Dam Breach Research Articles

Assessment of the environmental radiological impact in the emergency exposure phase through the simulation of a uranium mining tailings dam breach

This work is aiming at estimating the radiation doses to members of the public in case of an emergency exposure situation related to a hypothetical uranium mining tailings dam rupture at the UDC - Decommissioning Unit of Caldas, MG, Brazil. The calculations will help to managing the exposures of emergency workers and residents in the region downstream the dam. The computer code chosen to perform the simulations was FLO-2D@ software. Due to the uncertainties involved, mainly regarding the waste rheology and activity concentrations and in parameters values to be used in the dose assessment, considerations were made for the study to present results derived from conservative assumptions. Through the creation of flood maps, it was possible to estimate the extent of the areas affected by the released materials. The results showed that in a scenario of the tailings dam breach, deposition of mud shall extend over 20 km downstream affecting an area of nearly 3 km2. Total dose for a member of the public living in most affected areas would be around 43 mSv/y in the early phase after the accident. Although only shielding would be recommended under current radiation protection regulation, evacuation/relocation is suggested due to the presence of long-lived radionuclides. This protective measure would probably already be indicated by the accident itself, regardless of radiological reasons. More realistic assessment should be performed before returning people, considering long-term environmental transport and uses of the area. It must also be considered that long-term exposures have more restricted recommended acceptable levels than those for the emergency phase.

Flood propagation modeling: Case study the Grand Ethiopian Renaissance dam failure

Despite significant improvements in design methodologies, dams and water-retaining structures failures continue to occur. Dams’ failure analysis plays a crucial role in the development of dam safety planning and emergency action. Since the Grand Ethiopian Renaissance Dam (GERD) has been built, there have been many concerns about its safety and its effects on downstream countries in case of its failure. In this paper, the GERD break was modeled by using the USACE Hydrologic Engineering Center’s River Analysis System (HEC-RAS). Two dimensions model under different failure scenarios was suggested. Moreover, outflow hydrographs and flood inundation maps were presented due to dam breach. Finally, it was concluded that, in case of catastrophic failure, flow depths may vary from 3 to 10 m in some residential areas, such as Khartoum. Furthermore, the water surface elevation may reach 184 m above msl (mean sea level) in Lake Nasser in case of dam failure with a fully stored GERD reservoir. Moreover, the maximum flow would reach 325,928 m3/sec which is more than 21.5 times the total capacity of the dam spillway. Finally, the paper’s outcomes may assist decision-makers in developing alternate plans to deal with the dangers of GERD break.

Study of key aspects in simplified modelling of man-made earthen dams breaching: breach shape, erosion process and hydraulics

The physical process of man-made earthen dams breaching has many aspects that are still poorly understood and under investigation. In this context, dam-breach simplified physically based models are very valuable as they provide quick and accurate solutions that have an application value, although the phenomenon is not yet fully clarified at a theoretical level. This work intends to evaluate the validity and the mutual interaction of the suggested assumptions regarding the following key aspects for a simplified modelling: (1) the geometry of the breach cross-section; (2) the characteristics of the water flow through the breach; (3) the breach erosion law; (4) the morphology of the reservoir. The main findings of this study, in relation to the outlined key aspects, are the following. (1) The breach geometry, assumed of triangular/trapezoidal shape, plays an important role in the computation of the outflow hydrograph, but in this work a dimensionless analysis was performed, from which it was found that there is a low sensitivity region, identified by medium values of a dimensionless parameter which characterizes the dam-reservoir system. (2) The water flow through the breach can be considered in a critical state, with convincing results in terms of numerical reconstruction of the entire discharge hydrographs. (3) The breach erosion law can be related to the mean shear stress of the water flow, by means of a parameter that needs to be calibrated. In this regard, the calibration has been performed choosing a number of historical cases falling in the low sensitivity region identified in point 1, so that the results of the calibration were not affected by the shape assumed for the breach. (4) The morphology of the reservoir affects the evolution of the dam breaching process and, therefore, the shape of the calculated hydrograph; thus, it must be taken into consideration by introducing a level-volume curve into the calculation.

