Breach Parameters Research Articles

Investigating the Influence of Dam-Breach Parameters on Dam-Break Connected Flood Hydrograph

The dam-break connected flood hydrograph properties primarily depend on the breach geometry and the time for the breach to fully develop. Therefore, the prediction of dam’s breach geometry is essential in dam-break studies. To understand the impact of breach parameters on flood peak hydrograph, five of the most common breach prediction methods are implemented in the presented study to estimate the flood hydrographs using 2-dimensional HEC-RAS model. The Ürkmez Dam is chosen as the case study due to the presence of a residential settlement located right at the dam downstream where undesirably any breach of the dam body can have inevitable and dramatical risks on downstream populations and properties. Various levels for reservoir storage are investigated in each method. In order to assess the impact of each breach parameter on the resulting flood hydrographs, sensitivity analysis is carried out. The peak discharge rates and the times to peak for each analyzed scenario are investigated and discussed. Results reveal that Froehlich approach is the most reasonable method for estimating dam-breach parameters as far as exemplified in the Ürkmez Dam case. Furthermore, sensitivity analysis points out that the parameter of the breach side slope has no major influence on the time to peak while having an insignificant impact on the peak discharge. Besides, the study exhibits that both the peak discharge and the time to peak characteristics are highly sensitive to breach time formation parameter. In the light of these targeted findings, the study is aimed to contribute to other relevant research in designating the set of key parameters in experimental or modeling efforts in a way to limit the uncertainty that substantially originates from personal judgment.

Effects of grain composition on the stability, breach process, and breach parameters of landslide dams

The sudden breach of a landslide dam seriously threatens the safety of people and property downstream. The failure mechanism of landslide dams is significantly affected by the grain size distribution of the dam material. In this study, a series of experiments are conducted to investigate the effects of grain composition on the stability, breach process, and breach parameters of landslide dams. The results show that dams remain stable with seepage for a coarse-dominated dam, fail by overtopping along with piping for a fines-dominated dam, and fail by overtopping alone for a balanced-composition dam. The failure mode is regulated by the composition of dam material, stress condition and hydraulic gradient. Backward erosion occurs for dams with fines contents <5 % due to the movement of debris, during which the width:depth ratio of the cross section first decreases and then increases. By contrast, for dams with fines contents higher than 15 %, headcutting occurs and a step-pool structure develops because the small grains are more easily washed away than the coarse grains. In this scenario, the width:depth ratio first increases and then decreases. Dam longevity nonlinearly increases with increasing fines content. The breach hydrography changes from a single peak to multiple peaks with increasing fines content, and the peak discharge is sensitive to the median diameter of dam material. In addition, the breach degree, defined as the ratio of the releasing potential energy (total potential energy minus the residual potential energy) to the total potential energy of the lake upstream of the landslide dam, is controlled by this median diameter. This study improves our understanding of failure mechanisms and aids the hazard assessment of landslide dams.

Dam Break Analysis using HEC-RAS: A Case Study of Karjan Dam

A dam is a structure constructed across river which stores water and supplies water for various purposes. Though the dams have many benefits, there is always a threat of dam break floods which are devastating in nature. Hence it becomes essential to analyze and simulate dam failure scenarios to understand the severity of dam break flood and identify areas under threat which helps in land use planning and developing emergency response plans. This study attempts to carry out dam break/breach analysis for the Karjan dam using a two-dimensional hydraulic model called Hydraulic Engineering Center’s River Analysis System (HEC-RAS). RAS-Mapper tool is used to extract river geometry data from the Cartosat-1 digital elevation model (DEM) and to generate the inundation map to identify the areas affected. The study involves the prediction of breach parameters, breach flood hydrograph, peak flow, flood arrival time, and generation of inundation maps. The dam break model is simulated for unsteady flow conditions using Probable Maximum Flood (PMF) corresponding to different failure scenarios. HEC-RAS tool is utilized to determine the breach outflow hydrograph and hydraulic conditions at critical downstream locations. The outcome will assist the local government in making proper planning and development decisions. Key Words: Arc-GIS, Dam break analysis, Karjan dam, Flood Inundation, HEC-RAS

Influence of Dam Breach Parameter Statistical Definition on Resulting Rupture Maximum Discharge

