Nice little garage but you're going to have a continuous problem with water coming in unless there is some drainage across the front of the doors. I just scanned through the build of your garage and looked at the pictures. I wouldn't have built it like that and not sure what your builder was thinking.
I would have poured a short (formed when the floor was done)stem wall or laid a single course of block to set the walls on. The bottom plate of your walls is set right on the floor and doesn't even appear to be PT lumber. It also appears that the driveway is virtually level with the garage floor. Even having gutters with a driving rain, I think you're going to have water in there. Hopefully, the O/H doors don't face the prevailing wind.
Good luck on the gutters as I hope it solves your water problem, not much can piss you off having water coming in every time it rains. I was there at one time.
+1 to all of this.
Not trying to rag on the OP, but I agree with the above. Our garage (built in the 1990s) was built with a very small step up from the driveway level to the garage floor, so water can't run in, in most cases. As the poster above notes, it appears the boards are right on the floor. My garage has a short concrete wall that's part of the foundation. The building walls rest on this concrete riser. So, on the rare occasions where water can get it, it doesn't touch the wood part of the walls, just the short concrete risers the walls sit on.
EDIT - attached are a couple pics, since I'm probably doing a bad job of explaining.
There's a depression in the floor around the garage doors, so it's very difficult for water to run into the garage.
The walls rest on part of the foundation that's raised up an inch or so, so water that gets in or is spilled doesn't contact the wood that makes up the walls.