Johnson Creek (Willamette River tributary)

Johnson Creek: A Tributary of the Willamette River

Imagine a river that weaves through the heart of Oregon’s Portland metropolitan area, carrying with it stories of Native American heritage, early settlers, and modern urban challenges. That river is Johnson Creek, a 25-mile tributary of the mighty Willamette River. How does this creek shape the landscape and communities around it?

The Natural History

Johnson Creek flows through sediments deposited by glacial floods on basalt substrate. This geological journey has created a unique habitat for salmon and other fish, making Johnson Creek a vital part of the ecosystem. Can you imagine the life that thrives in these waters?

The Human Impact

Before European settlement, the watershed was heavily forested. Native Americans used this land for fishing and hunting, living in harmony with nature. However, as settlers arrived, they began to clear the land for farming, naming the creek after William Johnson who built a water-powered sawmill in 1846. The creek has experienced seasonal floods due to urban density increase. These floods have been managed through various measures over the years, including lining the stream with rock in the 1930s and implementing flood-control measures since the 1990s.

A Watershed Divided

The Johnson Creek watershed is divided into two hydrologic areas: the Portland Terraces (40% of the watershed) and the Boring Hills/Kelso Slope (60%). Most rain percolates into the ground in the northern area, while most rain runs quickly into the creek or its tributaries in the southern area. How does this division affect water management?

Risk and Resilience

Soil erosion is a risk in some areas, particularly around Powell Butte and the Boring Lava Domes. The watershed’s soils vary in permeability and ability to retain water, with clays dominating the eastern end of the watershed. What measures are being taken to mitigate these risks?

Urban Development and Flooding

Floods became more frequent due to urban development and removal of vegetation. In 1930, about 90% of the creek was cleared and lined. However, this channel failed to prevent overflows, which damaged structures in 1964. The U.S. National Weather Service defines Johnson Creek’s flood stage as 11 feet, with a flow rate of about 1,200 cubic feet per second. The creek has exceeded this threshold 37 times since 1941, with at least seven causing major property damage. What lessons can we learn from these events?

Restoration and Conservation

The Johnson Creek Watershed Council (JCWC) is a nonprofit group organized in 1995 to protect the creek and its watershed. JCWC’s projects involve controlling invasive species, planting native riparian vegetation, improving fish passage, and creating off-channel flood storage. How can we support these efforts?

Water Quality and Wildlife

Johnson Creek’s water quality was rated ‘very poor’ by the Oregon Department of Environmental Quality from 1986-1995 due to high concentrations of nitrates and phosphates, as well as fecal coliform bacteria and total solids. High temperatures cause problems for aquatic life in the watershed. What steps are being taken to improve water quality?

Biodiversity

The creek is home to sensitive species such as long-toed, northwestern, and Columbia salamanders, red-legged frogs, painted turtles, great horned owls, toads, hawks, coyotes, and tall bugbane (Actaea elata). How do these species contribute to the ecosystem?

A Community Effort

Parks in the area include Johnson Creek Park, Crystal Springs Rhododendron Garden, Tideman Johnson Natural Area, Leach Botanical Garden, Beggars Tick Wildlife Refuge, Powell Butte Nature Park, Gresham’s Main City Park, and a 102-acre preservation area purchased by Metro in 2007. The total land area is 57% covered with plant life, with 70% within the urban growth boundary, consisting of residential, commercial, rural, parks, and open space. How can we balance development with conservation?

Johnson Creek is more than just a river; it’s a lifeline for the community, a testament to resilience and adaptation. As we continue to navigate the challenges of urbanization, let us remember the importance of preserving our natural heritage. Every effort counts in protecting this vital waterway.