However rare, dam breach occurrences are recently reported and associated with significant damage to life and property. The rupture of the structural dam wall generates severe flow rates that exceed spillway capacity consequently generating unprecedented flooding scenarios. The present research aims to assess the influence of the dam breach statistical configuration on the most relevant parameters to predict the rupture maximum discharge (RMD). McBreach© software was used to provide the necessary inputs for the operation of the HEC-RAS dam breach module. McBreach© automates the process of batch mode simulations providing a Monte Carlo approach to characterize the breach parameters stochastically. Thus, a sensitivity analysis was performed to identify the most influential breach parameters, followed by an uncertainty assessment regarding their statistical definition of the resultant RMD. Analysis showed that the overtopping failure mode discharges are most sensitive to the breach formation time (tf) parameter, followed by the final height breach (Inv) and the final width of the breach (B), which combined are responsible for 85% of the rupture’s maximum discharge. Further results indicated highly variable RMD magnitudes (up to 300%) depending on the breach parameter’s statistical definition (i.e., probability density function and associated statistical parameters). The latter significantly impacts the estimated flood risk associated with the breach, the flood zone delimitation, preparation of emergency action plans (EAP) and scaling of future dam projects. Consequently, there is a plausible need for additional investigations to reduce this uncertainty and, therefore, the risk associated with it.

Modeling and Risk Analysis of Dam-Break Flooding in a Semi-Arid Montane Watershed: A Case Study of the Yabous Dam, Northeastern Algeria

The risk related to embankment dam breaches needs to be evaluated in order to prepare emergency action plans. The physical and hydrodynamic parameters of the flood wave generated from the dam failure event correspond to various breach parameters, such as width, slope, and formation time. This study aimed to simulate the dam breach failure scenario of the Yabous dam (northeast Algeria) and analyze its influence on the related areas (urban and natural environments) downstream of the dam. The simulation was completed using the sensitivity analysis method to assess the impact of breach parameters and flooding on the dam break scenario. The flood wave propagation associated with the dam break was simulated using the one-dimensional HEC-RAS hydraulic model. This study applied a sensitivity analysis of three breach parameters (slope, width, and formation time) on five sites selected downstream of the embankment dam. The simulation showed that the maximum flow of the flood wave recorded at the level of the breach was 8768 m3/s, which gradually attenuated along the river course to reach 1972.7 m3/s at about 8.5 km downstream the dam. This study established the map of flood risk areas that illustrated zones threatened by the flooding wave triggered by the dam failure due to extreme rainfall events. The sensitivity analysis showed that flood wave flow, height, and width revealed positive and similar changes for the increases in adjustments (±25% and ±50%) of breach width and slope in the five sites. However, flood wave parameters of breach formation time showed significant trends that changed in the opposite direction compared to breach slope and width. Meanwhile, the adjustments (±25% and ±50%) of the flood hydrograph did not significantly influence the flood parameters downstream of the dam. In the present study, the HEC-RAS 1-D modeling demonstrated effectiveness in simulating the propagation of flood waves downstream of the dam in the event of dam failure and highlighted the impact of the breach parameters and the flood hydrographical pattern on flood wave parameters.

Two-Dimensional Dam Break Modelling of Beris Dam using HEC-RAS

Dam is built for various functions such as water supply, flood and sediment control, electricity generation and irrigation. Floods due to dam breaches create higher peak flows than floods produced by heavy rainfall. When a dam collapses, the stored water may cause devastating catastrophe towards downstream areas by causing fatalities and property damages. The aim of this study is to perform a two-dimensional dam break modelling of Beris Dam due to probable maximum flood (PMF). The HEC-RAS software was used to predict the breach outflow’s hydrograph and produce the flood inundation and velocity map. Dam breach parameters were calculated using Froehlich and MacDonald and Langridge-Monopolis (MDLM) equations. A 4-day simulation conducted showed that a breach was initiated at almost 10.35 am, 34 hours and 35 minutes after the PMF scenario. Peak discharge during the PMF failure is 10,745.12 m3/s at 12.45 pm the next day which is after 2 hours and 10 minutes of dam breach initiation. Felda Lubuk Merbau, Kampung Betong, Jeniang, Padang Serai and Kota Kuala Muda are among the areas affected by the simulated Beris Dam break. Information obtained on flood velocity, depth and arrival time are useful to local authorities in order to respond effectively and immediately in the event of dam break.

