A wet spring season continued for the Inland Northwest during the last week of May as another, wet storm system moved through the region producing in the neighborhood of half to one and a half inches of liquid precipitation over Northern Washington May 25-26th. Many basins were already swollen from wet conditions and excessive snowmelt earlier in the month and soils were very saturated and unstable in some locations. As a result, rivers, small streams, and creeks continued to rise near bankfull to above flood stages.  Additionally, several landslides occurred in the Okanogan National Forest.

Flood in OKANOGAN, WASHINGTON
From 27-MAY-11 00:00:00 to 31-MAY-11 23:00:00 (PST-8)
Location: MAZAMA ARPT
Flood cause: Heavy Rain / Snow Melt
Property damage: 8.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Several roads sustained water damage from flooding creeks and streams within the Okanogan National Forest.  These roads include West Chewuch Road, Volstead Road, Cub Creek Road, Boulder Creek, and Harts Pass.  The extent of the damage is not known at this time and damage costs were estimated.

Flood in CHELAN, WASHINGTON
From 28-MAY-11 17:00:00 to 29-MAY-11 18:00:00 (PST-8)
Location: OLDS
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

A swollen Columbia River flooded portions of the Apple Capital Recreation Loop Trail just north of Confluence State Park the evening of the 28th through the 29th.  The flow on the Columbia River hit 335,500 CFS at Rocky Reach Dam.  The high river levels also submerged parts of the sandy spit and pedestrian bridge at Walla Walla Point Park.  Restrooms were closed at Kirby Billingsley Hydro Park for public safety concerns due to high water levels threatening electrical wiring which supplied the restrooms pumping system.

Debris Flow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 31-MAY-11 07:00:00 to 31-MAY-11 08:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Several landslides occurred in the Okanogan National Forest within the War, Scaffold, and Eagle creeks area of the Twisp River. The largest slide was along the War Creek Ridge which inundated about 100 yards of the Forest Service Road leading to the War Creek Trailhead. A survey done from a helicopter shortly after the slide indicated two long channels, which was estimated to be some 30 feet deep. The time of the slide is estimated based on reports.

Debris Flow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 31-MAY-11 15:35:00 to 31-MAY-11 16:00:00 (PST-8)
Property damage: 14.00K
Crop damage: 17.00K
Reported by: Public

A massive landslide occurred in the Pearrygin Lake area just outside Winthrop, WA
on the afternoon of May 31st.  The Okanogan Sheriff's Office reported that the landslide was about 40 acres long and covered 200 yards of Walter Road and majority of a property located at the end of Walter's Road.  The mudslide damaged and spun the homeowner's travel trailer around, damaged a hot tub, pushed a pickup truck 75 feet, but missed his home by 50 feet.  The property owner stated that he had roughly 13 thousand in property damage; 40-60 thousand in cleanup cost; and additional loss due to the range and alfalfa fields being covered in mud and large logs.  The property owner estimated it would be three years before the fields could be planted again.  Agriculture losses were estimated to be near 17 thousand dollars over the three year period.  The slide may have also compromised the aquafer in the area.  Springs which fed the aquifer were torn apart and are currently running down the top of the slide much like a stream.  Residents in the area are digging new holding ponds to mitigate the loss of spring water.  Additionally, a U.S. Forest Service vehicle and four employees were trapped behind the slide but were able to walk through the slide that afternoon and return to town.  The slide was believed to be caused when Pearrygin Creek got dammed upstream and changed course toward Walter Road.   There were no injuries.