Flash floods are never just water, it's more like a concrete slurry (often <25% water content) with tons of dirt, rocks and debris.
Even just a few inches (often just 3-4) of this will cause your car to stall and be swept away.
In a few seconds this moves you into areas more than 10 inches deep, when most cars start to float. At least for a while before you drown.
Turn around.