usually it's not the water that warps the rotors, as not many people drive through 5-10" deep pudles slow enough to envelope the rotor.

The warping comes from heating the rotors to a high temp, and then you come to a stop at a light for more than a minute, this causes a temp diference form where the caliper is clamping the pads to the rotor, and the rotors exposed surface area.

is usually wise to leave a good space between you and the guy in front, so you can slowly roll forward and not come to a complete stop until the rotors are cooled down, usually you shouldn't come to a complete stop after hard canyon driving, or durring brake in of the rotors. gotta give them time to cool.

If you must come to a complete stop use the Emergency brake to hold the car!