2019_KittitasCountyHMP_Volume 1_For Adoption

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CHAPTER 4. KITTITAS COUNTY PROFILE 4-3 overgrazing was beginning to take its toll on the range. As a result, the federal government began to regulate grazing in 1897. This led to a gradual shift from open grazing to fenced pastures and hay feeding. Two events—better rail transportation around the turn of the century and irrigation projects in the 1930s— helped expand the county’s cattle industry. The railroads provided more effective transport of cattle to the nation’s eastern markets. Irrigation projects enhanced the quality of pastures and spurred the growth of row crops, whose by-products were converted into inexpensive cattle feed. By the 1960s, the number of Kittitas County cattle had more than doubled, to approximately 70,000. However, price controls and rising feed costs in the early 1970s prompted many ranchers to change from cattle to hay and grain production. 4.3. PHYSICAL SETTING 4.3.1 Geology Kittitas County possesses a diverse topography that is dominated by the Cascade and Wenatchee Mountains. From the high Cascades, the land slopes generally downward to the east and south to the Columbia River. The eastern part of the county consists of low, rolling to moderately steep glacial terraces and long, narrow valleys. The southeast section of the county is characterized by moderately steep to steep glacial terraces and steep, rough, broken mountain foothills. The major geological features of Kittitas County are the Cascade and Wenatchee Mountains on the west and north portions, the south-central Yakima River Valley, and the Boylston and Saddle Mountains at the southeastern edge along the Columbia River. Within these elevations, slope, geologic and soil conditions vary dramatically, including steep mountain peaks, foothills, broad rich valleys, and near-desert areas. Alpine and continental glaciers moved through this region shaping the mountains and depositing materials to create the geology and soils of the region. The primary types of glacial deposits in the county are outwash and till. Outwash consists of unconsolidated sand, gravel and rocks and results from runoff of melting glaciers. Outwash is usually loose and highly permeable. Glacial till, or hardpan, consists of unsorted clay, sand, grave, or rock that has been compacted by the weight of the glacial ice into a highly impervious, concrete-like material. Bedrock geology in the county is varied. Underlying the Cle Elum River drainage is the non-marine sedimentary Swauk formation dating back to the Tertiary period of geologic time from 1.6 to 65 million years ago. Composed of conglomerate sandstone and shale interbeds, the Swauk formation extends as far north as Lake Wenatchee. As these interbeds were later subjected to the mountain-building forces during the emergence of the Cascades, a complex range of land forms was produced that created a history of geologic instability present to this day. Other major bedrock formations in Kittitas County include metamorphic rocks, granite intrusions, and thick sequences of volcanic and marine sedimentary rock. 4.3.2 Slope Stability Slope stability refers to the potential of land slippage due to factors such as steepness, composition of materials, and water content within soils. Slopes that have been landscaped and altered from their natural vegetated state or saturated by septic tanks are also subject to sliding. Slumping can also occur when water infiltrates the soil and comes in contact with an impermeable layer. Although the upper layers of soil may not become saturated, water perches on the impermeable layer and causes a slippery interface resulting in the downward and outward movement of weak rock or unconsolidated material. Much of the western and northern portions of the county contain slopes of 15 percent or greater. Slopes less than 15 percent are generally found in the river basins in the eastern portions of the county.