You might as well add some sand and cement and make yourself a concrete road.

It's an intriguing suggestion, but my gut reaction is that concrete in the ruts might be more trouble in the long run. Water regularly rushes through this area during floods, and I could see it eroding away the soil at the side of the concrete tracks, leaving them higher than the surrounding ground. That would make the concrete tracks tricky to drive on since you could slip off the side (and tear up your tires in the process.) I've seen concrete tracks end up this way, but don't know how common/likely it is.

Actually I was kind of joking

I would imagine that to build a really long-lasting road in an area that floods it would have to be raised above the water level and have a proper foundation. Which is probably way too much work for you two.

You might get away with pouring a relatively thick (say 4"?) slab of concrete in a trench at ground level. You don't want it to get too wet when it's curing, otherwise it will shrink too much and crack. If you'd dig a 4" deep trench, line it with plastic foil and pour concrete in it, it might work. The concrete should be thick enough so that the concentrated loads from the truck tires doesn't cause the underside to fail in tension, as concrete is prone to. 4" sounds plenty thick to me, but you should really ask an expert. Generally, concrete gets stronger when you use less water. So you should use a relatively water-poor mix and prevent the concrete from absorbing water from the wet soil, hence the plastic. But that also means that it takes longer to cure and doesn't pour very well. For a slab that's not much of a problem, though.

But if you really want to build a road, you should talk to to a roadbuilding engineer. This really isn't my field.

I'm glad you were joking --- Mark thought the idea was way too much work, given that there's no way we could get a concrete truck back here, so we'd be mixing all of it by hand.

Make a couple of wooden moulds, say 2 by 8 feet, 4 inches thick and on wheels. Use those to cast big concrete tiles. Roll the moulds to the end of the road, flip them over and pry off the mould leaving the slab in place. Every tile extends the road and makes it possible to get further.

That sounds extremely time-consuming. Even more problematic since we don't actually own any concrete-truck accessible spot, so we'd be doing it out on the public road.... (We have a right of way through someone else's property to our parking area, where our land begins.)