More than 7,000 species of arthropods, a variety of amphibians and reptiles, and slugs occur. The growing season lasts 140 to 240 days. Surface Water Characteristics. There are large riverine systems with merging streams. The Puget Trough portion is joined by estuaries and ocean sound.
Wetlands are abundant.
Both natural and man-made lakes are scattered throughout the Section. Fires were commonly set by Native Americans and trappers, hunters, and settlers. Floods from intense winter storms occurred at frequent intervals prior to construction of dams. The Willamette Valley is a dominantly intensive agricultural area. Grazing by sheep and cattle is common.