The benefits of rain on fire seem obvious. But firefighting officials were concerned Saturday about erosion and flooding threats in the Columbia River Gorge posed by several days of anticipated precipitation.

Given two weeks of steady burn activity in the Gorge, those officials believe some damage is inevitable. But it was impossible to forecast the extent Saturday, they said, in part because the Eagle Creek fire is still burning.

"Usually it takes years - four to five - for vegetation to grow back and the ground to stabilize," said Steven Sobieszczyk, a U.S. Geological Survey hydrologist in Portland.

Even before the Eagle Creek fire, the Gorge presented great potential for landslide, experts say. With steep hillsides denuded of ground cover and a tree crown canopy, precipitation will have an unimpeded pounding into the surface. Determing how to deal with its damaging effects, they say, will depend on figuring out first where the worst damage has occurred.

This much was clear on Saturday:

Rain could arrive in Portland and the rest of the Pacific Northwest late Sunday morning and continue through much of the week. Snow levels will be around 9,000 feet Sunday then drop to 5,000 to 6,000 feet by Monday and remain near that level through the week. For comparison: Timberline Lodge is located at 6,000 feet; Government Camp is at 4,416 feet; and Mount Defiance, the tallest point in the Columbia River Gorge, is 4,960 feet.

"We're going to have a major shift in the weather pattern," National Weather Service meteorologist Laurel McCoy said. "We've been so dry and hot these past few months."

The Eagle Creek fire, which started at about 4 p.m. Sept. 2, has burned 45,579 acres and, as of Saturday afternoon, was 32 percent contained. Dry and windy conditions were expected to grow the fire on the southern and western edges.

The rain is "going to dampen the fire," fire spokesman Dave Schmitt said, "and in many cases it's going to go a long ways to putting it out, especially along with edges in the high country where we've been reluctant to put people."

Schmitt said fire crews spent part of Saturday removing equipment from fire lines, in part because of the anticipated fire-extinguishing benefits of rain, in part because of the anticipated difficulty of moving tools and equipment on rain-slickened terrain.

Sobieszczyk, the USGS hydrologist, said the conditions in much of the Gorge are treacherous.

"There's nothing to stabilize the ground," he said. "You have water falling directly on the ground, with ash and debris. The cover is gone, the understory is burned off."

Sobieszczyk pointed to a home in Dodson, demolished in February 1996, as an example of the destructive power of a Gorge landslide. The home, 10 miles west of Cascade Locks, still stands but is uninhabitable.

The U.S. Forest Service is expected to dispatch a Burned Area Emergency Response team to map the fire's severity in all portions of the Gorge once the Eagle Creek fire is extinguished, Sobieszczyk said.

"Once you do that," he said. "You can learn where the most severe burns are."

In the meantime, the Oregon Department of Geology and Mineral Industries expects to release an updated landslide hazards map next week, said Bill Burns, geology engineer and landslide specialist.

The map, envisioned and prepared long before the Eagle Creek fire, would be valuable to land managers because it will show them up-to-date data on the most vulnerable parts of the Gorge.

The Forest Service "can bring that data into their own system," Burns said, "and see where they burn overlaps with landslides."

The Oregon Department of Transportation, meanwhile, is looking a long-term closure of a 12-mile portion of the Historic Columbia River Highway -- Larch Mountain to Ainsworth State Park -- and an uncertain timeline for reopening the eastbound lanes of Interstate 84 between Troutdale and Hood River. The interstate's westbound lanes were opened Thursday evening, though they were closed briefly Saturday morning for tree removal.

"We have the rock scalers out there. They're been out there all week," dislodging rocks in obvious need of removal, ODOT spokesman Don Hamilton said. "There are dangers and we're going to find out how the rain is going to affect them...by next week we should know more."

--Allan Brettman

503-294-5900

@allanbrettman