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Many of Iraqi's high-hazard dams lack an Emergency Action Plan, which should include a flood inundation map to show which downstream areas would be flooded if the dams were to fail. This article presents the results of the simulation of a hypothetical 2D dam break for the 58 m high Khassa Chai dam in Kirkuk, Iraq, using HEC-RAS 2D 5.0.7 software. The Khassa Chai dam is situated 7.4 km north of Kirkuk. The simulations revealed that the dam-break flood will affect eight major bridges and the majority of Kirkuk city's metropolitan neighborhoods. Within an hour, the floodwaters will reach the city's center. The flood hazard map revealed that if the Khassa Chai dam fails, many people, vehicles, and structures will be at danger. The findings of this paper can be used to identify evacuation routes and refuge sites as well as build suitable warning systems in order to limit the risk for fatalities if the Khassa Chai dam fails. Moreover, as the effect of modeling bridges downstream of failed dams has not been explored yet, to the knowledge of the authors, eight bridges have been modeled. It was concluded that ignoring bridges in such a large dam break model will not affect the results significantly, which saves the time of data collection and model development. [ABSTRACT FROM AUTHOR]

Copyright of Mine Water & the Environment is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper the authors demonstrate that the simple power function gives a good description of the reservoir morphology. This function proved to be suitable for application on 97 reservoirs taken from three different geographical regions in the world. The power function is suitable to obtain an accurate fitting of the reservoir rating curve using a very limited number of surveyed elevations and volumes or areas. In particular it is shown that two points are enough for a good fitting of the curve, or even only one if volume and surface for an elevation close to normal or maximum pool are both available. The results obtained for dam breach calculations using this equation, have the same quality of those achieved using the elevation-volume table. The paper stresses that the exponent of power equation can be expressed by a formula which has a precise morphological meaning, as it represents the ratio between the volume which the reservoir would have if it were a cylinder with its base area and height equal to the respective maximum values of the actual reservoir, and the real volume of the reservoir. [ABSTRACT FROM AUTHOR]

An Ms 6.5 earthquake shocked the Ludian County, Yunnan Province, China, on 3 August 2014 and triggered the Hongshiyan landslide dam. The dam, with a height of 83 m and a lake capacity of 260 × 10 m, threatened more than 10,000 people. A unique feature of this landslide dam was that it formed between a man-made dam and a hydropower plant. An existing drainage tunnel connecting the lake and the hydropower plant became a natural drainage conduit for the landslide dam, which played an important role in the mitigation of the landslide dam risks. This paper reports a quantitative risk assessment for the Hongshiyan landslide dam considering both engineering and non-engineering risk mitigation measures. The risk assessment is divided into three stages according to the implementation of two engineering measures: construction of a diversion channel and excavation of a branch drainage tunnel. The dam breaching hydrographs, flood zones, population at risk, and likely fatalities in each of the three stages are analysed. The optimum evacuation strategy in each stage is also studied based on the principle of minimum total consequence. It is found that the diversion channel decreases the dam breaching peak discharge and the associated risks significantly. The branch drainage tunnel prevent the landslide dam from overtopping failure in non-flooded period; however, the landslide dam may fail by overtopping in a future flood if the inflow rate is larger than the outflow rate through the drainage tunnels, resulting in serious losses of lives and properties. The dam breaching risks in all the three stages could be largely reduced by the optimal evacuation decision, which shows that timely evacuation is vital to save life and properties. The study provides a scientific basis for decision making in landslide dam risk management. [ABSTRACT FROM AUTHOR]

The massive 8.0-magnitude Wenchuan Earthquake triggered huge landslides, avalanches, and debris flows that blocked rivers and created 34 important quake lakes, including the Tangjiashan Quake Lake on the Tongkou River. More than half of these lakes were identified to be of moderate or high hazard levels, so activities needed to be undertaken for hazard mitigation of potential flooding. This paper presents the mitigation processes of quake lake hazards, which involve various techniques such as rapid hazard analysis, scenario-based mitigation planning, and real-time forecasting of outburst flooding for implementation actions. The shortage of hydrologic and geological data and the nature of emergency situations raise substantial challenges in the hazard mitigation of quake lakes. This paper suggests a potential approach in dealing with quake lake hazards, which integrates the automatic monitoring network, hydrologic models, and hydrodynamic models with a comprehensive indicator for hazard levels. The necessity of improving the integrated methodology is highlighted. [ABSTRACT FROM AUTHOR]

