The Johnson Creek Watershed varies from heavily developed urban areas in the lower and middle reaches (Milwaukie, Portland and Gresham) to rural and agricultural areas in the upper watershed.

The area north of the Johnson Creek mainstem is mostly flat, with large floodplain areas, particularly in Lents. These floodplains are thought to be a remnant of large glacial floods that occurred about 15,000 years ago.

Johnson Creek is one of the last free-flowing streams in the Portland area and provides important habitat for coho and Chinook salmon, steelhead and cutthroat trout.

During the last 200 years, people have altered the Johnson Creek watershed in an attempt to reduce flood impacts and to make it easier to develop the land near the creek. In the 1930s the Works Progress Administration widened, deepened and rock-lined 15 miles of Johnson Creek in an effort to prevent future flooding. Despite that effort, Johnson Creek has exceeded flood stage 44 times since 1940 (as of September 2020).

Current efforts to restore Johnson Creek focus on restoring its natural resource functions. This type of restoration provides flood storage, water quality benefits, and increases fish and wildlife habitat by returning some of the natural historic conditions and functions to the watershed.

Johnson Creek provides important habitat for coho and Chinook salmon, steelhead and cutthroat trout. While these species still exist in Johnson Creek and its tributaries, their long-term survival depends on our ability to restore habitat and improve water quality.