Abstract The salt concentration of seawater is a significantly sensitive factor in the seawater reverse osmosis desalination plant that applies different pressures in freshwater production, depending on the salinity of the seawater. For the efficient operation of the plant, it needs to be grounded on investigations and analyses of seawater salt concentration and water temperature distribution and change. The conventional research methods, however, have temporal and spatial limitations. This research uses the latest satellite data to analyze the flows and the seasonal temperature distributions of ocean currents that affect mostly the changes in the seawater salt concentration in the neighboring waters of the seawater desalination plant that is being built in Gijang-gun, Busan, South Korea. The results of this research showed that the ocean current in the neighboring waters of Gijang-gun, Busan had a relatively slow velocity (average: 0.05 m/s) but formed very comprehensive flow shapes as the warm and cold currents met and that the degree of the salinity change was significant because the temperatures of the sea surface differed considerably in summer unlike in the other seasons.
This study focused on the improvement of field investigation process of digital mapping by location-based image data and structured digital map. We analyzed previous methods to find the parts to be improved and suggested new methods. Main concepts of new methods are conducting investigation work indoor and linked the work with map editing for carrying out both work simultaneously by using location-based image data and structured digital map. Pilot project were carried out to compare suggested new methods with previous methods and the applicability were analyzed.
본 연구에서는 인천만의 장기간 조위관측자료를 웨이블릿 방법을 통해 분석하여 평균해수변 결정을 위한 최적의 기간을 제시하고, 적정기간에 대한 우리나라의 수직기준을 새롭게 결정하였다. 그 후 결정된 평균해수면과 연안의 지상기준점(ICGP) 간의 정밀한 높이차를 결정하기 위하여 해수면에 대한 직접적인 레이저 관측을 수행하였으며, 결정된 높이차를 전체 조위관측자료에 대해 선형보간법으로 보정하여 ICGP의 정표고를 계산하였다. 최종적으로는 계산된 ICGP의 정표고를 정밀 GPS 관측과 중력지오이드모델을 이용한 GPS 수준측량 방법을 통해 수준원점 (ORBM)과 연결하고, 새로운 평균해수변 기준의 수준원점 정표고를 결정하였다. 그 결과, 본 연구에서 결정된 인천만의 평균해수면은 1910년대의 평균해수면에 비해 약 0.026m가 변동된 것으로분 석되었으며, 새로운 평균해수면을 기준으로 GPS 수준측량에 의해 재정의된 ORBM 성과는기존성과와 약 0.035m의 차이를 나타내었다. 새로운 ORBM 성과에서 나타난 0.009m의 연결오차는 GPS 수준측량시 GPS 타원체고 결정오차와 지오이드모델링 오차 등에 기인한 것으로 판단된다. 본 연구를 통해서 정밀한 GPS 수준측량만으로 새로운 평균해수변에 기준한 ORBM 정표고 성과를 정밀하게 결정할 수 있었으며, 향후 정표고 체계로의 효율적인 전환을 위해서는 장기간의 조위관측자료를 이용한 수직기준 결정과 함께 GPS 수준측량을 통한 수준성과의 연결을 적극적으로 고려할 필요가 있다. In this study, we suggested the period of tide observations is proper to calculate the mean sea level(MSL) precisely on Incheon tide station using wavelet analysis, and newly determined then the vertical reference surface of Korea using the calculated MSL. In order to calculate the height difference between the calculated MSL and specific ground station (ICGP) near the Incheon tide stations, we performed the laser measurements directly to the sea surface where located below ICGP. The orthometric-height of ICGP was determined that corrected the height difference to the calculated MSL using linear interpolation method. Finally, we connected the orthometric-height of ICGP with the original benchmark (ORBM) using GPS leveling methods for determining the new orthometric-height of ORBM. As the results, there is a variation amount of 0.026m between the new MSL was calculated in this study and old MSL was calculated in 1910's. Also, there is a difference of 0.035m between the new and old orthometric-heights of ORBM. The connection (or leveling) error of 0.009m was revealed in new orthometric height of ORBM with consideration of MSL variation which may caused by the error of GPS ellipsoid height and/or geoid model. In this study, we could be determined precisely the orthometric-height of ORBM based on the new MSL of Incheon Bay using only GPS leveling method, not a spirit leveling method. Therefore, it is necessary to determine the vertical datum strictly using long-term and continuously tide observations more than 19 years and to use the GPS leveling method widely in the height leveling work for the effective changeover from the orthonormal to the orthometric in national height system.
In disaster management, it is essential to evaluate how dangerous the disasters are and how vulnerable our communities are to them. The Region Safety Index and the Region Safety Levels provide information about the level of safety in a local area against disasters, but this information is not enough for use in disaster management. This study proposes a vulnerability assessment method that utilizes the concept of a vulnerability function to analyze disaster records, weather data, and statistical data using a GIS program. We identified regions vulnerable to heavy rain using vulnerability figures and analyzed time-series changes in region vulnerability. This vulnerability assessment provides specific information on disasters and can be used by disaster managers as empirical information for planning and implementing disaster management plans.
risk analysis, risk assessment, vulnerability assessment, light detection and ranging sensorIn this study, we performed the hazard assessment, vulnerability assessment, and risk analysis of debris flows using a digital elevation model (DEM) obtained from a light detection and ranging (LiDAR) sensor, a numerical analysis model, and a geographic information system (GIS) spatial analysis technique to evaluate the debris flow disaster risk in Bukhansan National Park, which is located in an urban area of Seoul.The debris flow disaster risk analysis involved analyzing the debris flow disaster hazard zones and the exposure and vulnerability to risk elements for different rainfall frequency scenarios, and we determined the risks for two watersheds.We identified the potential risk elements at the watersheds and estimated the total amount of risk to buildings that could occur annually from debris flow disasters.Risk maps were drawn by determining the targets exposed to debris flow hazards at each watershed and by measuring the degree of vulnerability and loss at the watersheds.The findings of this study suggest that it is possible to provide important information to support efficient decision-making processes, such as establishing a hazard zone management plan and preparing structural and non-structural measures to minimize the damage through disaster risk management.
'%3e%3cg id='b'%3e%3cpath id='a' stroke='%23000' stroke-width='2' d='M-6-25H6m-12 3H6m-12 3H6'/%3e%3cuse xlink:href='%23a' y='44'/%3e%3c/g%3e%3cpath stroke='%23fff' d='M0 17v10'/%3e%3ccircle r='12' fill='%23cd2e3a'/%3e%3cpath fill='%230047a0' d='M0-12A6 6 0 0 0 0 0a6 6 0 0 1 0 12 12 12 0 0 1 0-24z'/%3e%3c/g%3e%3cg transform='rotate(-123.69)'%3e%3cuse xlink:href='%23b'/%3e%3cpath stroke='%23fff' d='M0-23.5v3M0 17v3.5m0 3v3'/%3e%3c/g%3e%3c/svg%3e)