Flood Control Dam #678, presumably one of Dimwit Flathead's dam projects, was built in the Eastlands sometime after Flood Control Dam #3 (which was completed in 783 GUE). Little is known of this dam, save that the forces of Ellron allied with the Enchanters' Guild, and Thaddeus Kaine clashed here in 935, which resulted in heavy loses for Kaine.

Thaddeus summarized the battle to Sophia Hamilton in a letter dated Augur 14, 935:

It is rainy and grim here. The fields are muddy and littered with corpses. I am tired of all this. All I want in the world is to return to my castle and back to you. The battle at Flood Control Dam number 678 was more brutal than I expected. Ellron and his hordes somehow had found out about my strategy. Backed by the Enchanters, he has discovered some magical scroll which causes weapons to turn to fudge. It is disheartening and sticky. Our surprise attack was foiled and I lost half my men. Ellron is becoming more and more powerful. Unless I do something, he may gain control of the entire terrain. Morale is low. The worst are the damn night attacks of grues. We barely have enough torches to light a fourth of our camp for more than a few more nights.

SOURCE(S): Zork: Nemesis