The navigation channel reliability monitoring and evaluation study for Willapa Bay Washington described in this report was performed by the U.S. Army Engineer Research and Development Center Coastal and Hydraulics Laboratory for the U.S. Army Engineer District Seattle (NWS). The study was established under a Partnering Agreement between the NWS and the Willapa Port Commission for determining the feasibility of maintaining a reliable navigation channel through the Willapa Bay entrance. Willapa Bay is a large estuarine system located on the southern end of the Washington coast Its spring or diurnal range tidal prism is one of the largest of all inlets on the coast of the continental United States. The shifting channels at the entrance to Willapa Bay make navigation unreliable, and the local port cannot maintain or attract commercial users. Local interests obtained Congressional support to determine if an economical deep-draft channel can be established through the entrance bar. An economical channel implies a route that can be traversed safely under typical waves and tidal currents. The study was conducted in a multi-disciplinary approach involving engineering analysis, field measurements, geomorphologic analysis, and numerical modeling of waves, currents, and sediment transport in evaluation of alternative channel designs. These topics are covered in the main text of the report, with additional details and data compilations contained in appendices.

Beaches, barrier islands and tidal inlets are valuable coastal resources and provide desirable environments that are often densely populated. They are dynamic landforms that change constantly, driven by both normal processes and energetic storms. They behave as one interconnected system and must be understood and managed as such. This book discusses their various morphologic features, as well as the processes that shape them and future challenges due to environmental change. A major focus is placed on the interaction between sandy beaches and tidal inlets, and the sediment exchange among various morphologic features. Balancing these valuable sediment resources while maintaining the natural sediment exchange constitutes a major goal of modern shore protection and coastal management. Illustrated with numerous aerial photographs to demonstrate how beaches and tidal inlets interact, this book provides a valuable reference for graduate students, researchers and professionals working in coastal management and geomorphology.