopolis formed the basis of the modelling, coupled with MIKE 11 software to obtain the breach outflow due to Probable Maximum Flood (PMF). This paper will therefore discuss the model setup, simulation procedure and comparison of the prediction with existing equations.

Dynamic decision making for dam-break emergency management – Part 2: Application to Tangjiashan landslide dam failure

Abstract. Tangjiashan landslide dam, which was triggered by the Ms = 8.0 Wenchuan earthquake in 2008 in China, threatened 1.2 million people downstream of the dam. All people in Beichuan Town 3.5 km downstream of the dam and 197 thousand people in Mianyang City 85 km downstream of the dam were evacuated 10 days before the breaching of the dam. Making such an important decision under uncertainty was difficult. This paper applied a dynamic decision-making framework for dam-break emergency management (DYDEM) to help rational decision in the emergency management of the Tangjiashan landslide dam. Three stages are identified with different levels of hydrological, geological and social-economic information along the timeline of the landslide dam failure event. The probability of dam failure is taken as a time series. The dam breaching parameters are predicted with a set of empirical models in stage 1 when no soil property information is known, and a physical model in stages 2 and 3 when knowledge of soil properties has been obtained. The flood routing downstream of the dam in these three stages is analyzed to evaluate the population at risk (PAR). The flood consequences, including evacuation costs, flood damage and monetized loss of life, are evaluated as functions of warning time using a human risk analysis model based on Bayesian networks. Finally, dynamic decision analysis is conducted to find the optimal time to evacuate the population at risk with minimum total loss in each of these three stages.

Analysis of human risks due to dam break floods—part 2: application to Tangjiashan landslide dam failure

The Tangjiashan landslide dam was formed during the Ms8.0 Wenchuan earthquake in 2008 and posed high risks to 1.2 million people downstream the dam. A human risk analysis model (HURAM) reported in the companion paper is applied to evaluate the human risk in the Tangjiashan landslide dam failure. The characteristics of this landslide dam are introduced first. The breaching parameters in two cases (i.e., the actual case and a high erodibility case) are predicted with a physically based model, and the flood routing processes in these two cases are simulated using numerical analysis. The population at risk downstream of the landslide dam is then obtained based on the results of the flood routing simulations. Subsequently, the human risks are analyzed with HURAM using Bayesian networks. Fourteen influence parameters and their interrelationships are considered in a systematic structure in the case study. A change in anyone of them may affect the other parameters and leads to loss of life. HURAM allows not only cause-to-result inference, but also result-to-cause inference by updating the Bayesian network with specific information from the study case. The uncertainties of the parameters and their relationships are studied both at the global level using multiple sources of information and at the local level by updating the prior probabilities.