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- Environmental and Water Resources Journals
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- Water Resources Planning and Management: An Overview
The study of dam-break analysis is considered important to predict the peak discharge during dam failure. This is essential to assess economic, social and environmental impacts downstream and to prepare the emergency response plan. Dam breach parameters such as breach width, breach height and breach formation time are the key variables to estimate the peak discharge during dam break.
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Francesco Macchione, Pierfranco Costabile, Carmelina Costanzo, Gianluca De Lorenzo, Babak Razdar; Dam breach modelling: influence on downstream water levels and a proposal of a physically based module for flood propagation software. Journal of Hydroinformatics 1 July ; 18 4 : — The influence exerted by the method used for computing the dam breach hydrograph on the simulated maximum water levels throughout the downstream valley is essential for selecting a specific computing module to be implemented in the numerical codes used by practitioners.
This module should be able to balance the need for a reasonable physical description of the phenomenon and, at the same time, limit as much as possible the maximum number of parameters. In order to feed a debate on this field, in this paper the performances of some parametric models used for the dam breach module implemented in the popular HEC-RAS software, and a simplified but physically based model have been analysed.
The performances of the dam breach models have been assessed with reference to the historical event of the Big Bay dam, using both one-dimensional and two-dimensional 1-D and 2-D flood propagation modelling.
The results show that the physically based model considered here, without any operations of ad hoc calibration, has provided the best results in predicting computation of that event. Therefore, it may be proposed as a valid alternative to parametric models, which need the estimation of some parameters that can add further uncertainties in studies like these.
Flooding events are among the most catastrophic natural disasters that might provoke significant damage in properties downstream and even loss of lives. For a reliable flood risk assessment, there is a need of suitable numerical codes in order to carry out accurate computations, extended to wide areas, aimed at flood mapping and, consequently, at the implementation of defensive measures.
Accurate simulations of these situations involve several key aspects ranging from the choice of the mathematical model and numerical schemes to be used in the flow propagation to the characterization of the topography and representation of the constructions that might interact with the flow patterns. In urbanized areas, it is important to describe the influence of buildings on the flow behaviour see, for instance, Vojinovic et al.
More generally, it is necessary to analyse the interaction of the flow with other man-made or natural elements. Among the first ones, bridges play an important role because their piers might provoke significant backwater effects. These effects may present significant variations in water elevation on the cross section, together with a transversal regime transition within the cross section, even in straight reaches of rivers Costabile et al.
Moreover, the bridges are often obstructed by sediment or wood materials Ruiz-Villanueva et al. As regards the natural elements, often there is the need to deal with river reaches that receive significant distributed or localized lateral inflows.
In this context, an important aspect is the availability of LIDAR Light Detection and Ranging data, adequately filtered, in order to automatically recognize structures that can interact with the flow propagation Abdullah et al. For floods due to storm events, other specific issues have to be faced. In all cases, it is extremely important to assess the risk to people caused by flooding see, for instance, Russo et al.
Further complications arise in the delimitation of flood-prone areas due to dam failures. In particular, the problem related to the computation of dam breach hydrograph shows more difficulties in cases of failures of earthfill dams, because of the physical phenomenon consisting of a progressive failure induced by the interaction between water and embankment.
The prediction of these phenomena is gaining growing attention throughout the international hydraulic research community e. Several models have been proposed in the literature to simulate these kinds of situations. Generally, these approaches include also a sudden removal of blocks or side collapses caused by undermining, and geotechnical or geometrical relationships are used for assessing the stability of breach sides.
However, it is important to underline that no exhaustive theory about breach morphology and breach enlargement process, based on fluid-mechanics and soil-mechanics considerations, has been proposed yet. Moreover, they have a complex mathematical structure, describing physical processes characterized by several physical parameters, and require high computational times.
For this reason, several propagation software programs include specific modules for dam breaching based on the so-called parametric models Wahl Therefore, in such an approach, parameters such as the breach formation time and the final geometry of the breach have to be fixed a priori or estimated using empirical formulas.
These relations are based on analyses of the data of historic events of dam failures, and estimate of breach width or failure time peak flow, as functions of representative quantities of the dam and the reservoir, such as the dam height or the water depth of the reservoir before failure, the storage volume, etc.
Wahl considered several of these methods and quantified their prediction uncertainties. One of the most important drawbacks of the parametric model is that the downcutting rate is not related to the hydraulic flow variables but, instead, is assumed a priori similarly to the failure time. Therefore, the stopping of breach developing is generally arbitrary, because it is not at all in relationship with the physical characteristics of the flow through the breach.
For this reason, the use of physically based models would be better. However, as noted above, more complicated models need several parameters and, therefore, should be used carefully only by experts. In order to avoid the drawbacks associated with the use of more complex physically based models and the physical inconsistencies of the parametric models, a possible alternative choice is the application of simplified physically based models.
Among the models belonging to this category, the dam-breach model proposed by Macchione predicts, in a simple but physically based manner, not only the peak discharge, but also the whole outflow hydrograph and breach development.
