Estuary Technical Group reports on tidal wetland restoration in Tillamook

The Southern Flow Corridor is located at the south end of Tillamook Bay on the northern Oregon coast. Tidal marsh reference sites (purple and orange areas) are located nearby.

Before restoration, the Southern Flow Corridor site was diked agricultural land. Much of the site was formerly pasture and had heavy growth of non-native, invasive reed canarygrass (foreground and middle ground of photo above). The 10-foot-tall white poles in the photo mark Estuary Technical Group monitoring locations.

After restoration, reed canarygrass, a non-native invasive plant species, died back across much of the Southern Flow Corridor (left). Overall, non-native plant cover decreased across most of the site after restoration (right panel, blue dots), while non-native plant cover remained about the same at reference sites (right panel, green dots).

Native tidal marsh species returning to the Southern Flow Corridor site include Baltic rush (left), Pacific silverweed (center), and Lyngbye’s sedge (right). Photos by Chris Janousek.

Vegetation change at Southern Flow Corridor was driven mainly by the restoration of tidal flooding and salinity. Salinity across the site increased after restoration (left panel, blue dots); salinity increased the most at lower elevations (right panel) where tidal inundation was most frequent.

The most dramatic changes in vegetation were seen on the lower parts of the site, which are flooded most frequently by the tides.

The Confedered Tribes of Siletz Indians monitored fish use of the restoration site by seining in the channels.