• Journal of The Geomorphological Association of Korea
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• v.28 no.3
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• pp.13-26
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• 2021

In mountain gully, channelized debris flow is an important phenomenon in the process of topographical change. Social infrastructure as roads may be damaged by channelized debris flows, but there has been little information about their occurrence and movement to prepare for the risk of the debris flow. Most of the channelized debris flows occur during heavy rains in mountainous valleys that are difficult to access, so there are not many field data. In this study, the topographical characteristics of the catchment, the rainfall and runoff related to the debris flow, the sedimentary pattern and the cross-sectional change of the channel bed, and the underflow velocity of the gravel bed have been investigated and analyzed in the Singi gully where the channelized debris flows occurred. In the catchment, there was almost no sediment runoff because the vegetation combine with the debris landforms and covered the surface. Therefore, the obvious cause of the channelized debris flows is the collapse of the slope and bed of the gully. Even if the gravel, cobbles, and boulders of the channel bed were lost by debris flow, the thalweg change due to debris flow may not be significant because they are supplied from the gully side slope normally. After the gabion structures were installed, the debris flow increased the thalweg change, bed erosion and side slope of the gully. Various sedimentary structures in the gully were classified according to the factors supporting the sedimentation. The hypsometric curve of the gully reflects the debris landforms and vegetation characteristics of the watershed and the sediment runoff due to debris flow, etc. The relationship between the flow velocity and the hydraulic gradient was non-linear under the condition that the porous medium with gully bed gravels is saturated with water. These results may be used as basic data for channelized debris flow research.

• Journal of Korea Water Resources Association
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• v.57 no.6
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• pp.421-435
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• 2024

In April 2023, a wildfire broke out in Gangneung located in the east coast region due to the influence of the Yanggang-local wind. In this study, GIS-based RUSLE(Revised Universal Soil Loss Equation) and SEMMA (Soil Erosion Model for Mountain Areas) were used to evaluate the erosion rate due to vegetation recovery in a small watershed of the Gangneung WUI(Wildland-Urban Interface) fire. The small watershed of WUI fire has a low altitude range of 10-30 m and the average slope of 10.0±7.4° which corresponds to a gentle slope. The soil texture was loamy sand with a high organic content and the deep soil depth. As herbaceous layer regenerated profusely in the gully after the wildfire, the NDVI (Normalized Difference Vegetation Index) reached a maximum of 0.55. Simulation results of erosion rates showed that RUSLE ranged from 0.07-94.9 t/ha/storm and SEMMA ranged from 0.24-83.6 t/ha/storm. RUSLE overestimated the average erosion rate by 1.19-1.48 times compared to SEMMA. The erosion rates were estimated to be high in the middle slope where burned pine trees were widely distributed and the slope was steep and to be relatively low in the hollow below the gully where herbaceous layer recovers rapidly. SEMMA showed a rapid increase in erosion sensitivity under at certain vegetation covers with NDVI below 0.25 (Ic = 0.35) on post-fire hillslopes. Gentle slopes with high organic content and rapid recovery of natural vegetation had relatively low erosion rate compared to steep slopes. As subsequent infrastructure and human damages due to sediment disaster by heavy rain is anticipated in WUI fire areas, the research results may be used as basic data for targeted management and decision making on the implementation of emergency treatment after the wildfire.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.13-33
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• 2021