The model considers the following issues: the geometry of the embankment, the shape of the reservoir, the shape of the breach and the hydraulic characteristics of the flow through the breach and its erosive capacity.
The model needs only one calibration parameter and can be easily applied to real cases. Excellent results have been obtained using a single value for the single calibration parameter in the simulation of 12 historic earthfill dam failures, with a discharge range covering three orders of magnitude.
Independently from the complexity of the mathematical model used for the generation of dam breach hydrograph, it is important to observe that the model validation is usually carried out by reproducing historical observed data of discharge peak values and typical breach features top width, side slope and so on. All the mentioned works on the dam breach analysis focused on what has been observed at the dam site. However, a major challenge in flood mapping due to dam breaching events is understanding the influence exerted by the method used for computing the dam breach hydrograph on the flood hazard and, in particular, on the simulated maximum water levels along the valley.
This paper deals with this latter issue. Therefore, this paper is based on the evaluation of dam breach models by considering the effects that the computed hydrographs induce on the maximum water levels simulated downstream, shifting the interest from the dam site to the downstream areas.
This issue does not seem to be unimportant because the relevant elements for civil protection and flood risk activities are represented by the consequences induced by the flood propagation on the areas downstream, such as maximum water levels and maximum extent of flood-prone areas, flow velocity, front arrival times, etc. In the authors' opinion, it is necessary to feed a debate on this field not only for scientific purposes but also for selecting a specific computing module, to be implemented in the technical propagation software.
In particular, our intention here is to propose a method able to balance the need for a reasonable physical description of the phenomenon and, at the same time, limiting as much as possible the maximum number of parameters that the user should estimate to run the model. In particular, this last issue gained importance in the context of the reduction of the entire modelling uncertainty, ranging from the generation to the propagation of flood events.
The lack of specific studies aimed at clarifying the issues described above is somewhat expected because it is quite unusual to have well-documented historical events for both the breach generation and the water marks downstream.
In particular, the breach information is quite limited to its final dimensions and, sometimes, to an estimation of the evolution time. The water surface data are almost never linked to the reservoir emptying, which can be important information for the estimation of discharge coming from the breach.
Moreover, it is quite unusual to have records on the flood marks signs or other effects induced on the river bed, or on the man-made structures, downstream. For this reason, any time it is possible to have well-documented test cases, these are extremely useful for model validation. This consideration holds for each field of water resources engineering, independently from the modelling techniques used e.
This event has been studied by Yochum et al. Following the work by Yochum et al. For the reasons explained above, this study aims to assess the performances and limits of the parametric models, widely used for technical studies, analysing their effects from the point of view of accuracy on the maximum water levels simulated downstream using two-dimensional 2-D fully dynamic SWE.
As a valid alternative to the parametric models, we propose to use the Macchione model, whose predictive ability and ease of use have already been mentioned. For the dam breaching, we have not considered more complex mathematical models because they are generally characterized by several physical parameters whose estimations introduce further uncertainties in the analysis.
The propagation was preliminarily carried out with a one-dimensional 1-D approach by means of the HEC-RAS unsteady flow option, and using as reference solution that obtained by Yochum et al.
A three-dimensional approach was not considered because the flooded areas are too large and, therefore, the computational times required for its application are not feasible for a common computing machine. The Big Bay dam breach happened in , 12 years after its construction. The dam was composed of homogeneous material. It was m long and For further information, the reader can refer to Yochum et al. At this time, a total of homes or businesses have been damaged by the flood waters.
Of the damaged structures, 48 were completely destroyed, 37 sustained major damage and 19 sustained minor damage. In addition, 30 roads were damaged or closed during the event. The affected area stretched some 17 miles west of the dam to where Lower Little Creek meets the Pearl River.
The HWM positions are listed in Altinakar et al. The dam failure was induced by a piping phenomenon. The breach evolution is described in the event report by Burge According to the report, the embankment failed with the reservoir level at about 0.
During the event, Burge recorded the breach enlargement process providing the following estimations: uncontrolled release of the lake pool began at approximately p. For this reason, it seems that the most significant part of the flow hydrograph was developed between and p. The final breach geometry, estimated by Yochum et al. The breach finally reached the original ground elevation In this work, the Macchione model has been used for the numerical simulation of the dam-breaching hydrograph.
The range 0. In particular, the mean value 0. The numerical simulation of the event has been carried out using the available observed data concerning, essentially, the observed breach, the total volume that came out from the breach and the reservoir emptying time.
As noted by Macchione , the representative parameter of the total eroded volume is the mean breach width and not the top one. For this reason, information about the temporal enlargement of top width is not so important, because the temporal evolution of the breach shape is unknown.
Therefore, the attention here is devoted to the final mean width of the breach reported by Yochum et al. Using the data related to the observed breach, three discharge hydrographs have been obtained using the Macchione model.
