• The Korean Journal of Quaternary Research
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• v.15 no.1
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• pp.37-45
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• 2001

Morphometric parameters such as cone height, cone height/width ratio($H_{co}$/$W_{co}$), cone height/difference between cone width and crater width ratio($H_{co}$/$W_{co-cr}$) and slope angle are measured to investigate the rates of slope development of scoria cones in Cheju Island. The parameters systematically decrease with increasing age of scoria cones, suggesting that comparative morphology of scoria cones is a useful age indicator. Cone age is most highly correlated with $H_{co}$/($W_{co-cr}$ or average slope angle because summit craters are infilled and eventually removed by erosional processes. The average slope angle is estimated as $\theta_{ave}$= $tan^{-1}$/〔2.$H_{co}$/$W_{co-cr}$〕. Cheju Island was formed through four eruptive stages during Pleistocene. The youngest cones of stage 4(0.1~0.025Ma) have a mean average slope angle of 23.6$\pm$1.7$^{\circ}$, whereas stage 3(0.3~0.1Ma) and stage 2(0.6~0.3Ma) cones have mean values of 18.9$\pm$$1.7^{\circ}C$and 12.6$\pm$$1.9^{\circ}C$, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.380-384
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• 2016

홍수완화의 관점에서 강을 관리하기 위하여 수자원의 이용과 생태계보전, 하천흐름과 형태학적 변화들에 대하여 충분히 이해하고 합리적으로 설명하는 것이 필요하다. 최근에 수변지역에서 발달된 식생은 홍수시에 감속영역과 생물들의 피난처를 제공하는 것 이외에 횡단방향의 혼합작용을 활성화하여 유사와 식물의 씨앗 및 입자성 유기물(POM)을 포착하는 기능을 하고 특히 흐름과 유사이송 및 하도 지형변화에 큰 영향을 주기 때문에 중요하다. 입자성 유기물(POM)은 하천생태계를 지탱하는 에너지원으로서 다양한 형태로 존재하고 미생물의 분해를 받아 무기화된 식생의 번무와 물질순환의 시발점이 되기도 하지만 현재까지 식생영역 내에서 그 공급과정에 관련이 있는 운동기구에 관한 연구는 아직 부족한 실정이다. 따라서 본 연구는 식생영역의 유사퇴적 및 분급작용, 입자성 유기물의 포착을 일으키는 원인과 흐름의 특징 중 식생영역 내에서 흐름방향으로 감속에 주목하여 수리 모형실험을 실시하였고 수변식생에서 부유사와 POM의 퇴적과정에 대하여 검토 및 모델링을 실시하였다. 수리 모형실험 결과 CPOM과 FPOM 모두 유사의 퇴적없이 그 자체로는 퇴적이 되지 않았고 수변식생의 종방향 이송의 경우 식생에 의해 퇴적된 부유사가 사련 형태로 형성이 되어 CPOM이 사련의 배후에서 캡쳐 되었다. 또한 두가지 샘플 움직임의 상호작용은 사련의 파고와 파장의 전파속도를 감소시켰다. 식생지역에서 횡방향 분산의 경우에 대해서는 각각의 유사 크기에 대한 퇴적물의 능선은 식생의 경계를 따라 형성되었고 운동의 범위는 유사 퇴적의 능선에 의해 촉진되어 횡방향으로 확산하며 확장되었다. 이러한 결과를 바탕으로 제한된 경험적인 지식보다 오히려 실험을 통하여 식생을 동반하는 장소에서 유사와 POM의 거동특성 차이 및 간섭작용을 명확히 한 후 현장에서 관측된 현상과 비교 검증이 필요하다고 사료되며 추후에 운동기구를 모델링 및 업그레이드 해 나가는 것이 앞으로의 하천생태계 예측평가에 필요하다고 판단된다.

• Journal of the Korean Geographical Society
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• v.43 no.3
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• pp.276-295
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• 2008

Recent disputes on mountain ranges in Korea have partially been derived from the discordance of the spatial distribution and the extent of mountain ranges presented by different researchers and school textbooks. The lack of consensus on the definition and genesis of mountain ranges adds further confusion. In order to overcome these problems, it is necessary to provide genetically classified mountain range maps for different usages, map scales and educational purposes. This paper first argues that mountain ranges and mountain ridges should separately be used as different conceptual frameworks to explain complex spatial distribution of mountains in Korea. The new mountain range map (sanmaekdo) proposed in this research puts strong emphasis on tectonic movement and denudational processes to explain the spatial distribution of mountains. The new mountain range map has 15 mountain ranges (sanmaek: in total, which are further divided into 7 primary and 8 secondary mountain ranges. The new mountain range map eliminates Jeogyuryeongsanmaek, Myohyangsanmaek, Myeoraksanmaek, and Masingnyeongsanmaek from the existing map, since these have a vague definition and obscure spatial distribution. On the contrary, few new primary mountain ranges (Gilju-Myeongcheonsanmaek, Yangsansanmaek, Jirisanmaek) and secondary mountain ranges (Wolchulsanmaek and Buksubaeksanmaek) are added to the new mountain range map. Other mountain ranges also show a large difference both in their spatial distribution and the extent of mountain ranges, compared with the previous map. This is especially the case for Nangnimsanmaek, Hamgyeongsanmaek, Taebaeksanmaek, and Sobaeksanmaek. A few new names are also assigned to Macheollyeongsanmaek (Baekdusanmaek), Gwangjusanmaek (Hwaaksanmaek), Charyeongsanmaek (Chiaksanmaek), and Horyeongsanmaek (Naejangsanmaek), even though they show similar spatial distribution patterns with the ones in the existing map.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.271-278
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• 1993

Sand ripple. the smallest bottom configuration, is one of the most important factors in the mechanism of sand transport. This paper deals with characteristics of ripple geometry generated by regular and irregular waves. Especially. rearrangement of ripple spacing caused by increasing or decreasing waves is investigated through movable bed experiments. Nondimensional length of rearranged ripples becomes very close to that of measured ripples in the field Furthermore, stochastic characteristics and occurrence limits of three dimensional ripples are investigated through the wave number spectrum calculated from the measured bottom topography.

