Friday, January 21, 2011
You know a river is acting crazy when kayakers measure its flow in BFS instead of CFS. That's BFS for board-feet-per-second; and Sunday's mid-morning rate of raw lumber floating under Tucker Bridge was somewhere between impressive and downright ludicrous.
At 13.2 feet, the Hood reached flood stage by that morning, making the river a boiling blend of chocolate tree soup that shook the ground as it carried boulders downstream.
With disregard to what most would call obvious red flags, a group of boaters suited up, hauled their kayaks and a large raft to a vaguely calm part of the river under Tucker Bridge and departed on an extreme and very fast journey to the Columbia River.
The high-velocity ping pong ride carried the boaters quickly past the former Powerdale Dam site, where the sound of rocks rolling along the river bottom created a constant, thunderous growl.
The group had to pull out and walk around the railroad trestle just outside downtown, where water reached to the bottom of the bridge and logs jammed into the steel sent water spilling onto the tracks.
Not far downstream, the boaters pulled out near the confluence of the Hood and Columbia, where debris ranging from fetch-sized sticks to old growth timber floated around before either heading downriver or finding a place to rest in the sand.
Several days of rain over the last week was topped Sunday by a record-setting soak that saw 1.12 inches of precipitation in Hood River and up to six times that much on Mount Hood. Mt. Hood Meadows recorded 5.45 inches and Timberline 6.76 inches of rain in a 24-hour period, which sent rivers on all sides of the mountain into a raging state of craziness. The amount measured at the Oregon State University Experiment Station was the highest on record for any Jan. 16 since 1953, when 1.06 inches made the 24-hour record.
Aside from a few minor reports, however, no major damage or incidences in Hood River County were reported from the flooding.
County 9-11 dispatch reported six high water/weather-related calls for assistance between Friday and Sunday. On Jan. 14, two trees were reported down across Cloud Cap Road. The following day a tree was reported down across Herman Creek Road. On Sunday another down tree was reported in Parkdale, high water was reported at Toll Bridge Park and at a bridge on Woodworth Road.
The crossing at Woodworth flooded over the road and as a result the bridge was closed through Monday.
Residents on the south side of the mountain were not as lucky, as much heavier rainfall focused over Timberline and its drainages caused more extensive flooding that took out homes, power lines, cars, a stretch of Lolo Pass Road and anything else standing in its way.
"The main reason we don't see a lot of flood damage in the valley is the limited number of structures we have in flood plains," said Anne Saxby, district manager of the Hood River Soil and Water Conservation District. "We have very incised channels for much of our rivers, and not a lot of development in flood plains; so it limits the risk of damage during flooding."
Having a limited or nonexistent snow pack in rural areas also contributed to the lack of flooding over the weekend, as smaller streams and drainage ditches were clear of melting snow and debris.
"The soil was able to handle the water pretty well," Saxby said. "One thing that benefits farmers around here during these events is that, by virtue of having so many orchards, our soil is well-protected from erosion."
Farther up on Mount Hood, where many areas are highly prone to erosion, the presence of an established snowpack actually protected from landslides and debris flows. Snowpack and ice hold loose soil in place and help channel water into drainages.
This weather event was similar in scope to flooding in 2006 that triggered massive debris flows in several of Mount Hood's canyons; including one in Eliot Canyon that swept the length of the valley and deposited roughly 26 acres of sediment at the mouth of the Hood River.
The difference, however, is one that geologists note as a key detail: The event in 2006 occurred in November, when a significant snowpack hadn't been established to stabilize the loose lower walls of Eliot Canyon.
"We are transitioning quickly back to normal," said Dave Tragethon of Mt. Hood Meadows Ski Resort, who reported a change from rain to snow on the slopes by Monday afternoon. "Our snowpack absorbed most of the moisture. It's a little sad; if temperatures were about eight degrees lower, we would have potentially had 10 feet of new snow."
As it is, the area reports 73 inches as its base; down 16 inches from the start of the rain last week.
Raging creeks and rivers created a tree soup of sorts that carried a significant amount of wood downstream to the mouth of the Hood River, where the massive delta caused a backup of the lumber medley headed toward the Columbia. Log jams came to rest in calm waters on both the east and west sides of the delta. By Monday west winds into the 40 mile an hour range pushed a significant amount of wood onto the windward edge of the sandbar.
"Just based on a visual check of the area, there's no obvious damage to anything," said Michael McElwee, Port of Hood River executive director. "We'll have to wait for the water to come down to know for sure, but it looks like the event wasn't anything very unusual."
McElwee noted that once the Columbia River is raised and lowered a few times, as is typical in the spring, a majority of the loose material on or near the delta should be washed away.
"It's always interesting to see what happens after something like this," he said. "There's clearly some additional sediment buildup at the mouth of the river, but we'll have to wait until the water goes down to really see what's going on down there."