Breach Progression Observation in Rockfill Dam Models Using Photogrammetry

Dam failures are examples of man-made disasters that have stimulated investigation into the processes related to the failure of different dam types. Embankment dam breaching during an overtopping event is one of the major modes of failure for this dam type, comprising both earthfill and rockfill dams. This paper presents the results of a series of laboratory tests on breach initiation and progression in rockfill dams. Especially eight breaching tests of 1 m-high 1:10 scale embankment dams constructed of scaled well-graded rockfill were conducted. Tests were performed with and without an impervious core and under different inflow discharges. Controlling instrumentation includes up to nine video cameras used for image analysis and photogrammetry. A previously little-used technique of dynamic 3D photogrammetry has been applied to prepare 3D models every 5 s throughout the breaching process, allowing us to track in detail breach development. These dynamic 3D models along with pressure sensor data, flow data, and side-view video are used to provide data on erosion rates throughout the breaching process. One important purpose of this research is to test methods of observing a rapidly changing morphology such as an embankment dam breach that can easily be scaled up to large-scale and prototype-scale tests. The resulting data sets are further intended for the verification of existing empirical and numerical models for slope stability and breach development as well as the development of new models.

Experimental study on the longitudinal evolution of the overtopping breaching of concrete-face sand-gravel dams

Experimental study on the longitudinal evolution of the overtopping breaching of concrete-face sand-gravel dams

Refined mathematical model for the breaching of concrete-face sand-gravel dams due to overtopping failure

Refined mathematical model for the breaching of concrete-face sand-gravel dams due to overtopping failure

Dam Incidents and Failures – Cases in the Czech Republic

Abstract Dam incidents and failures mainly occur during extreme floods. In the Czech Republic (CR), large-scale regional floods were recorded in different regions in 1985, 1987, 1997, 2002, 2006, 2010, and 2013, while local floods especially occurred in 1991, 1996, 1997, 1998, 2002, 2004, 2005, 2009, and 2010. During these events, numerous incidents and total breaches of small dams were recorded, and a few large dams were also critically endangered, although they were not completely breached. This paper presents a comprehensive summary of incidents and failures affecting small dams in the CR since 1985. The most significant incidents concerning large dams are listed as well. The statistics show that 62 small dams were completely breached and that 350 were seriously damaged over 35 years in the period 1985–2020. The annual frequency amounts to 1.85 collapsed and 10 small damaged dams per year. The most common causes of the complete breaching of dams were overtopping (85 %) and internal erosion (15 %).

Primary and potential secondary risks of landslide outburst floods

Outburst floods triggered by breaching of landslide dams may cause severe loss of life and property downstream. Accurate identification and assessment of such floods, especially when leading to secondary impacts, are critical. In 2018, the Baige landslide in the Tibetan Plateau twice blocked the Jinsha River, eventually resulting in a severe outburst flood. The Baige landslide remains active, and it is possible that a breach happens again. Based on numerical simulation using a hydrodynamic model, remote sensing, and field investigation, we reproduce the outburst flood process and assess the hazard associated with future floods. The results show that the hydrodynamic model could accurately simulate the outburst flood process, with overall accuracy and Kappa accuracy for the flood extent of 0.956 and 0.911. Three future dam break scenarios were considered with landslide dams of heights 30 m, 35 m, and 51 m. The potential storage capacity and length of upstream flow back up in the upstream valley for these heights were 142 × 106m3/32 km, 182 × 106m3/40 km, and 331 × 106m3/50 km. Failure of these three dams leads to maximum inundation extents of 0.18 km2, 0.34 km2, and 0.43 km2, which is significant out-of-bank flow and serious infrastructure impacts. These results demonstrate the seriousness of secondary hazards associated with this region.

Assessment of Gualaxo do Norte River water quality (Minas Gerais, Brazil) affected by the dam breach of Fundão utilizing exploratory multivariate techniques.

At the end of 2015, the Fundão dam belonging to the Samarco S.A. mining company was ruptured, releasing a flood of mud into the Gualaxo do Norte River, which advanced into the Doce River. The aim of the present study was to apply exploratory multivariate approaches to water quality data obtained during sampling campaigns at the Gualaxo do Norte River during the dry and rainy seasons, between July 2016 and June 2017. A total of 27 locations along the river were sampled, covering unaffected areas and regions influenced by the tailings waste from the dam. Determinations of chemical, physical, and microbiological water quality parameters were performed. Application of principal component analysis (PCA) resulted in the first two components together explaining 39.49% and 37.91% of the total variance for the dry and rainy season data, respectively. In both cases, the PCA groups were related to variables such as turbidity and total solids, which both presented higher values in regions affected by the mud flow. These results are in agreement with those obtained by the Kohonen neural network method, where two-dimensional maps confirmed the samples according to the affected and unaffected area by the disaster.

