Sorry for the somewhat scatter-shot posting on the Red River flooding on the North Dakota/Minnesota border, but as we speak I’m sort of figuring this out.
Here’s the basic low down. There are two major settlements threatened by flooding: Grand Forks and Fargo/Moorehead. The former was hit very badly (including a major fire that burned many buildings in town down to the waterline) in the late 1990s (see this post for some more details of that flood). But the bigger threat at the moment seems to be in Fargo/Moorehead (up river from Grand Forks). However, the peak flood stage will be reached at Grand Forks after it has been reached at Fargo/Moorehead, so don’t hold your breath.
Dikes have been built in the Fargo/Moorehead area up to a height of 43 feet, and the flooding is expected to peak at 42 feet. that peak will be reached over the next 24 hours; by about 7 or 8 PM Saturday. However, the maximum flood stage will be maintained for a few days, through mid week. The dikes may be tall enough that they will not be topped, but they also have to stay up long enough that they keep the floods back.
These dikes are not 43 feet high, of course. They are built up from the surrounding landscape to a height of 43 feet above some datum.
How far off can the numbers be on the flood prediction? A foot either way is not impossible, but the predictions are usually pretty good. At this very moment (as I write this) the flood height is actually about a half a foot lower than it was predicted to be. The reduction from predicted flood level seems to be because of the cold weather … some of the water that should be showing up is busy being ice somewhere else. But it will be warmer tomorrow, and likely that will be undone.