Level IV: (1a) Coastal Lowlands
Characteristic features include wet forests, shallow freshwater lakes, estuarine marshes, and low-gradient, meandering tannic streams and rivers. Residential, commercial, and recreational developments are expanding in the coastal corridor. Many wetlands in the floodplains of the region’s streams have been drained and converted into pastures for dairy farms, and associated stream degradation has occurred.
Mature forests in the region are dominated by a canopy of Sitka spruce, western hemlock, and Douglas-fir, with salal, sword fern, vine maple, and Oregon grape in the shrub layer. The riparian zone supports red alder, western redcedar, and bigleaf maple with an understory of salmonberry; California bay-laurel is common in the south.
Soil textures range from silty clay loam to sandy loam. The region covers 633 square miles (1,639 km2) in Oregon and 353 square miles (914 km2) in Washington, with the largest contiguous areas found near Grays Harbor, Willapa Bay, the mouth of the Columbia River, Tillamook Bay, and along the southern Oregon Coast.