Sensitivity analysis for dam breach parameters using different approaches for earth-fill dam

The prediction of dams breach geometry crucial in studies of dam breaking. The hydrographs characteristics of flood that resulting from breaking of dam is mainly depend on the geometry of breach and the time formation of breach. Five approaches (Froehlich, Macdonald and Langridge-Monopolis, Von thun &amp; Gillete, USBR and Singh % Snorrason) was used in order to predict dam breach parameters (breach width, breach side slope, breach formation time). The Sensitivity analysis was performed in order to assess the effect of each parameter on the resulting hydrograph of the flood. HEC-RAS model was used to calculate the effect of each parameter on the hydrograph of the flood that resulted. The width of breach (Bavg), side slope (z) and formation time of breach (tf) increased by 25%, 50%, 75% and 100% and decreased by 25%, 50% and 75%, respectively. Flood hydrograph was estimated at the dam site for each case. Sensitivity analysis was performed in order to check the effect of each parameter of breach and time of breaching. Sensitivity analysis was performed with Froehlich method with the mode of overtopping failure and maximum operating level at 107.5 meter above sea level. Result of sensitivity analysis show that peak discharge and time to reach it is adequately sensitive to breach side slope, highly sensitive to the breach formation time and less sensitive to breach width.

Dam break analysis using 1D geometry at Jatigede Dam, Sumedang

Dam breaks can result in flash floods which have enormous destructive power. This destructive force becomes even more significant when the dam break occurs in a dam with a large capacity. An example is the Jatigede Dam, which has a capacity of 1,060 million m3. To determine the flash flood characteristics and potential impact of the collapse of the Jatigede Dam, an analysis of the dam break was carried out using HEC-RAS software. The dam break scenario uses a Probable Maximum Flood (PMF) inflow with the partial opening of two spillway gates in the middle, which causes the dam overtopping. The Froehlich and Von Thun, and Gillette regression methods were used to defining the breach parameters. Based on the dam break analysis, the simulated flash flood of the Von Thun-Gillette method resulted in a higher velocity and lower water surface elevation than the Froehlich method. The difference in the velocity, dimension of the breach shape, water surface elevation, and discharge is caused by the breaching shape and breach formation time.

Dam break analysis using HEC-RAS and HEC-GeoRAS: A case study of Hidkal dam, Karnataka state, India

A dam is a structure constructed across river which stores water and supplies water for various purposes. Though the dams have many benefits, there is always a threat of dam break floods which are devastating in nature. Hence it becomes essential to analyze and simulate dam failure scenarios to understand the severity of dam break flood and identify areas under threat which helps in land use planning and developing emergency response plans. This study attempts to carry out dam break/breach analysis for the Hidkal dam using a one-dimensional hydraulic model called Hydraulic Engineering Center's River Analysis System (HEC-RAS). HEC-GeoRAS tool is used to extract river geometry data from the Cartosat-1 digital elevation model (DEM) and to generate the inundation map to identify the areas affected. The study involves the prediction of breach parameters, breach flood hydrograph, peak flow, flood arrival time, and generation of inundation maps. The dam break model is simulated for unsteady flow conditions using Probable Maximum Flood (PMF) corresponding to piping and overtopping failure scenarios. HEC-RAS tool is utilized to determine the breach outflow hydrograph and hydraulic conditions at critical downstream locations. Further, the breach outflow hydrographs are routed using dynamic flood wave routing. Further HEC-RAS model is simulated for breach parameters derived from five different empirical methods, and the results are compared. A sensitivity analysis is also carried out to know the variation of peak flow and maximum stage with respect to the breach parameters. The immediate downstream of the dam experience a peak flow of 72,085.45 m3/s and 78,454.82 m3/s and the corresponding inundation area of 75.224 km2 and 79.205 km2 due to piping failure and overtopping failure, respectively. Around twenty village located on the downstream of dam location gets affected due to flood produced by dam break. The analysis shows that overtopping failure is more severe than failure due to piping. The study shall further help authorities concerned to develop an emergency response plan and flood mitigation measures.

