I forgot to mention my favorite source of portable shade: an umbrella. It's a little easier to walk along with than a tarp.

I have been broke down (stuck) in Utah's west desert. Fortunately it did not turn into a survival situation. When I was a kid our small motor home got high centered crossing a sandy wash. We had plenty of water, food, shovels, and a hydraulic jack. The temp during the day was about 95 degrees F with no A/C. My dad and I dug us out and it took about 14 hours. It was miserable work but at no time were we in danger because we had the gear to deal with it.

Regards, Vince