A large amount of loose deposit between the sides of a landslide lake may slide into a reservoir at any time because of influences such as earthquakes, heavy rainfall or other triggering factors. These factors can cause the formation of a huge surge and result in the instantaneous failure of a landslide dam. The failure of a landslide dam can threaten people's lives and property downstream. This paper analyzes the destruction mechanism of landslide dams because of a surge and the impact of the contact area, the landslide height, and the distance between the entry point and the dam site for a dam break through physical experiment and compares the experimental results with the calculated values. Experimental results show that the contact area and the landslide height have a significant impact on the dam-break surge. A measure based on the previously mentioned factors can be made to reduce the dam failure risk caused by a landslide surge. Two empirical methods (Pan's method and Miller's method) are used to predict the landslide surge wave and compared with the experimental results; the simulated results show that the Miller's method used for predicting the landslide surge wave is more reasonable. [ABSTRACT FROM AUTHOR]

This paper presents two Artificial Neural Network (ANN) based models for the prediction of peak outflow from breached embankment dams using two effective parameters including height and volume of water behind the dam at the time of failure. Estimation of optimal weights and biases in the training phase of the ANN is analysed by two different algorithms including Levenberg-Marquardt (LM) as a standard technique used to solve nonlinear least squares problems and Imperialist Competitive Algorithm (ICA) as a new evolutionary algorithm in the evolutionary computation field. Comparison of the obtained results with those of the conventional approach based on regression analysis shows a better performance of the ANN model trained with ICA. Investigation on the uncertainty band of the models indicated that LM predictions have the least uncertainty band whilst ICA's have the lowest mean prediction error. More analysis on the models' uncertainty is conducted by a Monte Carlo simulation in which 1000 randomly generated sets of input data are sampled from the database of historical dam failures. The result of 1000 ANN models which have been analysed with three statistical measures including p-factor, d-factor, and DDR confirms that LM predictions have more limited uncertainty band. [ABSTRACT FROM AUTHOR]

The delineation of the areas exposed to flood hazard caused by a dam existence upstream and its possible failure needs a thorough analysis of the hypothetical dam break incident. The study presented in this paper focusses on the simulation of the dam breach formation and the calculation of the resulting outflow hydrograph using a semi- analytical approach. More specifically the method presented addresses the dam break incident of an embankment dam caused by overtopping. The analysis is based on the assumptions of constant vertical erosion rate for the formation of the breach and the parabolic shape of the breach. Two solutions are presented dependent on whether the capacity of the reservoir is considered prismatic or it is a power function of the water depth in the reservoir. Finally the proposed method is illustrated through the analysis of a hypothetical dam break incident. [ABSTRACT FROM AUTHOR]

A coupled 2D mathematical modelling study of landslide dam failure and flood is presented, complementing our experimental investigation presented in the companion paper. The model is built upon the shallow water hydrodynamic equations. The governing equations are numerically solved using the total-variation-diminishing version of the second-order weighted-average-flux method along with the HLLC (Harten, Lax and van Leer with Contact wave restored) approximate Riemann solver. Two parameters related to bed-load sediment transport and critical slope stability are calibrated using the measured stage hydrographs from two runs of the flume experiments. The calibrated model is then applied to other independent runs of the experiments featuring different inflow discharges, dam geometry, dam composition and initial breach dimensions. It is found to be able to satisfactorily reproduce the measured stage hydrographs and the widening of initial breach. The experimental observation of the prime role of the inflow discharge and initial breach in dictating the dam failure process and flood is unequivocally resolved, along with the impacts of dam geometry as well the content of cohesive clay and gravel in the dam. Interestingly, the downstream peak discharge and stage of the flood are substantially reduced by initial breach, which clearly exemplifies its role in modulating the flooding. [ABSTRACT FROM AUTHOR]

