Padden Creek 24th to 30th Streets Restoration

Overview

Functional floodplains, off-channel habitats, and riparian buffers are important aspects of functional watersheds. Unfortunately, many of these features are often missing or reduced along urban streams. This is the case for Padden Creek, where these features have been impacted by urban development and stream channelization, exacerbating the water quality problems in Padden Creek. Padden Creek is on Washington State’s 303(d) list of water quality-impaired waters for dissolved oxygen, temperature, and fecal coliform, and has a TMDL for temperature.

Padden Creek 24th-30th Street Restoration Project is a multi-phased restoration project to address impaired conditions. The goals of this project are to improve water quality and aquatic functions in Padden Creek through enhancing floodplain, instream, and riparian functions between 24th and 30th Streets.

The project is divided into three phases. Phase 1 is located in the center of the reach, roughly between Padden Creek’s confluence with Connelly Creek upstream to the Happy Valley Park footbridge (see map below). Phase 1 includes floodplain enhancement and the enhancement of instream, off-channel, and riparian buffer structure and function. Phases 2 and 3 include stream relocation and buffer restoration.

Phase 1 Overview Map (Click the image below to open a PDF version)

More Information

The focus of Phase 1 is the restoration of Padden Creek at its confluence with Connelly Creek. The Phase 1 project area is an undeveloped floodplain owned by the City and connected to private undeveloped land to the north, creating one of the widest remaining undeveloped riparian corridors in the lower Padden sub-watershed.

Phase 1 will:

  • Restore and enhance approximately 2 acres of riparian buffers with native vegetation, including approximately 1.25 acres of wetland and approximately 1.6 acres of floodplain.
  • Enhance approximately 550 linear feet of stream channel with pools, riffles, fish-friendly sediment, backwaters, and side channels.
  • Install approximately 12 large woody debris structures.

Phase 1 will restore and enhance approximately two acres of riparian buffers through the removal of invasive species and the installation of native plant species. The enhanced buffers will create effective shade over time, facilitate the biofiltration of fecal bacteria and stormwater pollutants, and provide a source of woody debris for stream structure and function.

Phase 1 will also improve aquatic function through the formation of pools and riffles, the creation of side channels and backwaters, the addition of large woody debris, and the enhancement of some of the last remaining riparian wetlands in the watershed.

Floodplain enhancement will include maximizing floodplain extent and increasing the connectivity between groundwater and surface water. Increased connectivity will stabilize stream temperature by minimizing baseflow attenuations. Wetland enhancement will decrease stream temperatures through groundwater recharge and the stabilization of baseflow. Large woody debris will decrease stream temperatures through enhanced hyporheic exchange, improving the vertical connectivity between groundwater and surface water. Phase 1 actions that decrease stream temperature will also increase dissolved oxygen, as they are inversely related. Phase 1 will also directly increase dissolved oxygen levels through the creation of riffles.

Padden Creek is on Washington State’s 303(d) list of water quality-impaired waters for dissolved oxygen, temperature, and fecal coliform. Padden Creek also has a TMDL for temperature (Hood & Cristea 2011). Padden Creek contains ESA-listed Chinook salmon and steelhead trout, and according to Washington State water quality standards, the 7-day average of daily maximum temperatures in Padden Creek should not exceed the core summer salmonid threshold of 16 degrees Celsius. However, long-term monitoring by the City has shown that point-in-time summer water temperatures have exceeded this threshold.

Since 2014, the City has invested over $9.5 million in the Padden Creek corridor through the Padden Creek Daylighting Project, Padden Estuary Restoration, and the Harris Street Stormwater Treatment Facility. Phase 1 will complement more recent WSDOT fish passage improvements in Padden Creek at I-5 and Fairhaven Parkway.

Resources

Contact

Analiese Burns
Habitat and Restoration Manager
Public Works Department, Natural Resources
acburns@cob.org

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