Seine Commercial craft (barges and push-tows) can use the river from Marcilly-sur-Seine, to its mouth. At Paris, there are 37 bridges. The river is only above sea level from its mouth, making it slow flowing and thus easily navigable. The Seine Maritime, from the English Channel at Le Havre to Rouen, is the only portion of the Seine used by ocean-going craft. The tidal section of the Seine Maritime is followed by a canalized section ("Basse Seine") with four large multiple locks until the mouth of the Oise at Conflans-Sainte-Honorine (170 km). Smaller locks at Bougival and at Suresnes lift the
Course of the Willamette River Park on the left. Between the Hawthorne and Steel bridges, the Eastbank Esplanade and I-5 are on the river's right. Downstream of the Broadway Bridge, the river flows under the Fremont Bridge, which carries Interstate 405 and U.S. Route 30. Between the bridge and Sauvie Island, Route 30 runs roughly parallel to the left of the river between it and Forest Park in the Tualatin Mountains (West Hills). Below this, Swan Island and its marine terminals, run by the Port of Portland, is on the right at about from the mouth, and Balch Creek enters from the left. Near Swan