This paper analyses the causes of the catastrophic failure of an earth dam that took place on 21 January 2001 during the first filling test in the NE of Spain (Altorricón village, Huesca Province). The San Juan reservoir, with a capacity of 850,000 m3, was built in 1999 on gypsiferous mantled pediment deposits overlying Tertiary dispersive clay sediments. The basin of the reservoir was excavated in the alluvial cover and Tertiary bedrock. An earth dam was constructed on the pediment surface along the perimeter of the artificial basin. The dam has a core of compacted clay material derived from the excavation, which is indented 1 m in the Tertiary shales of the bedrock, cutting the highly pervious alluvial mantle. Field observations, analysis of the basin and dam materials and eyewitnesses accounts have helped to infer the processes involved in the failure of the earth dam. These processes include (1) subsidence and ravelling (suffosion) processes induced by the dissolution of the 4-m-thick detrital cover with a gypsum content of around 40%; (2) piping processes affecting the embankments and core of the dam built with dispersive clays that have high exchangeable sodium percentage (ESP) and show active pipes; and (3) water circulation through biogenic burrows in the pediment deposits. This case study demonstrates the frequently hidden limitations that evaporite sediments and dispersive clay materials pose to the construction of dams. It also shows that highly permeable surficial deposits should be stripped before the construction of the dam structure. [ABSTRACT FROM AUTHOR]

This paper, Part I in a series of two, develops a mathematical model for earthern dam breach erosion. This model constitutes an extension of the Breach Erosion of Earthfill Dams (BEED) model developed by Singh and Scarlatos (1987). Two aspects are emphasized: the evolution of the dam breach, and the subsequent flood and sediment routing. Simulation of dam breach evolution is based on hydrologic, geometric and geotechnic considerations. Einstein-Brown and Bagnold equations are utilized to compute the rate of erosion in the breached section. A water routing scheme, based on a modified version of the Muskingum method to simulate flow exchange between channel and floodplains, is used to route the resulting breach hydrograph. A sediment routing scheme based on the Muskingum method, modified to simulate deposition in floodplains, and deposition and scouring in the channel, is utilized to route the breach sediment graph. In Part II, the model is tested against historical dam failures, and an analysis is made to determine its sensitivity to various parameters. [ABSTRACT FROM AUTHOR]

Common analytical assessment methods for concrete dams are unlikely to predict material fracture in the dam body because of the assumption of rigid body behavior and uniform- or linear stress distribution along a predetermined failure surface. Hence, probabilistic non-linear finite element analysis, calibrated from scale model tests, was implemented in this study to investigate the impact of concrete material parameters (modulus of elasticity, tensile strength, compressive strength, fracture energy) on the ultimate capacity of scaled model dams. The investigated dam section has two types of large asperities, located near the downstream and/or upstream end of the rock–concrete interface. These large-scale asperities significantly increased the interface roughness. Post-processing of the numerical simulations showed interlocking between the buttress and the downstream asperity leading to fracture of the buttress with the capacity being determined mainly by the tensile strength of the buttress material. The capacity of a model with an asperity near the upstream side, with lower inclination, was less dependent on the material parameters of the buttress as failure occurred by sliding along the interface, even with inferior material parameters. Results of this study show that material parameters of the concrete in a dam body can govern the load capacity of the dam granted that significant geometrical variations in the rock–concrete interface exists. The material parameters of the dam body and their impact on the capacity with respect to the failure mechanism that developed for some of the studied models are not commonly considered to be decisive for the load capacity. Also, no analytical assessment method for this type of failure exists. This implies that common assessment methods may misjudge the capacity and important parameters for certain failure types that may develop in dams. [ABSTRACT FROM AUTHOR]

