The Mega Flood Route - The Washington Coast to Missoula Mt

We'd recommend visiting the Palouse district in south-eastern Washington. The view from the top of Steptoe Butte is awesome. We'd second visiting Palouse Falls. And definitely visit Dry Falls.

Hi Everyone
We really appreciate all the replies we received. I am currently printing them out and will take them with us. There are great suggestions as to what to see and how to do it. We sat down with several maps this morning and and started doing some serious planning. We were surprised at how far north the Dry Falls were. Not what we had in our "preconcepts" thinking. We are already changing our planned route. It was also unanticipated how hard it was to find many of the landmarks on paper maps. We hadn't used the reference keys in years but found it necessary this time around. Funny how map skills get forgotten with disuse.

Regards and Appreciation
Bill and Carole

We are thinking of getting a hosting position in central Washington to explore this more in depth.
Have a good book on the subject “Glacial Lake Missoula and it’s Humongous Floods” by David Alt.
We have also spent time at Grand Coulee Dam and that area, some great areas to see!

An eastern Washington prof has a nice series of videos about Washington geology including several of the flood sites.

Nick on the Rocks - Dry Falls

and related links.

I'm sure there are guide books and other geological explanations. I've used a Roadside guide and field trip notes from Geological conferences.

Basically anything downstream from Missoula will show some evidence of these floods. That starts with MT200, ID200 past Sandpoint. Around Spokane the floods spread out. Much went down the Columbia River gorge, now Lake Roosevelt, and then flowed south around the current site of Grand Coulee Dam (there was an ice dam from another glace lobe further down stream).

WA155 follows this route SW from the Dam along Banks Lake. WA17 continues SW past the Dry Falls and Sun Lakes. Look at the area with Google Maps Terrain and Sat view modes to see the scouring.

Further west on US2 is Mosses Coulee, a dry canyon carved by the floods. WA172 north of US2 crosses moraines left by glaciers.

WA28 Wenatchee to Quincy gives you views of the downstream end of Mosses Coulee, and giant gavel bars deposited by the floods.

There's more evidence of erosion and deposition all along the Columbia to Portland. The flood waters formed lakes at constrictions like Wallula Gap (on the stateline) and backed up into side valleys at places like Portland. They also flowed overland between the Columbia and the Snake.

Palouse Falls off of WA261 (south from Washtucna, WA26) is a prime example of erosion as the flood waters drained into the Snake canyon. Again Terrain maps view is particularly revealing.

The irrigation system across central WA takes advantage of the flood geology. For example irrigation drain water collects in the Potholes on WA262. There isn't a lot of flood evidence on I90 except around the Columbia river crossing.

Most of SE Washington is covered with the Columbia basalts - thick layers of lava. Often that lava cooled in a columnar form that makes steep cliffs with plucked by flood waters. In other places they removed old soils, leaving bare rock out crops.

Major areas were covered by glacial loess, fine wind blown sediment. This forms rolling hills in SE Washington around Pullman, the Palouse. Scouring of these loess hills can be seen south of the Potholes.

http://www.sevenwondersofwashingtonstate.com/the-channeled-scablands.html



Just follow the arrows on this map. :)

Good for you! Few people have heard of Eastern Washington’s basalt “Channelled Scablands” nor care how it was formed by the great Missoula Flood thousands of years ago.

Pretty much choose any east-west route through that part of the State and you will experience it. Some of my favorites: (1) US2 from Spokane to Waterville...at Coulee City you can head north on WA155 along Banks Lake to Grand Coulee Dam. The coulees in this area are awesome. (2) The entire Palouse Hills region in SE Washington...US195 from Spokane to Pullman and down to Clarkston, WA/Lewiston, ID. and west from Clarkston on US12 through Walls Walls and onward on I-82 through the Tri-Cities and Yakima. (3) WA26 from Pullman to Vantage which is on the Columbia...this highway passes through the “potholes” region, hundreds of lakes formed by the flood...this area basically encompasses most of the huge region from here all the way north to Grand Coulee. Palouse Falls is just south of WA26 between Hooper and Washtucna.

I am a Western Washington native, but I went to college in Pullman, and I love Eastern Washington. Have done a lot of exploring. If your objective is to experience the Channelled Scablands, that part of the State is a tremendous classroom. You might also get good info through WSU in Pullman.

I skimmed the surface. Ok to PM me.

I'm not sure of entire route....
The light show at one of the dams on hwy97 in WA (forget the name of dam)...be sure to look at the time when it starts and when it gets over. Makes a late evening if any younger kids involved as still sunlight till late. But kids might enjoy http://stonerosefossil.org/ if going in that direction. Sure would be nice to read about a trip report when finished.