• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.3
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• pp.37-50
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• 2019

In this study, we analyzed the soil salinity of Saemangeum agricultural land using GIS spatial interpolation method. Dominant soils series of experimental sites were Munpo (coarseloamy, mixed, non-acid, mesic, typically fluvaquents), which was based on the fluvio-marine deposit. Soil samples were periodically collected at 0~20cm and 20~40cm layer from each site. First, the distribution characteristics of EC, ESP, and SAR according to spatial interpolation were analyzed using 142 sample points. Through the error analysis of 143 validation points, the IDW method for EC and SAR, and the Kriging interpolation method for ESP were selected as the optimal interpolation method. Using the optimal interpolation method, the characteristics of EC, ESP, and SAR were analyzed for the change of soil salinity from 2014 to 2016. As a result, EC, ESP and SAR were decreased by 0.26mg/L, 5.97mg/L and 0.73mg/L respectively due to the dilution effect caused by rainfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.214-214
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• 2017

우리나라는 도시화 및 산업화로 도시지역의 대부분이 불투수층으로 변화하였으며, 국지성 호우의증가로 홍수 저감시설의 방어능력이 취약한 실정이다. 따라서 홍수방어 개선을 위한 여러 방안들이 이루어지고 있으며, 그 중 저류지는 도시지역에서 유역 하류의 홍수피해 저감 및 흐름을 지체시켜 유출률을 감소시키는 시설물로 홍수 저감을 위한 시설물로 가장 많이 사용되고 있다. 저류지는 큰 규모일수록 유역의 하류지역에 설치할 경우 가장 큰 유출저감효과를 가지는 것으로 알려져 있다. 하지만 저류지의 위치를 유역의 하류가 아닌 상류지역에 설치할 경우에는 단기간 강우의 시간적 분포가 강우 초기에 집중될 경우 저류지의 허용용량이 초기에 도달하게 되어 추가적인 강우가 발생할 경우 본래의 역할을 하지 못하는 경우가 빈번하게 발생하고 있다. 그러므로 다양한 강우강도 및 시간적 분포를 고려하여 유역의 특성 및 저류지의 설치위치에 따른 관계를 분석할 필요가 있다. 본 연구에서는 도시화, 산업화 인구집중으로 인해 동일규모의 강우에서도 우수유출이 증대되고 있는 도시지역에서 원활한 내수배제를 위해 기존의 우수관거를 연계한 저류시스템인 간선저류지 개념을 적용하여 강우강도 및 시간적 분포에 따른 간선저류지의 관련매개변수를 분석하였다. 대상유역은 세장형, 집중형, 중앙형의 3가지 형상의 가상유역으로 선정하여 다양한 지속기간의 강우량을 적용하였으며, 간선저류지의 설치위치는 전체 유역면적에 대한 저류지 상류부 면적의 비(저류지 상류부 면적비, DUAR ; Dimensionless Upstream Area Ratio)를 20%, 40%, 60%, 80%로 변화시키면서 강우의 시간적 분포에 따른 간선저류지의 매개변수 분석에 관한 연구를 진행하였다.

• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.37-45
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• 2021

Flooding damage may occur due to an unexpected increase in rainfall in summer. Previously, the roughness coefficient, which is a major factor of conveyance, was calculated through on-site measurement, but in case of on-site measurement, there are many limits in accurately grasping changes in vegetation. In this study, the vegetation index (NDVI) was calculated using the Sentinel-2 optical images, and the modified roughness coefficient was calculated through the density and distribution area of the vegetation. Then the calculated roughness coefficient was applied to HEC-RAS 1D model and verified by comparing the results with the water level at the water level station directly downstream of the Soyang River dam. As a result, the error rate of the water level decreased about 14% compared to applying the previous roughness coefficient. Through this, it is expected that it will be possible to refine the flood level of rivers in consideration of seasonal flood characteristics and to efficiently maintain rivers in specific sections.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.299-299
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• 2023

