• Journal of The Geomorphological Association of Korea
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• v.27 no.3
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• pp.87-103
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• 2020

The purpose of this study is to evaluate the risk of cropland and man-made infrastructures in a landslide-prone area using a GIS-based method. To achieve this goal, a landslide inventory map was prepared based on aerial photograph analysis as well as field observations. A total of 550 landslides have been counted in the entire study area. For model analysis and validation, extracted landslides were randomly selected and divided into two groups. The landslide causative factors such as slope, aspect, curvature, topographic wetness index, elevation, forest type, forest crown density, geology, land-use, soil drainage, and soil texture were used in the analysis. Moreover, to identify the correlation between landslides and causative factors, pixels were divided into several classes and frequency ratio was also extracted. A landslide susceptibility map was constructed using a bayesian predictive model (BPM) based on the entire events. In the cross validation process, the landslide susceptibility map as well as observation data were plotted with a receiver operating characteristic (ROC) curve then the area under the curve (AUC) was calculated and tried to extract a success rate curve. The results showed that, the BPM produced 85.8% accuracy. We believed that the model was acceptable for the landslide susceptibility analysis of the study area. In addition, for risk assessment, monetary value (local) and vulnerability scale were added for each social thematic data layers, which were then converted into US dollar considering landslide occurrence time. Moreover, the total number of the study area pixels and predictive landslide affected pixels were considered for making a probability table. Matching with the affected number, 5,000 landslide pixels were assumed to run for final calculation. Based on the result, cropland showed the estimated total risk as US $ 35.4 million and man-made infrastructure risk amounted to US $ 39.3 million.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.83-99
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• 2021

Burn severity analysis using satellite imagery has high capabilities for research and management in inaccessible areas. We extracted the forest fire area of the DMZ (Demilitarized Zone) in the western Imjin Estuary which is restricted to access due to the confrontation between South and North Korea. Then we analyzed the forest fire severity and recoverability using atmospheric corrected Surface Reflectance Level-2 data collected from Landsat-8 OLI (Operational Land Imagery) / TIRS (Thermal Infrared Sensor). Normalized Burn Ratio (NBR), differenced NBR (dNBR), and Relative dNBR (RdNBR) were analyzed based on changes in the spectral pattern of satellite images to estimate burn severity area and intensity. Also, we evaluated the recoverability after a forest fire using a land cover map which is constructed from the NBR, dNBR, and RdNBR analyzed results. The results of dNBR and RdNBR analysis for the six years (during May 30, 2014 - May 30, 2020) showed that the intensity of monthly burn severity was affected by seasonal changes after the outbreak and the intensity of annual burn severity gradually decreased after the fire events. The regrowth of vegetation was detected in most of the affected areas for three years (until May 2020) after the forest fire reoccurred in May 2017. The monthly recoverability (from April 2014 to December 2015) of forests and grass fields was increased and decreased per month depending on the vegetation growth rate of each season. In the case of annual recoverability, the growth of forest and grass field was reset caused by the recurrence of a forest fire in 2017, then gradually recovered with grass fields from 2017 to 2020. We confirmed that remote sensing was effectively applied to research of the burn severity and recoverability in the DMZ. This study would also provide implications for the management and construction statistics database of the forest fire in the DMZ.

• Journal of The Geomorphological Association of Korea
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• v.18 no.3
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• pp.93-105
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• 2011

'This study aims to make a choice of 'the new ten beauty spots in Daegu city' based on the analysis of survey of 390 persons selected randomly. The main results are as follows. First, there is no distinctive regional character in making a choice of 'the new ten beauty spots in Daegu city'. Second, 'Gong-Ryeong-jeok-Seol(公嶺積雪) and Buk-Byeok-Hyang-Rim(北壁香林)' among 'Daegusibyeong(大丘十詠)' written by geo-jeong Seo in the Chosun(朝鮮) dynasty are included into 'The new ten beauty spots in Daegu city'. Third, The most picturesque place is Mt. Palgong in Daegu city. Fourth, most people estimate a historical nature as the most important factor in making a choice of 'The new ten beauty spots in Daegu city', but it has not been found such tendency in the selected places as 'The new ten beauty spots in Daegu city'. Fifth, both male and female have chosen Mt. Biseul, Duryu tower, Mt. Palgong and Daegu stadium as 'The new ten beauty spots in Daegu city'. Sixth, natives of Daegu as well as non-natives of Daegu tend to highly prefer Duryu tower, Mt. Biseul and Mt. Palgong.

