GRAND FORKS, N.D. (AP) _ Evacuations spread through little towns up the Red River Valley today as the flood that left this city a ghost town flowed relentlessly across the flat prairie toward Canada.

Communities rushed to reinforce flood walls and move potentially harmful materials out of the way

``Basically, we're evacuating all of the rural areas and all of the cities and towns in about the eastern 15 percent of Pembina County,'' said Andrew Thostenson, extension agent for the agricultural county north of Grand Forks and next to the Canadian border.

``The flooding is coming,'' he said.

Authorities said about 1,000 people still needed to be evacuated. ``Quite a few people have left,'' Thostenson said.

President Clinton flew to the area today and headed for the Grand Forks Air Force base west of town, which has become a shelter for about 2,000 people from the city.

In southern Pembina County, a crack in a dike prompted evacuations today in Drayton, a town of 1,000 people.

``Drayton right now is basically empty,'' said National Guard Sgt. Rob Keller.

A fertilizer plant in Drayton put out a call for help and a fleet of trucks arrived to move some 360 tons of dry fertilizer that officials had feared would ruin the local water supply if the flood soaked it into the ground.

``It was very scary, that's for sure,'' said Kent Satrang, manager of the Cenex fertilizer plant.

In Grand Forks, the Red River had risen so high that even the equipment used to measure the flood was swamped. U.S. Geological Survey officials said they could not definitely say the river had finally crested, though they said it was holding steady at about 54 feet _ 26 feet above flood stage.

``We've been having a lot of difficulty just getting the measurements, because protection and property has to come first,'' said Russ Harkness, acting district chief for USGS in North Dakota.

The river had chased out nearly all the 50,000 residents of Grand Forks.

``We knew we were losing it all, so we pulled all the steaks out of the freezer and had one last good supper,'' John Neppel said Monday from Bemidji, Minn., where his family had taken refuge.

People who stayed behind have had to cope with filthy, icy floodwater that cut off drinking water supplies and blocked firefighters from getting to a blaze that ravaged three downtown business blocks.

Cleanup for the city itself could cost in the tens of millions, and damage could top $1 billion, local officials said.

``We will rebuild Grand Forks, North Dakota, to better than it was before,'' Gov. Ed Schafer said on NBC's ``Today'' show this morning.

Portable bathrooms and water tanks were set up in Grand Forks' unsubmerged west end. Residents were limited to one 1-gallon jug of water a day. The sale of alcohol was banned; barrooms and liquor stores were ordered shut by Mayor Pat Owens, who was worried about her residents' exhausted state of body and mind.

National Guard soldiers in small boats zoomed past submerged cars on their way to rescue people trapped in their homes. Some homes floated off foundations.

``I want to go back to something, at least the frame of the house,'' said Jennifer Butler, who left her downtown apartment and was staying with her parents in the west end.

The National Guard Armory was a center for everything from pet information to tetanus shots, cots and quick meals.

Volunteers dished up beef stew, salad, bratwurst and milk. Out front, people left their names so friends and relatives could find them.

Neppel spent Monday trying to locate his 18-year-old son, Chad. They became separated when the family hurriedly split up during the evacuation Friday night.

``I think he's OK, but I don't know,'' Neppel said, his voice breaking.

``I just want to know that he's safe,'' he said. ``I want to give him some reassurance that we'll get together soon.''