• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.552-561
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• 2023

The seafloor topography of Gomso Bay on the west coast of Korea was investigated using subtidal bathymetry and tidal-flat altimetry. Gomso Bay consists of 80% tidal flats and 20% subtidal zone, and is divided into an outer bay and an inner bay by the Jujincheon esturary channel. The outer bay tidal flat, has few tidal channels, has a concave topographic profile, and is characterized by the development of chenier and intertidal sand bars, giving it the appearance of gently sloping, dissipative beaches. The inner bay tidal flat has wide upper and middle tidal flats with a well-developed tidal channel system without cheniers. Moreover, the topographical cross-section between these tidal channels is convex upward, and shows the characteristics of a depositional environment greatly influenced by tidal channels and tidal action. An analysis of the horizontal movement of the tidal flat environment over the past 37 years investigating changes in the iso-depth lines in the Gomso-Bay tidal flat between 1981 and 2018 revealed that the Gomso-Bay tidal flat retreated gradually landward. As a result of analyzing the erosion and sedimentation characteristics of Gomso Bay, assuming that most of the water depth changes were due to changes in the elevation of the sea floor and sea level, an average of 1 cm (0 mm/y) of sediment was eroded in the outer bay over the past 37 years (1981-2018), In the inner bay, an average of 50 cm (14 mm/y) was deposited. Notably, the high tidal flats of the outer bay were largely eroded. Monitoring photographs of the coast showed that most of the erosion of the high tidal flats in the outer bay occurred in a short period around 1999 (probably 1997-2002), and that the erosion resulted from the erosion of sand dunes and high-tide beaches caused by temporarily greatly raised high tide levels and storms.

• Journal of Biosystems Engineering
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• v.30 no.1 s.108
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• pp.45-55
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• 2005

Knowledge of the relationship between crop yield and yield-limiting factors is essential for precision farming. However, developing this knowledge is not easy because these yield-limiting factors are interrelated and affect crop yield in different ways. In this study, data for grain yield and yield-limiting factors, including crop chlorophyll content, soil chemical properties, and topography were collected for a small (0.3 ha) rice paddy field in Korea and a large (36 ha) upland corn field in the USA, and relationships were investigated with path analysis. Using this approach, the effects of limiting factors on crop yield could be separated into direct effects and indirect effects acting through other factors. Path analysis provided more insight into these complex relationships than did simple correlation or multiple linear regression analysis. Results of correlation analysis for the rice paddy field showed that EC, Ca, and $SiO_2$ had significant (P<0.1) correlations with rice yield, while pH, Ca, Mg, Na, $SiO_2,\;and\;P_2O_5$ had significant correlations with the SPAD chlorophyll reading. Path analysis provided additional information about the importance and contribution paths of soil variables to rice yield and growth. Ca had the highest direct effect (0.52) and indirect effect via Mg (-0.37) on rice yield. The indirect effect of Mg through Ca (0.51) was higher than the direct effect (-0.38). Path analysis also enabled more appropriate selection of important factors limiting crop yield by considering cause-and-effect relationships among predictor and response variables. For example, although pH showed a positive correlation (r=0.35) with SPAD readings, the correlation was mainly due to the indirect positive effects acting through Mg and $SiO_2$, while pH not only showed negative direct effects, but also negatively impacted indirect effects of other variables on SPAD readings. For the large upland Missouri corn field, two topographic factors, elevation and slope, had significant (P<0.1) direct effects on yield and highly significant (P<0.01) correlations with other limiting factors. Based on the correlation analysis alone, P and K were determined to be nutrients that would increase corn yield for this field. With the help of path analysis, however, increases in Mg could also be expected to increase corn yield in this case. In general, path analysis results were consistent with published optimum ranges of nutrients for rice and com production. We conclude that path analysis can be a useful tool to investigate interrelationships between crop yield and yield limiting factors on a site-specific basis.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.519-528
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• 2016

