Squaxin Island Tribe's Natural Resources

Squaxin Island Tribe's Natural Resource Department Weblog

Squaxin Island Tribe's Natural Resources header image 2

Monitoring and adaptive management of the Nisqually Delta after tidal marsh restoration

October 23rd, 2014 by bbougher Comments Off on Monitoring and adaptive management of the Nisqually Delta after tidal marsh restoration

Blogging by Sayre Hodgson, Chris’s collaborator at the Nisqually Indian Tribe’s natural resources department.

Chris Ellings following up on a previous talk in 2009 at this symposium, now that there is more to report on the restoration.

Historic condition- was very diverse habitat, but like most P.S. deltas it was diked for agriculture 1904-1910.  Luckily industrial development in the delta was avoided.  USFWS created the Nisqually Nat. Wildlife Refuge and Nisqually Indian Tribe purchased a farm on the other side of the river.  Now 900 acres of tidal area have been restored. This is the largest restoration project of its kind north of San Francisco Bay, hopefully more will happen.

Largescale process based monitoring – process- hydrodynamics, sediment supply, structure- habitat development, and biological response.

Looked at hydrology in restored and undisturbed areas, and freshwater marsh behind the dike prior to Sept 2009.  After restoration there was an incomplete tidal prism as channels developed and full tidal prism develops over time.

Channel development- short term responses were looked at by comparing cross sections before and after.  There was up to 1 m of erosion in the channels, organic matter was carried out by the tides.  Restoration impacted channel shapes outside of the diked area as well. Deposition on the seaward side of the dike was redistributing.  There were big channel changes outside the diked area to accommodate the new tidal prism.

Vegetation development- seeds were available, colonization happened quickly.  2002 phase 1 restoration has really nice vegetation coverage occurring.  Newly restored Madrone slough (NNWR) coverage of plants decreased- this is freshwater marsh dying, being replaced by mud, without a lot of vegetation colonization occurring yet, is predominantly mud.  What’s needed is sediment to come down the river and be distributed in the restoration area to build the marsh back up.  With climate change and sea level rise we need to keep pace to maintain salt marsh habitat as well.

With USGS we developed a sediment budget for the Nisqually River.  Over 50% of the sediment is not going into salt marshes, it’s pushed into mudflats and offshore, due to lack of distributaries and reduced sediment budget (approx. 92% of sediment is trapped by the dams upstream).

Fish use the channels since right after restoration.  High fish densities seen in restored channels.

Invertebrates- the restored site is producing similar species composition to reference sites.

UW student Aaron David did a bioenergetics study, found fish feeding in restored areas grew faster than those from reference areas, but with more variability due to temperature spikes, etc.

Otoliths (bone like structures in ear) show increase in time rearing in the delta for Chinook.  Perhaps density dependence was alleviated.

Many partners were involved in this research (USGS, USFWS- NNWR, Ducks Unlimited, Nisqually River Council, etc.)

 

Tags: South Sound Science 14