Successful sediment management at the watershed scale requires an understanding of the erosion, transport and sedimentation processes at the specific site scale. However, studies on the sediment runoff characteristics in a small uppermost watershed, which serves as a sediment supply function, are very rare. Therefore, this study attempted to investigate the fluctuations in major sediment supply areas and sediment runoff in the uppermost mountain small watershed, and for this purpose, ArcSWAT (Soil and Water Assessment Tools with GIS interface) was applied to the Woldong reservoir catchment located in Gosam-myeon, Anseong-si, Gyeonggi-do. The model results were manually calibrated using the monitoring data of the Woldong reservoir sedimentation rate from 2005 to 2007. It was estimated that annual average of 34.4 tons/year of sediment was discharged from the Woldong reservoir basin. This estimate almost coincided with the monitoring data of the Woldong reservoir during the low flow period but tended to be somewhat underestimated during the high flow period. Although the SWAT model does not fully reflect the erosion process of gully and in-channel, this underestimation is probably due to the spatial connectivity of sediment transport and the storage and reactivation of the sediment being transported. Most of the forested hillslopes with a well-developed organic horizon were evaluated as having a low risk of erosion, while the places with the highest risk of erosion were predicted to be distributed in the logged area with some weeds or shrubs (classified as pasture) with relatively steeper slopes, and in the bare land. The results of this study are expected to be useful in developing strategies for sediment control and reservoir management.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.193-202
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• 2011

Kompsat EOC-1 imagery, high resolution air-photo imagery and Shalstab model were used to analyze the geomorphic characteristics of the place of debris flow occurred by typhon "RUSA" in 2002, Macheon-Myen, Gyeongsang prefecture, Republic of Korea. On gully-head over 35 degree of slope angle, almost debris flow started, where slope angle is more than internal friction angle. The result simulated by Shalstab model presented larger vulnerable area to debris flow than the area where debris flow really occurred, this error would be attributed to the assumption for steady-state condition with full saturated surface. To predict the debris flow accurately, further study for rainfall and soil water flow will be needed.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.2
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• pp.85-92
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• 2008

This study, the one concerning the evaluation analysis of the function of the wind generation using KLAM_21, has examined closely how the wind really flows on the space of the city, working with the object of case location. In the first place, the cold air formed at upper stream of Sincheon river, a ravine of whole area of Gachang gully and an inclined plane of neighboring mountainous district, flows to the north and expands itself along the upper stream of the Sincheon river, and as the time passes, it is tending upwards in the change of the volume and height as well as of the velocity and direction, of the cold air. It was learned that this phenomenon has made it clear that the spatial features of this area give rise to very good condition in generating and flowing the cold air. Meanwhile, it has been shown that in the area of park in the Ap-mountain, the generation and flow of the cold air are much interrupted because of the overpass traversing the whole area of the park of Ap-mountain, the congested area of large-scaled apartments and the urban development activities constructing the building in the park, and the volume and height of the cold air has been grown very small. In conclusion, It has been learned that for maximization of the spatial effect of the wind corridor, the areas where the cold air is generated, flowed, accumulated, and maintained, have to be connected spatially, and this spatial connection has a close relation with spatial features of the area.

• Journal of the Korean Geographical Society
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• v.38 no.4
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• pp.630-639
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• 2003

This study aims to analysis the distribution and change of cropland and forest, the Onseong, Saebyeol, and Eundeok counties on the lower reach of Duman(Tumen) river, northeast Korea, using 1992 year Landsat TM data, 2000 year Landsat ETM data, and digital terrain elevation data(DTED). Land cover and land use of the study areas are classified into cropland, forest, village, and water body, using the supervised classification method including 1:50,000 DTED analysis, image band composition, and principal component analysis(PCA). Results of quantitative analysis present that each growth rate of cropland of Onseong and Eundeok are 22.8% and 14.7% corresponding to decreasing rates of forest, 8% and 13.6% during 8 years from 1992 to 2000. In Onseong, Saebyeol, and Eundeok, each values of mean elevations and slope gradients increased to 192m, 95m, and 91m from 157m, 85m, and 78m, and to 6.6$^{\circ}$, 3.0$^{\circ}$, and 4.4$^{\circ}$ from 5.2$^{\circ}$, 2.5$^{\circ}$, and 3.0$^{\circ}$. Especially, in case of newly developed cropland, the values of mean elevation and mean gradient have 225m, 122m, and 127m, and 9.4$^{\circ}$, 5.1$^{\circ}$, and 8.0$^{\circ}$, in above three regions. These new croplands were developing along to deeper valleys and toward lower hill and mountain slope up to knickpoint zone of gradient change. Deforested lands for cropland have formed irregular pattern of patch-type, and become sources for the sheet erosion, rilling and gulleying in mountain slope and sedimentation in local river channel. Though there were no field checking, analysis using landsat images and GIS mapping can help understand actual environmental problems relating to cropland development of mountain slope in North Korea.

