OTTUMWA — Flooding on the Des Moines River has been going on for weeks in southeast Iowa, but what happened Monday night is new.

Storms hammered the area for hours on end. When one ended another formed and hit the same area, sending a month’s worth of rain into some areas in just a few hours.

Appanoose County took the worst of it. One report to the National Weather Service from north of Centerville recorded 7.1 inches of rain beginning at 6 p.m. Another report indicated three feet of water flowing over the intersection of 285th Avenue and 570th Street.

The rain turned normally quiet streams into roaring torrents and it appears to have been enough to put Lake Rathbun at risk of going over the emergency spillway for the first time since the Flood of 1993.

Phil Brown, operations manager for the lake, said forecasters expect Rathbun’s level to top the spillway today or tomorrow. But the timing and severity depend heavily on how much water flows in from feeder streams or from new storms.

“The current forecast does have us coming up over the spillway elevation,” Brown said.

That forecast indicates spillway flows of 1,000-1,500 cubic feet per second. That’s more than what happened in 1993 but only a fraction of the total spillway capacity.

To Brown, the real issue with water coming off the emergency spillway is that it is uncontrolled. Water released from the dam under normal conditions is a similar volume, but the dam can control how much or how little comes out.

The possibility of the lake running out the emergency spillway prompted evacuation of some particularly vulnerable residents. Russ Strickler lives just outside the evacuation area, so he went to the dam to see for himself.

“I’m on a dead end road right on the Chariton River,” he said, and was surprised when the river rose by six feet in less than a day. “It’s in my backyard.”

Strickler should be fine, though he is considering moving a friend’s boat to his house as a precaution until the water goes down. Not everyone stayed dry. Rosie Mini Storage on the north end of town had one building flooded, though several others stayed out of the water.

John Arnold spent much of Tuesday out on the roads for Appanoose County Emergency Management. His Centerville home got five inches of rain, but he heard about some locations in southwestern Appanoose County that saw 8-9 inches.

Arnold said many roads remained under water Tuesday. Even where the water had gone down crews were still closing bridges until an inspector could get in and make sure they were safe.

The issue isn’t the bridge deck that’s at risk. It’s the ground around the supports. Fast-moving water can scour away the earth, dangerously weakening the bridge. Debris from floodwaters can also cause damage that’s not visible to the untrained eye.

“The public needs to be very careful. If water is over the road, don’t drive onto it. If there are barricades, don’t remove them or try to get around them,” Arnold said.

Another major concern was Centerville’s western treatment plant for waste water. It was partially under water because Cooper Creek was way beyond its banks. Officials said the eastern plant remained fully operational.

Arnold estimated Appanoose County sustained more than $1 million in damage to its roads and bridges. It will be several days before all the roads reopen.

The damage prompted Gov. Chet Culver to issue a disaster proclamation for Appanoose County.

While the most dramatic changes took place with smaller bodies of water, the Des Moines River at Ottumwa jumped again. Records show the river was at 16.57 feet at 6:30 p.m., before the rain hit, and rose to 17.18 feet before midnight. That’s more than six feet above flood stage and forecasters predict it will crest again at 17.4 feet today.

In Ottumwa, a lightning strike knocked out power for some residents. That outage also knocked pumps near Vine Street offline, allowing the water to rise near some neighborhoods.

Davis County dodged the worst of the storm. County Engineer Dave Grove said southwestern Davis County got the most rain, but it didn’t compare to the extreme amounts in Appanoose County.

The heavy rains did wash out a couple spots, but Grove said crews bladed the roads and put in new rock to get them back to normal.