Bart Schultz
The country has a humid continental climate and a humid subtropical climate, with more precipitation in the summer during a short rainy season, which begins in late June to late July and continues through September. Winters can be extremely cold. The southern coast is prone to typhoons in late summer, bringing storms, heavy rains, and sometimes flooding. Average annual precipitation ranges from 1,370 mm in Seoul to 1,470 mm in Busan.
South Korea can be divided into an eastern region with high mountain ranges and narrow coastal plains, a western region with broad coastal plains and rolling hills, a southwestern region with mountains and valleys, and a southeastern region dominated by the Nakdong River Basin. The polders are mainly located in the West and Southeast.
South Korea, and in fact North Korea also, have the somewhat favourable situation that a lot of silt from the Yellow River is supplied to the Yellow Sea. The Yellow Sea may also owe its name to this. It is also reported that part of the silt in the Yellow Sea comes from sandstorms in the Gobi Desert. In any case, there is a lot of very fertile silt in the Yellow Sea, which causes a siltation of two to three centimetres per year along the west coast of the Korean peninsula, which produces fertile land when reclaimed.
Coastal land reclamation in Korea has a long history, as described by Sang-Hyun Park and others. They state that coastal land reclamation began in 330 with the construction of the Byeokgolje Dam. Since then, and especially in the twentieth century, large-scale land reclamation projects have been carried out, consisting of a multitude of dikes and polders with a total area of approximately 1,350 square kilometres. Some large land reclamations concern the polders on Gangwa Island, Yeongsan, Shihwa, polders in the Nakdong River Delta and Saemangeum. A contribution by me about the latter land reclamation was placed on Flevolands Geheugen in 2020.
During one of my visits to South Korea, we were shown a plan for the construction of a new city for half a million inhabitants in the proposed Shihwa polder. We noticed that there was almost no open water in the plan. When it rains in Korea, it often rains much harder than in the Netherlands. We asked why there was so little space reserved for open water. We were kindly told that it would flow down the mountain. We said: "You are now at the bottom and you will have to pump out almost all the excess water." That was a bit of a disappointment, because the land in the proposed reclamation would be worth a lot of money, and you don't get that for open water. We then made a draft plan with them which, as far as we could see, included sufficient open water and large pumping stations.
A special condition with the reclamations is the tide, which rises along the west coast from South to North to about seven metres at the border with North Korea. On the one hand this is favourable, because at low tide a lot of excess water can be discharged from the polder areas, but on the other hand it usually also requires a large sea dike to keep the water outside the polder at high tide. In addition, inner dikes and irrigation and drainage systems are usually needed. The reclamations are therefore expensive, but economically certainly justified due to the extremely high land prices in South Korea.
There are also major objections to the reclamations, mainly from a fishing and environmental perspective. The Koreans therefore assume that the Saemangeum project, which is now more or less complete, will probably be their last reclamation project. Given the high demand for land, I wonder if this will indeed be the case.
