Flooding caused by rain and snowmelt continues to wreak havoc on roads and threaten structures in Union and Wallowa counties.

Flooding in Union County has forced the closures of Pierce Road, Alicel Lane and Rhinehart Lane, a portion of Highway 237 and left much of Hilgard State Park under water over the past three days. Floodwaters in Wallowa County have forced the closure of all or portions of Jim Town and Whiskey Roads. The picture overall in Wallowa County is so bad that its board of commissioners declared a state of emergency Tuesday due to flooding throughout the county.

Motorists are being urged to be very cautious when driving on flooded roads.

“You don’t know how deep the water is and what is under it,” said Union County Public Works Director Doug Wright.

The flooding is caused by spring snowmelt and unusually heavy rainfall, according to Marilyn Lohmann, a hydrologist with the National Weather Service office in Pendleton.

“The rain has compounded the problem,” Lohmann said.

She said late Tuesday morning Union and Wallowa counties had received two to three inches of rain over the past 48 hours. The amount of precipitation is very high for this time of year.

“It is a once-in-a-20-year event,” Lohmann said.

She said many parts of the region over that 48-hour period received two to three times as much rain than they normally do in all of April. Lohmann explained that the excessive rain was caused by a pool of moisture that came in from the Pacific Ocean.

Union is among the local cities hardest hit by flooding. On Tuesday, portions of Little Creek overflowed. Among the areas impacted by the high water was the Forest Service ranger station building, which is owned by the city and includes structures renters live in.

Water seeped into one of the homes and was pumped out between 5 a.m. and 6 a.m. Tuesday, said Union’s city administrator, Doug Wiggins. The ranger station structures have not had to be evacuated.

Also in Union, floodwaters have surrounded two homes near the Eastern Oregon Livestock Show Grounds.

“The houses (appear to be) on islands,” Wiggins said Tuesday morning.

Fortunately, as of Tuesday evening, water has not seeped into either of the homes.

In La Grande, flooding in the south end of town caused the closure of 18th Street for several hours early Tuesday morning when water from a ditch spilled onto the road. Crews then used sandbags to divert the water back into the ditch, said City of La Grande Public Works Director Kyle Carpenter.

La Grande public works crews have also been working to prevent Mill Creek, which runs north down a hill to C Avenue and then through a culvert, from overflowing.

“We are closely monitoring its level,” Carpenter said.

Crews have been checking Mill Creek day and night and removing large amounts of rocks and other debris from the stream with a backhoe to keep it within its banks. Carpenter said if the stream jumps its banks, crews will use sandbags to divert the water down to C Avenue.

No other streams in La Grande have been posing a problem, he said.

“Mill Creek is only one acting up,” Carpenter said.

He said this may be because Mill Creek draws from many sources of water.

The threat of flooding will exist in Northeast Oregon at least through Friday. The National Weather Service has a flood warning in place for streams and creeks in Union County and western Wallowa County through 4:45 p.m. today. The NWS also has a flood warning for the Grande Ronde River near Perry which will be in effect through Friday.