Using Ecological and Geomorphic Indicators to Determine Nearshore Restoration Design Parameters
Presentation Abstract
Determination of excavation and fill removal limits are always difficult in nearshore restoration projects. Degree of site subsidence, and complex interactions of waves, tides, and tidal currents, and fluvial inputs, can obscure definitive estimates of future high water marks of different types of water (fresh water, salt water, etc.). In the case of salmon restoration projects, however, often the target is not necessarily an elevation, but rather a target species of vegetation, which has site-specific elevation preferences. At Secret Harbor, vegetative indicators were used in conjunction with water level measurements to determine final grading elevations. Because of the remote location of the site, and unusual topographic features defining it, there was not a close tide gage to determine tidal elevations. The fluvial input to the site further complicated matters. Because of a degraded dike, a small area (approximately 100 square feet) of the marsh to be restored was subject to tidal inundation and had remnant marsh vegetation (pickleweed). The limited presence of pickleweed was particularly valuable to validate the water level measurements. It also was helpful during construction as it provided the contractor a convenient check on the grading elevations. Post project monitoring indicates that the marsh elevation is set correctly – regularly inundated on high tides in the winter, but not during the summer. In addition to the vegetation clues, landward extent of the marsh was apparently constrained by a tall (3-5 feet) existing road prism. Here the road prism was cored and found to have large amounts of woody debris a small distance (one foot) below the elevation of the road. In addition to its curvelinear shape and the presence of similar features elsewhere in the central Salish Sea, it was determined that this feature was a former beach berm and likely predated development; thus providing a natural landward limit for the marsh.
Session Title
Session S-05F: Ecosystem Restoration: Geomorphic Context, Design Considerations, and Success Stories
Conference Track
Restoration
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
1-5-2014 10:30 AM
End Date
1-5-2014 12:00 PM
Location
Room 602-603
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Marsh ecology--Washington (State)--Cypress Island; Fluvial geomorphology--Washington (State)--Cypress Island; Restoration ecology--Washington (State)--Cypress Island
Geographic Coverage
Salish Sea (B.C. and Wash.); Cypress Island (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Using Ecological and Geomorphic Indicators to Determine Nearshore Restoration Design Parameters
Room 602-603
Determination of excavation and fill removal limits are always difficult in nearshore restoration projects. Degree of site subsidence, and complex interactions of waves, tides, and tidal currents, and fluvial inputs, can obscure definitive estimates of future high water marks of different types of water (fresh water, salt water, etc.). In the case of salmon restoration projects, however, often the target is not necessarily an elevation, but rather a target species of vegetation, which has site-specific elevation preferences. At Secret Harbor, vegetative indicators were used in conjunction with water level measurements to determine final grading elevations. Because of the remote location of the site, and unusual topographic features defining it, there was not a close tide gage to determine tidal elevations. The fluvial input to the site further complicated matters. Because of a degraded dike, a small area (approximately 100 square feet) of the marsh to be restored was subject to tidal inundation and had remnant marsh vegetation (pickleweed). The limited presence of pickleweed was particularly valuable to validate the water level measurements. It also was helpful during construction as it provided the contractor a convenient check on the grading elevations. Post project monitoring indicates that the marsh elevation is set correctly – regularly inundated on high tides in the winter, but not during the summer. In addition to the vegetation clues, landward extent of the marsh was apparently constrained by a tall (3-5 feet) existing road prism. Here the road prism was cored and found to have large amounts of woody debris a small distance (one foot) below the elevation of the road. In addition to its curvelinear shape and the presence of similar features elsewhere in the central Salish Sea, it was determined that this feature was a former beach berm and likely predated development; thus providing a natural landward limit for the marsh.
