Emergency Spillway Research Articles

Numerical assessment of the risk of GERD break on the downstream countries

The potential effects of Grand Ethiopian Renaissance Dam (GERD) failure on the downstream countries were numerically assessed. Flow discharge reaching Lake Nasser and the corresponding water levels were determined, and the inundated areas were defined as a result of GERD failure. High-resolution digital elevation model was developed with 2670-km length starting from GERD till Aswan High Dam. GERD’s reservoir, urban, and rural lands downstream of the GERD were presented using a numerical model. The modeled areas included parts of Ethiopia, Sudan, and Egypt, not to mention Toshka Spillway. The model areas were not divided into parts because of calculating the water levels at the existence of intermediate dams as model outputs. In case possible failure of GERD, Roseires and Sennar dams could collapse. Meanwhile, Merowe dam can sustain with the operation of its emergency spillway. Wave height reaches 100-m downstream of the GERD and 64-m and 31-m downstream of the Roseires and Merowe dams, respectively.

Surface and subsurface structural mapping for delineating the active emergency spillway fault, Aswan, Egypt, using integrated geophysical data

The High Dam is one of the world’s biggest embankments dams. Moreover, the new city of Aswan, which locates on the western side of the Nile River, is one of the cities that was established to overcome the growing population problem. Therefore, the detailed geophysical studies for the active faults are of more importance for assessing the seismic stability for both of them. Indeed, the emergency spillway fault was documented as a normal and inactive fault. While, a moderate earthquake (ML = 4.6) was recorded along this fault in 2010, about 4.5 km away from the Dam. Hence, its activity must be re-evaluated. The seismic activity along the fault and its extension has been studied. The seismicity distributions and the fault plane solution indicate normal faulting with a strike-slip component and shallow focal depth. Moreover, pore pressure and fluid diffusion play an essential role in fault activation process. On the other hand, the magnetic data for the research area was subjected to a detailed analysis. 2D spectrum analysis and 3D Euler deconvolution methods, were used to analyze and interpret the aeromagnetic anomaly data so as to better understand the tectonic framework of the study region. Finally, the integrated geophysical data delineate the trend of the emergency spillway fault which extends NW–SE. This fault could assist in updating the current seismic source model around the High Dam and new Aswan city for evaluating the seismic hazard for both of them.

Specifications and Accuracy of Rainfall Forecast Required for Pre-Release at Multi-Purpose Reservoirs in Japan

Pre-release is the discharge from a reservoir before a flood to enhance flood control capability. Its success depends on the performance of rainfall forecasting. However, there is little information regarding the causal relationship between its performance and the success of pre-release. Therefore, the rainfall forecast required for pre-release at 326 multi-purpose reservoirs in Japan is shown quantitatively in this paper. In our analysis, pre-release was simulated based on tentative rainfall forecasts made using observed rainfall data from a period of 17 years (2006 to 2022) with some processing. Then, outputs were evaluated in terms of two risks: not avoiding emergency spillway gate operation and no recovery of water use capacity. The results of five elements were reached: (1) the characteristics of situations requiring pre-release, the required (2) forecast length and (3) spatial resolution, the required accuracy of (4) the rainfall amount, and (5) the position of rainfall zone. For (1), pre-release is required nationwide in typhoons or stationary fronts at a frequency of four instances per year. For (2) and (3), assuming perfect accuracy, the current specifications of rainfall forecast in Japan: forecast length of 84 h or more and the combined use of 5 km and 20 km spatial resolution are generally effective in themselves. For (4) and (5), possible uncertainties in the rainfall amount and the position of rainfall zone needs to be decreased by one digit for avoiding emergency spillway gate operations, while excessive pre-release tends not to result in no recovery of water use capacity.

Study of the hydrogeological, engineering-geological and hydrological regime of the Kaiyndy Lake basin for an emergency spillway from Kaiyndy Lake

This article provides information on the stability of the natural dam of Lake Kaiyndy in the study area. Lake Kaiyndy is located in the middle part of the basin and is fed by melted snow and rainwater. The flow of water from the lake is carried out by the surface. The lake belongs to the high category of mudflow hazard. During the technogenic development of this territory, one should consider the negative impact of the additional load on the stability of the sides of the canyon and not expand the development of the territory towards the river. In the event of a lake outburst, the road bridge of the village of Zhalanash - the village of Saty, residential buildings and farmland of the village of Algabas and Zhanatalap of the Kegen district, the village of Shelek, the village of Masak, the village of Baiseit, the village of Malybay, with. Zhanasharua of the Enbekshikazakh district and the Bartogay reservoir of the Almaty region, road bridges, power lines. The total number of people in the risk zone is more than 2-3 thousand people. Also, the Kuldzhinsky Trakt highways, the Western China-Western Europe auto-ban, irrigation systems, the waterworks of the Kunaev BAC and other linear communications fall into the zone of influence. Lake Kaiyndy is a place of mass visits by tourists and vacationers. In summer, the number of people at risk can reach several hundred.

