David R Michalsen, Steven D Babcock, Lihwa Lin


The U.S. Army Corps of Engineers, Seattle District has completed a feasibility study and determined barrier island restoration to be the most appropriate long-term coastal flood and storm damage reduction measure for the Shoalwater Indian Reservation. Over the last century, Cape Shoalwater has receded more than 2.8 miles. By 1990, the Shoalwater Reservation’s only remaining protection from storm wave attack was a series of barrier islands fronting Tokeland Peninsula. Extreme water levels coincident with strong winter storms have historically inundated this low lying topography and are responsible for the erosion and overwash of the protective barrier island known as Graveyard Spit. Here a simple risk assessment tool is presented for identifying flood risk to the Shoalwater Reservation infrastructure. Statistical analysis of extreme water levels and numerical modeling is utilized to determine the extent of inundation. From the analysis it was determined 54% of the inventoried infrastructure is at risk during a storm event equivalent to the observed event on March 3, 1999. With the barrier island restoration it was found that this risk is reduced to 7%.


extreme water levels; barrier island restoration; flood risk; wave modeling

Full Text:



FEMA 2005. Guidelines for Coastal Flood Hazard Analysis and Mapping for the Pacific Coast of the United States.

Goda, Y. 2000. Random seas and design of maritime structures, World Scientific, Singapore.


Komar, P. D. 1998. Beach processes and sedimentation. 2nd ed. Upper Saddle River, NJ: PrenticeHall, Inc.

Kraus, N. C. (Editor). 2000. Study of Navigation Channel Feasibility, Willapa Bay, Washington. ERDC/CHL TR-00-6. Vicksburg, MS: U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory.

Lin, L.,Demirbilek, Z., Mase, H., Zheng, J. and F. Yamada. 2008. CMS-WAVE: A nearshore spectral wave processes model for coastal inlets and navigation projects. Coastal and Hydraulics Engineering Technical Report ERDC/CHL TR-08-13. Vicksburg, MS: U.S. Army Engineer Research and Development Center.

Mase, H. 2001. Multi-directional random wave transformation model based on energy balance equation. Coastal Engineering Journal 43(4), 317-337.

Mase, H., K. Oki, T. Hedges, and H. J. Li. 2005. Extended energy-balance-equation wave model for multi-directional random wave transformation. Ocean Engineering 32, 961-985.

Michalsen, D.R. 2004. An investigation of wave field transformation and shoreline morphology near steep bathymetric features." Masters' thesis, Dept. of Civil, Construction and Environmental Engineering, Oregon State Univ., Corvallis, Ore.

Michalsen, D., Haller, M.C. and Suh, K-D. 2008. Wave reflection from nearshore depressions, J. Waterway, Port, Coastal, and Ocean Engineering, 134(1), 1-11.

Pugh, D.T. and Vassie, J.M. 1978. Extreme sea levels from tide and surge probability. Proc. 16th Coastal Engineering Conference. Hamburg, Germany. pp. 911-930

Taylor, L.A., B.W. Eakins, K.S. Carignan, and R.R. Warnken. 2008. Digital Elevation Model for Astoria, Oregon: Procedures, Data Sources and Analysis. Prepared for the Pacific Marine Environmental Laboratory (PMEL) NOAA Center for Tsunami Research by the NOAA National Geophysical Data Center (NGDC). May 30, 2008

Terich, T., and T. Levenseller. 1986. The Severe Erosion of Cape Shoalwater, Washington. Journal of Coastal Research, Vol. 2, No. 4, pp. 465-477.

U.S. Army Corps of Engineers, Seattle District. 2009a, Final Post-Authorization Decision Document: Shoalwater Bay Shoreline Erosion, Washington.

U.S. Army Corps of Engineers, Seattle District. 2009b, Appendix 1: Engineering Analysis and Design Shoalwater Bay Shoreline Erosion, Washington.

USGS 2004. Shoalwater Bay Tribe Erosion Study. Prepared in Cooperation with Washington Department of Ecology. Unpublished report.