The Ridgefield National Wildlife Refuge Carty Unit located just north of downtown Ridgefield includes several nice hiking trails. Keep in mind that the refuge is primarily managed for the benefit of wildlife, so some areas are closed to access all year, and other areas are closed during certain seasons.
The Cathlapotle Plankhouse was built as a reconstruction of a traditional native structure and provides a great educational resource. Trails north of the plankhouse wind through forest and riparian areas. This is a popular bird watching area, and for good reason. Decades ago I used to walk out this trail to sit and watch the beavers as they worked in the large wetland area. That wetland has now largely transformed into grassland and the beavers have moved on.
There are about 2 miles of trails in the area north of the Plankhouse which wind through the forest and around Lancaster lake. North of the refuge is land managed for resource conservation, so some trails are closed to access at that point. Be aware also that there is Poison Oak in the area, and some trails may be closed to manage vegetation.
Within the next couple years, a trail connecting the Carty Unit entrance to downtown Ridgefield will be completed, and a connecting trail through the unit, around the west side of Carty Lake connecting to the Port of Ridgefield will be completed. This will make for a nice approximately 2 mile loop trail that can be walked from Ridgefield through the refuge.