Description

This MLRA is in Idaho , Washington and Montana. In Idaho and Washington, It makes up about 5,660 square miles (14,670 square kilometers). The cities of Spokane, Washington, and Coeur d’Alene, Idaho, are in this MLRA. Although most of the valley floors are privately owned, the valley borders commonly are part of numerous national forests, including the Kaniksu and Colville National Forests in Washington and Idaho This area is in the Northern Rocky Mountains Province of the Rocky Mountain System. It is an area of deeply dissected mountain valleys. The deep valleys are typically bordered by mountains trending north to south. In the valleys, nearly level, broad flood plains are bordered by gently sloping to strongly sloping terraces and alluvial fans. In many areas, the valleys have been modified by glaciation. In the northern part of the area, glacial debris dams created lakes in the valleys for a period of time in the past. In these areas, lacustrine sediments cover much of the valley floors. Elevation ranges from 1,540 feet (470 meters) to 5,085 feet (1,550 meters). This MLRA is entirely within the Kootenai-Pend Oreille-Spokane (1701) Hydrologic Unit. The mountains bordering the valleys in this MLRA are uplifted fault blocks that have been recently glaciated. Streams eroding the mountains have created alluvial fans at the edges of the valleys and have deposited silt, sand, and gravel as alluvial valley fill throughout the area. Modern streams have reworked the valley fill deposits, creating terraces and flood plains at the lower elevations in the valleys. Glacial lake deposits occur in some of the valleys in the northern part of the MLRA. Glacial outburst flooding has deposited large amounts of outwash in the southwestern portion of the MLRA. The average annual precipitation is 15 to 53 inches (375 to 1340 millimeters) with the highest amounts in northern Idaho. Precipitation is fairly evenly distributed throughout fall, winter, and spring but is low in summer. Rainfall occurs as high-intensity, convective thunderstorms during spring and fall. Most of the precipitation in winter is snow. The average annual temperature is 39 to 50 degrees F (4 to 10 degrees C). The freeze-free period averages 115 days and ranges from 85 to 140 days. The dominant soil orders in this MLRA are Inceptisols, Mollisols, and Andisols. The soils in the area have a mesic or frigid soil temperature regime and, a xeric or udic soil moisture regime, and mixed mineralogy. They generally are very deep, well drained, and loamy or loamy skeletal. Vitrixerands formed in glacial outwash or ablation till on stream terraces, terrace escarpments, and till plains. Haploxerepts formed in glacial outwash on outwash plains and outwash terraces. Dystroxerepts and Udivitrands formed on slopes of foothills and mountains. This area supports conifer forests and grassland vegetation. Bluebunch wheatgrass, rough fescue, Idaho fescue, and bearded wheatgrass are the major species on the grassland in the valleys and foothills. Douglas-fir, ponderosa pine, grand fir, western red cedar, western hemlock, pinegrass, common snowberry, mallow ninebark, and white spirea are the major forest species. Some of the major wildlife species in this area are elk, mule deer, white-tailed deer, antelope, coyote, bobcat, badger, beaver, mink, otter, muskrat, cottontail, ground squirrel, pheasant, gray partridge, sharp-tailed grouse, sage grouse, blue grouse, spruce grouse, and ruffed grouse. The species of fish in the area include rainbow, brown, and brook trout. More than one-half of this area is in farms and ranches. A large acreage is used for hay, grain, or pasture for livestock feed. In areas where precipitation is adequate, dry-farmed wheat is grown Beef cattle and sheep are the principal kinds of livestock, but dairying is an important enterprise near the larger towns. Much of the part of this MLRA in northern Idaho is forested. In Montana, this MLRA includes the Flathead Valleys, with the predominant landscape as valleys with landforms including floodplains, stream terraces, outwash, lacustrine terraces, foothills, glacial moraines. The estimated acres are 1,412,271 and it is primarily private lands. Land use is development and agriculture. Climatically, this LRU has a frigid soil temperature regime and a xeric soil moisture regime. It has a mean annual air temperature of 43 degrees Fahrenheit (ranging 33-58 degrees Fahrenheit), mean frost free days of 94 (ranging 60-110 days) and mean annual precipitation ranging 14-19 (but can go up to 23 inches in higher areas). Majority of the elevations range is 1000-4000 feet, with some areas up to 5000 feet. Vegetation is predominantly Douglas Fir-Ponderosa Pine-Lodgepole Pine Forest / Woodland and montane grassland, minor amount of Engelmann Spruce-Subalpine Fir, and open water, developed areas and agriculture. Trace Western Redcedar and Western Hemlock and Grand Fir. The geology is predominantly fluvial and bedform topography related to Cordilleran glaciation. Rock types are dominantly metasedimentary of the Belt Supergroup (Ravalli group) with some Tertiary sediments, eolian deposits, open water, Glacial lake deposits. The soils are dominantly very deep, well-developed soils formed in alluvium, lacustrine deposits, glacial outwash and till from metasedimentary parent materials. These tend to be well drained, neutral to moderately alkaline soils with both skeletal and non-skeletal sandy loam, loam and clay loam textures. Poorly drained soils are present as well but are generally confined to areas along riparian corridors. Volcanic ash influenced soils occur here as well but tend to be limited to stable footslope positions marginal to the valley floor. This is related to the EPA land classification framework of: Level 3 the Northern Rockies and includes numerous Level 4 including: Stillwater-Swan Wooded Valley, Tobacco Plains, Flathead Valley, a small part of the Western Canadian Rockies (Level 3 is Canadian Rockies) and a small part of the rattlesnake-Blackfoot-south Swan-Northern Garnet-Sapphire Mountains and the Foothill Potholes (both in the Middle Rockies Level 3 subdivision). This area is related predominantly to the USFS Provinces: Predominantly resides in the northern portion in M333Bc (Flathead River Valley), the middle portion of 430Hi in M333Cb (Canadian Rockies-Whitefish-Swan Mountains) and the southern portion in M332Bp (Avon-Nevada Valleys).