• Economic and Environmental Geology
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• v.6 no.1
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• pp.29-64
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• 1973

A land resources survey in the semi-arid area, Mula in S. E. Spain, of $400km^2$ is compiled. The basic aim of the project is to investigate the intrinsic qualities of the land resources of the area by means of applying an integrated method of natural resources survey mainly concerning with analysis and synthesis of land complexes, each of them represents an area or a group of areas with similar patterns of landforms, soils and vegetation, based on a geomorphological approach. The area is characterized by a linear arrangement of relief pattern with an asymmetric homoclinal repetition of slope attitudes elongating WSW-ENE, dipping steeply on the NW sides and gently on the SE sides, which have been resulted from the post-Alpine folding of the Triassic to Cretaceous limestone, the Eocene limestone, the Oligocene sandstone and the lower Miocene limestone and marl, and the post-lower Miocene faulting, tilting and subsequent differential erosion of the Miocene sedimentary formations. An integrated body of information in geology, landforms, soils and vegetation, which are significantry interrelated as an environmental complex, has been obtained. Using this data, 26 land complexes developing on the various situations of landforms, such as folded mountain ranges, tilted tablelands, bevelled cuestas, degraded hill-lands associating with enormous foots lopes, undulating terrains and terraced or flat plains, have been differentiated, mapped and described. The soils of the area are mostly light colored calcic lithosols which have been derived dominantly from the marly parent materials and developed into remarkable slope catenas in some places depending on the relief conditions. The land uses of the area are mainly characterized by the perennially irrigated cultivation of citrus orchards along the terraced alluvial deposits fringing the Segura and Mula River, and the dry-land cereal cultivation on gentler slopes. Pioneer dry-land cultivations within the shrubs on steeper slopes are restricted to the unchannelled tributary drainage floors. The availability of water is a fundamental controlling factor for existence of native and cultivated vegetation as a whole, and a number of active processes including sheet wash and gully erosion, especially on the scarp slopes, are the other important factors to be considered in conservation and management of the land in the area.

• Journal of the Korean association of regional geographers
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• v.19 no.2
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• pp.234-245
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• 2013

In order to examine the amount and rate of soil erosion on Ridge Traversing Trail in Jirisan National Park, a cross-sectional area of hiking trail were monitored at 16 sites in Nogodan - Samdobong section from November 2011 to April 2012. Although all sites demonstrates an enlarged cross-section of trail, the amount of soil erosion varies from site to site: 54.9 to $908.8cm^2$. It suggests that the erosional rate ranges from $0.1cm^2/day$ to $1.72cm^2/day$. The erosional amount is also varied with a trail type: $109.3cm^2$ for a shallow gully-like trail to $573.2cm^2$ for a unilateral trail. However, the cross-sectional change is larger on a sidewall than a tread irrespective of a trail type. The erosional amounts of November to April are smaller than that of May to October. In particular, the erosional amount of November 2011 to April 2012 is smaller than the depositional amount, implying a reduced cross-section of trail. Pipkrake action puts loose soil particles on a sidewall on March and April, and then rainwash due to a heavy rainfall takes them away after May. It seems to be the most predominant erosional process in Ridge Traversing Trail. A sidewall facing north shows a larger amount of erosion than a sidewall facing south. It also implies a difference in the development of a pipkrake according to an aspect. The small amount of erosion and cross-sectional decrease, which is usually observed on April, results from the combined effect of frost heaving, pipkrake action, a small rainfall and a temporary suspension of trampling. It is necessary to establish the monitoring system of trail erosion in terms of the management of hiking trail in a mountain national park.