First, make sure you follow the Texas regulations on pumping water from a stream, and on making any alterations to a stream bank!
Will you have AC electricity available at the pump site? That gives you a lot more options.
One option to protect your equipment from floods is to put it inside a double-wall plastic culvert that is emplaced vertically. Put in a tee with a smaller pipe to the creek that can easily handle your pump flow rate. Leave the vertical culvert open-topped, with the top above normal flood stage. That way your float switch should be protected, yet still operate based on the water level in the creek.
Another option is to just build your intake and float as cheaply as possible and run a cable up to a tree. Recover your equipment after a flood and repair as needed. That might actually be cheaper than a large initial investment to protect your equipment.
