Abstract Title

Session S-05F: Ecosystem Restoration: Geomorphic Context, Design Considerations, and Success Stories

Keywords

Restoration

Start Date

1-5-2014 10:30 AM

End Date

1-5-2014 12:00 PM

Description

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.

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May 1st, 10:30 AM May 1st, 12:00 PM

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.