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Hatfield Marine Science Center Dynamic Revetment Project DSL permit # 45455-FP, Monitoring Report February, 2015
Citation:
Nelson, Walt. Hatfield Marine Science Center Dynamic Revetment Project DSL permit # 45455-FP, Monitoring Report February, 2015. Oregon State University, Corvallis, OR, 2015.
Impact/Purpose:
A Dynamic Revetment (gravel beach) was installed in November, 2011 on the shoreline along the northeastern edge of the Hatfield Marine Science Center (HMSC) to mitigate erosion that threatened HMSC critical infrastructure. The report provides details of a multiagency effort to conduct shoreline topographic and biological monitoring for the narrow purpose of compliance to requirements of a dredge and fill permit needed to protect EPA infrastructure at HMSC. The study is not a part of and has no impact on ORD research under current RAPs.
Description:
Stabilization of the Yaquina Bay shoreline along the northeastern edge of the Hatfield Marine Science Center (HMSC) campus became necessary to halt erosion that threatened both HMSC critical infrastructure (seawater storage tank) and public access to the HMSC Nature Trail. A Dynamic Revetment (gravel beach) was installed in November, 2011 on 260 feet of shoreline to mitigate erosion. Shoreline topographic and biological monitoring was initiated before and has continued after the project completion. Monitoring of beach profiles indicated that as of January 2015, the 2011 Dynamic Revetment Project (DRP) has generally successfully stabilized the shoreline in the project area. Beach profile data also indicated that the 2007 DRP continued to be successful in stabilizing further retreat of the shoreline. In both areas, some loss of gravel at the top of the shore profile due to overtopping of the beach during highest tides was noted, and some additional placement of gravel at these locations is recommended. Rapid erosion has continued in the adjacent Reference beach area and over the period 2009-2015 has been as great as 11 m (36 ft). The erosion in the Reference area adjacent to the south end of new gravel beach appears entirely a function of antecedent erosion that is taking place along the entire length of this shore and is not related to any end effects associated with the expanded gravel beach.Monitoring of beach wrack invertebrates, fish, and vegetation was conducted in 2014. Per unit of beach wrack biomass, the density of wrack invertebrates was significantly greater in the DRP area as compared to both the 2007 DRP area and the Reference area. Total amount of beach wrack was much sparser in the Reference area because of vertical beach scarps generated by erosion that appeared to limit wrack accumulation. As has been a consistent pattern, fish were significantly more abundant in the Reference area compared to the DRP. However, this pattern was present in the pre-project sampling, and the Reference area may have a higher degree of physical habitat complexity, resulting from root masses of trees that have been eroded onto the shore. Chum salmon were recorded from both the DRP and Reference area in 2014 in approximately equal numbers. Preliminary assessment of fish using stationary GoPro® camera samples suggested that there is active fish usage of the DRP gravel shoreline. Sampling issues continue to be problematic for quantitative comparisons of fish abundance. As has consistently been observed, vegetation coverage was significantly greater and presence of non-living substrata was significantly less in the Reference area as compared to the DRP. These differences are consistent with pre-project site differences, probably resulting from a low area of the shoreline which allows increased flooding and associated disturbance in the DRP back shore area. Fish and wrack invertebrates, such as beach hoppers, continue to utilize the DRP project area. Biological differences in fish and vegetation observed in the post-project monitoring in 2014 tended to reflect differences in habitat that were present before the DRP project.
