Dune Fields of the Upper Columbia River, WA
"Palouse windstorms thicken Okanogan soils"
In the Okanogan Highlands of northeastern Washington, forest soils are very thick on north and east facing slopes. Dust (windblown silt) delivered from the south is trapped by vegetation on relatively wet, cold aspects. The result is grass-tree mosaic that is aspect controlled. Lower down, atop the broad, sagebrush-covered glacial terraces that line the Columbia River, fields of sand dunes have grown large in the past several thousand years. IN contrast to silt particles that are easily swept up by strong winds and routinely carried hundreds of miles, sand-sized particles hug the ground and and steadily march downwind. In general, the sand is being transported to the northeast by prevailing winds, but dune migration is significantly influenced by the local topography, which introduces some variation.
Here are a few examples of dune fields along Lake Roosevelt and Okanogan River. Most are vegetated, so its unlikely you would even notice them driving by. But these bare earth lidar images cut through the vegetation to reveal the ground surface beneath. Remarkable just how many square miles of the canyon are covered by sand dunes. All images are from Washington Lidar Portal and are shown at the same scale. I've added dune migration direction arrows - only a best guess in some places.
Locations for eight of the thirteen sand dune sites shown below. The remaining five are north (upstream) of the map area.
Intersection of Hwy 25 N and Miles-Creston Rd just east of the bridge at Spokane River mouth (above Fort Spokane).
Inchelium Hwy at Roper Creek inlet.
Near landfill on Carson Flats, north of the Colville River mouth.
Northport-Flat Creek Rd east of Kelly Hill.
Flat west of China Creek between Bossburg and Evans.
Marble Flat, Crown Creek and Hwy 25 North. Location not shown on regional map.
Northport-Waneta Rd at Deep Creek. Location not shown on regional map.
South of Mitchell Mountain and east of Goodeve Creek. Location not shown on regional map.
Morris Creek just south of the Waneta US/Canada border crossing. Location not shown on regional map.
Swede Flats along Miles-Creston Rd.
Is this correct? Steep faces of dunes east of Hwy 97 are south-facing. Okanogan River at Wakefield RR Bridge between Monse and Mallott.
Bissell Flat just west of the Nespelem River mouth.
Sand Hills just south of Redford Canyon along Ninemile-Hellgate Rd.