There are many undesirable outcomes that result from driving on flooded streets. Your car can get damaged or you could stall out and end up stranded in a pool of rising water. Even if you manage to not get stuck, there is still the possibility of hydroplaning and ending up with your car wrapped around a telephone pole or an innocent bystander. It might be tempting because you need to pick something up or do that really important thing but always remember the reasons why you should never drive in a flood and make a rational decision.
Water can be very powerful for a number of reasons. The volume of water and the speed of flow can combine to generate huge forces that cars have no chance against. If the water gets high enough the buoyancy created by the water will lift the car and send it with the flow of the water. Eventually the car will take on too much water and sink. When that happens the only course of action is to abandon the car and try to escape. There is a high possibility of being stranded on the top of your car needing to be rescued.
It is hard to tell how deep the water may be or how fast it may be flowing so it is easy to be fooled by the water. There may be debris in the water that you cannot see or it may be flowing too fast so that you cannot avoid it and that could potentially do some serious damage to your car. The water itself is muddy and if exposed long enough and the flow is severe enough it will act like sandpaper and mar the finish of your car. Sure it can be polished and buffed out but staying off the road in the first place could prevent it all and save you time.
It seems to happen every year when the flash flooding occurs because people are unprepared and or underestimate the severity of the flood. It is best to play it safe and in the process protect your car from unnecessary damage, and to have peace of mind. You never know if it is someone else that may hydroplane and end up in an accident with you. Staying off of the roads when there is flooding is the only way to ensure that none of these ill effects will happen to you.