Breaching the Dike at Port Susan Bay

Backhoes dug away at an old sea dike at Port Susan Bay Preserve in September, removing the dike and cutting deep channels for bay waters to work their way into an old tidal marsh that had been cut off for 50 years.

Estuarine ecologist Roger Fuller has been studying Port Susan Bay for about 10 years, and had learned that the dike has been restricting the flow of fresh water to the northern reaches of the bay, significantly changing the topography and composition of the bay and damaging habitat for salmon and other marine life.

Breaching the dike and installing a new flood gate structure is creating jobs and will pay off for local communities with more salmon, a healthier bay and better flood protection for local farmers in the Stillaguamish delta of Snohomish County.

Watch a KING-TV news video about the project here.

The breaching came after months of preparatory work. Since April, contractors have built a new dike along the eastern edge of the Port Susan Bay Preserve and partnered with the Stillaguamish Flood Control District to build an emergency floodgate that will provide flood relief for farmland on Florence Island, between Hatt Slough and the Old Stilly Channel.

The Conservancy owns the 4,122-acre Port Susan Bay Preserve, which encompasses much of the Stillaguamish River estuary.

Port Susan Bay is a critical nursery for marine life. Sandwiched between two of Puget Sound’s largest rivers – the Skagit and the Stillaguamish – it supports juvenile salmon, birds and farmers. Juvenile salmon have deep cool channels where they can hide and transition slowly to the salt water environment of their adulthood. Seal pups haul out on the mud flats and feed on the fish in the channels. Huge flocks of shorebirds, ducks, terns and other birds sweep across the marsh and mudflats to feed on abundant invertebrates.

With the restoration project complete, tidal wetlands that support estuary-dependent animals will be restored, juvenile Chinook salmon will gain access to restored habitats, and a stronger connection between the river and tidal habitats in the northeastern portion of Port Susan Bay will improve the resilience of the bay and estuary to sea level rise. Healthier tidal wetlands will mean more food in the system for salmon, waterfowl, Dungeness crabs and people..

Funding for the project comes from the state Puget Sound Acquisition and Restoration Program, Salmon Recovery Funding Board, Estuary and Salmon Restoration Program, the new state construction bill, NOAA’s Estuary Habitat Restoration Program and private donations.


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