• Journal of The Geomorphological Association of Korea
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• v.27 no.3
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• pp.41-51
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• 2020

This study tried to reveal incision rate distribution of streams on the northern part of the Sobaek Mountain Range with OSL age dating and geomorphic analysis, and factors influencing on the distribution were also discussed. With results from the previous studies, a total of 10 sites from 7 streams in the study area showed the rates ranging from 0.220 m/ka to 0.297 m/ka. Namhan-gang and Geum-cheon indicated the highest and lowest rates, respectively. Both sides in the northern section in the study area showed similar rates, while the western side in the middle section and the eastern side in the southern section showed higher rates than the other sides. Higher rates were also found from the eastern and northern sides where the Range runs N-S and E-W directions, respectively. Certain relationships with altitude and distance from the divide can be recognized from the rates and may be attributed to active incision with altitude and location of the uplift axis near the present divide. The rates on granite and sedimentary rock were higher than those on metamorphic rock, indicating that bedrock type is one of the important factors influencing on stream incision. Tectonic movement seemed to play some roles in the rates, because areas with lineaments showed lower rates. This study suggests that incision rate distribution of streams on the northern part of the Sobaek Mountain Range reflects various local geomorphic and geologic conditions.

• Journal of The Geomorphological Association of Korea
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• v.26 no.4
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• pp.1-20
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• 2019

In order to establish appropriate policy to control sediment-associated problems, it is necessary to identify the physical characteristics of the reservoir sediments in particulate form in the Yeongsan River. Two time-integrated suspended sediment samplers were installed at Seungchon and Juksan weir on the upper and middle Yeongsan River in July 2012. Reservoir sediment samples were obtained at monthly intervals until October 2014. During the monitoring period, a total of 38 sediment samples were obtained and analyzed. Seasonal trends of suspended sedimentation rates and grain size distributions were examined based on variations in precipitation and discharge fluctuations. Moreover, stream flow characteristics, which has a great influence on the physical characteristics of the river sediment, was analyzed using flow duration curve for the period 2003-2019 at Naju gauging station. Sedimentation rates during summer, when heavy rainfall was concentrated due to the monsoonal front and typhoon, were very high, indicating the positive relationship between sediment concentration and discharge. Particle size analysis of the collected sediment showed that coarse silt and very fine sand-sized sediment dominated most of the Seungchon weir sediment. On the other hand, medium silt-sized sediment dominated the downstream Juksan weir except for a few summer samples. These results implied that the physical characteristics of the suspended sediment are determined not only due to flow fluctuations, but also with regard to the antecedent rainfall conditions, hillslope-channel connectivity, and the supply of materials from various contributing regions. This information about flow characteristics and temporal variations in reservoir sediment can be used for safe management of the weir and discussing the issues on the dismantling of the weirs.

• Journal of The Geomorphological Association of Korea
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• v.28 no.2
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• pp.45-57
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• 2021

In this study, the changes in morphology of Dokdo's gravel beach and its responses due to a storm event were analyzed using the aerial photos and 3D LiDAR data obtained during an ecosystem survey of the Dokdo in 2020. Dongdo Island's gravel beach, shown by aerial photo analysis, increased in area due to sedimentation after the construction of a dock, but there was no more significant changes in area after having grown to Sutdolbawi inside the dock. The changes in volume of the gravel beach were indicated based on 3D data acquired in May and November 2020. A strong typhoon that passed in September, 2002, caused erosion on the backshore and sedimentation on the foreshore and formed the berm by about 1.5 to 2 m high. The analysis showed that the sedimentation was 94.76 m³ in volume and 329 m² in area and the erosion was 250.75 m³ in volume and 603m² in area, which suggested that the overall change of the gravel beach was erosion. The changes in the morphology of the gravel beach on Seodo Island occurred with the seasons along with the changes in area. In addition, berms of different altitudes appeared on the southern and northern sides of the spit, which was also estimated to have formed by the seasonal current direction and wave energy.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.203-212
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• 2011

The objective of this paper is to identify the present-day surficial sediment distribution patterns of the tidal river, Gongneungcheon, through the grain size and statistical analysis. Four major findings of this study are as follows; First, the composition of sediments over the study area are mainly silt in texture. Second, the surficial sediment distribution reveals that grain size becomes coarser as they approach seawards not only in summer but also in winter. It can be concluded that tidal flows play a significant role, especially in winter, in the distribution of surficial sediments in Gongneungcheon. However, samples obtained in summer were relatively small in mean size and showed better sorting compared to those obtained in winter. Third, the mean sizes of the samples on the transects decrease as the distance from the channel increases. Finally, the artificial structure such as a floodgate affects the distribution of the sediments.

