Abstract
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%.
Highlights
The Shoalwater Bay Indian Reservation is located on the northern shore of Willapa Bay, a large natural estuary located on the southwest coast of Washington State, USA
Extreme water levels coincident with strong winter storms are capable of inundating this low lying topography following the erosion and overwash of the protective barrier islands known as Graveyard Spit
To quantify the benefits of the project, a simple tool is presented for identifying flood risk to the Shoalwater Indian Reservation infrastructure
Summary
The Shoalwater Bay Indian Reservation is located on the northern shore of Willapa Bay, a large natural estuary located on the southwest coast of Washington State, USA. The northern shoreline of Willapa Bay has changed substantially since the Shoalwater Reservation was established in 1866 (Terich and Levensellar 1986). By 1990 the Shoalwater Reservation only remaining protection from storm wave attack was a series of barrier islands fronting Tokeland Peninsula (see Figure 1). Tidal currents and storm waves have severely eroded the protective barrier islands known as Graveyard Spit. The increased wave energy through North Cove has led to an increase in the severity and frequency of flooding and erosion of Reservation uplands during storm events. The feasibility of hard and soft engineering alternatives were evaluated by a multi agency technical team and the analysis determined barrier island dune restoration with periodic nourishment was the most appropriate long term solution to mitigate future erosion and flood damage risk (USACE 2009a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
