Chuluong Choi

Impacts of changes in climate and land use/land cover under IPCC RCP scenarios on streamflow in the Hoeya River Basin, Korea

This study examined the separate and combined impacts of future changes in climate and land use/land cover (LULC) on streamflow in the Hoeya River Basin, South Korea, using the representative concentration pathway (RCP) 4.5 and 8.5 scenarios of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). First, a LULC change model was developed using RCP 4.5 and RCP 8.5 storylines and logistic regression. Three scenarios (climate change only, LULC change only, and climate and LULC change combined) were established, and the streamflow in future periods under these scenarios was simulated by the Soil and Water Assessment Tool (SWAT) model. Each scenario showed distinct seasonal variations in streamflow. Under climate change only, streamflow increased in spring and winter but decreased in summer and autumn, whereas LULC change increased high flow during wet periods but decreased low flow in dry periods. Although the LULC change had less effect than climate change on the changes in streamflow, the effect of LULC change on streamflow was significant. The result for the combined scenario was similar to that of the climate change only scenario, but with larger seasonal changes in streamflow. Although the effects of LULC change were smaller than those caused by climate change, LULC changes may heighten the problems of increased seasonal variability in streamflow caused by climate change. The results obtained in this study provide further insight into the availability of future streamflow and can aid in water resource management planning in the study area.

Mapping urban growth probability in South Korea: comparison of frequency ratio, analytic hierarchy process, and logistic regression models and use of the environmental conservation value assessment

Rapid industrialization and economic growth in South Korea since the 1970s have resulted in severe environmental disturbance and pollution, problems aggravated by the imprudent expansion of urban areas. This paper analyzes and predicts urban growth patterns with the aim of contributing to more efficient urban planning. Urban growth probability index (UGPI) maps were prepared using the frequency ratio (FR), analytic hierarchy process (AHP), and logistic regression (LR) methods, with and without considering development restrictions based on the national environmental conservation value assessment map (ECVAM). Environmental and legal restrictions were associated with an average difference of 41.70% in conservation areas and an 81.32% average difference in agriculture and forest land use–land cover (LULC). Accuracy of the models was examined by area under the curve (AUC) analysis. Accuracies of UGPI maps produced with the ECVAM were higher than UGPI maps produced without the ECVAM. In addition, effectiveness and accuracy tests based on LULC showed that the UGPI maps produced with the ECVAM had a higher rate of accuracy that UGPI maps produces without the ECVAM. Using the ECVAM and assuming that urban and built-up areas will be 1.5 times greater than in 2005 and that environmental restrictions are removed, urban development can be expected to more than double in conservation areas and borderlands, increase by more than 1.5 times in developable areas, and decrease by half in old downtown areas. If legal restrictions are removed, urban development is expected to occur mostly in former conservation areas, followed by borderlands, old downtowns, and developable areas.

Radiometric characterization and validation for the KOMPSAT-3 sensor

A radiometric characterization of the Korea Multi-Purpose Satellite (KOMPSAT) Series multispectral imagery was performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG). This paper presents a vicarious radiometric calibration performed by KARI and PKNU RSG in 2012 and 2014. Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3 sensors at Zuunmod, Mongolia and Goheung, South Korea, were significant for multispectral bands. KOMPSAT-3 calibration coefficients for all bands estimated in 2012 continued to agree well with calibration coefficients estimated in 2014 (within 1.5%). As a result of this study, KARI will update and publish the KOMPSAT-3 multispectral radiometric calibration coefficients as official values. The average difference in TOA reflectance between KOMPSAT-3 and Landsat-8 images over the Libya 4, Libya and Railroad Valley Playa, USA, in the red–green–blue region was under 3%, whereas in the near-infrared band, the TOA reflectance of KOMPSAT-3 was lower than that of Landsat-8 due to the difference in the bandwidths of two sensors. The KOMPSAT-3 sensor includes a bandwidth near 940 nm that can be strongly absorbed by water vapour and therefore displayed low reflectance.

