2.4 STUDY AREA
Korea has long coastlines and various coastal terrains, as it is
surrounded by the sea on three sides. According to recent data, the
lengths of the coastline for the western, southern, and eastern coasts
of South Korea span approximately 4,900, 3,300, and 600 km, respectively
(Ministry of Oceans and Fisheries, 2003). The west coast has numerous
bays, peninsulas, capes, and islands due to the crooked and broken
coastline. In particular, a ria coast is developing in the coastal areas
of the Dadohae and Taean Peninsula, where the coastlines are extremely
crooked. Furthermore, this is also a place where numerous soils of
terrestrial origin are transported and deposited owing to the gentle the
terrain slope, severe tidal differences, and the flow through of Korea’s
great rivers. Consequently, large tidal flats develop along the west
coast, and low hilly mountains or large and small coastal plains are
distributed inland.
Among the sea areas under the influence of seawater intrusion in South
Korea, this study targeted the western coast with severe tidal
differences, where the coastline is long, and the terrain slope is
gentle. The selected study area was a coastal area of the inland,
excluding islands in the north, where urban areas are concentrated on
the western coast of South Korea. The study area consists of nine
administrative districts: Incheon, Asan, Ansan, Gimpo, Hwaseong,
Siheung, Pyeongtaek, Dangjin, and Osan. In all of these nine areas, the
manufacturing industry is developing and urbanization is accelerating,
and there is a continuous influx of population. Incheon is the
third-largest city in terms of population in South Korea after Seoul and
Busan, and has a developed logistics industry as it hosts the Incheon
International Airport and Incheon Port. Ansan is a planned industrial
city, where a population of a similar size to the residential one flows
during the day due to numerous manufacturing plants. The manufacturing
industry was also developed in Gimpo, Hwaseong, Siheung, Pyeongtaek,
Dangjin, and Osan. There is Sihwa Lake Seawall in Siheung, Hwaseong, and
Ansan, where industrial clusters and tourist attractions were developed.
Daebu Island, the only island in the study area, was included in the
study area because it is connected to a freshwater lake through the
Sihwa Lake Seawall. The total area of the study is 3976.59
km2, and the length of the coastline is 608.1 km. The
automatic monitoring data and drill logs of the National Groundwater
Information Center were used to assess the seawater intrusion
vulnerability of the study area. There were 58 groundwater level
stations in total. Further, seawater levels were observed at nine
seawater level stations. Figure 2 shows the locations of the study area,
rivers, coastlines, groundwater level stations, and sea water level
stations.