Saemangeum in South Korea is a 40,100 ha ongoing "reclamation" project to dam the estuaries of the Mangyeung and Dongjin Rivers thus replacing vast bird-rich tidal-flats and sea-shallows with land and a huge freshwater reservoir, both still lacking any clear end use. Pictures on this link show a destroyed ecosystem.
Started in 1991, the 33-km long seawall was finally completed on 21st April, 2006.
It is the largest known project of its kind, destroying the single most important site for staging shorebirds in the whole of the Yellow Sea - itself a core area for migrant shorebirds of the East Asian/Australasian Flyway.
Huge objection to this environmental destruction has got nowhere.