• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.25-33
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• 2021

This study was conducted to understand the deposition characteristics of debris flow and to analyze the reduction effect of debris flow damage by installing a berm. Flume experiments were performed in consideration of various channel slope and volumetric sediment concontration. In order to analyze the reduction effect of debris flow damage by installing a berm, the cases of not installing a berm and the cases of installing a berm were compared. In this study, the runout distance, total travel distance, and mobility ratio were analyzed among the deposition characteristics of debris flow. First, the deposition characteristics of debris flow according to the change of the channel slope were analyzed, and the deposition characteristics of debris flow due to the change of volumetric sediment concentration were analyzed. In addition, the change rate of debris flow deposition characteristics when a berm was installed was calculated based on the case when a berm was not installed. As a result of the experiments, it was confirmed that the channel slope and volumetric sediment concentration had a significant effect on the deposition characteristics of debris flow. In addition, when a berm is installed on the slope, the runout distance and mobility ratio of debris flow are greatly decreased, and the total travel distance is increased. This means that installing a berm delays the movement of debris flow and reduces the potential mobility of debris flow. The results of this study will provide useful information for understanding the deposition characteristics of debris flow. Furthermore, it is expected to help in the design of a berm.

• Journal of the Korean GEO-environmental Society
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• v.14 no.11
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• pp.5-12
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• 2013

The purpose of this study is to estimate the behavior and the mechanism of debris flow at the end of mountain side when a berm was set on the inclined plane. The numerical model was performed by using the Finite Difference Method(FDM) based on the equation for the mass conservation and momentum conservation. In order to measure the behavior of the debris flow, the debris flow of a straight channel slope and the debris flow of channel slope with 3 types of berms were compared. First, the flow discharge and the sediment volume concentration at the downstream of the channel slope, depending on the various berm width and the different inflow discharges at the upstream of the channel were analyzed. The longer the berm width, the flow discharge at the downstream of the channel was decreased and the high flow fluctuation was reduced by a berm. And it means that a berm can effect for the delay of the debris flow. Through Root Mean Square ratio(RMS) comparison, the flow discharge of the channel slope with a berm was lower than that of a straight channel slope. The longer the berm width, for the sediment volume concentration, an inflection point did not show but mild curve. Because the low sediment concentration with water mixture by a berm continuously flow at the downstream end, it will be effect for reducing the disaster caused by debris flow. The results of this study will provide useful information in predicting and preventing disaster caused by the debris flow.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.2
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• pp.112-122
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• 2012

The damage analysis of coastal structure is very important as it involves many design parameters to be considered for the better and safe design of structure. In the present study experimental data for non-reshaped berm breakwater are collected from Marine Structures Laboratory, Department of Applied Mechanics and Hydraulics, NITK, Surathkal, India. Soft computing techniques like Artificial Neural Network (ANN), Support Vector Machine (SVM) and Adaptive Neuro Fuzzy Inference system (ANFIS) models are constructed using experimental data sets to predict the damage level of non-reshaped berm breakwater. The experimental data are used to train ANN, SVM and ANFIS models and results are determined in terms of statistical measures like mean square error, root mean square error, correla-tion coefficient and scatter index. The result shows that soft computing techniques i.e., ANN, SVM and ANFIS can be efficient tools in predicting damage levels of non reshaped berm breakwater.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1919-1924
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• 2006

In this study, the run-up of water waves on slopes of s-berm breakwaters was investigated by performing a series of hydraulic experiments. The run-up height was analyzed in detail by using the effects of wave steepness and surf similarity parameter. In general, the run-up heights were decreased as the height and the width of berm were increased. However, the variation of run-up height was small for change of wave steepness and surf similarity parameter.

