Affected Environment

CHAPTER 4. AFFECTED ENVIRONMENT Lower Columbia River Ecosystem several broad bays that extend more than 30 miles to the Pacific Ocean. At its mouth The three Refuges addressed in this CCP are below Astoria, Oregon, the river passes positioned in the lower part of the Columbia between two jetties approximately two miles River. The lower Columbia River apart as it enters the Pacific Ocean. ecosystem extends 146 river miles, from Bonneville Dam to the Pacific Ocean Historically, flooding within the Columbia (Figure 4-1). The basin of the lower River was the product of regional Columbia River includes the basins of lower precipitation, the rate and volume of tributary streams, the largest of which are snowmelt, and synchronization of runoff the Willamette, Cowlitz, Kalama, Sandy, between the Columbia and Snake River and Lewis Rivers. drainages. Construction of over 200 dams on the Columbia River and its tributaries has The Columbia River runs a varied course dramatically altered the historic hydrology. from the Bonneville Dam to the Pacific Dams now impose additional water level Ocean. It is relatively narrow–925-feet- fluctuations to meet demands for hydro- wide–directly below the dam. After it electricity, agriculture, navigation, pool emerges from the Columbia River Gorge at recharge, recreation, fisheries, and water Steigerwald Lake Refuge, about 20 miles quality priorities.32 Spring flood elevations east of Portland, the river valley widens to on the lower Columbia River average 37 include a broad floodplain. Elongated percent lower today than prior to dam islands divide the river and form sloughs construction.19 Regulated winter flows are and side-channels in the formerly marshy typically less than 200,000 cubic feet per lowlands. The floodplain expands around second (cfs). Peak flows in May and June the confluence of the Columbia and have declined from about 600,000 cfs to Willamette Rivers. Here, the sloughs and 350,000 cfs. Prior to dam construction, lakes of North Portland, the Vancouver average spring floods regularly inundated lowlands, Sauvie Island, and Ridgefield 170,000 acres of bottomland along the lower Refuge contain the Portland metropolitan Columbia River for periods of up to 60 days. area’s last major remnants of the wetland Major spring flood events inundated up to and riparian system formerly nourished by 300,000 acres of the lower Columbia River annual flooding of the non-dammed rivers. floodplain.8 Downstream from St. Helens, Oregon, the Columbia River cuts through the coast Over half of the historic riverine wetlands in range, a passage marked by steep- the lower Columbia River below Bonneville shouldered bluffs and broad alluvial Dam have been lost or substantially floodplains. The river channel, dotted with degraded as a result of diking, draining, low islands of deposited sediments filling, dredging, and flow regulation.8 throughout its lower reaches, opens out Since 1948, the most notable habitat below Skamokawa, Washington, into changes have occurred in the vicinity of the Chapter 4 - Affected Environment 4-1 Columbia Gorge Refuges Draft CCP/EA Chapter 4 - Affected Environment 4-2 Columbia Gorge Refuges Draft CCP/EA Portland/Vancouver area.35 Urban and other occurring for millions of years. The developed habitat has increased Cascade Range of today is only the most dramatically, with a corresponding decrease recent of a series of continental margin in wetland, riparian scrub-shrub, coniferous mountains that began forming about 17 forest, broadleaf forest, and agricultural million years ago. Beacon Rock, west of habitat. Pierce Refuge, is the plug of an earlier continental margin volcano. Many of what Despite these dramatic habitat losses, are now the highest points in the Gorge, numerous natural areas remain in the lower such as Hamilton Mountain above Pierce Columbia River with high levels of Refuge, were once channels of the Columbia biological significance (Figure 4-1). Each River that filled with lava (basalt) and were of these sites contains important habitats for subsequently uplifted by the rise of the fish and wildlife. Collectively, the Gorge Cascade Range. The broad valley Portland Refuges and the remaining biologically and Vancouver occupy was formed by important areas contribute to the spreading of the continental crust. maintenance of biological diversity and integrity and ecosystem health in the lower The complex nature of crustal collisions is Columbia River system. reflected in the Gorge. Layers of rock in Gorge walls that were once level, are tipped Physical Environment to the south by as much as 10 degrees. An overview of the Gorge and areas to the east Geology and Geomorphology reveals that these tipped layers are on the southern flank of a huge wrinkle in the From dramatic cliffs surrounding Pierce continental crust, one of several features Refuge to open prairies of Steigerwald Lake known as the Yakima Fold Belt. The Refuge, the Columbia River Gorge Yakima fold has contributed to spectacular encapsulates