The Oregon Dunes are located between the Coos River in North Bend and the Siuslaw River in Florence. These dunes are the largest expanse of coastal sand dunes in North America with some reaching an elevation of 500 feet (150 m) above sea level. Coastal dunes form where the shoreline is flat and wide, where there is a large and consistent sand supply, and where there are prevailing onshore winds. Ocean waves transport suspended sand onshore in energetic surf zones. Waves run up the beach slope, lose energy, and deposit the sand. Onshore winds then continue transporting the finer sand grains up the beach face. Obstacles such as vegetation, fences or other structures tend to slow down the wind and this leads to the deposition of sand grains. The height of coastal dunes is a function of wind velocity that contributes to dune building as well as dune erosion during severe storm events. Learn more about the Oregon Dunes here, and about dune formation here. Click here to download the CoastView app and explore more of the Oregon Dunes.