The assessment of the capacity of the existing detention reservoir – Lubina

The presented article describes the assessment of the capacity of the existing detention reservoir with an alternative proposal for raising the dam and constructing an emergency spillway. The subject of the investigation was the capacity of the river bed under the polder too. The calculations were performed by numerical 2D modelling in the HEC-RAS program. Morphology data were obtained from own in-situ measurements and based on publically available data – DTM (digital terrain model).

Dimension Analysis Of The Emergency Spillway Of Tirawan Dam With The Application Of The System Dynamic Model

Tirawan Dam emergency spillway is planned to be able to drain the initial flood discharge when the gate above the main spillway is closed so that there will be sufficient time to open the gate to pass the peak flood discharge through the spillway safely. The emergency spillway elevation is designed to accommodate maximum water as a natural reserve during the dry season. This study aims to analyze the factors that play a role in emergency spillway design in meeting the availability of optimal raw water storage and increasing the safety factor against flooding using a simulation modeling method with the help of the Vensim PLE program. The modeling is made in three stages. The first is the analysis of the system model, the second is the creation of a caustic diagram, and the third stage is the simulation of the model and scenario model. The simulation results of this model scenario obtained an effective emergency spillway elevation of +69.50 m and a width of 20 m. The spillway can pass the Q1000 design flood without the control gate operation with a freeboard of 0.41 m with a raw water reserve of 240,649.69 m3. From the simulation results, it is also known that the operation of the main spillway serves to add a safety factor to the discharge capacity of the flood discharge during an emergency condition and cannot be operated to optimize the reservoir.

Challenges in flood control operation and dissemination of information - Lessons from the record-breaking heavy rain in July 2018, Japan

In July 2018, a record-breaking heavy rain hit western part of Japan, leaving severe damages. 213 dams under the jurisdiction of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) were engaged in flood control operation, and greatly contributed to the reduction of flood damages. Meanwhile, in case of 8 dams, the amount of rainfall was so huge that the emergency spillway gate operation by discharging equal to inflow volume was obliged to execute which caused severe flood damages in some of the downstream areas. In December 2018, Special Panel set up by MLIT finalized a report urging enhancement of flood control capability of dams and dissemination of related information, in preparation for the risk of extreme rainfall which may increase under changing climate condition. This paper briefly introduces the report, outlining the flood control activities at the 2018 flood event as well as the contents of the proposal.

Matematičko modeliranje tečenja i pronosa nanosa - primjer brane na rijeci Tisi

High flow velocities downstream of the Tisa Dam at Novi Bečej (Serbia), produced by the large difference between water levels in the upstream and downstream reaches, cause bank erosion by the right bank immediately downstream of the emergency spillway, threatening stability of the dam itself. Due to complex interaction between the parameters of flow and sediment transport at the given location, an approach involving a spatial (3D) mathematical model of flow and sediment transport, aimed at solving such complex processes, is investigated in this paper. An optimum solution meeting all requirements for the stability of structures in question has been reached by the model, through comparison of the results generated by the existing conditions with the result provided by the measures proposed to fix the problems.

Influence of mechanical layering and natural fractures on undercutting and rapid headward erosion (recession) at Canyon Lake spillway, Texas, U.S.A

