• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.258-266
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• 2019

This study was conducted to apply natural river technologies to levees and examine the results. The new eco-friendly bio-polymer was applied, a combination of eco-friendly biopolymers and soil, to levee slope to enhance durability and eco-friendliness and to establish reinforcement measures against unstable levees due to overtopping. A semi-prototype levee of 1 m in height, 3 m in width, with a 1:2 slope and 5 m length, was constructed at the Andong River Experiment Center. The bio-soil mixed with the biopolymer and the soil at an appropriate ratio was treated with a 5 cm thickness on the surface of levee to perform the stability evaluation according to overtopping. Using the pixel-based analysis technique using the image analysis program, the breached area of levee slope was calculated over time. As a result, the time for complete decay occurs more than 12 times than that of ordinary soil levee. Therefore, when the new substance is applied to the surface of levee, the decay delay effect appears to be high.

• Ecology and Resilient Infrastructure
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• v.6 no.2
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• pp.120-127
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• 2019

Medium-scale levee experiments were performed to monitor the infiltration and failure of levee body by applying fiber optic temperature sensing. In this study, bio-polymer soil was spread in the levee slope to increase the strength and intensity. Therefore, the infiltration and failure by overflows were produced in a different way compared to general soil type of levees. This was also observed in the experiment data for temperature changes monitored by fiber-optic distributed temperature sensing system. Through the analysis of temperature changes at specific location by time, the location and initiation time for physical changes and infiltration in levee body could be identified based on temperature variation. In this experiment, the time of rapid changes in temperature was ahead in the inland slope rather than the forceland slope. It was corresponding to the levee failure sequence of first inland slope failure and then the forceland slope failure.

• Journal of Korea Water Resources Association
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• v.54 no.3
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• pp.181-190
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• 2021

In this study, a large-scale levee breach experiment from lateral overflow was conducted to verify the effect of the new reinforcement method applied to the levee's surface. The new method could prevent levee failure and minimize damage caused by overflow in rivers. The levee was designed at the height of 2.5 m, a length of 12 m, and a slope of 1:2. A new material mixed with biopolymer powder, water, weathered granite, and loess in an appropriate ratio was sprayed on the levee body's surface at a thickness of about 5 cm, and vegetation recruitment was also monitored. At the Andong River Experiment Center, a flow (4 ㎥/s) was introduced from the upstream of the A3 channel to induce the lateral overflow. The change of lateral overflow was measured using an acoustic doppler current profiler in the upstream and downstream. Additionally, cameras and drones were used to analyze the process of the levee breach. Also, a new method using 3D point cloud for calculating the surface loss rate of the levee over time was suggested to evaluate the performance of the levee reinforcement method. It was compared to existing method based on image analysis and the result was reasonable. The proposed 3D point cloud methodology could be a solution for evaluating the performance of levee reinforcement methods.

• Ecology and Resilient Infrastructure
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• v.7 no.3
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• pp.181-188
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• 2020

In this study, a temperature distribution sensing method using optical fiber was applied to a large-scale levee experiment, and the applicability of wide-area levee or embankment monitoring technology to observe the changes inside the levee was reviewed. The optical fiber was buried in a large-scale levee, and the temporal and spatial temperature changes were measured according to the water level changes in the reservoir. As the water level of the reservoir increased, the temperature of the embankment slope decreased, and as the infiltration progressed, a change in the spatial location of the temperature change was detected. The temperature change due to embankment infiltration varied depending on the time of the infiltration progress, and the change assumed to be the seepage line could be observed. This study has demonstrated that information about temperature changes inside the levee can be interpreted as the information on the locations that are judged to be relatively vulnerable, investigating the changes in the condition inside the levee.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.34-39
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• 2017

Typical flow regime of overflow at barrier or weir constructed in mid and small streams becomes as the submerged flow during most flood events. One of major causes of barrier failure has been reported as the levee-scour near the conjuction node between barrier and levee. However, most related design guidelines in Korea have not mentioned about the protection of levee around barrier or weir in detail. Furthermore, most previous researches have focused on the flow characteristics of overflow around several types of weirs but they did not have considered the material properties of levee itself. In this study, local scour near barrier was investigated with different material properties of levee under the submerged overflow condition which is assumed to reenact a flood event. Based on results from Fritz et al. and Mavis et al., a theoretical formula was also proposed in initial stage of laboratory experiments. And hydraulic experiments were carried out for the verification of the proposed formula. Levee was installed in the prismetic trapezoidal open channel and most parts were made of concrete except for movable section in which scour was expected to occur for the efficiency of experimental procedure. Each compaction of movable section in levee was followed by the basis of the KS F 2312. Further, after performing the experiments to find the optimum water content for each sediment, the specific amount of water was injected before flowing water. The difference between the proposed theoretical formula and experiment results was not much but considerable, which might be caused by the effect of compaction. For theoretical approach, it seemed that the formula did not take into account the compaction of levee, thus the correction coefficient for levee compaction determined in the literature was considered. Finally, the formula for the length of scour around barrier or weir was proposed, which can be useful to predict a levee in the reference design of revetment in mid and small streams. As shortly future study, scour length of levee around barrier or weir under different flow conditions such as perfect overflow condition will be studied and it will be able to contribute to suggest the design formula or criteria under all overflow conditions near barrier or weir.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.1-8
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• 2018