Centrifugal model tests and numerical modeling on overtopping-induced breach processes of landslide dams

This study used the 400 g-ton geotechnical centrifuge model test system at the Nanjing Hydraulic Research Institute (NHRI) to investigate the breach evolution characteristics and hydrograph process of overtopping-induced breaching of landslide dams. It was achieved by taking advantage of the “time-space amplification” effect created by high-speed rotation using a centrifuge overweight force field. The effects of dam height, slope ratio, and soil gradation on the overtopping failure process of landslide dams were investigated by centrifugal model tests for the first time. In addition, a detailed physically-based dam breach model was developed to simulate the overtopping failure of landslide dams. Results show that the breach process of a landslide dam can be divided into four stages based on the measured breach morphology evolution process and the abrupt variations of breach flow discharge: initial scour on the downstream slope, retrogressive erosion to the dammed lake, erosion along the breach channel, and breach stabilization. Moreover, the peak breach flow is most sensitive to the dam height, followed by the average particle size; the time to peak is mainly affected by the slope ratio, and the relative residual dam height is primarily susceptible to the average particle size. In practice, the calculated results are consistent with the measured results. This study provides a scientific reference for the cognition of the overtopping-induced breach mechanism of landslide dams.

Hydrological and Hydrodynamic Modeling for Flash Flood and Embankment Dam Break Scenario: Hazard Mapping of Extreme Storm Events

Simulation of dam breach scenarios can help in the preparation of emergency action plans for real dam breaks or flash flooding events. The purpose of this study was to identify flood-prone areas in the Al Wala Valley in the governorate of Madaba in Jordan through analysis of the Al Wala Dam. Modelling of dam breaches was conducted under two scenarios: a Clear Day scenario and a Probable Maximum Flood (PMF) scenario. The former scenario does not address the various dam failure modes; rather, it addresses the formation and development of a breach as a result of structural failures like the sliding of dam blocks in the case of a concrete dam or piping failures in the case of embankment dams. The PMF scenarios, however, simulate unsteady flow in pipes and overtopping failure via consideration of runoff hydrography. In the PMF scenario, flood-prone areas can be identified by in-depth analysis of data from previous extreme rainfall events. The related hydrologic and hydraulic data can then be modelled using intensity-duration-frequency curves applied to an hour-by-hour simulation to discover the areas most at risk of flooding in the future. In the present study, data were collected from inlet of flow to Al Wala Valley on 10 January 2013. The collected data, which included rainfall and discharge data, were fed to the HEC-HMS software in order to calibrate the hydrological parameters of the watershed of the Al Wala Dam. Additionally, the HEC-RAS tool was employed to determine the breach outflow hydrography and hydraulic conditions across various critical downstream locations, which were determined by use of dynamic flood wave-routing models. The simulations revealed that, in the case of the Clear Day scenario, downstream inundation would cover an area of 5.262 km2 in the event of a pipe failure. However, in the event of a six-hour storm, a twelve-hour storm, and a twenty-four-hour storm, the flooded area would rise to 6.837 km2, 8.518 km2, and 9.390 km2, respectively. In the event of an overtopping failure, 13.171 km2 would be inundated, according to the Clear Day scenario. On the other hand, in the event of a six-hour storm, a twelve-hour storm, and a twenty four-hour storm, the flooded area would rise to 13.302 km2, 14.249 km2, and 14.594 km2, respectively.

Review on risk assessments of dammed lakes

As one type of natural disaster, dammed lakes pose a serious threat to the safety of lives and properties downstream. Scientific risk assessments of dammed lakes are key for pre-disaster prevention and post-disaster rescue. However, due to the lack of basic information and uncertainty surrounding materials and loads, risk assessments of dammed lakes are more complex than those of artificial reservoir dams, and comprehensive assessment methods are lacking. Based on the evolution of dammed lake hazard chains, starting with the concept of a dammed lake risk assessment, this paper focused on six aspects: worldwide dammed lake databases, hazard assessments for landslide dams, breach mechanisms and breach processes, flood routing after landslide dam breaching, loss assessments, and risk mitigation measures. A comprehensive review was conducted on the qualitative and quantitative risk assessment methods around the world, as well as future outlooks.

