Growing trees on the valley floor

I am considering buying a site on the valley floor of the Bitterroot Valley in Lolo MT. The water table is about 3 feet down, and the site is mostly flat and right next to the Bitterroot River. Currently it is just in hay without irragation. I would like to do plant all kinds of trees and am looking for any advise or resources anyone can point me to about things I would want to know about growing trees on this type of land.

If I just chose hardy stock would I be alright to plant typical fruit trees? Does a river have a microclimate advantage like a lake or pond would? Any ideas for this type of land?

Two cautions right off: flood danger. Most "ordinary" fruit trees are intolerant of waterlogging around the roots, especially during the growing season. I would ask around and do research as to the flood potential, both in winter/early spring, and in the summer. You may be able to get by with mounds or ridges. Second one: frost danger.....cold air on a still night flows downhill and collects on low ground. Unless the valley floor itself slopes pretty dramatically downhill as it goes downstream, you are very likely in a frost pocket which will be a danger to the early -bloomers.

I know that the property is in the 100 year floodplain, so the potential for flooding definitely exists. Does anyone have experience using fruit rootstocks adapted to heavy/wet soils in an area that is occasionally inundated with water? Of course I wouldn't be planting the whole piece of land in fruit and relying on it to pay my bills, but I would want to feel confident that if I planted a little home orchard it wouldn't all die from a really wet month or a few days of flooding.

What about other perennial food bearing plants and trees? I am specifically wanting to plant perennial forage crops and trees to feed chickens and pigs. Can anyone give me ideas on what trees could be grown for this purpose that would not die if the soil were periodically inundated?

There are a few fruits and nuts that are adapted to bottomlands and are more tolerant of wet than most. Persimmon (on American rootstock), mulberry, and pecan come first to mind. These also have the advantage of blooming later than most and so are more likely to escape spring frosts. The question to resolve is whether any of them are winter hardy in your zone. I would say there are probably mulberries, at least, that could deal. They are not the most easily picked or marketed fruits, though.

Being in the 100 year floodplain and with the water table 3ft below means that you are fine in terms of wet root. You are in zone 4, so that will limit some of you tree options.
You could have been a 4a but the valley that you are in made it a zone 4b 'micro climate'. http://www.plantmaps.com/interactive-montana-usda-plant-zone-hardiness-map.php

In terms of nuts the Chestnut family and Walnut family will grow, but most of the others will not.
In terms of fruits you can even grow apricot so you aren't really limited. Check out these guys and look for plants/cultivars rated for at least zone 4. https://onegreenworld.com/Apricot/337/