HAMBURG, Iowa — Floodwaters that breached a Missouri River levee near the Missouri-Iowa border are approaching a makeshift floodwall hurriedly built to protect this small town from the river's creeping advance.

The water, which breached the primary levee on Monday, was expected to reach the temporary structure guarding Hamburg, five miles to the northeast, sometime today, said Robert Michaels, the Army Corps of Engineers official who has overseen the new levee.

It was finished Wednesday, and most of those living in the threatened parts of town are gone.

Meanwhile, any hopes the breaches might alleviate the long-term flooding threat for communities downstream have been short-lived, as river levels that dipped slightly from the release of pressure began their reascent Wednesday.

The river has been rising for weeks as the corps releases increasing amounts of water from its upstream dams to clear out heavy spring rain and snowmelt.

Parts of Montana, North Dakota and South Dakota already have been flooded, and towns and cities farther south were still bracing for the worst. South Dakota officials estimate the state already has spent about $10 million in the first two weeks of work to prevent flooding in Pierre, Fort Pierre and Dakota Dunes.