• Journal of The Geomorphological Association of Korea
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• v.18 no.1
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• pp.15-27
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• 2011

The canals of China·Northern Europe are different from those of Korea in the phases of the times and physical environment as follows. As the coefficient of river regime is high and the slopes of river is high in our country, the sediments are much deposited on the floor and river channels are meandered and the depth of water are low. So we should dredge the river floor and should construct the dams and lock gates. These will cause streams to be late and to be flooded. The rising and falling of groundwater tables may be fatal to the buildings. The ecosystem will be ruined by water pollution and rising of water levels. We are concerned about the economy of the canals, the low velocity of the canals, reduction of the transportation cost, transshipment cost and terminal cost, tourism·leisure-typed waterway and extreme cost of waterway development. It is proper for us to put in good order and control waterway simply by means of annual schedule, not to construct canal.

• Journal of The Geomorphological Association of Korea
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• v.26 no.3
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• pp.53-67
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• 2019

The purpose of this study is to identify the quality of landslide susceptibility in a landslide-prone area (Jinbu-myeon, Gangwon-do, South Korea) by spatial prediction modeling approach and compare the results obtained. For this goal, a landslide inventory map was prepared mainly based on past historical information and aerial photographs analysis (Daum Map, 2008), as well as some field observation. Altogether, 550 landslides were counted at the whole study area. Among them, 182 landslides are debris flow and each group of landslides was constructed in the inventory map separately. Then, the landslide inventory was randomly selected through Excel; 50% landslide was used for model analysis and the remaining 50% was used for validation purpose. Total 12 contributing factors, such as slope, aspect, curvature, topographic wetness index (TWI), elevation, forest type, forest timber diameter, forest crown density, geology, landuse, soil depth, and soil drainage were used in the analysis. Moreover, to find out the co-relation between landslide causative factors and incidents landslide, pixels were divided into several classes and frequency ratio for individual class was extracted. Eventually, six landslide susceptibility maps were constructed using the Bayesian Predictive Discriminant (BPD), Empirical Likelihood Ratio (ELR), and Linear Regression Method (LRM) models based on different category dada. Finally, in the cross validation process, landslide susceptibility map was plotted with a receiver operating characteristic (ROC) curve and calculated the area under the curve (AUC) and tried to extract success rate curve. The result showed that Bayesian, likelihood and linear models were of 85.52%, 85.23%, and 83.49% accuracy respectively for total data. Subsequently, in the category of debris flow landslide, results are little better compare with total data and its contained 86.33%, 85.53% and 84.17% accuracy. It means all three models were reasonable methods for landslide susceptibility analysis. The models have proved to produce reliable predictions for regional spatial planning or land-use planning.

• Journal of The Geomorphological Association of Korea
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• v.27 no.2
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• pp.65-80
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• 2020

This paper deals with risk assessment of life in a landslide-prone area by a GIS-based modeling method. Landslide susceptibility maps can provide a probability of landslide prone areas to mitigate or proper control this problems and to take any development plan and disaster management. A landslide inventory map of the study area was prepared based on past historical information and aerial photography analysis. A total of 550 landslides have been counted at the whole study area. The extracted landslides were randomly selected and divided into two different groups, 50% of the landslides were used for model calibration and the other were used for validation purpose. Eleven causative factors (continuous and thematic) such as slope, aspect, curvature, topographic wetness index, elevation, forest type, forest crown density, geology, land-use, soil drainage, and soil texture were used in hazard analysis. The correlation between landslides and these factors, pixels were divided into several classes and frequency ratio was also extracted. Eventually, a landslide susceptibility map was constructed using a logistic regression model based on entire events. Moreover, the landslide susceptibility map was plotted with a receiver operating characteristic (ROC) curve and calculated the area under the curve (AUC) and tried to extract a success rate curve. Based on the results, logistic regression produced an 85.18% accuracy, so we believed that the model was reliable and acceptable for the landslide susceptibility analysis on the study area. In addition, for risk assessment, vulnerability scale were added for social thematic data layer. The study area predictive landslide affected pixels 2,000 and 5,000 were also calculated for making a probability table. In final calculation, the 2,000 predictive landslide affected pixels were assumed to run. The total population causalities were estimated as 7.75 person that was relatively close to the actual number published in Korean Annual Disaster Report, 2006.