토양수분(soil moisture)은 수문인자의 하나로서 토양 내에 함유된 물의 양을 의미하며, 그 총량은 미미하지만 대기와 지표면 사이에서 일어나는 복잡한 물순환과 에너지 교환을 이해하는데 있어 필수적이다. 현재 국내에서는 「수자원의 조사·계획 및 관리에 관한 법률」(이하 수자원법)에 근거해 토양수분량 관측이 이루어지고 있으며, 수자원 분야의 한국수자원조사기술원 외에도 농업, 임업 분야에서도 다양한 기관에서 지상관측소를 구축해 토양수분량을 측정하고 있다. 국내 지상관측소에서는 주로 지점규모(point scale)로 토양수분량을 관측하는 장비가 사용되고 있으며, 유전율식 장비인 TDR(Time Domain Reflectometry), FDR(Frequency Domain Reflectometry)이나 토양수분장력을 측정하는 장력계(Tensiometer)가 널리 쓰이고 있다. 수자원분야에서는 토양 내 수분의 양을 직관적으로 확인할 수 있는 유전율식 장비가 대중적으로 사용되고 있으며, 최근에는 우주선(Cosmic-Ray)으로부터 발생하는 고속중성자(Fast Neutron)를 통해 중규모 면단위(field scale) 토양수분량을 관측하는 장비인 CRNP(Cosmic-Ray Neutron Probe)에 대한 연구도 활발히 진행되고 있다. 이러한 장비는 주로 야외에 설치해 운영하고 있기 때문에 장비 훼손이나 전원공급의 어려움으로 결측이나 오측이 발생할 수 있다. 토양수분량 시계열자료의 결측이나 오측이 일반적인 감쇄기에 발생했다면 선형보간법으로도 간단히 보간할 수 있지만, 강우에 의한 상승기에 발생했다면 해당 강우사상에서의 토양수분량의 상한치를 알기 어려워 결측보간에 어려움이 있다. 본 연구에서는 토양수분량 시계열자료의 강우기간 결측을 보간하는 방법으로 누적분포함수 역변환 샘플링방법을 선택하였다. 연구에는 음성군(차곡리) 토양수분량 관측소 2021년 자료가 사용되었으며, 관측소 56개 지점 중 임의의 지점에 결측구간을 생성한 뒤 해당 지점과의 상관계수가 높은 지점의 누적분포함수를 이용해 역변환 샘플링 방식으로 임의 지점의 결측을 보간하고 그 결과를 기존값과 비교해 보간 방법의 정확도를 평가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.245-245
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• 2020

설계홍수량의 결정은 하천기본계획, 댐 설계 등 수리·수문학적으로 중요한 변수 중 하나이다. 설계홍수량 산정을 위해서는 확률강우량 산정 및 강우-유출 모형의 일련의 과정을 통해 이루어지며, 홍수량 산정 표준지침(2018)에 자세히 수록되어 있다. 그러나 국내외 다양한 연구에서는 빈도별 확률홍수량의 경우 계측된 유량자료를 활용하여 직접 홍수빈도해석을 수행하는 것이 가장 정확한 방법이라 알려져 있지만, 홍수빈도해석을 위한 자연유량이 부족할 뿐만 아니라 홍수수문곡선(hydrograph)을 얻을 수 없는 단점이 있다. 더불어 우리나라의 경우 주요지점을 제외하고는 계측이 잘 이루어지지 않고 있으며, 수위-유량관계곡선(rating-curve)을 통해 산정된 유량자료를 활용하고 있어 자료의 신뢰성이 낮은 문제가 있다. 이러한 이유로 우리나라에서는 강우-유출 모형을 활용하여 빈도별 홍수량을 산정하고 있으며, 확률강우량의 시간분포를 입력자료로 하여 홍수수문곡선을 취득하고 있다. 그러나 확률강우량의 우량주상도 변환시 국내에서는 일반적으로 Huff 4분위법을 활용하지만, 실제홍수사상과 비교했을 때 과소 및 과대 추정하는 경우가 많다. 더불어 분포된 우량주상도를 면밀히 살펴보면 빈도해석된 확률강우량과 비교하였을 때 상당히 낮은 강우 빈도를 가지고 있다. 즉, 우량주상도는 특정 지속시간의 확률강우량을 Huff 분포를 활용하여 얻어지지만, 관측소별로 산정된 확률강우량의 빈도개념이 무너진다는 것이다. 이러한 결과로 인해 확률홍수량은 확률강우량과의 빈도개념의 상이하다고 할 수 있으며, 홍수빈도해석과의 비교에서도 차이를 보이고 있어 우량주상도의 개선 연구가 필요하다. 따라서 본 연구에서는 기존에 일관적으로 사용되어지는 Huff 3분위 50%를 지양하고, Huff의 다양한 분위(quartile)과 Blocking 방법 등을 비교·검토하여 보다 국내 실정에 부합하는 확률강우량의 우량주상도를 제공할 수 있는 연구를 진행하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.431-436
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• 2008

Recently, the rapid development of GIS technology has made it possible to handle a various data associated with spatially hydrological parameters with their attribute information. Therefore, there has been a shift in focus from lumped runoff models to distributed runoff models, as the latter can consider temporal and spatial variations of discharge. In this research, a distributed rainfall-runoff model based on physical kinematic wave for analysis of surface and river flow was used to simulate temporal and spatial distribution of long-term discharge. The snowfall and melting process model based on Hydro-BEAM was developed, and various hydrological parameters for input data of the model was extracted from basic GIS data such as DEM, land cover and soil map. The developed model was applied for the Shonai River basin(532) in Japan, which has sufficient meteorological and hydrological data, and displayed precise runoff results to be compared to the hydrograph.