much of the geological history events such as giant landslides. The most of the Pacific Northwest. Landforms, famous of the slides is the Bonneville, stratigraphy, and rocks found in the Gorge located just up the Columbia from Pierce reflect the collision of crustal plates, Refuge. The Bonneville Landslide occurred eruptions of innumerable volcanoes, only about 500 years ago, dammed the enormous landslides, and floods beyond Columbia River, and inspired the Native human experience. Visitors to the Gorge American legend of the Bridge of the Gods. can see the Columbia River slicing through As the river cut through slide debris, huge these landforms and visualize this fans of gravel and sand spread downstream. remarkable story. Remnants of these gravelly fans form Pierce and Ives Islands. The spawning gravels Geology of the Columbia River Gorge used by chum salmon and cobble substrate revolves around the collision of North that grows Columbia yellowcress at Pierce America with the oceanic crust under the were originally deposited by the Columbia Pacific Ocean. This process has been as it cut through the landslide. Chapter 4 - Affected Environment 4-3 Columbia Gorge Refuges Draft CCP/EA Over the last several million years, as the This flood deposited a large mass of modern Cascade Range rose, the powerful driftwood at Franz Lake Refuge, setting off Columbia cut through the rising rock, and the sequence of events that formed the lake. the Gorge was born. Well after the Gorge began forming, the climate of the Earth Soils changed dramatically. Beginning about 2 million years ago, winter snows that fell in Over the ages, slides and washes have the mountains and plains of northern transported soils and rock from the walls of Europe and North America did not melt the Gorge to the valley floor. This during the unusually cool summers. The colluvium comprises the higher terraces and accumulating snow eventually formed steeper slopes of the Gorge Refuges. The glaciers. One such glacier dammed the soils of the lower elevations of the Gorge Clark Fork in northern Idaho to form Glacial Refuges are predominately alluvial in origin. Lake Missoula. The ice dam broke and Materials transported by the river settle out reformed repeatedly, each time releasing along the river’s margin or into the tremendous volumes of water. On reaching floodplain. Before the construction of the the Columbia River Gorge, the flood waters many Columbia River dams, most of the attained elevations of at least 1,000 feet. acreage encompassed on the Refuges was When the floods reached the Steigerwald subject to inundation by the seasonal Lake Refuge area, they spread out across the freshets. Remnant channels cut by flood Portland Basin. Much of Vancouver, waters are still evident on the Gorge Washington, and Portland, Oregon, are built Refuges. Soil texture ranges from gently on sand and gravel bars left by the floods. sloping silty soils to steep gradient gravelly After the glaciers that once mantled the soils. These soil textures and characteristics Cascade Range melted, the once deeply have been mapped and described by the entrenched valley of the Columbia at and Natural Resource Conservation Service in below Steigerwald Lake Refuge filled with their Soil Survey of Skamania County Area, sand and silt, forming the broad floodplain Washington, and Soil Survey of Clark seen there today. County, Washington. The principle soil type of the Gorge Refuges is loam (7-27% During the period of historic records, clay particles, 28-50% silt, and less than geological events in the Gorge have been 52% sand). less dramatic, but not without reminders of its unsettled past. Small landslides and Climate debris flows occur frequently, including one at Dodson, Oregon, in 1996 that closed The predominant climate of western Interstate 84. Continued settling of the Washington is mild and rainy. In fall and Bonneville Landslide has twice fractured a winter, low pressure forms in the Gulf of natural gas pipeline that crosses it. Before Alaska with high pressure centers shifting to construction of flood control dams in the the south. Circulation of air around the low upper Columbia, spring floods were much pressure in the north Pacific Ocean bring a larger, including the flood of record in 1894. prevailing flow of warm, moist, marine air Chapter 4 - Affected Environment 4-4 Columbia Gorge Refuges Draft CCP/EA into western Washington. The Coast Range The drier air mass makes precipitation less protects much of western Washington from likely, with only 20 percent of rainfall in the severe winter storms moving inland from the Gorge occurring from April to September. ocean. A colder and drier continental air Summer winds tend to be more moderate mass is typical for winters in the eastern and directed up the Columbia River between portion of the State. The moist marine air May and October. mass of the west and cool continental air mass of the east are largely separated by the Hydrology Cascade Range.

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