Future Glacial Lake Outburst Flood (GLOF) hazard of the South Lhonak Lake, Sikkim Himalaya

The Teesta basin in Sikkim Himalaya hosts numerous glacial lakes in the high altitude glacierized region, including one of the largest and the fastest-growing South Lhonak Lake. While these lakes are mainly located in remote and unsettled mountain valleys, far-reaching glacial lake outburst floods (GLOFs) may claim lives and damage assets up to tens of kilometers downstream. Therefore, evaluating GLOF hazard associated with current and potential future glacier-retreat-driven changes is of high importance. In this work, we assess the future GLOF hazard of the South Lhonak Lake by integrating glacier and hydrodynamic modeling to calculate the lake's future volume and hydraulic GLOF characteristics and impacts along the valley. We identify the increased susceptibility of the lake to potential avalanche impacts as the lake grows in the future. Here we model six avalanche scenarios of varying magnitudes to evaluate the impact-wave generated in the lake and overtopping flow at the dam. Avalanche simulations indicate that the frontal moraine is susceptible to overtopping. The overtopping flow hydraulics is evaluated along the channel assuming no erosion of the moraine. Further, we consider three lake-breach scenarios to model GLOFs originating from the lake, flow propagation, and its downstream impacts. The uncertainty in the breach parameters including breach width and time of failure are calculated to estimate the upper and the lower hydraulic limits of potential future GLOF events. Further, the uncertainty in the flow hydraulics was evaluated using dynamic flood routing of six GLOFs that originate from the lake. Hydrodynamic GLOF modeling resulted in a predicted peak discharge of 4311 m3s−1, 8000 m3s−1, and 12,487 m3s−1 for breach depths of 20 m, 30 m, and 40 m respectively. The large-potential scenario suggests that maximum flow depth and flow velocity at Chungthang, a town proximally located to a major hydropower station built-in 2015, could reach up to 25–30 m and 6–9 m s−1, respectively. Mapping infrastructure exposed to GLOFs in the Teesta valley shows that many settlements and assets located along the river channel at Chungthang are potentially exposed to future GLOFs, indicating the need to conduct a full environmental impact assessment and potentially undertake GLOF risk mitigation measures.

Baur dam breach analysis using various manning’s roughness values

This paper describes the importance of flood mapping in terms of saving downstream agricultural area. Flood can cause high impact on the nearby crops productivity which further affects the country’s economy. The Baur dam has a Culturable Command Area of 31453,6572 hectares. It’s key focus is on describing the importance of Manning’s roughness value in dam breach modelling and shows it’s bad impact on downstream areas of dam. In this work hypothetical breach modelling of Baur dam is performed by using Hydrologic Engineer’s Centre- River Analysis System (HEC-RAS). Details about study area, breach parameters, modelling procedure, and outflow flood values are also described in this paper. Flow hydrographs are plotted at different Manning’s roughness value for the two populated downstream areas of dam and it has been observed from results that as roughness value increases flow decreases which justifies Manning’s theory. As a Final result Inundation maps are plotted with the detail of inundated area values for different Manning’s values so that the effect of roughness can be analysed numerically on study area. The Manning’s roughness value of 0.030 causes 37.75km2 inundated area in the downstream of dam.1

Dam breach analysis: a case of Gidabo dam, Southern Ethiopia

Gidabo dam provides flood control and irrigation water supply for sugarcane and rice cultivation. The dam has 25.8 m height and 335 m crest length with side ogee spillway to pass 10,000 years’ flood. There were different economic developments downstream of the dam including irrigation command area and irrigation structures. Since Nature is full of uncertainties, it is likely that Gidabo dam can be subjected to sudden breaches due to the probable maximum flood. Therefore, dam breach analysis and flood inundation map preparation should be conducted. The Hydrologic Engineering Center’s River Analysis System new version was used to analyze the dam breach for overtopping failure. River analysis system Mapper which is Geographic information system tool of Hydrologic Engineering Center’s River Analysis and Geographic information system were used to develop flood inundation map. Dam breach parameters were calculated within the Geographic information system model by using beach parameter calculator tab. A two-dimensional unsteady flow simulation of the dam breach was performed by using the inflow hydrograph as upstream boundary condition. From the rainfall data analysis, the probable maximum precipitation resulting probable maximum flood was found 277 mm results a peak inflow of 6387 m3/s. It was found that the breach bottom width was 143 m while the breach side slope (horizontal: vertical) was 1.4:1 and 2.7 h breach formation time. The peak breach outflow was found to be 15,848.85 m3/s which covers 2050 hectares with maximum depth of 12.14 m.

