Shoalwater Bay Erosion: Executive Summary


A focus on the Shoalwater Bay Erosion Project with excerpts of key parts of the army corps of engineers work to protect Shoalwater Bay tribal lands from continuing erosion. 

Shoalwater Bay Erosion: Executive Summary

The Shoalwater Bay Shoreline Erosion, Washington, study was conducted in accordance with Section 545 of the Water Resources Development Act (WRDA) of 2000, as amended by Section 5153 of WRDA 2007. Section 545(a) of WRDA 2000 directed the Secretary of the Army to conduct a study to determine the feasibility of providing coastal erosion protection for the tribal reservation of the Shoalwater Bay Indian Tribe (Shoalwater Tribe) in the State of Washington. Section 545(b) provides that the Secretary shall construct and maintain a project at Federal expense if the Secretary determines that the project: (a) is a cost-effective means of providing coastal erosion protection; (b) is environmentally acceptable and technically feasible; and (c) will improve the economic and social conditions of the Shoalwater Tribe.

In accordance with Section 545(a), the investigation of the coastal processes at Willapa Bay affecting the Shoalwater Bay Indian Reservation (Shoalwater Reservation) has been completed. The interagency investigation conclusively demonstrated that (1) erosion of the natural barrier dune on Graveyard Spit has reached a critical stage and (2) modest engineering solutions are technically feasible to significantly reduce coastal erosion and the risk to the Shoalwater Reservation from flooding and coastal storm damage. If no action is taken, the Shoalwater Tribe will incur total loss of remaining subsistence habitat in the North Cove embayment and is under immediate and growing threat of severe damage to tribal facilities and infrastructure due to storm wave attack and flooding. Erosion of Graveyard Spit has significantly compromised its historical function as a storm barrier for the Shoalwater Reservation. Without prompt action, the Shoalwater Reservation will incur increasingly frequent and severe flood and coastal storm damage to Tribal facilities, infrastructure, and subsistence habitat alike.

The Shoalwater Tribe is a Federally recognized Tribe. The U.S. Army Corps of Engineers (Corps), as an agency within the Federal government, has consulted with the Shoalwater Tribe on a government-to-government basis throughout the planning process for the proposed project. The Shoalwater Tribe’s efforts to preserve their land and heritage have been carefully considered by the Corps, and the proposed project has the full support of the Shoalwater Tribe and the Bureau of Indian Affairs.

The Shoalwater Reservation was established in 1866 by Executive Order of President Andrew Johnson. The Shoalwater Reservation is located on the Tokeland Peninsula on the north shore of the entrance to Willapa Bay, a very large estuarine system on the Pacific Ocean coast of Washington. Willapa Bay is approximately 28 miles north of the mouth of the Columbia River and 12 miles south of the entrance to Grays Harbor. The Shoalwater Reservation is slightly greater than one-square mile in area and consists of 440 acres of uplands and 700 acres of important tide flat and intertidal habitat in North Cove. All Reservation land is tribally owned, and is bounded by steep natural hillsides to the east and north and by Willapa Bay to the south.

The immediate effect of erosion of the barrier dune on Graveyard Spit is increased exposure of the Shoalwater Tribe’s North Cove embayment to damaging wave energy during coastal storm events. The erosion and storm wave overtopping of the barrier dune has in-filled North Cove with sand and large woody debris and significantly degraded tide flat and intertidal habitat in the embayment. North Cove no longer sustains tribal subsistence shellfish beds, and native plant populations have diminished. This has resulted in a lost opportunity for subsistence shellfish gathering and significantly reduced harvest of culturally significant native plant species for tribal crafts and ceremonial use.

The increased wave energy in North Cove has, in turn, led to an increase in the severity and frequency of flooding and erosion of Shoalwater Reservation uplands during storm events which occur during periods of extreme water levels. The upland flooding and shoreline erosion is due to increased wave height in the North Cove embayment which is the direct result of storm waves overwashing the eroded barrier dune on Graveyard Spit that fronts the Shoalwater Reservation.

Winter storms in 1998-1999 caused two breaches to form in the barrier dune, resulting in storm wave run-up and flooding of shoreline areas where tribal development is concentrated. To provide partial protection to the Tribal Center, a 1,700-foot-long shoreline flood berm was constructed in 2001 by the Corps. In December 2007, a 300 foot extension of the flood berm was constructed by the Corps. Six of the twelve extreme water levels recorded since 1973 have occurred since 1999. Coastal storms that coincided with these extreme water levels in March 1999, December 2001, February 2006, and December 2007 resulted in significant erosion and storm wave overtopping of the barrier dune, some erosion of the shoreline, and flooding of tribal uplands. These events have created a growing sense of urgency on the part of the Shoalwater Tribe for implementation of long-term coastal erosion protection and storm damage reduction measures.

A wide array of alternative plans were formulated and evaluated against identified problems and opportunities, and planning objectives and criteria. Four alternative plans, plus the No Action alternative, were carried forward for detailed evaluation: sea dike (Alternative 4), sea dike to Reservation boundary (Alternative 4a), barrier dune restoration (Alternative 6), and barrier dune restoration with flood berm extension (Alternative 7). Each plan would provide a technically feasible solution to identified coastal erosion and storm damage problems. The sea dike alternatives were found to have the highest initial construction and annualized cost, and are not environmentally acceptable. The barrier dune with flood berm extension alternative will require expensive mitigation of unavoidable wetland impacts associated with the flood berm extension, and has higher initial construction and annualized costs than barrier dune restoration (Alternative 6).

Barrier dune restoration (Alternative 6) is the most appropriate long term solution to the coastal erosion and resulting storm damage problems affecting the Shoalwater Reservation. Alternative 6 will afford effective coastal erosion protection and storm damage reduction to the entire Shoalwater Reservation. With a total first cost for initial construction of $9,827,000, periodic nourishment/monitoring every five years at a cost of $4,512,000, a total present value of $25,882,000, and a total average annual cost of $1,336,000, Alternative 6 best satisfies planning objectives and criteria, and meets all criteria specified in the WRDA 2000 Section 545 conditional project authorization.

Barrier dune restoration is a cost effective means of providing coastal erosion protection and storm damage reduction, is environmentally acceptable, and is technically feasible. By reducing coastal erosion and related coastal storm damage problems, Alternative 6 will improve the economic and social conditions of the Shoalwater Bay Indian Tribe. Barrier dune restoration will significantly reduce flooding and coastal storm damage to Tribal uplands, as well as prevent further degradation of the 700-acre North Cove embayment subsistence tide flat and intertidal habitat. Alternative 6 is fully consistent with the Corps’ environmental operating principles, and will be environmentally sustainable. Implementation of the project will improve the quality of life for present and future generations of Shoalwater Bay Tribal members. This is a vitally important project to a remotely located Native American community in a highly vulnerable location along the Washington coast.


US Army Corps of Engineers, Seattle Washington. Shoalwater Bay Shoreline Erosion, Washington. Flood and Coastal Storm Damage Reduction. Shoalwater Bay Indian Reservation. [Excerpt pages 1-3].

For a PDF version of the entire report go to:  Shoalwater Decision Doc.

Shoalwater Bay