Level IV: (1f) Willapa Hills
The Willapa Hills ecoregion (named for the Willapa Hills) consists of low, rolling hills and low, gently sloping mountains with medium gradient streams and rivers. It rises to an elevation of approximately 1,300 feet (396 m).
This region has a lower drainage density than other upland areas in the Coast Range. Logging is relatively easy and less expensive in this accessible terrain, and industrial timberland has almost completely replaced the historic forests. When disturbed, the silt- and clay-textured soils are easily eroded, thereby degrading stream quality.
The vegetation consists of Douglas-fir and western hemlock forests, with sword fern, vine maple, salal, Oregon grape, and rhododendron shrub layer. Wetter slopes and riparian areas support red alder, western redcedar, bigleaf maple, salmonberry, and oxalis.
Large herds of Roosevelt elk winter in the region.
The region covers 1,277 square miles (3,307 km2) in southwestern Washington and 751 square miles (1,945 km2) in northwestern Oregon, inland from the coast. In Oregon it is a small area along the Columia and the hills to the south. The transition out of the Portland/Vancouver Basin starts around Deer Island and continues into Rainier before entering the volcanics of ecoregion 1d.