ASSESSMENT OF SMARTPHONE-BASED TECHNOLOGY FOR REMOTE ENVIRONMENTAL MONITORING AND ITS DEVELOPMENT

Many countries are increasing their research on monitoring technology to identify and systematically manage various domestic changes. In particular, the need for remote monitoring is increasing in response to climatic disasters, such as flooding, storms, and rising tides caused by global warming. We developed a smartphone-based environmental monitoring system that enables remote monitoring in any place and at any time. The overall system is composed of a 24-hour smartphone-based imaging system, a monitoring information management system to receive the monitoring information, and stereo image rectification software that provides lens distortion correction, geometric correction, and stereo matching of the monitoring images. The system was developed using the Samsung Galaxy S with the Android OS, as well as open source–based software and other hardware. It is easy to install, control remotely, and monitor the status of imaging devices. We assessed the accuracy of the micro-electro-mechanical system (MEMS) sensors of the smartphone to evaluate the applicability of our environmental monitoring system. The assessment was conducted via survey using metric cameras, a global positioning system receiver, a three-dimensional laser scanner and total station, geometric correction, and digital elevation models generated with camera internal elements, external elements, and ground control points. We demonstrated the effectiveness of the system, and showed that the accuracy of the MEMS sensor and camera calibration have a significant effect on image analysis.

Evaluating the suitability of the EGM2008 geopotential model for the Korean peninsula using parallel computing on a diskless cluster

This paper describes a hybrid MPI/OpenMP approach to using diskless computing clusters to solve time-consuming problems related to ultra-high-degree and -order spherical harmonic analysis using the EGM2008 geopotential model with least-squares collocation to improve the accuracy of EGM2008-derived geoid heights. The proposed hybrid approach conducted 2190-degree and -order spherical harmonic analysis and least-squares collocation fitting using a cluster system of low-performance nodes and achieved a maximum parallel efficiency of 99%. Calculation of the associated Legendre functions and numerical stability were ensured for both 64 and 128bits in an EGM2008 spherical harmonic analysis for the Korean Peninsula using parallelization modeling. EGM2008 not only described the gravity field of the Korean Peninsula well, but its results were also very accurate compared to those of other global geopotential models. EGM2008-derived geoid heights were fitted with GPS/leveling data from least-squares collocation, which improved their accuracy. For this procedure, parallelization modeling was used to explore the optimum correlation length representing the highest accuracy. After the geoid heights were fitted, their accuracy was evaluated for several cases to determine the optimum distance of GPS/leveling points for least-squares fitting around the Korean Peninsula, and to determine the optimum correlation length by comparing the various results. A correlation length of 119.4km showed the best fitting results for the case using 102 GPS/leveling points with 40-km intervals.

Predicting soil erosion under land-cover area and climate changes using the revised universal soil loss equation

Loss of soil has become a problem worldwide, and as concerns about the environment grow, active research has begun regarding soil erosion and soil-preservation polices. This study analyzed the trend of soil loss in South Korea over the past 30-year and predicted future soil loss in 2020 using the revised universal soil loss equation. In the period 1975-2005, soil loss showed an increasing trend, the 2005 value represents a 0.59 Mg/ha (2.58%) increase. Scenario 1 assumes that urban areas have a similar trend to that between 1975 and 2005 and that precipitation amount follows scenario A1B of the IPCC. The soil loss amount for 2020 land-cover map that account for the ECVAM should increase by 25.0~26.3% compared to 1975. In the case where the ECVAM is not considered, soil loss should increase by 27.7~31.8%. In Scenario 2, in which the urban area and precipitation follow the same trend as between 1975 and 2005, soil loss for 2020 land-cover map that consider the ECVAM will increase by 6.8%~7.9% compared to 1975. When the ECVAM is not considered, soil loss will increase by 9.1~12.6%. The environmental and legislative value of preservation should be considered to minimize erosion and allow for more sustainable development.

An ecosystem service value assessment of land-use change in South Korea using remote sensing data and geographic information system

In Korea, rapid industrialization and economic growth have led to serious problems including reduced open space, environmental degradation, traffic congestion, and urban sprawl. These problems have been exacerbated by the absence of effective conservation and governance, and have resulted in various social conflicts. This study analyzed ecosystem service value over the past 20 years using previously reported coefficients. In addition, using logistic regression, we projected the land-cover distribution in 2020 according to the Environmental Conservation Value Assessment Map and analyzed ecosystem service value based on land use changes. Between 1985 and 2005, built-up areas had increased threefold. In the same time period, forest, grassland, and wetland areas decreased. Because of these trends, ecosystem service value decreased from 7,300 million USD to 6,525 million USD. By analyzing land-cover distribution with 2020 land-cover maps, we determined that farmland, grassland, and bare land areas had declined by approximately 24.3%. The 2020 land-cover map with considering ECVAM showed a decrease of 89 million USD in ecosystem service value, while the map without considering ECVAM showed a decrease of 165 million USD. The results of this analysis indicate that environmentally sustainable systems and urban development must be applied to achieve sustainable development and environmental protection.

