Reconstruction of the History of the Byeokgolje Dam Constructed in the Tidal Lowlands in Korea

It was long thought that seadike construction in Korea's tidal areas had begun in Ganghwa Island, located in the Yellow Sea, after the Mongolian invasion of Korea in ad 1235. In the history books, the Byeokgolje Dam, which was built across the tidal Wonpyeongcheon Stream and Lowland around ad 330, was only described as a water reservoir, but nowadays several historians assume that the Byeokgolje Dam was the first dike constructed in Korean tidal lowlands, but was also used to store fresh water. In this study, we investigate whether the Byeokgolje Dam was indeed constructed as a seadike and we assess its contribution to the sustainable development of this tidal area. We conclude that the dam was indeed built as a seadike because we have discovered that the bottom elevation of the dam is below seawater level during high tide. In 1415, the Byeokgolje Dam was rehabilitated and enlarged to store more water; however, it was ruined by an extreme flood in 1420. Since that time and until the Saemangeum Seadike was closed in 2006, the reservoir area inside the dam was gradually reclaimed for agricultural land and residential areas. This was possible because enough sediment was available both from the coastal water and the upstream river. We describe that in the course of time, sequential tidal reclamation works have been carried out in the estuaries of the Dongjingang and Mangyeonggang rivers. Copyright © 2018 John Wiley & Sons, Ltd. Résumé Longtemps, on pensait que la construction de digues de protection maritime dans les zones d'estran de Corée avait commencé dans l'île de Ganghwa, située dans la mer Jaune, après l'invasion mongole en 1235 apr. J.‐C. Dans les livres d'histoire, le barrage de Byeokgolje, qui a été construit en travers de la rivière Wonpyeongcheon vers 330 av. J.‐C., a été décrit comme un réservoir d'eau, mais aujourd'hui, plusieurs historiens supposent que le barrage Byeokgolje est la première digue construite dans un bas‐fond d'estran, et qu'il était également utilisé pour stocker de l'eau douce. Dans cette étude, nous étudierons si le barrage de Byeokgolje a été construit en tant que tel et nous évaluerons sa contribution au développement durable de cette zone d'estran. Nous en concluons que le barrage a été construit en tant que tel parce que nous avons découvert que l'altitude la plus basse du barrage était inférieure au niveau des marées hautes. En 1415, le barrage de Byeokgolje a été réhabilité et agrandi pour stocker plus d'eau, mais il a ét