• Ecology and Resilient Infrastructure
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• v.7 no.1
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• pp.1-14
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• 2020

In fluvial and riparian ecosystems, biogeomorphological research has considered the complex, multi-way relationships between biological and hydro-geomorphological components over a wide range of spatial and temporal scales. In this review, we discussed the scope and processes of fluvial biogeomorphology by explaining (1) the multi-lateral interactions between organisms and hydrogeomorphic conditions, (2) the relationships between biodiversity and habitat heterogeneity, and (3) the effects of disturbance on ecosystem patterns. Over time, an organism-landform complex along streams transitions in the sequences of geomorphic, pioneer, biogeomorphic, and ecological stages. Over space, water flow and sediment distributions interact with vegetation to modify channel topography. It is the habitat heterogeneity in streams that enhances riparian biodiversity. However, in the areas downstream of a dam, habitat types and conditions are substantially damaged and biodiversity should be reduced. In South Korea, riparian vegetation flourishes in general and, in particular, invasive species actively colonize in accordance with the changes in the fluvial conditions driven by local disturbances and global climate change. Therefore, the importance of understanding reciprocal relationships between living organisms and hydrogeomorphic conditions will ever increase in this era of rapid climate change and anthropogenic pressure. The fluvial biogeomorphic framework reviewed in this article will contribute to the ecological management and restoration of streams in Korea.

• Journal of the Korean Geographical Society
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• v.46 no.6
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• pp.673-692
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• 2011

Advances in computer technology have enabled us to develop and use numerical landscape evolution models (NLEMs) for exploring the dynamics of geomorphic system from a variety of viewpoints which previously could have not been taken. However, as of yet there have been no trials using or developing NLEMs in Korea. The purpose of this research is to develop a 2 dimensional NLEM on a geological time scale and evaluate its usefulness. The newly developed NLEM (ND-NLEM) treats bedrock weathering as one of the major geomorphic processes and attempts to simulate the thickness of soil. As such it is possible to model the weathering-limited as well as the transport-limited environment on hillslopes. Moreover the ND-NLEM includes not only slow and continuous mass transport like soil creep, but also rapid and discrete mass transport like landslides. Bedrock incision is simulated in the ND-NLEM where fluvial transport capacity is large enough to move all channel bed loads, such that ND-NLEM can model the detachment-limited environment. Furthermore the ND-NLEM adopts the D-infinity algorithm when routing flows in the model domain, so it reduces distortion due to the use of the steepest descent slope flow direction algorithm. In the experiments to evaluate the usefulness of the ND-NLEM, characteristics of the channel network observed from the model results were similar to those of the case study area for comparison, and the hypsometry curve log during the experiment showed rational evidence of landscape evolution. Therefore, the ND-NLEM is shown to be useful for simulating landscape evolution on a geological time scale.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.177-191
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• 2011

This paper describes a dune field on shoreline of Young Gwang. To clarify geomorphic characteristics, made an analysis of grain size of the sand sediments samples and surface texture of quartz grains, and field survey. The following results were obtained : 1) Young Gwang sand dune is taking to pieces by human impact, and dose not move ahead the process of sand dune. 2) there was a turbulence of sand sediments outcrops saying to the cryoturbation that represents cold climatic environments, 3) Constituents of sand dune are mainly fine and very fine sand(2.5~4.5Φ) consisted by quartz and feldspar. Young Gwang sand grians have some analogy with different sites in west coast 4) In surface texture, roundness is thought to have been formed sub-angular, and some V cracks represented mechanical weathering environments. Especially, the dune environment has significant cultural and archaeological values arising from the occupation of human in the past. Those areas where occupation is known provide a valuable source of past records relating to human settlement.

• Journal of Korea Water Resources Association
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• v.52 no.11
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• pp.917-929
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• 2019

Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

• Journal of the Korean Geographical Society
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• v.39 no.6 s.105
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• pp.863-872
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• 2004

The coastal alluvial plain, sand dune, tidal nat might be the most prominent coastal landscape in western coast of Korea. The purpose of this paper is to examine the irrigation and drainage systems of the alluvial plain in the tidal coast. This study is concerned on the geomorphological and cultural landscapes of the alluvial plain in the western coast of the South Jeolla Province. The alluvial deposits have developed mainly by the actions of tidal currents, rather than transporting sediments by stream. The transformation of plain has been affected by human agency since 1920's. Dwellers have constructed the reservoir, banks, dammed pools, lock gates, and tide-dykes for the reclamation, irrigation, and drainage on the alluvial plain, coastal sanddune, and tidal flats.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.308-320
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• 2021

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.