The benefits of dams are unquestionable, with the water impoundment upstream and flood-control downstream usually being sufficient to increase investments and promote growth. However, their presence brings risks to the downstream population and the environment. This paper employs a fuzzy approximate reasoning for dam safety risk assessment, initially using a FAHP to weight the importance of the indicators suggested by a dam expert and then adopts linguistic variables in a two-stage risk assessment. In the first stage, we compute the risk of dam collapse, hereinafter called dam break, through indicators such as design premises and safety procedures. In the second stage, we evaluate the combined effect between the risk of a dam collapse and the socioeconomic and environmental impact on the surrounding area, hereinafter called potential risk. The danger scale of dam break and the hazard scale of potential risk were constructed. The risk assessment of the Simplicio Hydroelectric plant, located in Brazil's Southern region, showed that the risk classification of the proposed method attached great importance to the downstream consequences. The accuracy of the evaluation results was proved through a study of the Oroville Dam, whose spillway faced a failure event. These findings indicate the importance of extracting the knowledge of experts and incorporating it in the model specification through fuzzification of variables and the rule-based construction. [ABSTRACT FROM AUTHOR]

The historical records show that the Northwestern Algeria has experienced more than 130 floods, which were sometimes catastrophic. They caused more than 1000 deaths and significant damage. In this work, we try to reconstruct the most devastating and deadly historical flood that occurred on November 26 and 27, 1927. This event is interesting to discuss disaster scenario because of its extent and impacts and the availability of data. For this purpose, we used historical press reports, scientific papers, and archival reports. This work allowed the reconstruction of the hydroclimatic situation during the flood and the regional scale impacts. It presents also the catastrophic flooding of the Ain Sefra river at Mostaganem and that of El Hammam river, as well as the Fergoug dam breaking at Mohammadia. The main factor triggering these floods was the heavy rainfall. Other factors have increased the damage such as the occupation of high-risk areas and the human failure. This event caused 430 killed persons, more than 1200 disaster victims, and around one billion francs losses. These effects evidence the high vulnerability of the Northwestern Algeria to the occurrence of floods. For that, if a similar event occurs in the future, it can be extremely negative. [ABSTRACT FROM AUTHOR]

There are different methods to identify dispersive soil and several studies have attempted to produce a reliable method for this goal. Some studies have shown incompatibility between field observations and laboratory test results, especially for a chemical criterion. In this study, the dispersivity potential of 328 soil samples having a broad distribution in Iran was evaluated using pinhole and chemical tests in saturated soil extract. The compatibility of the Sherard chemical criterion and pinhole test results was first evaluated. Then, a modified criterion in the general form of the Sherard chemical criterion was suggested based on the pinhole test results to evaluate the dispersivity potential of the clay soil. The results show 44% compatibility between the Sherard chemical criterion and pinhole tests results for the studied samples while the proposed criterion shows 67% of compatibility. [ABSTRACT FROM AUTHOR]

Tailings impoundments are the important structures for the normal mine production, which are also the potential major hazard sources of mine safety. On the basis of the previous tailings dam break model experiment and numerical simulation results, the important characteristic parameters were selected to develop a hazard degree evaluation index system for the disasters induced by the discharged tailings flow from dam failure. The evaluation model was established further by using the uncertainty measurement theory. The results show that the hazard degrees of three characteristic regions (village locations) in the downstream of tailings impoundment were evaluated; it was determined that, the regional safety level of village I was "dangerous", while those for villages II and III were "relatively safe". Moreover, the evolution process of discharged tailings flow was divided into three characteristic stages on the whole, and a greater sand burst amount was associated with a greater risk to the downstream of the tailings impoundment. The results were highly consistent with the results of the laboratory dam break model experiments and numerical simulations. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the application of semi-theoretical models to predict peak discharges for breached embankment dams, it is often encountered to be lack of necessary model parameters such as breach height. In order to solve this deficiency and improve the application of the semi-theoretical models for estimating the peak discharge, a mathematical relation is proposed to predict the breach height (Hb) using the water depth above breach bottom (Hw) based on a subset of a composite database (72 historical dam failures). The breach height relation has a high coefficient of determination (R2) when it is applied in the composite database. Using the prediction by the breach height relation as a substitute for the observation, these semi-theoretical models used here produce similar results in terms of both prediction accuracy and uncertainty. Moreover, the dispersion of the flood peak discharge predicted by forecasting models is weakened and the skewness is improved by adopting the breach height relation. Therefore, the application of semi-theoretical models to predict peak discharges can be improved obviously. So, it is found that the breach height using the proposed relation can be a satisfactory substitute when the observed value of Hb is unavailable in a dam failure. Besides, the prediction accuracy will decrease slightly with the increase of database, but the decrease is limited. It should be noted that the proposed breach height relation is only suitable for predicting the height of embankment dam breach in principle. [ABSTRACT FROM AUTHOR]