Influence of dam break scenarios on flood wave characteristics. Case study – Paltinu Dam, Romania

Among the various constructive types of dams, the arch dams breaches are the largest and the quickest to occur, leading to the most catastrophic flood waves. Therefore, prediction of the shape, magnitude and arrival time of the breach waves is of utmost importance for flood risk management. The study analyses in GIS environment the influence of different dam breach scenarios on the evolution in time and space of the flood wave. As a study case it was chosen the 108m in height, Paltinu arch-dam (Romania), built on Doftana River and its about 19km river reach down to the confluence with Prahova River. Several breach widths and depths are considered in the analysed scenarios, coupled with selected inflow hydrographs and initial reservoir water elevation, to assess their influence on the dam break wave characteristics and downstream flooded areas. To model the flood wave routing following the dam brake, HEC-RAS software is used. Inundation boundaries, characteristic depths and velocities, as well as arrival time in selected control sections are compared and conclusions are drawn.

Optimization of magnetic separation of hematite contained in the depressed product from vazante mine s zinc ore flotation

The mining industry has seen a significant decline in mill feed grade in recent years, resulting in an ongoing build-up of materials not recovered at the mineral processing plants whose economic value has not yet been determined. Tailings dams have been the preferred method of disposal of such materials. However, recent dam breach events and the growing demand for mineral goods have enhanced the appeal of a more effective use of mined materials to prevent tailings accumulation and reduce social and environmental impacts, in line with the environmental, social and governance (ESG) principles that most companies have adopted. Different techniques can be used to recover economically valuable minerals contained in such materials, among which magnetic separation stands out for reasons of cost, production capacity, and recent developments of new equipment and matrices for wet high-intensity magnetic separators. The outcome includes gains in capacity, grade, and recovery yield. This paper assessed the use of a matrix developed by the company Gaustec, called BigFlux, in the magnetic separation of depressed product from the flotation process at Nexa Resources’s Vazante mine. Laboratory-scale magnetic separation tests were conducted using standard and an optimized matrix. For a 59% iron concentrate, the metallurgical recovery using such optimized matrix reached 72.6%, up 4% from the figure resulting from the use of the standard matrix, thus indicating that the use of the optimized matrix can improve the magnetite recovery process of the studied material.

DAM BREACH ANALYSIS AND PARAMETER SENSITIVITY ANALYSIS ALONG A RIVER REACH USING HECRAS

A dam break is a low-probability, high risk catastrophe event that is extremely destructive and has a substantial negative socio-economic impact on downstream and nearby areas. Simulating dam breach and analyzing flood propagation downstream from those events is vital for identifying and minimizing the risks associated downstream of dam location. This study is intended to anlayse the effect of overtopping failure of dam for two scenario (a) base-case scenario (scenario with average value of dam breach parameters from their range) and (b) worst case scenario (the breach with largest geometry, shortest formation time and highest peak outflow magnitude). Further, a hydrodyanmic modelling is perfomed to investigate the sensitivity analysis (local and global) of five dam breach parameters (dam breach elevation, dam breach width, breach formation time, weir coefficient, trigger failure elevation) on breach outflow in a proposed hydropower project located in Nepal. Aeronautical Reconnaissance Coverage Geographic Information System (ArcGIS), Hydraulic Engineering Center River Analysis System (HEC-RAS) and OriginPro 2022b are utilized to analyse the effect of dam breach and parameter sensitivity.
 Generation of outflow hydrograph shows that worst case scenario has devasting effect downstream with innudation of 1047 of househols and 50.83 kilometers of roads. The breach velocty was recorded as 15.16 m/s and 20.85 m/s for base and worst case respectively. The minimum depth and maximum depth of flooding downstream from dam location was found to be 24.51 m and 73.6 m for base case and 47.43 m and 106.75 m for worst case. Due to backwater effect at Bheri river, peak flow at 14 km downstream from dam reduces significantly to 124852.57 m3/s and 244204.41 m3/s for base and worst case respectively. From local sensitivty analysis it has been found that, dam breach elevation is more sensitive and triggering failure elevation is less sensitive for peak outflow hydrograph. Whereas, dam breach width seems more sensitive and TFE seems least sensitive for peak outflow using Monte Carlo Simulation for gloal sensitivity.