Propagating Dam Breach Parametric Uncertainty in a River Reach Using the HEC-RAS Software

Dam break studies consist of two submodels: (a) the dam breach submodel which derives the flood hydrograph and (b) the hydrodynamic submodel which, using the flood hydrograph, derives the flood peaks and maximum water depths in the downstream reaches of the river. In this paper, a thorough investigation of the uncertainty observed in the output of the hydrodynamic model, due to the seven dam breach parameters, is performed in a real-world case study (Papadiana Dam, located at Tavronitis River in Crete, Greece). Three levels of uncertainty are examined (flow peak of the flood hydrograph at the dam location, flow peaks and maximum water depths downstream along the river) with two methods: (a) a Morris-based sensitivity analysis for investigating the influence of each parameter on the final results; (b) a Monte Carlo-based forward uncertainty analysis for defining the distribution of uncertainty band and its statistical characteristics. Among others, it is found that uncertainty of the flow peaks is greater than the uncertainty of the maximum water depths, whereas there is a decreasing trend of uncertainty as we move downstream along the river.

Dam Break Analysis of Temenggor Dam Using HEC-RAS

Embankment dam is commonly built in Malaysia as it provides benefits to the local population, mainly agricultural activity and flood control measures. However, its massive potential energy reservoir would impose risk of sudden containment breach leading to loss of life and property at inhabited downstream area. This paper deemed to provide a dam break analysis of Temenggor Dam to generate breach hydrograph and inundation map as a result of dam break event under piping and overtopping failure. The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) is capable to model 1-dimensional (1-D) and 2-dimensional (2-D) dam failure event by utilizing hydrological and terrain information generating unsteady-state flow simulation of the dam breach. The process for gathering and preparing data, estimating breach parameters, creating one dimensional and two-dimensional unsteady-flow model in HEC-RAS, performing a dam failure analysis for two dam failure scenarios and mapping the flood propagation are outlined in this paper. From 1-D analysis, it is found that the breach flow of Temenggor Dam failure can achieve 281,588 m3/s for piping failure and 331,030 m3/s for overtopping failure. 2-D analysis’ breach flow attained 268,341 m3/s and 328,869 m3/s for piping and overtopping failure, respectively. Furthermore, the expected arrival time of flood wave at selected locations also presented in this paper. 1-D model produced comparable breach hydrograph result of Temenggor Dam against 2-D model with the advantage of significantly shorter simulation time requirement. However, 2-D model able to generate inundation map due to dam failure in wider area which can provide insight of flood hazard risk level and contribution for emergency action plan development.

Estimation of breach outflow hydrograph using selected regression breach equations

Embankment dam is commonly built in Malaysia as it provides essential benefits to the local population, such as agricultural activity and flood control measures. However, the release of high potential energy by the impoundment imposes risk of catastrophic event during the dam failure. Therefore, estimation of flood arrival time under dam break event can be beneficial as primary information using numerical model to simulate the breaching process of the embankment dam. The purpose of this study is to establish dam breach profile of Temenggor Dam in predicting breach outflow hydrograph. A few selected regression equations for breach parameters will be tested namely Froehlich, Macdonald and Langridge-Monopolis and Von Thun and Gillete. One-dimensional dam break modelling were performed based on the calculated breach parameters for overtopping and piping failure. Hydrologic Engineering Center’s River Analysis System (HEC-RAS) software is used for the dam break analysis. Results obtained from the study indicated that overtopping failure yields the highest peak breach flow of 202,099 m3/s, compared to piping failure’s highest peak discharge of 201,126 m3/s.

New Empirical Model for Breaching of Earth-Rock Dams

AbstractEmpirical models are widely used in dam risk analysis because they can estimate the dam breach parameters easily, which enables a quantitative analysis of the breach process to be conducted...