Failure modes for earth dams are extensively reviewed and analysed using a three-pronged approach including a literature review, physical observations of a representative earth dam site and finite element structural analysis of the dam wall. Several failure scenarios are used for predicting consequences in terms of downstream inundation and damage. The fluid flow component is performed using the mesh-free smoothed particle hydrodynamics method. For a representative earthen dam, piping and landslip are identified as key failure modes based on a combination of finite element analysis, theory and physical observations. Inundation behaviour is very different for the two failure modes. The landslip failure is the most critical one for the dam studied with flood water breaking the river bank and affecting surrounding property and farmland. For the piping failures, water flow from the initial pipes formed for significant periods before they collapse, but the flow rates are small compared with that of the much larger landslip mode. After failure, fragments of the collapsing wall block the breach and can considerably restrict the flood discharge. In some cases, the water pressure is able to push the obstructing material downstream and some minor flooding occurs, but in others cases the breach can remain blocked with little flooding occurring. A prototype risk framework is developed using the small database of the pre-computed flooding scenarios and key variables that affect inundation such as water level in the reservoir. This can be used to estimate inundation maps for as yet non-computed scenarios through interpolation and superposition techniques. The implementation of the risk framework is demonstrated by the estimation of inundation maps for two in-between non-computed reservoir levels. Inundation due to multiple breaches is also estimated by superposition of three single-breach scenarios. Results are compared against the simulated multiple breach. A preliminary implementation of this risk framework into a geographic information system is also described. [ABSTRACT FROM AUTHOR]

This study proposes an automatic identification approach for landslide dam formation using a real-time abnormal hydrology record and artificial neural network (ANN). In Taiwan, natural dams occur frequently and have the potential to cause significant disasters, especially in the presence of fragile geological conditions such as steep mountains, earthquakes, intense typhoon, and storm events. During a river blockage event, obtaining immediate real-time information can be difficult or even impossible due to extreme weather conditions, remote locations, and the mountainous terrain of the area. As a result of these issues, there is a strong need for a practical tool that can not only detect the occurrence of this type of natural dam but also estimate the potential real-time risk of dam failure. In order to develop the appropriate safety response, a rapid preliminary assessment of the failure type must be identified, followed by a thorough investigation into the failure process after the event has occurred. In this study, a new method is developed that applies an ANN model (1) to evaluate, in real time, the occurrence of a natural dam and the storage changes behind that dam; (2) to rapidly assess the natural dam failure type and failure process; and (3) to reconstruct the dam height variation during the dam failure process after the event. The proposed methodology is applied to Chi-Shan River Basin located in Kaohsiung, Taiwan, during Typhoon Morakot in 2009. In 3 days, Typhoon Morakot produced 1,911 mm of precipitation. The typhoon event produced a landslide dam and a debris flow that inundated Hsiaolin Village, causing 398 deaths. The tragic results of this case study demonstrate the need for an applicable, accurate, and efficient method to evaluate dam formation and its failure rate. [ABSTRACT FROM AUTHOR]