• Journal of the Korean earth science society
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• v.41 no.1
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• pp.19-30
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• 2020

To understand the impact of typhoons on Gamji gravel beach Taejongdae in Busan, we carried out beach profiling using a VRS-GPS system and a Drone photogrammetry for the typhoons 'Kong-rey' invaded in October 2018 and 'Danas' in July 2019. In addition, grain sizes are analyzed to investigate the overall distribution pattern of gravels on the beach, and the beach topography is surveyed periodically to confirm the recovery rate of the beach. Grain-size analysis reveals that mean gravel sizes, in general, become finer from -6.2Φ to -5.4Φ towards the east in the seashore line direction. Variation in mean sizes is obviously observed in the cross-shore direction. Gravels in the swash zone are relatively fine about -4.5Φ in size and equant in shape, whereas the coarse and oblate gravels ranged from -5Φ to -6Φ are found in the berm. Gamji gravel beach particularly has two lines of berms: a lower berm situated facing beach and an upper berm about 10 m landward. After the typhoon Kong-rey passed by, about 1.4 m of severe erosion in upper berm occurred, and the berm eventually disappeared. On the backshore of the upper berm about 50 cm of erosion took place so that the elevation became lower. However, tangible erosion was not observed in the lower berm. When typhoon Danas hit, rated as mild storm, both upper and lower berm were eroded out. However, about 50 cm of deposition occurred only in the backshore. Only three days later, the new lower berm was formed, meaning that sedimentation rate must be high. This result indicates that Gamji gravel beach is recovered very fast from erosion caused by the typhoons when it is under the fair-weather condition even though beach morphology changes dramatically in a short period of time. Gravel beach is estimated to be or evaluated very resilient to typhoon erosion.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.03a
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• pp.81-88
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• 1997

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2303-2315
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• 2013

In general, the waterway was installed for drain water from steep slope and waterway cover was set up to prevent overflow and water separation at berm of waterway. In this study, hydraulic experiment was conducted to analyze the flow characteristics and enact standard design criteria of the waterway. Hydraulic experimental apparatus which can change the slope of waterway and the length of berm were installed to analyze of flow characteristics at the waterway. The slopes of waterway were $40^{\circ}$, $50^{\circ}$, $60^{\circ}$, and $70^{\circ}$ and the range of discharge were 1.0~5.6 ${\ell}/s$. The flow in berm was distinguished two types such as hydraulic jump and splash flow. These kinds of flows depended on the rates of discharge in waterway. When inlet discharge was below 1.1~2.0 ${\ell}/s$, the separation phenomenon of water was generated at upper and lower portion in berm by the splash flow. The scattering range of water particles and length of water separation was measured depending on the slope of waterway. The start point of scattering was about 20 cm(1.3B) from the place connected upper waterway with brem and the length of water separation was till 210 cm(3.5B) from the place connected lower waterway with brem. Therefore, the waterway cover needed to install from starting of berm to 1B and from the lower part of berm to 3.5B.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.147-153
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• 2006

In this study, the run-up of water waves on slopes of s-berm breakwaters was investigated by performing a series of hydraulic experiments. The run-up height was analyzed in detail by using the effects of wave steepness and surf similarity parameter. In general, the run-up heights were decreased as the height and the width of berm were increased. However, the variation of run-up height was small for change of wave steepness and surf similarity parameter.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.202-208
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• 2001

Explicit approximation has been developed to estimate the run-up height on S-berm breakwater on the basis of Saville's hypothetical slope method. For the explicit expression of run-up height several relations are developed to represent the ratio of run-up height against breakwater slope with various conditions of water depth and wave steepness. For the verification of explicit approximation the results are compared with Saville's measurement data and simple expression of Delft Hydraulic Laboratory.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.113-118
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• 2002

Wave overtopping is one of the most important hydraulic responses of breakwater because it significantly affects its functional efficiency, the safety of transit and mooring on the rear side, wave transmission in the sheltered area, rear side armor stones and to some extent, the structural safety itself. The hydrodynamic characteristics of low crest breakwater by the overtopping rate can be summarized as follows: 1. It is better to use maximum overtopping rate than to use mean overtopping rate for design of coastal structures. 2. Maximum overtopping rate was increase with wave steepness (between 0.01 and 0.02). 3. Overtopping rate is decreased when relation length of berm was over wave length.