Levee breaches can result from flooding due to torrential rainfalls, which are linked with recent abnormal climates and the aging of river levees. Breaches have caused enormous property damage and human casualties in lowland areas. Overtopping was found to be the cause for approximately 40% of all cases of breach. In this study, the reasons and mechanisms behind levee breaches were analyzed using hydraulic model testing. The overtopping stability and time delay effect of breaches were assessed for levees made with a new environmentally friendly substance. Image analysis revealed that the total breach time of the levees made with the new substance was about 2.25 times greater than that of an earthen levee. The initial breach rate of a general earthen levee was about 1.43 times higher than that of levees covered with the new substance, and the body collapsed rapidly. The breach mechanisms of levees covered with the new substance were completely different, and it is possible to prevent rapid breaches by mitigation of the breach speed on the slope by resisting overtopping.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.461-470
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• 2011

Abrupt and gradual levee breach analyses on the flat domain were implemented by laboratory experiments and numerical simulations. To avoid the reflective wave from the side wall the experiment was performed in a large domain surrounded by waterway. A numerical model was developed for solving the two-dimensional gradual levee breach flow. The results of the numerical simulation developed in this study showed good agreement with those of the experimental data. However, even if the numerical schemes effectively replicated the trends of the observed water depth for the first shock, there were little differences for the second shock. In addition, even though the model considered the Smagorinsky horizontal eddy viscosity, the location and height of the hydraulic jump in the numerical simulation were not fairly well agree with experimental measurements. This shows the shallow water equation solver has a limitation which does not exactly reproduce the energy dissipation from the hydraulic jump. Further study might be required, considering the energy dissipation due to the hydraulic jump or transition flow from reflective wave.

• Journal of Korea Water Resources Association
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• v.41 no.11
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• pp.1135-1142
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• 2008

Collapse of the levee surrounding structure(culvert) accounts for l0 % of collapse factors of the river levees. In particular, in 2002, the levee collapse that happened at "Nakdong River" at flood usually happened around culverts. This levee collapse has mechanism that the cavity expands with internal erosion at flood after the pore and cavity are formed between culvert and levee copula which are heterogeneity material. The study regarding the cavity or flowing detection around a culvert for safety management of a river levee is in the proceeding. In this study, the characteristic of two sensors could be figured out through an experiment about displacement measure of Flex sensor and FBG sensor and the decision of more suitable sensor was possible for safety supervision of river levee. According to an experiment result, several characteristics of FBG sensor could be known in consistency of the measure data and minute displacement measure part regarding displacement measure and this characteristic may supplement a shortcoming of Flex sensor at this time.

• Ecology and Resilient Infrastructure
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• v.1 no.1
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• pp.29-38
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• 2014

This study analyzed shear stress and erosion characteristic of a vegetated levee embankment with root fiber quantity, which is an important factor for evaluating the stability of it. The averaged root fiber quantity in a vegetated levee revetment was measured by the sampler manufactured by this research. The Phragmites Japonica Steud which is somewhat dominant species in a vegetated levee embankment was selected as an experimental vegetation. As a result of experiment of each flow regime, the shear stress was increased while root fiber quantity was increased and the erosion rate was exponentially decreased as the root fiber quantity was increased. The erosion rate was exponentially decreased as the shear stress was increased which is shown that the increase of shear stress by root fiber quantity results in the increase of erosion resistance in a vegetated soil. The relationship between shear stress and erosion rate with root fiber quantity were analyzed and their regression equations were suggested with high determination coefficients. The hydraulic stability is governed by the increase of shear stress by root fiber quantity and the Froude number of flow characteristic in a vegetated levee revetment.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.941-949
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• 2016

The flow characteristics of the broad-crested side weir considering the levee's side slope of main channel ($ES_{ch}$) was investigated through hydraulic experiment in order to estimate the discharge coefficient equation. For applicability to actual river, levee's side slope of main channel 1:0.5, 1:1 and 1:2 were selected. Experimental results show that the new estimated equation for the discharge coefficient including $ES_{ch}$ is reasonable and effective in actual applications by comparing estimated and measured discharge over side weirs. Through a multiple linear regression analysis the importance of variabes were ordered as $ES_{ch}$ > $h/y_u$ > $L/y_u$ > $Fr_u$. Especially the discharge coefficient equation without $Fr_u$ was suggested, and the high applicability was reviewed by comparing the measured and calculated overflow of broad-chested side weir.