The 2,360 BP eruption of Mount Meager, British Columbia began as an explosive, dacitic sub-Plinian eruption that waned rapidly to a sustained period of Vulcanian, eruption-triggered dome collapse events producing voluminous block and ash flow (BAF) deposits. The earliest BAF deposits accumulated rapidly enough immediately downslope of the vent to retain heat and weld; using the deposit as a paleoviscometer determines an effective viscosity of 10-10 Pa s during welding. This prolific production of hot lava and block and ash flows, in a steep mountainous terrain, created a ∼110 m high, largely impermeable dam capped by permeable, non-welded BAF deposits and unconsolidated avalanche deposits that blocked the flow of the Lillooet River and created a temporary lake. The welded pyroclastic dam was compromised and overtopped at least once before the peak dam height was reached. Renewed eruption caused buildup of the dam to a maximum of 780 m above sea level (asl) and grew the temporary lake to an elevation of 740 m asl and a minimum volume of 0.55 km. The rise of lake level led to catastrophic failure of the top of the dam, generating an outburst flood that carved a canyon through most of the dam and resulted in a voluminous lahar that is traced at least 65 km downstream. Based on current flow rates of the Lillooet River, the lake would have overtopped the final dam at a minimum of 39-65 days after its formation. The peak deluge lasted approximately 8 h and eroded a 2.5-km long canyon into the still-hot dam core before returning to background flow rates. [ABSTRACT FROM AUTHOR]

The standard procedure in Quebec, Canada, for evaluating the failure of an embankment dam, per the Loi sur la sécurité des barrages, specifies a 30-min-long failure scenario with a breach width equal to four times the maximal height of the dam. We demonstrate a new method for evaluating the flood overtopping failure scenario for embankment dams with concrete upstream slope protection, using Toulnustouc dam for example computations. Our new methodology computes safety factors for a range of potential failure mechanisms taking into account geotechnical, hydraulic, and structural factors. We compile the results of our investigations of the various dam failure mechanisms and compare the corresponding dam failure hydrographs to the current hydrograph specified in the standard analysis procedures. Our investigations tend to invalidate the current standard procedures for evaluating the failure of rock-fill dams with concrete upstream faces, by indicating that the current standard procedures underestimate the peak failure discharge and overestimate the time to the peak discharge. [ABSTRACT FROM AUTHOR]

After the catastrophic failure of a red mud reservoir in Hungary, we performed a persistent scatterer radar interferometry (PSI) deformation analysis to investigate the stability and motion history of the entire area focusing on the dam walls of the collapsed structure. Our aim was to contribute to the better understanding of the disaster and, more importantly, to see whether it was possible to prognosticate and consequently prevent the failure of the reservoir and to help avoiding such occurrences worldwide. Our earlier data revealed that the surroundings were generally very stable over the investigated 8 years time interval, whereas significant continuous motions were detected on the embankments. After these first results, we continued our PSI deformation study with the processing and evaluation of the complete ascending pass ENVISAT dataset and later with the combination of the results of the two different observation geometries. From our descending and ascending data, it was possible to combine motions determined in line-of-sight directions and to investigate horizontal and vertical components allowing the estimation of 'total' velocity vectors, magnitude and directions, at those locations of the reservoir and on the entire study area where reflections from both projections were available. It was also possible to get information from several other segments of the embankments of the failed reservoir where the descending geometry was unfavorable. With the combination, the complete ENVISAT PSI analysis using both ascending and descending orbit data enabled us to constrain the role of the soil structure and to look at the differential uplift or subsidence due to swelling soil effect. It also enabled us to constrain the role of the deposited mud, slurry, and accumulated water, and the strength and design of the structure in the failure of the red mud reservoir. Models were also constructed to visualize the observed motions of the reservoir embankments and to highlight the location of strain and stress accumulation providing significant constraints on the natural and anthropogenic origin of the disaster. [ABSTRACT FROM AUTHOR]

Landslide dam failure can trigger catastrophic flooding in the downstream. However, field observation of such flooding is rarely available, while laboratory experimental studies are sparse. The mechanism of landslide dam failure and the flood has so far remained insufficiently understood. Here, we present an experimental investigation of landslide dam failure and the flood. A total of 28 runs of experiments are carried out in a flume of 80 m × 1.2 m × 0.8 m, with differing inflow discharge, dam composition, dam geometry, and initial breach dimension. An array of twelve automatic water-level probes is deployed to measure the stage hydrographs along the flume, and the video recording of the dam failure processes facilitates an estimation of the widening of initial breach. Under the present experimental conditions with dams composed of homogeneous materials, landslide dam failure is primarily caused by erosion of overtopping flow, and lateral mass collapse is also considerable during the cause of breach widening. Cohesive clay may act to mitigate the seepage through the dam and thus its subsidence and appreciably modulate the dam failure process and the flood. However, the impacts of clay may be readily overwhelmed by a large inflow discharge and initial breach. Gravels in the dam may appreciably depress the rate of the dam failure process and thus modify the flood. The present work provides new experimental data set for testing mathematical models of the flood flow due to landslide dam failure. [ABSTRACT FROM AUTHOR]

