Hood, W., 2021. Leque 2nd-year Post-Restoration Tidal Marsh Monitoring Report. Skagit River System Cooperative, La Conner, WA. pp. 20.

The Leque tidal marsh restoration site is located in the Stillaguamish River Delta
opposite the mouth of the old Stillaguamish River. European-American settlement in the late
19th century converted most of the Stillaguamish Delta from tidal marsh and floodplain swamp
to agricultural use through the construction of dikes that prevented tidal and riverine flooding
and allowed replacement of native vegetation by agricultural crops. Leque Island was diked in
the 1870s and used for farming until 1990, when farming became infeasible on the site.
To provide critical rearing habitat for threatened Chinook salmon, the 103-ha (254.5-ac)
Leque site was restored to tidal and riverine flooding in 2019 through the nearly complete
removal of dikes around its perimeter. Additionally, six large tidal channels were excavated de
novo or enlarged on the site to approach allometric predictions derived from nearby reference
tidal marshes (Hood 2015, 2018). The channel conceptual restoration plan was modified during
implementation by omitting excavation of the two smallest channels in the design, extending
the excavation of some other channels, and excavating seven large ponds, located adjacent to
and communicating with the three largest tidal channels. Omission of the two smallest
channels was a minor modification. Excavation of the large ponds was done to provide
additional sediment for a spur dike, built at the request of the town of Stanwood to protect a
nearby proposed public park. An additional benefit was that the ponds would provide shallow
water habitat for waterfowl. Because the ponds are directly connected to tidal channels, they
were also thought likely to provide significant habitat to juvenile salmon.
Dike removal and channel construction were hypothesized to be sufficient for allowing
native vegetation recolonization of the site and for juvenile Chinook salmon to occupy the
excavated channels and benefit from primary and secondary production on the site. Tidal
marsh vegetation colonization is typically not constrained by the supply of seeds or other
propagules from nearby tidal marshes, so no vegetation planting occurred as part of the
restoration. This report describes early assessment of vegetation colonization two years after
site restoration. It also describes the planform tidal channel geometry of excavated tidal
channels, the location of surveyed channel cross-sections and profiles, and spot measurements
of excavated pond elevations.