Frequently torrential rain is occurred by climate change and urbanization. Urban is formed with road, residential and underground area. Without detailed topographic flooded analysis consideration can take a result which are wrong flooded depth and flooded area. Especially, flood analysis error of population and assets in dense downtown is causing a big problem for establishments and disaster response of flood measures. It can lead to casualties and property damage. Urban flood analysis is divided into sewer flow analysis and surface inundation analysis. Accuracy is very important point of these analysis. In this study, to confirm the effects of the elevation data precision in the process of flooded analysis were studied using 10m DEM, LiDAR data and 1:1,000 digital map. Study area is Dorim-stream basin in the Darim drainage basin, Sinrim 3 drainage basin, Sinrim 4 drainage basin. Flooding simulation through 2010's heavy rain by using XP-SWMM. Result, from 10m DEM, shows wrong flood depth which is more than 1m. In particular, some of the overflow manhole is not seen occurrence. Accordingly, detailed surface data is very important factor and it should be very careful when using the 10m DEM.

• Journal of Korea Water Resources Association
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• v.50 no.5
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• pp.315-324
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• 2017

In this study, the HEC-GeoRAS model was used to estimate the changes of flood inundation depth and area of the Hyeoam-cheon basin after the channel migration and river improvement. The target area was extremely damaged due to the heavy rainfall on 25th August, 2014 after the costruction. According to the results of the analysis, the HEC-GeoRAS model can be used to accurately estimate the changes of flood innundation depth and area in agrecultural lands and lowlands of which the topographic changes and elevation differences are small. The inundation depths were increased 0.99 m in heavy rainfall and 0.39 m in 100 year frequency flood. The inundation areas in 100 year frequency flood were reduced in inundation depths under 1.5 m while they were increased in depths above 4.5 m. It was concluded that the loss of natural resevoir capacity of agricultural lands and lowlands due to the channel migration and river improvement caused the damage of flood in 2014 and the decrease of actual effective widths of the channel added the damage.

• Ecology and Resilient Infrastructure
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• v.4 no.2
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• pp.97-104
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• 2017

For the restoration of lateral connectivity between channel and floodplain, it is important to find the former floodplain and to characterize its land use in streams which were channelized by the levee construction for the flood protection. The aim of this study is to map the former floodplains and to assess its land use pattern in the Cheongmi-cheon Stream, Korea. The former floodplains were explored by being overlapped on a digital elevation model (DEM), digital topographic map and design flood level using a geographical information system (GIS) in the Cheongmi-cheon Stream basin. The land use of the identified former floodplains was classified by land-use map. The total number of the former floodplains was 104 and their total area was $11.9km^2$ in the Cheongmi-cheon Stream. The land use pattern of the former floodplains was mostly farmland (87.1%). The former floodplains were usually surrounded by mountain forest in the downstream of the Cheongmi-cheon Stream. These former floodplains are probably suitable for restoration of lateral connectivity because of lower ratio of urban area but higher ratio of farmland. The results of delineation and land use analysis of the former floodplain can be used as a baseline data for planning stream restoration in the Cheongmi-cheon Stream.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.5
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• pp.539-550
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• 2014

High resolution satellite images have to be oriented and geometrically processed from GCPs(Ground Control Points) to generate precise DEMs(Digital Elevation Models) and topographic maps. In Korea, thousands of national UCPS(Unified Control Points) are established and distributed all over the country by the Korean NGII(National Geographic Information Institute). For that reason, UCPs can be easily searched and downloaded by the national-control-point-record-issues system. Following the study, we suggested the sky-view and road-view from web-portals for searching and identifying UCPs on the images. To evaluate the usefulness of UCPs in RPCs(rational polynomial coefficients) adjustment of the high resolution satellite images, the one UCP, which of using simple the control point, has been applied to adjust the vendor-provided RPCs of the KOMPSAT-3 images. As a result, the positioning error of corrected RPCs was approximately one pixel and one meter. From this experiment, we conclude that the UCPs will be able to replace the survey GCPs for mapping with the satellite images or aerial images.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.65-76
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• 2006

