To be accurate, the car did not hydroplane due to flash flooding.
It hydroplaned due to speed.
There is a reason why some people spend $200 on a tire. Cheap tires are more prone to hydroplaning than a high performance tire.
The flash flooding caused water in the street. It can be very hard to tell how deep the water is in that situation. From safemotorist.com
“Hydroplaning occurs when a tire encounters more water than it can scatter. Water pressure in the front of the wheel pushes water under the tire, and the tire is then separated from the road surface by a thin film of water and loses traction. The result is loss of steering, braking and power control.”
Speed is a definite factor as hydroplaning is most likely to occur when a vehicle is going over 35 mph.
My point is that the driver may not have realized he was going at a dangerous rate of speed because of the difficulty of gauging water depth during flash flood conditions. He may even have been driving below the normal speed limit. We don’t know. He was driving under dangerous conditions and had an accident. How much driver error contributed is not known.