Wetlands Overview

History of the Wetlands

Land Use History

rainbowBefore European settlement, the lowland portion of the UWB/CCC campus site consisted of a complex array of channels, small backwater lakes, and depressions that were part of the junction environment where North Creek flowed into "Squawk Slough" (now the Sammamish River). The hydrologic characteristics of the UWB/CCC site were controlled by the interaction of runoff from the North Creek watershed and the natural fluctuations in water levels of Lake Washington.

The floodplain soils formed as a complex stratified mixture of organic deposits (mucks, peats), lake sediments, marsh sediments, volcanic ash, and floodplain alluvium. This depositional environment varied in character from lake to floodplain with the naturally fluctuating levels of the Lake Washington watershed. When lake levels were highest the area was a shallow part of a very large lake that included contemporary Lake Sammamish and Lake Washington. Diatomaceous layers in the soil profile indicate standing water for long periods of time. However, it appears that most of the time, the site supported a complex marsh to mixed marsh-forested wetland environment. Historical floodplain sediments are mostly well-sorted medium to very fine sands. Lake and marsh environments accumulated organic soils, mostly mucks, and a variety of fine grained, mostly silt, mineral sediments. Peat deposits up to ten or more feet deep exist on portions of the restoration site.

"" Historically, the floodplain would have been primarily forested with some scrub-shrub and emergent communities. Dominant tree species would have been Western red cedar, Black cottonwood, Douglas fir, Big-leaf maple, and Red alder. By 1895, the UWB/CCC site had been logged for the first time. Maps from 1916 indicate that large portions of the North Creek channel system, including the reach that runs through the UWB/CCC site, had been straightened and confined within artificial levees so that North Creek would serve as a flume for delivery of logs from upper portions of the North Creek watershed to Lake Washington mills. Following logging and since about the 1930's, the UWB/CCC site had been used for grazing or farming. To improve siteconditions for farming, extensive drainage systems (e.g., ditches and tile drains) were constructed by various owners in attempt to manage both groundwater and surface waters.

Construction of the Hiram Chittendom locks in 1913 - 1916 resulted in the lowering of Lake Washington by approximately 12 feet. This steepened the lower reaches of North Creek significantly. Urbanization in the upper portions of North Creek over the last 60 to 70 years has also had significant impacts on the hydrologic characteristics of the channel and floodplain. Increases in impervious surfaces have resulted in greater runoff and an increase in peak flows.