This study investigates the role of mechanical layering and fractures on flood-related erosional undercutting and resulting rapid spillway recession. In the summer of 2002, 86 cm of rain fell in an 8-day period across the Guadalupe River drainage basin in central Texas, causing Canyon Lake reservoir to completely fill and overtop the emergency spillway for the first time. The resulting flood incised a gorge into the mechanically layered Glen Rose Formation and caused headward erosion (recession) at the downstream edge of the emergency spillway. Comparison of pre- and post-flood imagery and assessment of flood records indicates that maximum recession localized at the northern end of the emergency spillway where 28 m recession occurred. This recession occurred at an estimated rate of up to 10 m/day during the first ~3 days of the flood, which is among the highest rates of recorded bedrock recession. Analysis of historical photographs, field observations and measurement of erosional undercutting, along with measurements of fracture orientation, fracture spacing, and mechanical rebound are used to understand rock mass characteristics that influenced erosional undercutting and rapid recession of the spillway. Evidence of significant undercutting was observed where incompetent argillaceous wackestone (marl) underlies competent limestone. These results reveal that the greatest amount and rate of recession of the spillway was associated with undercutting and toppling collapse of fracture-bounded limestone blocks. Block size may be a factor in continuation of the process, in that large blocks may accumulate at the base of the scarp and inhibit continued erosional undercutting, whereas in other areas smaller eroded blocks can be carried away by the floodwaters and undercutting may continue, facilitating recession. The combination of mechanical contrast between layers and natural fractures in competent layers together contributed to exceptionally high rates of headward erosion. Observed rock mass erodibility behavior was in the range of medium to high erodibility in limestone with widely spaced fractures that would normally be expected to have very low erodibility. Bulk rock mass erodibility in this situation was similar to the most erodibile layer, specifically, the marl at base of spillway pour-off cliff.

Future Changes in the Hydrologic Cycle Associated with Flood-Producing Storms in California

AbstractCalifornia receives much of its precipitation from cool-season atmospheric rivers, which contribute to water resources and flooding. In winter 2017, a large number of atmospheric rivers caused anomalous winter precipitation, near-saturated soils, and a partial melting of snowpack, which led to excessive runoff that damaged the emergency spillway of the Oroville Dam. Given the positive and negative impacts ARs have in California, it is necessary to understand how they will change in a future climate. While prior studies have examined future changes in the frequency of atmospheric rivers impacting the West Coast of the United States, these studies primarily use coarse global climate models that are unable to resolve the complex terrain of this region. Such a limitation is overcome by using a high-resolution convection-permitting regional climate model, which resolves complex topography and orographic rainfall processes that are the main drivers of heavy precipitation in landfalling atmospheric rivers. This high-resolution model is used to examine changes to precipitation and runoff in California’s cool season from 2002 to 2013, particularly in flood-producing storms associated with atmospheric rivers, in a future, warmer climate using a pseudo–global warming approach. In 45 flood-producing storms, precipitation and runoff increase by 21%–26% and 15%–34%, respectively, while SWE decreases by 32%–90%, with the greatest changes at mid-elevations. These trends are consistent with future precipitation changes during the entire cool season. Results suggest more intense floods and less snowpack available for water resources in the future, which should be carefully considered in California’s future water management plans.

THE KA LOKO TRAGEDY

The North Shore of Kauai is known for its beautiful beaches, scenery, and tropical paradise. However, the community has faced adversity and tragedy due to the lack of necessary engineering inspections, failure to apply for building permits, negligence, and complacency on behalf of property owner James H. Pflueger, the State of Hawaii, and County of Kauai. The Ka Loko dam broke on March 14, 2006 and the rushing waters wreaked havoc on the community causing mass destruction and ultimately claimed the lives of seven individuals. Multiple civil lawsuits and a criminal case followed where the owner pled no contest to seven counts of manslaughter and one count of reckless endangerment. The purpose of this paper is to conduct a brief analysis of the events surrounding the tragedy and extract the lessons learned and impacts it may have to prevent future disasters from occurring. Among the issues, it was discovered that the emergency spillway had been filled with earth, and that dam inspections were irregularly conducted.

Performance Evaluation of Jatibarang Reservoir Due to Land Use Changing

Jatibarang Reservoir is located on the Kreo River. These reservoir functions are flood control, water supply, and hydroelectric power. The total capacity is around 20.4 million m3. The spillway is designed at elevation +148.9 with a width of 15 m, capacity Q50 = 240 m3/s, and an emergency spillway at +151.80 m, the width of 60 m with a capacity of 1350 m3/s. This paper aims to evaluate the performance of reservoirs in their function as flood control, due to land-use changes in upstream of the reservoir catchment area. The method which was used is the HEC HMS. Land use map data is used for the 2016 and spatial planning map of Central Java province for 2011-2031. The results were obtained are the hydrological parameters increase in CN and imperviousness, decrease in initial storage, and initial abstraction wich increasing flood discharge. The impact of this, an emergency spillway that was designed for discharges higher than Q50, must function at discharge that smaller than Q50. The initial design, Q50 water level elevation below +151.8, but with the change in hydrological parameters, water level elevation of Q50 increase up to + 152.2.

