There are lots of dikes like these in the Netherlands, they protect the inhabitants from the water.

http://www.youtube.com/watch?v=J7Vy_dbaJwo

http://www.youtube.com/watch?v=q13JchcQFkc

http://www.youtube.com/watch?v=palt8T3Dl3Q

http://www.youtube.com/watch?v=8HnHPK0wJeU