We were disappointed in Dry Falls tbh. It was very hard to understand what we were looking at, and to get a feel of how things were.
If you can find them in your library or book store (or even on Amazon)then have a look at the Scenic Driving books for Oregon and Washington. Both have some drives which cover the Missoula floods areas.

Hello, well it's hard to follow the path of the floods but Missoula is the place to start and then it went through the Saint Joe river into the Coeur d'Alene river and down the Spokane river flowing into the Columbia river of course it took up large parts of the landscapes along the way. It took out soil to bedrock in the Columbia plateau and left large rocks the size of cars and bigger in the middle of nowhere. Get a good map of the floods and you're good to go.Just knowing this is where the worlds largest floods happened is awesome in it's self. A poster said Dry falls was a disappointment is right if you are expecting something like Niagara Falls but if you think about it in terms of the POWER of the floods carving out such a large strange area it's almost like a hand of God reached down and carved out the landscapes.

Enjoy it for what it is an awesome powerful reminder of what nature can do.

Oh yes in Spokane it carved out the river that flows through it including the falls in the middle of the city and the wonderful area of the "bowl and pitcher", it's a state park just minutes from the center it has strange rock formations made from the floods again it tells the power of what they can do.

Check out some of the massive channels that drained into what is now the Columbia River. By far my favorite out-of-the way spot is Frenchman Springs Coulee, near I-90, just past the town of Vantage:

Take I-90 to Exit 143 (Champs de Brionne Winery), near the town of George. Turn west onto Silica Rd (turn left if going E on I-90, turn right if going W on I-90), then After about a mile, turn left at the first intersection, onto Vantage St. (if you turn right instead, you will be on Frontage Rd). If you follow this road, it literally runs right into the Columbia River. Along the way, you can stop for great views atop one edge of the massive Coulee, and behind you are spectacular exposures of columnar basalt.

When in Missoula, check out Mt. Jumbo, just north of I-90, between Exits 105 and 107. You can easily see the various shorelines of Lake Missoula exposed on the flanks of this mountain.

Here are a couple of photos I took in Frenchman Springs Coulee, in the Facebook group, "Geology Rocks":

http://www.facebook.com/albert.friedman?ref=profile#/photo.php?pid=32&op=2&o=user&view=user&subj=2204596135&aid=-1&oid=2204596135&id=295000001

http://www.facebook.com/albert.friedman?ref=profile#/photo.php?pid=31&op=2&o=user&view=user&subj=2204596135&aid=-1&oid=2204596135&id=295000001

Traveling west on I-90, right after the 9 Mile Exit (after Huson), if you look to your left, right before you cross the river, you can see the lines from the water levels on the side of the mountains (or so says my sister from Missoula).

I'm getting into this a bit late - but hopefully I haven't missed you.
I grew up in the area you are talking about and I think you're right when you say what you're looking for is pretty specific. Most of it isn't located on a map, so much as people from the area simply knowing about it.
Since you can't very well just hope to find someone in the area who knows where to go here are my suggestions:
WSU has a great geology program and they have some field trip guides online. You might try emailing one of the faculty and asking them:
http://www.sees.wsu.edu/FieldGuides/index.html

Also, when I was taking a geology class from WSU I needed to identify a strange rock and emailed the state Geologist at the Department of Natural Resources. I got a prompt answer to my email and pictures and he was quite nice about it. So you might try emailing the currect state geologist (Dave Norman) and politely asking for some tips. If anyone should know - it should be him: http://www.dnr.wa.gov/Publications/ger_staff.pdf

I hope that helps!

To anyone in the future who might learn of, and consider this trip:

It really went impressively well!

If done ideally (not efficiently), a person would begin in Missoula, look up at "Mt. Jumbo", and see the numerous shorelines from repeated flooding that left what is now Missoula under 900 feet of water.

Then go northwest toward Camas Prairie, where you can see ripples in the floor of a valley, which were made by the repeated floods leaving the area under lots of water thousands of years ago.

Then go to Lake Pend Orielle, where historic markers denote the power and destruction of the floods.

Eventually go on to Grand Coulee and on down to Dry Falls (which really is awesome, no matter what somebody said above).

Obviously the walls of the path from Grand Coulee Dam to Dry Falls were carved by the floods long ago.

A very unique aspect of an ideal path for learning about these ancient floods comes on the main path between the Washington State towns of Soap Lake and Moses Lake:

On either side of the road, many miles from any sort of hills, there are giant collections of large boulders!!!

These boulders didn't fall from anywhere during the past 1000 years, they were carried there by the FLOODS! Now I'm sure local farmers may have moved some of the rocks a little bit, but there still aren't any hills around, so they had to come from somewhere.

Beyond that, Frenchman Coulee, and even Palouse Falls are in order before going to Wallula Gap and then on up the Columbia River toward Portland.

It is best to read a good deal about the floods and the evolution before setting out on such a journey. Otherwise perhaps "Dry Falls" won't impact you in the same way it did me.

Now back from a very interesting trip.

cool report. thanks.

You are right about the large boulders. That is one of those "local" things I mentioned. I remember seeing them here and there.

It sounds like you had a great time. If you haven't ever flown over that side of the state I would recommend it! The hills looks exactly like the ripples of sand you see in shallow water. It's quite amazing.