NERACA AIR SITU CIKARET DAN SITU KABANTENAN DI KABUPATEN BOGOR MENGGUNAKAN PEMODELAN HIDROLOGI SWAT

Bogor regency which is located in the middle of the Ciliwung basin centered in Cibinong city is experiencing rapid urban development. However, with the rapid urban development, most of these small lakes in either disappear or in degraded conditions. In this area presently still maintain 95 urban small lakes or locally known as ‘situ’. Situ has multifunction such as water retention for flood mitigation, irrigation for urban agriculture, fisheries, water sport activities, and ecotourism. The objective of this study was to analyze the water balance of situ. The model was calibrated and validated on the Kampung Kelapa river gauge with manual calibration. The Soil Water Assesment Tool (SWAT) is a hydrological model designed to predict the impact of land use and management on water, sediment and agricultural chemical yields in watersheds, The model was applied to Situ Kabantenan and Cikaret for modeling of the hydrological water balance. The SWAT model simulation was done for the periods of 2008–2015 while it used land use information in 2014. The Calibration was done in 2014 and the validation in 2013, the R2 and Nash Sutcliffe Efficiency (NSE) of the calibration were 0,58 and 0,55 respectively and the validations were 0,54 and 0,49 respectively. The monthly average of volume of Situ Kabantenan and Situ Cikaret from the simulation were 136,955 m3 and 508,907 m3, respectively. The annual inflow of Situ Cikaret was 24,693,822 m3/year and outflow was 25,177,593 m3/year, precipitation was 648,520 m3/year, evaporation was 166,543 m3/year, delta storage 1,794 m3/year, respectively. The average inflow discharge of Situ Cikaret (2008–2015) were 0.78 m3/s and outflow discharge was 0.80 m3/s. The water balance results showed that both sites were in good condition since they have never passed the emergency spillway, but their function needs to be optimized as a flood controller in the Ciliwung Watershed. This study also showed that the SWAT model can be utilized as a potential monitoring tool, especially for small urban lakes as water reservoirs.

Evaluation of Potential Reservoir Deficiency Due to Climate Change, Kesem Kebena Dam, Ethiopia

Abstract Flood is an excess inundation of water on a surface and difficult to manage. The flood occurred in previous decades of Afar region of Ethiopia, consequently, leads to the death of human beings, destruction of infrastructures, an annihilation of massive hydraulic structures, and downstream properties. The main responsible factors for the flood incidences of the region are climate change, global warming, deforestation, and desertification. Climate change, however, is the foremost reason of increasing flood hazard. To coincide with this, hydraulic structures are designed based on the previously recorded flow data of a river. In Ethiopia, numerous earthen dams are constructed. The water storage capacity of dams is determined by the appraised flood of the upstream catchment: however, when the catchment flood increases due to climate extremes, the constructed structures cannot carry and going to demolish. The extra water that rises due to climate change from the catchment has to be removed before joins to the reservoir. This study has evaluated the potential reservoir deficiency of Kesem Kebena dam due to climate change. The study has comprehended different methods based on scientific criteria and selects the appropriate measure. As per the research output, the excess water that will arise from the catchment and add to the reservoir can be controlled by diversion floodways (Emergency spillways). The study has determined the amount of excess flood join to the reservoir for the excess rainfall incident month (August) for 100 years return period. Its magnitude is 85.76m3/s. The emergency spillway is the best means to divert such unwanted water before joining to the reservoir. Its hydraulic design is discussed in the study.

Johnstown's Flood of 1889: Power Over Truth and the Science Behind the Disaster, Neil Coleman

<i>Johnstown's Flood of 1889: Power Over Truth and the Science Behind the Disaster</i>, Neil Coleman

Evaluating design criteria for high hazard dams in a changing climate

The 100-year flowrate is an important design criterion for emergency spillways of high hazard dams. With change in climate, there is the potential for these events to vary in frequency and magnitude. This work quantified how changes in the 100-year flowrate may affect emergency spillway activation. Peakflow data were used to analyze changes in the 100-year flowrate. Reservoir routing was used at a high hazard dam under potential future flow scenarios (-7%, +6%, +12%, +20%, and +30%). The spillway of the dam was predicted to be reached by approximately a 12% increase in 100-year flow, which was matched and exceeded by historical increases in 100-year flow from unregulated gages of up to 19%. These results suggest that emergency spillway designs need to consider potential changes in 100-year flow. This research was supported by the NASA WVSGC Graduate Research Fellowship.

