A stationary trough of low pressure off the Pacific Northwest Coast steered a deep fetch of subtropical moisture into the Idaho Panhandle which persisted from the end of March through April 7th bringing several rounds of heavy rain.  Mild temperatures and breezy winds accompanying the subtropical moisture feed resulted in excessive mid-elevation snowmelt. The combination of heavy rainfall and excessive runoff resulted in sharp rises in most basins within the Idaho Panhandle.  In addition, saturated soils became unstable in some locations resulting in debris flows.  There were no injuries or reports of damage to residences or businesses however, significant damage was observed along transportation infrastructure within Bonner, Boundary, Lewis, Nez Perce, and Shoshone Counties as well as the Nez Perce Reservation.

Debris Flow in CENTRAL PANHANDLE MOUNTAINS, IDAHO
From 01-APR-11 00:00:00 to 20-APR-11 23:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A large debris flow which began around noon on March 30th along Forest Road 208 continued to slide as of April 20th. The slide blocked access to six permanent residences.  There was an estimated 25,000 cubic yards of rock and mud over the road.  The estimated cost to remove the earth and fix any damage to the road was 330 thousand dollars.

Debris Flow in LEWIS AND SOUTHERN NEZ PERCE, IDAHO
From 02-APR-11 00:00:00 to 02-APR-11 01:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A landslide was observed along Flatiron Road at the south end of Sweetwater Creek near Waha.

Debris Flow in LEWISTON AREA, IDAHO
From 02-APR-11 00:00:00 to 02-APR-11 23:59:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A landslide was observed on the Old Winchester Grade above a pond which is adjacent to a private residence.  Exact time of the slide was unknown.

Debris Flow in LEWISTON AREA, IDAHO
From 04-APR-11 19:00:00 to 04-APR-11 23:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

The Lewiston Tribune reported a couple of small mudslides along highway 12 late Monday, April 4th that resulted in one road closure and some lane blockages.  The exact time and location of each slide was unknown.

Debris Flow in NORTHERN PANHANDLE, IDAHO
From 06-APR-11 00:00:00 to 06-APR-11 10:00:00 (PST-8)
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Cut slope failure 200 feet wide and 200 feet above Lions Den Road.  Ten foot rotational shear slid onto roadway.  Some areas of the slope had sheared but not slipped completely.  Estimated cost to remove slide and repair road is 500 thousand dollars.  Exact time of slide was unknown.

Debris Flow in NORTHERN PANHANDLE, IDAHO
From 06-APR-11 00:00:00 to 06-APR-11 10:00:00 (PST-8)
Property damage: 800.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Cut slope above Fleming Creek Road sheared and slid bringing trees and clay onto and across roadway.  Outside shoulder over fill is settled and roadway cracked along the mid-lane.  Damage occurred along a 2500 foot long section of the roadway.  Estimated cost to remove slide and repair roadway is $800 thousand.  Exact time of the slide was unknown.

Flood in LEWIS, IDAHO
From 02-APR-11 00:00:00 to 03-APR-11 00:00:00 (PST-8)
Location: KAMIAH
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flooding of Lawyer's Creek resulted in closures of Lawyer's Creek Road between highway 162 and Flying B Ranch.  The main creek split with one flow going toward Flying B Ranch where one resident reported at least one foot of water around his house.  The rest of the creek flowed eastward to Robinson's Pond where it ate away at the levy between the pond and highway spilling about three feet of water over the road.

Debris Flow in CENTRAL PANHANDLE MOUNTAINS, IDAHO
From 01-APR-11 00:00:00 to 02-APR-11 10:00:00 (PST-8)
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A 24 inch culvert separated under a two lane paved road (Dobson Pass, FR 456) on a steep hill causing the slope to slide down the hill taking one half of the paved lane with it.  The fill slope failure was 160 feet long and the paved roadway failure is 80 feet long.  At the Dobson Pass Narrows, the outside fill slope was sliding down the hill reducing the road to one lane.  The road shoulder was gone and pavement was undermined.  The site was 300 feet long.  The slide may have begun with heavy rainfall from March 31st and April 1st but was not discovered until April 2nd.  The estimated cost of damage to the roadway was $75,000.

Debris Flow in LEWIS AND SOUTHERN NEZ PERCE, IDAHO
From 02-APR-11 00:00:00 to 02-APR-11 23:59:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A house in the Waha area (40486 Hawkview Lane) and its hillside had minor sliding.  Residents at the location were evacuated by the Sheriff's Office.  Exact time of the slide was unknown.

Flood in BENEWAH, IDAHO
From 02-APR-11 10:00:00 to 03-APR-11 10:00:00 (PST-8)
Location: FERNWOOD
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

The Coeur D Alene Press reported that the St Maries River flooded it banks at Fernwood covering a manhole in town, leaking wastewater into the river.   There were no direct impacts to health or wildlife.

Flood in NEZ PERCE, IDAHO
From 02-APR-11 00:00:00 to 03-APR-11 23:59:00 (PST-8)
Location: NORTH LAPWAI
Flood cause: Heavy Rain / Snow Melt
Property damage: 600.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flooding of several creeks and streams resulted in damage, closures, and evacuations along numerous roads along with minor flooding of six homes.  Roads that were damaged include Webb Road, McCormack Ridge Road, Garden Gulch Road near Highway 95, Cottonwood Creek Road, Flatiron Road, and Mission Creek Road near Highway 95.  Reservation Line Road and Webb Canal Road were also closed for a short time due to flooding.  The worst of the flooding occurred along Webb Creek which flooded several low-lying areas, including the junction with Highway 95 and the junction with McCormick Ridge Road where reports stated water covered the bridge at the junction of McCormick Ridge Road.  The Web Store Smoke Shop was inundated with approximately one foot of water.  Around six homes along Webb Road experienced flooding up to the homes foundations.  Mission Creek also spilled out of its banks with water reported to be flowing down Mission Creek Road, over the Mission Creek Bridge, and into nearby pastures and front yards. Sweetwater Creek, Lapwai Creek and Cottonwood Creek also had minor flooding with the Spalding church suffering the greatest damage.  A culvert was plugged along Lapwai Creek near the intersection of Highway 95 and Garden Gulch Road causing road damage and a two day road closure.  A plugged culvert along Sweetwater Creek led to approximately 30 feet of pavement erosion along Flatiron Road and 1500 feet of ditch and shoulder erosion.  The Emergency Manager of Nez Perce County estimated flood damage to the roads was around $74,000 with most of the damage along Flatiron Road and Garden Gulch Road near Highway 95.  On the Nez Perce Indian Reservation, at least one septic tank was compromised due to flooding.  The flooding caused basement flooding in at least four homes throughout the reservation.  Two private bridges were destroyed or compromised and classified as unsafe for use.

Flood in BOUNDARY, IDAHO
From 06-APR-11 00:00:00 to 06-APR-11 16:00:00 (PST-8)
Location: MORAVIA
Flood cause: Heavy Rain / Snow Melt
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Deep Creek flooded portions of Deep Creek Loop, also listed as Old Highway 95 causing sloughing of the roadway and embankment.  Pavement damage was 500 feet by nine feet wide.  The route is a major county through route from Naples to Bonners Ferry.