Long-Term Evolution of Columbia River Tides

Abstract

A 170 km tidal channel connects the lower Columbia River ports of Portland and Vancouver to the Pacific Ocean. An increasing incidence of low water levels during summer and fall sometimes limits the draft of ships using the channel and can delay transits. Reduced spring freshet water levels have also decreased shallow-water habitat for juvenile salmon. Records from Tongue Point (km-30, 1925-date), and Vancouver (km-175, 1902-date) were used to analyze historic changes. Mean water levels (MWL) at Vancouver have dropped