Rapid quantitative study of check dam breach floods under extreme rainstorm

Rapid quantitative study of check dam breach floods under extreme rainstorm

Risk consequence assessment of dam breach in cascade reservoirs considering risk transmission and superposition

Compared with a single reservoir, the risk in cascade reservoirs has the transmission and superposition effect, which increases the complexity of its risk consequence assessment. In view of this problem, the direct consequence (DC) and potential consequence (PC) were defined as two parts of the dam breach risk consequence of cascade reservoirs. The upstream dam-break flood inundation line and the downstream reservoir land acquisition line were taken as the upper and lower boundaries of the assessment space, which made the risk consequence assessment more intuitive and further improved its scientificity and practicability. Subsequently, the conditional probability of downstream dam breach under the upstream dam-break flood was determined to quantify the risk transmission and superposition. On this basis, the relevant concepts and formulas for calculating the dam breach risk consequence in cascade reservoirs were proposed. Taking five cascade reservoirs as examples, the risk consequences of each cascade dam breach were evaluated. The results show that the proposed method is effective in assessing the risk consequence of dam breach in cascade reservoirs and is more in line with the connotation of dam risk management, which can provide reference for the design and risk control of cascade reservoirs.

Overtopping-Induced breaching process of concrete-faced rockfill dam: A case study of Upper Taum Sauk dam

The back analysis of the dam breaching process based on reported failure case data is of great significance for understanding dam breaching mechanisms and the ability to predict breach flow hydrograph during emergencies. According to the essential information and post-failure investigation report of the Upper Taum Sauk dam, the first pumped storage power station in the United States, the most probable failure mechanism for dam breach is studied. Furthermore, a detailed physically-based numerical model is developed to simulate the overtopping-induced breach process of the concrete-faced rockfill dam (CFRD). Highlights of the model include the establishment of a simulation method of the dam-break flow based on the actual three-dimensional terrain considering the water-retaining characteristics of concrete face slabs, and the times and lengths of failure for each concrete face slab under water load and self-weight, as well as the adoption of different transportation modes for the widely graded rockfill materials. The breach side slope sliding mechanism is considered during the dam breach process. It is worth noting that the hydraulic features of dam-break flow and breach morphology can be well described with a combination of renormalization group (RNG) k-ε turbulence model and volume of fluid (VOF) method. The calculated results of the Upper Taum Sauk dam breaching parameters agree with the measured values, which testify to the rationality of the proposed model. The obtained time-varying dynamic dam breach process of CFRD can be divided into three stages. Moreover, the sensitivity analysis indicated that, the presence and absence of concrete face slabs affect the breach process of the Upper Taum Sauk dam significantly. The performance comparison with the existing dam breach models also verifies the advancement of the detailed physically-based model. Hence, the addressed numerical method can be used as an effective tool for simulating the CFRD breach process.

Mosul dam issues: analysis of the problem based on several studies

Mosul Dam is the Middle East’s second-largest dam in terms of reservoir capacity. Since its inception in 1986, this dam has been plagued by seepage difficulties in its base caused by the breakdown of gypsum. Underneath the foundation, there are strata of anhydrite. This occurrence has sparked worry the dam’s stability. This paper presents a survey of studies conducted by several researchers on concerns related to the stability and safety of the Mosul Dam in Iraq. Additionally, the implications of the dam breach scenarios are to be presented and discussed. In another word, the Mosul Dam issues are assessed with different references to geologic challenges of the abutments and foundation, dissolution of gypsum and formation of sinkholes, dissolution of gypsum and seepage, and the probable scenarios for concerns of dam failure. After the ISIS conflict, maintenance has been disrupted and signs at the dam have triggered renewed concerns. Consequently, the Iraqi government have contracted the Italian engineering company Trevi to start remedial work on the dam. This work was in 2016. Therefore, the present state of Mosul Dam was declared as safe and stable.

Loss of Life Estimation using Life Safety Model for Dam Breach Flood Disaster in Malaysia

The need for an emergency disaster management related to damhas risen up in recentyears. This is dueto uncertainties in global weather predictions which also affect local Malaysian area. With unpredictable prolonged rainy weather, concerns on events that could lead to flooding has triggered the authority to review the evacuation strategies in critical locations.This paper describes an investigation on the effect of early warning system and people response delayto the rate of fatality in the event of flooding due to dam breach. The Life Safety Model is utilized as a tool for the simulation of people vehicle and building response to 2D hydraulic flow of the river originated from the dam. The study area is based on KenyirDam and its surrounding vicinity. A number of scenarios are simulatednamely cases with and without early warning system. For the case with early warning system, different triggering time is also investigated. On top of that, the effect of people responsedelay to the warning system is simulated. It was found that early warning system plays a critical role in reducing the number of fatalities due to flooding. Equally important is the time taken for the community to start evacuating whentriggered by the early warning system.From the result LSM, optimum evacuation parameters could be identified and used for the purpose of design, planning and implementation of local emergency evacuation plan in the event of dam-related flooding.