• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.220-220
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• 2021

2020년 장마는 6월 중순부터 8월 중순까지 전국적으로 평균 687 mm의 강수가 내려, 1973년 이후 역대 2위 강수량을 기록하였으며, 연이은 태풍으로 큰 인명 및 재산 피해가 발생하였다. 특히, 섬진강 및 한탄천 등에서 계획홍수위를 초과하는 홍수로 인해 상당수의 제방이 월류로 인해 붕괴된 것으로 나타났다. 따라서, 향후 기후변화에 따른 연평균 강수량이 증가할 것으로 전망되는 가운데 집중호우로 인한 제방 붕괴 피해를 최소화하기 위한 고도화된 기술 개발을 통한 선제적 재발 방지대책이 필요한 시점이다. 한국건설기술연구원은 바이오폴리머라는 새로운 친환경 신소재를 이용하여 제방의 안정성 평가 기술 개발 연구를 수행하고 있다. 이에 안동하천연구센터에서는 실규모에 준하는 제방모형(높이 3 m, 사면경사 1:2, 길이 10 m 이상)을 제작하고, 제방 표면에 바이오폴리머 신소재를 처리하여 전방 월류 흐름 유도에 따른 실규모 제방붕괴실험을 수행하였다. 또한, 신소재 보강 및 무보강 조건에 따른 영상분석 기반 붕괴지연효과를 정량적으로 분석하여 신소재의 성능을 평가하였다. 하지만, 기존에 수행된 실험은 댐 붕괴 흐름과 같이 홍수파가 발생하여 제내지로 퍼져 나가는 형태로 진행되어, 보강공법의 검증에 있어 실제 하천에서 발생하는 횡월류 흐름을 재현하지 못한다는 한계를 가지고 있다. 본 연구에서는 횡월류 흐름(0.6 m³/s 이상)을 발생시켜 수리실험에 따른 축척효과(scale effect)를 최소화하고, 현장에 대한 충분한 자연성을 재현하는 것을 목표로 하여 실험을 수행하였다. 실험 조건은 1) 신소재가 처리된 식생 제방, 2) 신소재가 처리되지 않은 식생 제방으로 각각의 조건에 따른 횡월류 흐름 및 제방 붕괴를 유도하여 영상분석 기법(이미지 픽셀분석 및 3D 포인트 클라우드 모델링)을 통한 침식 저항에 관한 분석결과를 제시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.54-54
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• 2020

본 연구에서는 제방의 세굴이나 붕괴를 방지하기 위해 바이오폴리머(Biopolymer) 기반 신소재를 활용한 흙 제방의 보강공법을 제시하였다. 바이오폴리머 기반 제방의 보강공법은 흙과 바이오폴리머를 소량만 섞어도 흙의 강도 증진시킴과 동시에 빗물에 대한 내침식성과 식생의 생장을 촉진하는 생태성도 뛰어나기 때문에 제방 사면을 보호할 수 있는 친환경적이고 효율적인 공법이다. 이에 안동하천연구센터는 실증실험을 통한 신소재 제방 보강공법의 안정성 검증을 목표로 2 건의 월류붕괴 실험을 수행하였다. 첫 번째는 흙 제방 조건(Case 1)이며, 두 번째는 바이오폴리머 혼합 토양을 사면에 도포한 후 식생이 활착된 조건(Case 2)이다. 제방 붕괴에 따른 수로 내 수위변화를 측정하기 위해 압력식 수위계를 설치하였으며, 영상분석을 위한 다수의 카메라 및 드론을 활용하여 실험의 전 과정을 실시간 촬영하였다. 또한, 제내지 측 사면을 대상으로 월류에 따른 붕괴 지연효과를 정량적으로 제시하기 위해 이미지 픽셀 변화 측정 기법을 통한 시간에 따른 표면 손실률을 산정하였다. 흙 제방과 신소재 처리 제방의 시간에 따른 표면손실률을 비교한 결과, Case 2의 사면손실률이 Case 1에 비해 약 1.5~2.3 배 지연되는 것을 확인하였다. 하지만 단일 조건만으로 실험군과 비교군의 붕괴지연 결과가 제방 성능을 평가함에 있어서 일반화될 수 없으므로 이러한 정량적 평가는 다소 한계가 있다. 향후 이러한 부족한 부분을 해결하기 위한 노력과 다양한 조건의 추가실험을 통한 계측 데이터 및 붕괴지연시간의 평균값을 도출하여 신소재 제방의 안정성을 평가하기 위한 타당한 결과를 도출할 예정이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.156-156
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• 2020