On October 4, 2010, the embankment of No. 10 red mud-waste product during bauxite refining-reservoir of MAL Co. Ltd. alumina plant collapsed. Around 700 000 cubic meter of alkaline slurry with 11-13 pH value flooded three nearby settlements. Ten people were killed, 123 wounded, and about 350 houses were damaged or became uninhabitable in one of the biggest industrial and ecological catastrophe in modern history of Hungary. Synthetic aperture radar interferometry (InSAR) is the only geodetic technique that can reveal the past stability and motion history of the broken reservoir. We performed a persistent scatterer InSAR (PSI) analysis to contribute to the better understanding of the disaster. The key question we address in this study is whether there were signs prior to October 4th event which may have prognosticated the disaster. The PSI results could reveal if the dam was stable in the past without prior signs of the failure or there were definite indications of deformation before the collapse and proper monitoring of motions could have highlighted the risk and the disaster may have been prevented. This is a rare event and its PSI study is unique and may be critical in understanding it and helping to prevent other similar occurrences. [ABSTRACT FROM AUTHOR]

Gypsum is a highly soluble rock and is dissolved readily to form caves, sinkholes, disappearing streams, and other karst features that typically are also present in limestones and dolomites. Gypsum karst is widespread in the USA and has caused problems at several sites where dams were built, or where dam construction was considered. Gypsum karst is present (at least locally) in most areas where gypsum crops out, or is less than 30–60 m below the land surface. These karst features can compromise on the ability of a dam to hold water in a reservoir, and can even cause collapse of a dam. Gypsum karst in the abutments or foundation of a dam can allow water to pass through, around, or under a dam, and solution channels can enlarge quickly, once water starts flowing through such a karst system. The common procedure for controlling gypsum karst beneath the dam is a deep cut-off trench, backfilled with impermeable material, or a close-spaced grout curtain that hopefully will fill all cavities. In Oklahoma, the proposed Upper Mangum Dam was abandoned before construction, because of extensive gypsum karst in the abutments and impoundment area. Catastrophic failure of the Quail Creek Dike in southwest Utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth-fill embankment. The dike was rebuilt, at a cost of US $12 million, with construction of a cut-off trench 600 m long and 25 m deep. Other dams in the USA with severe gypsum-karst leakage problems in recent years are Horsetooth and Carter Lake Dams, in Colorado, and Anchor Dam, in Wyoming. [ABSTRACT FROM AUTHOR]

On June 8 1994, a beaver dam on Rocky Creek, a small stream in central Alberta, failed and released about 7500 m3 of water. The estimated peak of the resulting flood wave was 15 m3 s-1, which is 3.5 times the maximum discharge recorded for the creek over 23 years. The flood wave destroyed five hydrometric stations, scoured some channel reaches, and deposited sediment in others.Large trees and debris from old beaver dams were carried downstream and deposited in piles across the channel and adjacent banks. The flood wave peak was dampened to 6% of the estimated upstream flood peak as it passed through a 90-ha wetland characterized by both organic and mineral soils, sedge meadow and willow, and containing a small lakeand several beaver ponds. Although the peak flow resulting from the dam outburst was extreme, the volume, most of which was probably detained in the wetland, was not. The volume amounted to only 7% of the combined basin runoff from precipitation and the beaver dam outburst. This extreme event showed that beaver activity can greatly affect thehydrology of small streams and demonstrated the importance of takingwetland storage into account when conducting hydrologic studies on watersheds that contain sizeable areas of wetlands. [ABSTRACT FROM AUTHOR]