Geography of South Korea - Topography and Drainage

Topography and Drainage

Early European visitors to Korea remarked that the land resembled "a sea in a heavy gale" because of the large number of successive mountain ranges that crisscross the peninsula. The highest mountains are in North Korea. The highest mountain peak in South Korea is Hallasan (1,950 m), which is the cone of a volcanic formation constituting Jeju Island. There are three major mountain ranges within South Korea: the Taebaek Mountains, and Sobaek ranges, and the Jiri Massif.

Unlike Japan or the northern provinces of China, the Korean Peninsula is geologically stable. There are no active volcanoes (aside from Baekdu Mountain on the border between North Korea and China, most recently active in 1903), and there have been no strong earthquakes. Historical records, however, describe volcanic activity on Mount Halla during the Goryeo Dynasty (918–1392).

South Korea has no extensive plains; its lowlands are the product of mountain erosion. Approximately 30 percent of the area of South Korea consists of lowlands, with the rest consisting of uplands and mountains. The great majority of the lowland area lies along the coasts, particularly the west coast, and along the major rivers. The most important lowlands are the Han River plain around Seoul, the Pyeongtaek coastal plain southwest of Seoul, the Geum River basin, the Nakdong River basin, and the Yeongsan and the Honam plains in the southwest. A narrow littoral plain extends along the east coast.

The Nakdong is South Korea's longest river (521 kilometers). The Han River, which flows through Seoul, is 514 kilometers long, and the Geum River is 401 kilometers long. Other major rivers include the Imjin, which flows through both North Korea and South Korea and forms an estuary with the Han River; the Bukhan, a tributary of the Han that also flows out of North Korea; and the Somjin. The major rivers flow north to south or east to west and empty into the Yellow Sea or the Korea Strait. They tend to be broad and shallow and to have wide seasonal variations in water flow.

In the early part of 20th century and especially the period during and after the World War II and the Korean War, much of the existing Korean forests were cut down, which led to problems with flooding and soil erosion. Combination of reforestation efforts (e.g. Arbor day was celebrated as a national holiday starting in 1949) and policies designed to reduce use of firewood as a source of energy (e.g. restriction of inflow of firewood into Seoul and other major cities starting in 1958) helped to spark a recovery in the 1950s. Comprehensive reforestation programs starting in the 1970s and continuing into the late 1990s aided in an acceleration of forest volume increase, and the forest cover reached a peak of 65% of national land area in 1980 as opposed to a low of 35% in 1955.

News that North Korea was constructing a huge multipurpose dam at the base of Geumgangsan (1,638 m) north of the DMZ caused considerable consternation in South Korea during the mid-1980s. South Korean authorities feared that once completed, a sudden release of the dam's waters into the Pukhan River during north-south hostilities could flood Seoul and paralyze the capital region. During 1987 the Geumgangsan Dam was a major issue that Seoul sought to raise in talks with Pyongyang. Though Seoul completed a "Peace Dam" on the Pukhan River to counteract the potential threat of Pyongyang's dam project before the 1988 Olympics, the North Korean project apparently still was in its initial stages of construction in 1990.

Maritime claims:
contiguous zone: 24 nmi (44.4 km; 27.6 mi)
continental shelf: not specified
exclusive economic zone: 200 nmi (370.4 km; 230.2 mi)
territorial sea: 12 nmi (22.2 km; 13.8 mi); between 3 nmi (5.6 km; 3.5 mi) and 12 nmi (22.2 km; 13.8 mi) in the Korea Strait

Elevation extremes:
lowest point: Sea level 0 m
highest point: Hallasan 1,950 m