가뭄은 다른 자연재해에 비해 진행 속도가 느리고 발생 시작 시기가 명확하지 않다. 또한 피해지역이 광범위하다는 점에서 사회, 경제적 피해와 농업 생산 시스템 및 수확량 등 농업 전반에 걸쳐 직접적인 영향을 미치고 있다. 전지구적 기후변화로 인해 국내의 가뭄 발생빈도는 2000년 이후 증가하고 있으며, 가뭄의 정량적 분석은 선제적 가뭄 대응을 위해 필요하다. 현재 국내에서는 여러 유관기관에서 지상 관측 데이터를 활용하여 가뭄을 모니터링하고, 가뭄 공간 분포 지도를 제공하고 있다. 하지만 지상 관측 데이터를 통한 가뭄 분포 지도는 미계측 지역에 대한 데이터 취득이 어렵고, 지형학적 특성을 고려하지 못하는 한계점이 있다. 이러한 한계점을 보완하기 위해 수자원 및 재해 분야에서 위성영상이 활용되고 있다. 위성영상을 활용한 가뭄 판단 및 예측에는 정규식생지수 (Normalized Difference Vegetation Index, NDVI)가 사용되고 있으며, 식생지수는 가뭄 발생, 진행 등에 있어 즉각적인 반응이 어렵다는 단점이 있다. 본 연구에서는 잠재 증발산과 실제 증발산의 비를 이용해 산정된 위성영상 기반 가뭄 지수인 Evaporative Stress Index (ESI)를 활용하였다. NASA (National Aeronautics and Space Administration)에서 제공하는 ESI는 전지구를 대상으로 5km 해상도로 제공하고 있다. 하지만 국내 가뭄 판단을 위해서는 높은 해상도의 영상이 필요하며, 본 연구에서는 MODIS (Moderate Resolution Imaging Spectroradiometer) 영상을 활용한 ESI의 산정을 통해 해상도의 문제를 개선하고자 한다. 산정한 500m 해상도의 ESI는 기존 5km 해상도의 ESI와 비교 검증하였으며, SPI 및 과거 가뭄 발생 현황 자료를 근거로 ROC (Receiver Operating Characteristics) 분석을 통해 시군 단위 농업가뭄평가의 적용성을 확인하고 한다.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.45-53
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• 2016

At present, coffee consumption amount is annually on the rise in Korea, which results in about 0.27 million tons of coffee waste annually. They are mostly classified as food waste and deserted with moisture contained, being a serious environmental issue. Existing slope greening techniques, which are vegetation based soil-media hydroseeding measures, have problems such as lack of coherence, dryness or lack of organic matters. Therefore in order to assess usability of Spent Coffee Ground (SCG), medium-to long-term growth test was conducted under the indoor and outdoor conditions. According to the result of growth test, when SCG was mixed with existing base materials, moisturizing power increased and organic matter content was reinforced, promoting germination and growth in a medium term. Among others, under the condition when supply of water was discontinued, withering rate was lower than existing base materials and diverse phenomena resulting from lack of nutrition decreased. Therefore, SCG as a waste organic matter with abundant nitrogen has the characteristic of inhibiting early growth but was found to have a quality favorable to long-term growth resulting from water containing ability and the supply of organic mater and is judged to be a material to replace or complement existing base materials.

• Ecology and Resilient Infrastructure
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• v.4 no.1
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• pp.12-23
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• 2017

The Naeseong Stream is a meandering sand-bed stream flowing through mountains and has so long maintained its geomorphological uniqueness characterized by extensive braided bare bars. Recently, its long-lasting landscape has been changed due to encroachment of vegetation. In this study being a part of long-term monitoring research morphological changes of the 56.8 km long study reach of the Naeseong Stream, which occurred during the period of 2012 - 2016 were analyzed. Airborne LiDAR and terrestrial cross-section surveys were carried out. Hydrological and on-site investigation data were also collected. Among the main four sites, two bend reaches showed point bars enlarged, while along the other two straight reaches mid-channel bars were either newly formed or increased in area and height. At the highest deposition point of each bar, vertical changes which were caused by one or two times of sediment deposition amounted to 0.6 - 1.4 m. On the contrary channel bed degradation was not obvious. Overall morphological changes in the study reach were attributed to deposition of sediment which occurred during the flood in July 2016 on the bar surfaces vegetated during the precedent dry seasons. These kind of geomorphological processes are thought to be the same as those related to the existing mid-channel islands along the mid- and downstream reach of the Naeseong Stream.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.347-378
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• 2020

