Many countries around the world are amplifying interest and studies on irrigation, flood control and environment with concern on serious water problems. Especially for irrigation in water supply vulnerable areas such as coastal areas - islands, business on underwater resource security facilities are promoted to secure stable water resources due to development of society and increase of life quality. Also, various policies such as reuse of leaking underwater, utilization of underwater at waterfront, and artificial recharge, etc are planned and designed. In order to develop small sized underwater resource secure technology, verification of seawater-freshwater interface is executed and how the balance between these will develop is a great interest of coastal areas - islands. In this study, seawater-freshwater interface behavior analysis experiment was conducted while reflecting properties of coastal areas - islands and executed hydraulic similitude of saltwater intrusion form control technology on abstraction. Key words : Experiments of hydraulic model, Coastal areas, Seawater-freshwater interface

지하수 의존도가 높은 제주도에서는 담수 지하수는 물론 어류의 육상 양식을 위한 염분이 높은 지하수도 활발하게 개발되고 있다. 본 연구는 제주도 성산유역을 대상으로 담수와 염수 지하수 개발이 지하수계에 미치는 영향을 분석하였다. 경계면 모델을 이용하여 담수와 염수의 흐름을 모의하고 담수와 염수 개발의 영향을 조사하였다. 담수 개발은 기존의 연구결과에서 익히 알려진 바와 같이 지하수위 강하와 해수쐐기 침투를 야기하는 것으로 나타났다. 염지하수 개발은 지하수위를 강하시키는 부정적 영향과 함께 해수침투를 저감시키는 긍정적 효과도 있는 것으로 나타났다. 담-염수 사이의 유한한 두께의 천이대에 대한 수정 Ghyben-Herzberg 비율을 유도하고 해수침투 관측정에서 관측된 자료와 비교하였다.

This study is aimed at the development of the adequate sediment yield formulas in Wi-Stream basin ; IHP representative basin in Korea. As a result of applying outstanding sediment yield formulas among the existing formulas. It is analyzed that including the Engelund & Hansen formula, Yang formula is proper to the Wi-Stream basin. And as a result of sensitivity analysis to the sediment parameters it is analyzed that Rijn and Ackers & White formula is more sensible than any other formulas which has been applied the velocity and depth among the parameters. Also, Engelund & Hansen and Yang formula is less sensible than any other formulas. In Wi-Stream basin, it is analyzed that Yang and Engelund & Hansen formula is the most suitable sediment yield formula in this study. But because the existing formulas had been developed in foreign countries and applied the foreign natural rivers and reservoirs, it makes careful use of Korean alluvial river and hoped that it will be developed the most adequate formula in Wi-Stream basin.

The characteristics of spring machanism in the Cheju Island were analyzed by statistical techniques. Basic characteristics, areal and altitudinal variations, and correlations of spring data were ivestigated. In this study, however, the subjects of the study are the 451 springs, the whole basin of Cheju Island devided into four groups. In this study, analyzed the spring phenomena on the basis of both the geologic elements and the topographic elements. Also, the spring zone in Cheju Island are classified into three types that the mountain area, the middle area, the coastal area in spring distribution by altitude. The quentity of spring and variability show subvariety on the average according to Meinzer`s classification and the whole basin of spring shows various distributions from Third to Sixth. The results of this study can be utilized to evaluate the condition of groundwater development in Cheju Island.