Monitoring and adaptive management of the Nisqually Delta after tidal marsh restoration: Restoring ecosystem function for salmon
This 2009 report by the Nisqually Tribe establishes key measures of restoration development, habitat processes, and Chinook salmon response for the largest delta restoration project in the Pacific Northwest.
Summary
This research conducted by the Nisqually Tribe and the U.S. Geological Survey generated the following key insights for consideration in the long-term management of the Nisqually Delta:
1. Juvenile Chinook rely heavily on all habitat components of the Nisqually Delta and Nisqually Reach nearshore for rearing, including the tidally influenced freshwater area around I-5, an area truncated by the I-5 Bridge and flood control dikes.
2. Juvenile Chinook respond rapidly and positively to delta restoration, even when the restored site lacks mature estuarine habitat characteristics like salt marsh vegetation.
3. Upstream land use can significantly alter the habitat forming processes of a delta. In the Nisqually, hydropower operations have dramatically reduced sediment supply to the delta. The near term habitat development of the restoration area as well as the long term viability of the delta is threatened by this constriction. Climate change induced sea level rise will drastically reduce delta structure and function if habitat forming processes are not restored or enhanced.
4. Upstream flood control, flood plain development, and the I-5 causeway exacerbate the impact of reduced sediment supply caused by hydropower development. Sediment routing to the delta from the Nisqually River relies heavily on tidal forcing via tidal channels, so much of the riverine sediment is lost offshore. The lack of distributary channels upstream of I-5 impairs the efficient distribution of sediment. Additionally, the I-5 causeway may inhibit the upstream retreat of estuarine habitats as sea level rises.
Citation
Ellings, C.S. 2009. Monitoring and Adaptive Management of the Nisqually Delta after Tidal Marsh Restoration: Restoring Ecosystem Function for Salmon. Niqually Indian Tribe, Olympia, Washington.