• Journal of Korean Society of Forest Science
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• v.112 no.4
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• pp.490-501
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• 2023

Laboratory column tests were conducted to analyze infiltration and water redistribution processes on the basis of rainfall. To efficiently measure moisture content within soil layers, this research developed a predictive model grounded in a convolutional neural network (CNN), a deep learning technique. The digital images obtained during the column tests were incorporated into the established CNN. The moisture content of each soil layer over time was effectively measured. The measured values were also in relatively good agreement with the moisture content determined using the moisture sensors installed for each soil layer. The use of CNN enabled a comprehensive understanding of continuous moisture distribution within the soil layers, as well as the infiltration process according to soil texture and initial moisture content conditions.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.4
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• pp.237-244
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• 2006

The SMG project has been driven to secure food and water resources by closing of the SMG dyke for the preparation of the unification of Korean peninsular. It was investigated for pollution loads, land use distribution and water consumption for environmental assessments in two watersheds, the Mankyeong River (MK) and the Dongjin River (DJ) to assess the role of agricultural land on the alleviation of pollution loads to the SMG basin. It is needed to give the priority in managing pollution sources to conserve freshwater in the Saemangeum (SMG) basin after the completion of the SMG reclamation from tideland. The MK has $700million\;m^3$ water of which 14.1% were used for living, 73.6% for agriculture and 12.3% for industry. The DJ has $505million\;m^3$ water of which 3.0% for living, 94.5% for agriculture and 2.5% for industry. As compared to proportion of each land of total area, agricultural land was 1.4 times larger, livestock farming 7 times larger, forest 0.74 times smaller, and built-up area 0.67 times smaller in DJ watershed than in MK watershed. Pollution sources in MK and DJ watersheds were originated at a higher proportion from population including the sewage disposal and a livestock farming area rather than from the land. Water consumption and land use distribution influenced the water quality of the rivers; DJ watershed had far lower value of electric conductivity, $BOD_5$, TN and TP than MK watershed. A large proportion of paddy field also influenced to reduce pollute loadings after rainfall; DJ watershed, which has a relatively large area of paddy fields, had a far lower delivery load after rainfall than MK watershed even though DJ watershed had large livestock farming area. As paddy fields was irrigated by Iksancheon water, 37% of nitrogen, 50% of phosphates and 14.0% of $BOD_5$ was removed by the paddy field just after flowing 150 meter, and rice plants could remove TN 100.0 kg, $P_2O_5$ 24.0 kg, and $K_2O$ 119.2 kg per hectare at harvest by irrigation of Iksancheon water. Conclusively, rice paddy fields played a positive role to conserve the water quality in the Iksancheon watershed.

• Journal of Korea Water Resources Association
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• v.52 no.9
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• pp.627-635
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• 2019

In Korea, snow damage has been happened in the region with no snowfalls in history. Also, casual damage was caused by heavy snow. Therefore, policy about the Natural Disaster Reduction Comprehensive Plan has been changed to include the mitigation measures of snow damage. However, since heavy snow damage was not frequent, studies on snowfall have not been conducted in different points. The characteristics of snow data commonly are not same to the rainfall data. For example, some parts of the southern coastal areas are snowless during the year, so there is often no values or zero values among the annual maximum daily snow accumulation. The characteristics of this type of data is similar to the censored data. Indeed, Busan observation sites have more than 36% of no data or zero data. Despite of the different characteristics, the frequency analysis for snow data has been implemented according to the procedures for rainfall data. The frequency analysis could be implemented in both way to include the zero data or exclude the zero data. The fitness of both results would not be high enough to represent the real data shape. Therefore, in this study, a methodology for selecting a probability density function was suggested considering the characteristics of snow data in Korea. A method to select probability density function using conditional joint probability distribution was proposed. As a result, fitness from the proposed method was higher than the conventional methods. This shows that the conventional methods (includes 0 or excludes 0) overestimated snow depth. The results of this study can affect the design standards of buildings and also contribute to the establishment of measures to reduce snow damage.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.287-298
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• 2018

The zooplankton community and environmental factor were investigated on a weekly basis from March to November 2015 in Lake Paldang, Korea. The seasonal succession of zooplankton community structure was influenced by hydraulic and hydrological factors such as inflow, outflow and rainfall. However, the hydraulic retention time in 2015 (16.3 day) was affected by the periods of water shortage that had continued since 2014 and increased substantially compared to 2013 (7.3 day). Therefore, the inflow and outflow discharge were decreased, and the water quality (COD, BOD, TOC, TP, Chl-a) of Lake Paldang (St.1) was the same characteristics as the river type Bukhan river (St.3), compared with the lake type Namhan river (St.2) and Gyeongan stream (St.4). Zooplankton community dominated by rotifers (Keratella cochlearis, Synchaeta oblonga) in spring (March to May). However, Copepod (Nauplius) and Cladoceran (Bosmina longirostris) dominated in St.4. In summer (June to August), there was a few strong rainfall event and the highest number of individuals dominated by Keratella cochlearis (Rotifera) and Difflugia corona (Protozoa) were shown during the study period. In autumn (October to November), the water temperature was decreased with decrease in the total number of individuals showing Nauplius (Copepoda) as the dominant species. As a result of the statistical analysis about zooplankton variation in environmental factors, the continuous periods of water shortage increased the hydraulic retention time and showed different characteristic for each site. St.1, St.3 and St.2, St.4 are shown in the same group (p<0.05), showing the each characteristics of river type and lake type. Therefore, the water quality of catchment area and distribution of zooplankton community would be attributed to hydraulic and hydrological factors.