OTREC-RR-11-17

River freight plays a vital role in the Lower Columbia River economy. The link to land transport can be disrupted if channel depths are shallower than expected. 70% of cargo is carried by vessels with a draft close to low water channel depth. A large vessel may have as little as 0.6 m clearance at low tide. River changes exacerbate the situation – low water levels have decreased 0.3-1.2 m since 1940. An ongoing 0.9 m channel deepening will cost about $150 million. Low water levels also increase emissions, as smaller loads mean more trips. Further, navigation and salmon habitat restoration are closely connected. Dredging is used to maintain the channel, and habitat restoration is an integral part of the channel deepening. New dredging strategies are needed to maintain the deepened channel, but dredging that removes material permanently may further lower water levels, limiting possibilities for habitat restoration and reducing clearance.