Since parts of Northern Europe still experiences Post-glacial rebound and will rise faster than the expected rise of the ocean level I find this project unnecessary. (I am still a sucker for megaprojects though)
“the post-glacial rebound of northern Great Britain (up to 10 cm per century) is causing a corresponding downward movement of the southern half of the island (up to 5 cm per century)”
IIRC, the Low Countries also are sinking because of post-glacial rebound.