Based on monthly average groundwater recharge over a nearly 10 year period, results of fully integrated hydrologic modeling of SWAT-MODFLOW, land cover, land use, soil type and hydrologic response unit (HRU) was used to assess the dominant influencing factors of groundwater recharge spatial patterns in Jangseong district. As dominant factors, land cover was FRSE (forest-evergreen) and soil type was Samgag. Landsat-8 OLI imaging spectrometer data were acquired in the period 2003 to 2004 and seasonal bare soil lines (BSL) were estimated through NIR-RED plot. Extent of slope of BSL was from 1.092 to 1.343 and the intercept was from -0.004 to -0.015. To know correlation between spatial groundwater recharge and soil-vegetation indices (PVI, NDVI, NDTI, NDRI), this study employed frequency and regression analysis. On May, RED band increased up 3 to 4 times compared to other seasons and only one turning point appeared as recharge-index with upward parabola bell shape as results of existing research. Considering precipitation, if the various studies for relationship between groundwater recharge and soil-vegetation index just like NDVI are performed, it is possible to estimate groundwater recharge through analyzing remote sensing data.

• Journal of Korean Society of Forest Science
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• v.89 no.5
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• pp.552-563
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• 2000

The aim of this study was to characterize the forest vegetation and site of Odaesan National Park for ecological forest management. The vegetation could be divided into two forest community groups, seven forest communities, and several subcommunities. South exposed, dry slopes were covered with forests of the Quercus mongolica-Acer pseudosieboldianum community group. Quercus mongolica-Acer pseudosieboldianum community group could be subdivided into ${\bullet}$ Rhododendron mucronulatum var. ciliatum community on dry sites, especially on south or south-westly exposed ridges or convex slopes; ${\bullet}$ Lespedeza${\times}$tomentella community on south exposed slopes, at low altitudes in the eastern part of the study area; ${\bullet}$ Carex humilis-Maackia amurensis community on south exposed slopes up to the montane region; ${\bullet}$ Quercus mongolica-Acer pseudo-sieboldianum typical community on south exposed middle and low slopes, and on upper and middle north exposed slopes; ${\bullet}$ Pimpinella brachycarpa community, preferably on moderately moist and cool sites. On north exposed, more humid and moist sites, forests of the Dryopteris crassirhizoma-Cornus controversa community group were found. This group was subdivided into ${\bullet}$ Acer tschonoskii var. rubripes-Acer tegmentosum community on moderately moist to moist, loamy soils on shady slopes; ${\bullet}$ Deutzia glabrata-Ulmus laciniata community on north exposed slopes with rocky soil and boulders, having high humidity. There are several rare and endangered species in Rhododendron mucronulatum var. ciliatum community, Carex humilis-Maackia amurensis community, Vicia venosa var. cuspidata subcommunity and Saxifraga punctata subcommunity, and the communities were located in azonal areas in topography. To protect the species, the areas should be categorized as an absolute conservation area, and any forest working should be prohibited in this area.

• 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 Geotechnical Society
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• v.29 no.1
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• pp.49-59
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• 2013

Heavy rainfall intensity may cause shallow slope failures and debris flow by rill erosion and scour on land surface. The paper represents the difference between native soil (weathered soil) and reinforced soil, which is mixed by hardening agent with flyash as main material, for investigating experimental findings of rill erosion and erosion. Results obtained from artificial rainfall simulator show that erosion rate of reinforced soil mixed with hardening agent is reduced by 20% because an amount of eroded soil on slope surface is inversely proportional to the increase of soil strength. For example, rainfall of 45mm (at the elapsed time of 25mins in rainfall intensity of 110mm/hr) triggers rill erosion on native soil surface, but the rill erosion on reinforced soil surface does not even occur at 330mm rainfall (at the elapsed time of 3hrs in rainfall intensity of 110mm/hr). As a result of slope stability analysis, it was found that the construction method for reinforced soil surface would be more economical, easy and fast construction technology than conventional reinforcement method.

• Journal of Korean Society of Forest Science
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• v.80 no.3
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• pp.265-278
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• 1991

The purpose of this study is to suggest objective basic data for the design and management of the national park roadside slopes through the quantitative analysis of the visual quality included in the physical environment of the Chi-ri national park, for this, visual volumes of physical elements have been evaluated by using the mesh analysis, spatial images structure of physical elements have been analyzed by factor analysis algorithm, and degree of visual quality have been measured mainly by questionnaires. Result of this thesis can be summarized as fallows. Visual volumes of the naked, rock, ground cover of seed spray, and artificial planting are found to be the main factor determining the visual quality. Factors covering the spatial image of the national park roadside slopes landscape have been found to be the overall synthetic evaluation, spatial, appeal, physical, openness and dignity factors such as the overall the spatial, physical and openness yield high factor scores. As for the factors determining the degree of visual quality of the roadside slopes, variables such as the summit, the constructions management, harmony of landscape, visual stability of roadside slopes, suitable artificial planting and suitable constructions.