Since the dam failure was induced by erosion at the base of the embankment, an initial triangular breach with height equal to dam height has been assumed for all the simulations.
Since M2 and M3 are based on observed data, they can be considered as two historical reconstructions of the event. M1 instead represents the results of the Macchione model used in a predictive mode, since it is based on the standard value suggested by Macchione for the parameter v e. Besides the hydrographs computed using the Macchione model, in this paper the hydrographs computed by Yochum et al. The following information is taken from Yochum et al. Breach progression was assumed to follow a sine wave.
The breach formation time is estimated to be 55 min. Volume of the HEC-RAS developed breach hydrograph was 17,, m 3 , matching the estimated storage available at the time of failure with an initial water surface elevation of The hydrograph used by Yochum et al.
The authors computed also another two hydrographs, which will be referred to here as FR and ML. An accurate 1-D numerical simulation of flood propagation was obtained by Yochum et al.
This module is based on the parametric approach for the dam breach modelling. This requires, as input, the values of the final breach width and its developing time.
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Journal of Water Resource and Protection Vol. This paper firstly described the dam break in the aspects of theories and models. Break parameters prediction, the understanding of dam break mechanics, peak outflow prediction were shown as the essential for the dam break analysis, and eventually determined the loss of the damages. The results show that dam break is a complicated and comprehensive process involving lots of principles. Combination of mechanics and case studies, reflection of predominant mechanisms of headcut erosion, more specific categorization of dam, prudent investigation and inference of dam break process are needed in developing a satisfactory dam break simulation model.
Water resource systems have benefited both people and their economies for many centuries. The services provided by such systems are multiple. Yet in many regions of the world they are not able to meet even basic drinking water and sanitation needs. Nor can many of these water resource systems support and maintain resilient biodiverse ecosystems. The inability of water resource systems to meet the diverse needs for water often reflect failures in planning, management, and decision-making—and at levels broader than water.
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation , human consumption , industrial use , aquaculture , and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees also known as dikes are used to manage or prevent water flow into specific land regions. The word dam can be traced back to Middle English ,  and before that, from Middle Dutch , as seen in the names of many old cities.
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The Commission is entrusted with the general responsibilities of initiating, coordinating and furthering in consultation of the State Governments concerned, schemes for control, conservation and utilization of water resources throughout the country, for purpose of Flood Control, Irrigation, Navigation, Drinking Water Supply and Water Power Development. It also undertakes the investigations, construction and execution of any such schemes as required. Each wing is placed under the charge of a full-time Member with the status of Ex-Officio Additional Secretary to the Government of India and comprising of number of Organizations responsible for the disposal of tasks and duties falling within their assigned scope of functions. The monthly newsletter of CWC Click here.
Scientific Research An Academic Publisher. Journal of Water Resource and Protection. Google-based Impact Factor: 1.
Но более страшным стало то, что он увидел в следующее мгновение. Скрытые тенью, на него смотрели глаза Грега Хейла, глаза, полные ужаса.
Water Resources Planning and Management: An Overview
Заместитель директора только что солгал директорской канцелярии. Я хочу знать. Бринкерхофф уже пожалел, что не дал ей спокойно уйти домой. Телефонный разговор со Стратмором взбесил. После истории с Попрыгунчиком всякий раз, когда Мидж казалось, что происходит что-то подозрительное, она сразу же превращалась из кокетки в дьявола, и, пока не выясняла все досконально, ничто не могло ее остановить. - Мидж, скорее всего это наши данные неточны, - решительно заявил Бринкерхофф.
Стратмор мысленно взвешивал это предложение. Оно было простым и ясным. Сьюзан остается в живых, Цифровая крепость обретает черный ход. Если не преследовать Хейла, черный ход останется секретом. Но Стратмор понимал, что Хейл не станет долго держать язык за зубами. И все же… секрет Цифровой крепости будет служить Хейлу единственной гарантией, и он, быть может, будет вести себя благоразумно. Как бы там ни было, Стратмор знал, что Хейла можно будет всегда ликвидировать в случае необходимости.
Y. Xiong, "A Dam Break Analysis Using HEC-RAS," Journal of Water Resource and Protection, Vol. 3 No. 6, , pp. doi: /jwarp
Она казалось напуганной еще сильнее, чем раньше. - Мистер, - сказала она дрожащим голосом, - я не говорила вам, как меня зовут. Откуда вы узнали.
Почему бы и. Испания отнюдь не криптографический центр мира. Никто даже не заподозрит, что эти буквы что-то означают. К тому же если пароль стандартный, из шестидесяти четырех знаков, то даже при свете дня никто их не прочтет, а если и прочтет, то не запомнит. - И Танкадо отдал это кольцо совершенно незнакомому человеку за мгновение до смерти? - с недоумением спросила Сьюзан.
Этот шифр есть продукт нового типа шифровального алгоритма, с таким нам еще не приходилось сталкиваться. Эти слова повергли Сьюзан в еще большее смятение.