Trip Report: Sandskiing the Oregon Dunes | Photo Tour The Oregon Dunes are a large expanse of coastal sand dunes stretching approximately 40 miles north of the Coos river in North Bend, to the Siuslaw river in Florence, OR.ย They are the largest expanse of coastal sand dunes in north America and in some places have reached a height of up to 150 meters above sea level! Living only […] Trip Report Bevan Waite | August 12, 2013 3 Comments