Enhancing the resilience to flooding induced by levee breaches in lowland areas: a methodology based on numerical modelling

Abstract. With the aim of improving resilience to flooding and increasing preparedness to face levee-breach-induced inundations, this paper presents a methodology for creating a wide database of numerically simulated flooding scenarios due to embankment failures, applicable to any lowland area protected by river levees. The analysis of the detailed spatial and temporal flood data obtained from these hypothetical scenarios is expected to contribute both to the development of civil protection planning and to immediate actions during a possible future flood event (comparable to one of the available simulations in the database) for which real-time modelling may not be feasible. The most relevant criteria concerning the choice of mathematical model, grid resolution, hydrological conditions, breach parameters and locations are discussed in detail. The proposed methodology, named RESILIENCE, is applied to a 1100 km2 pilot area in northern Italy. The creation of a wide database for the study area is made possible thanks to the adoption of a GPU-accelerated shallow-water numerical model which guarantees remarkable computational efficiency (ratios of physical to computational time up to 80) even for high-resolution meshes (2.5–5 m) and very large domains (&gt;1000 km2).

Breach parameters for cascade dams’ breaks using physical, empirical and numerical modeling

ABSTRACT The environmental, economic, and social consequences of dam breaks are catastrophic and require their prior knowledge to minimize risks. These consequences are directly related to rupture breach parameters, such as formation time and breach geometry (width, height, and lateral slopes). These parameters must be adequately representative of a real rupture to obtain a rupture hydrograph also representative (temporal evolution, volume, and peak flow). This representation becomes more reliable as the closer to the actual consequences of a rupture it is, thus creating conditions for an adequate emergency action plan. This research evaluates the parameters of breach formation for a possible rupture, specifically for the case of reservoirs in a sequence, also called cascade reservoirs. The adopted methodology uses physical reduced models and numerical modeling to define these parameters, trying to represent two cascade dams, based on a reference case, determining their values in each dam after the simulated rupture events.

A comparative study of embankment breach parameters in different breach locations

In general, when an embankment breach occurs, the breach expands laterally due to erosion of both breach sides. However, when the breach occurs close to a solid wall, the erosion occurs primarily on one side. This paper presents a study on the comparative parameters of the breaches that occurred at the middle of the embankment width, and at the location adjacent to a solid wall. A physical model is constructed such that the breaches could be observed. The downstream slopes of the embankment model were set at 1:1, 1:1.5, and 1:2. Cohesive soil was used to construct the embankments with the bulk density distributions ranging from 1.4 to 1.7 g/cm3. The experiments were conducted by allowing water to flow over the embankment at different flow rates. The breach dimensions were measured and transformed into dimensionless breach parameters. These dimensionless breach parameters were analysed to ascertain their relation with relevant dimensionless flow parameters. The results reveal that for the same embankment slope and discharge rate, the breach parameters change depending on the location of the breach, except for the parameter of the soil loss volume. The distance between the breach location and the solid wall affects the values of the maximum breach width, the maximum breach depth, and the maximum scour depth. There is shown that breach depth and scour depth for breaches adjacent to the solid wall are deeper than those of the breaches occurring in the middle section of the embankment. In addition to these findings, the empirical relation among these dimensionless breach parameters obtained from other case studies are also discussed.

Dam break analysis and flood disaster simulation in arid urban environment: the Um Al-Khair dam case study, Jeddah, Saudi Arabia

This study used a simulation methodology for dam break analysis and flood simulation in an urbanized arid region, namely Um Al-Khair dam in Jeddah, Saudi Arabia. The analysis was performed using the 2011 rainfall storm of 111 mm and 281 min duration. The results show that the rainfall depth corresponds to a return period between 50 and 100 years. The hydrograph resulting from this storm was estimated using a rainfall–runoff model. The hydrograph was found to fall in between 100- and 200-years return period. This confirms that it is not necessarily to have the same return period for both rainfall and its corresponding flood due to the nonlinearity of the rainfall–runoff process. The dam breach parameters and the inflow hydrograph were used to model the flood propagation due to Um Al-Khair dam breach using HEC-RAS-2D software. A comparison between the modeled and observed water depths showed a relatively reasonable correlation coefficient of 0.57 and the RMSE of the water depth is 0.45 m, which are acceptable in such studies under the scarcity of accurate field measurements.