Forecasting the Potential Effects of Climatic and Land-Use Changes on Shoreline Variation in Relation to Watershed Sediment Supply and Transport

ABSTRACT Kim, J.; Choi, J.; Choi, C., and Hwang, C., 2017. Forecasting the potential effects of climatic and land-use changes on shoreline variation in relation to watershed sediment supply and transport. This study investigated the potential effects of future climatic and land-use changes on sediment supply and shorelines in the Hoeya River estuary, Korea. Historical shoreline variations were determined along Jinha and Solgae Beaches for the period 1975–2013 using the Digital Shoreline Analysis System. Sediments during future periods were simulated in this watershed under the Representative Concentration Pathways 4.5 and 8.5 scenarios using the soil and water assessment tool model. Subsequently, this study analyzed the correlations between the beaches and the sediment supply. For the natural beaches BS-I (0.805) and BS-II (0.700) in 1975–2013, the river-supplied sediment was closely correlated to shoreline changes. The area of beach sediment for future periods was assessed based on R-squared values. The artificial beach BS-III (0.203), which had remained relatively stable in 1975–92, showed shoreline erosion following this period. This beach is now artificially supplied with sediment because of a training dike. In 1986, because of the presence of a dam, a decrease in the discharge volume of suspended solids from the watershed caused a clear erosional trend in artificial beach BS-IV (0.432) from 1975. Artificial activity in the study area has caused major changes to the shoreline, but the R-squared values are relatively low. In the future, the area of the natural beach will increase during spring and winter and will decrease during summer and autumn. Furthermore, these seasonal trends in future periods may be amplified by seasonal variability in the wave direction. These results are expected to improve the understanding of shoreline changes that contribute to sediment supply and transport in river watersheds, which has significant implications for the effective management of the coastal environment.

Radiometric cross-calibration of KOMPSAT-3 with Landsat-8

This paper presents a radiometric cross calibration of KOMPSAT-3 AEISS based on Landsat-8 OLI. Cross calibration between the two sensors using simultaneous image pairs, acquired during an underfly event over the Libya 4 pseudo invariant calibration site (PICS) site. The spectral profile of the target comes from the near-simultaneous EO-1 Hyperion data over these sites for apply Spectral Band Adjustment Factor (SBAF). The results indicate that the Top Of Atmosphere (TOA) reflectance measurements for KOMPSAT-3 agree with Landsat-8 to within 5% after the application of SBAF. To validate radiometric coefficient, comparison TOA reflectance executed in north Virginia, USA. The difference in TOA reflectance was calculated to within a maximum ±1.55%. There was a huge improvement when the standard deviation altered from 0.1 to 0.01, when applying the SBAF. The result of radiometric coefficient presented here appear to be a good standard for maintaining the optical quality of the KOMPSAT-3, for which prelaunch, onboard, and vicarious calibration data are lacking.

Simulating Land Use Change in the Seoul Metropolitan Area after Greenbelt Elimination Using the SLEUTH Model

The aim of this study was to analyze the effect of a policy aimed at the removal of a greenbelt on future urban growth. The SLEUTH model was applied to the Seoul Metropolitan Area, South Korea, to predict urban growth under three different greenbelt removal scenarios. The accuracy of the model was verified using historical data with ROC and Kappa statistics of 82.6 and 76.3%, indicating reasonable accuracy. In the scenarios, suburban development grew in proportion to the degree of reduction of the greenbelt. In two of the scenarios, suburban cities in the inner part of the greenbelt were integrated into the metropolitan area. In scenario 3, a complete removal of the greenbelt resulted in the highest rate of projected urban development. The Seoul Metropolitan Area is under continuous developmental pressure, and the sacrifice of a certain amount of protected land to satisfy this demand may be inevitable. Accordingly, effective urban growth management is necessary to promote ecofriendly and sustainable development in formerly protected areas and to strengthen protection in the areas that will remain protected. The model outputs will be used by the government and policy makers to devise a more flexible and sustainable urban growth management policy.