Experimental study and artificial intelligence-based modeling of discharge coefficient of converging ogee spillways

ABSTRACT Converging ogee spillway is employed as an emergency spillway constructed to control natural disasters such as instant floods. This paper presents an experimental study and artificial intelligence-based modeling of the discharge coefficient (Cd ) of the converging ogee spillway (with a curve axis). The ogee spillway structure was tested in both symmetrical and asymmetrical convergence of training walls ranging from 0° to 120°. Through the visual observation, it was found that the tailwater submergence, the depth of approach, the crest and spillway geometry, the head different from design head, and downstream floor position are the important factors that alter the Cd of the converging ogee spillway. Moreover, two different methods (e.g. gene expression programming (GEP) and adaptive neuro fuzzy inference systems (ANFIS)) were assessed for modeling the Cd using original experimental data. Based on the obtained results, both the GEP and ANFIS models have reliable performance in simulating the Cd . Moreover, the performance of GEP model was found to be slightly better than the ANFIS technique. According to the outcome of sensitivity analysis, the ratio of the total upstream head on the spillway to design head (H/Hd ) is the most important parameter for the optimum modeling of the Cd of the converging ogee spillway.

Influential parameters on submerged discharge capacity of converging ogee spillways based on experimental study and machine learning-based modeling

AbstractOgee spillways with converging training walls are applied to lower the hazard of accidental flooding in locations with limited construction operations due to their unique structure. Hence, this type of structure is proposed as an emergency spillway. The present study aimed at experimental and machine learning-based modeling of the submerged discharge capacity of the converging ogee spillway. Two experimental models of Germi-Chay dam spillway were utilized: one model having a curve axis which was made in 1:50 scale and the other with a straight axis in 1:75 scale. Using visual observation, it was found that the total upstream head, the submergence degree, the ogee-crest geometries and the convergence angle of training walls are the crucial factors which alter the submerged discharge capacity of the converging ogee spillway. Furthermore, two machine-learning techniques (e.g. artificial neural networks and gene expression programming) were applied for modeling the submerged discharge capacity applying experimental data. These models were compared with four well-known traditional relationships with respect to their basic theoretical concept. The obtained results indicated that the length ratio () had the most effective role in estimating the submerged discharge capacity.

Winter Storm Conditions Leading to Excessive Runoff above California’s Oroville Dam during January and February 2017

AbstractDuring winter 2016/17, California experienced numerous heavy precipitation events linked to land-falling atmospheric rivers (ARs) that filled reservoirs and ended a severe, multiyear drought. These events also caused floods, mudslides, and debris flows, resulting in major socioeconomic disruptions. During 2–11 February 2017, persistent heavy precipitation in the northern Sierra Nevada culminated in a rapid increase in the water level on Lake Oroville, necessitating the activation of an emergency spillway for the first time since the Oroville Dam was installed and forcing the evacuation of 188,000 people. The precipitation, which mostly fell as rain due to elevated freezing levels, was focused on the western slope of the Sierra Nevada in connection with orographic forcing linked to two successive ARs. Heavy rain fell on saturated soils and a snowpack produced by antecedent storms and thereby resulted in excessive runoff into Lake Oroville that led to a damaged spillway and complicated reservoir operations.

Grout Curtain Construction At Bolivar Dam, Ohio

Abstract Bolivar Dam, located in eastern Ohio, is an embankment dam constructed by the U.S. Army Corps of Engineers in 1937 as part of the Muskingum River Basin Project for flood control. As a result of seepage concerns observed at the dam during several flood events over the life of the project, seepage reduction measures, including a partial-depth seepage barrier wall through the embankment and a grout curtain in the left abutment, were designed and constructed. These dam safety modifications were constructed between 2014 and 2016. During flood events, Bolivar Dam experiences excessive seepage through the glacial outwash foundation as well as through a network of open joints within the left bedrock abutment. Seepage in the bedrock abutment could erode/scour the dam embankment at the bedrock contact, potentially leading to dam failure. To lower this potential risk of dam failure in the left abutment, a grout curtain was constructed between the new seepage barrier wall and an existing grout curtain across the emergency spillway. The new grout curtain is designed to impede groundwater seepage, resulting in reduced groundwater velocity/energy downstream of the grout curtain, thereby decreasing its potential to scour or transport fine-grained embankment material. The double-line grout curtain is approximately 65 ft (19.8 m) deep and 400 ft (121.9 m) long and was completed in November 2015 as part of a major dam safety modification project. Two thin limestone units encountered during drilling proved to be problematic and posed various challenges during construction. It was common during drilling to lose water circulation within the vicinity of these limestone units, which then required the use of downstaged grouting methods. The majority of the grout volume for the project was placed within these downstaged intervals. This article presents the risk-informed decisions that were made during both design and construction of the grout curtain and includes various lessons that were learned during this process.