This paper outlines the methodology of grid-based water balance for estimating the spatial distribution of recharge, which is applied to Woedo catchment in the northern area of the Jeju Island. The catchment is divided into grids and a daily water balance in each grid is computed for the period of 5 years. Daily rainfall data in each grid is interpolated from the data of 10 rainfall gauging stations. The spatial distributions of parameters such as SCS curve number, soil water retention capacity and crop coefficients are derived from GIS analyses of soil and land use characteristics. The SCS curve number is obtained by calibrating simulated runoffs with respect to the observed runoffs. The results show that the average annual rainfall increases from 1,665 mm/year to 3,382 mm/year in accordance with the topographic elevation, and the average annual recharge varies from 372 mm/year to 2,576 mm/year according to the average annual rainfall increases. Spatial variability of recharge is the highest among the water balance components such as rainfall, direct runoff, evaprotranspiration and recharge because the rate of runoff and evapotranspiration in the area with relatively low rainfall is higher than the other area.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.748-754
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• 2010

The contents of soil organic matter (SOM) and $Al_o+1/2Fe_o$ in soils are important criteria for the classification of new Andisols in Soil Taxonomy system. There are many soil types in Jeju Island with various soil forming environments. This paper was conducted to estimate the contents of soil organic matter and the content of ammonium oxalate extracted Al and Fe ($Al_o+1/2Fe_o$) using various environmental variables and to make soil property maps using a statistical analyses. The soil samples were collected from 321 locations and analyzed to measure the contents of SOM and $Al_o+1/2Fe_o$. It was analyzed the relationships among them and various environmental variables such as temperature, precipitation, net primary product, radiation, evapotranspiration, altitude, soil forming energy, topographic wetness index, elevation, difference surrounded area, and distances from the shore and the peak. We can exclude multi-collinearity among environmental variables with principal component analysis and reduce all the variables to 3 principal components. The contents of SOM and $Al_o+1/2Fe_o$ were estimated by multiple regression models and maps of them were made using the models.

• Korean Journal of Remote Sensing
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• v.36 no.3
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• pp.487-501
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• 2020

As a viable option for retrieval of LST (Land Surface Temperature), this paper presents a DNN (Deep Neural Network) based approach using 148 Landsat 8 images for South Korea. Because the brightness temperature and emissivity for the band 10 (approx. 11-㎛ wavelength) of Landsat 8 are derived by combining physics-based equations and empirical coefficients, they include uncertainties according to regional conditions such as meteorology, climate, topography, and vegetation. To overcome this, we used several land surface variables such as NDVI (Normalized Difference Vegetation Index), land cover types, topographic factors (elevation, slope, aspect, and ruggedness) as well as the T₀ calculated from the brightness temperature and emissivity. We optimized four seasonal DNN models using the input variables and in-situ observations from ASOS (Automated Synoptic Observing System) to retrieve the LST, which is an advanced approach when compared with the existing method of the bias correction using a linear equation. The validation statistics from the 1,728 matchups during 2013-2019 showed a good performance of the CC=0.910~0.917 and RMSE=3.245~3.365℃, especially for spring and fall. Also, our DNN models produced a stable LST for all types of land cover. A future work using big data from Landsat 5/7/8 with additional land surface variables will be necessary for a more reliable retrieval of LST for high-resolution satellite images.

• Ecology and Resilient Infrastructure
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• v.2 no.4
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• pp.324-329
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• 2015

For the restoration of lateral connectivity between rivers and floodplains, it is important to find the isolated former floodplain (IFF) and to characterize its land use in Korean rivers which were channelized by levee constructions for flood protection. The aim of this study is to map the IFF and to assess its land use pattern in the Nakdong River, Korea. The isolated former floodplain was explored by being overlapped on a digital elevation model (DEM), digital topographic map and design flood level using a geographical information system (GIS) in the Nakdong River basin. The land use of the identified IFF was classified by land-use map. The total number of IFFs was 384 and their total area was $291km^2$. While IFFs were usually surrounded by mountain forest in the upper river area, they tended to be located on wide plain areas in the downstream area of Nakdong River. The land use pattern of IFFs was mostly farmland (73.9%) and urban areas (12.7%) in the river. The results of delineation and land use analysis of isolated former floodplain in the Nakdong River will be used as a base line data for planning stream restoration.