If the soldiers were disregarding warnings to stay off the roads due to flooding, then, yes, the accident could have been prevented. If they were following orders, or trying to rescue others in need, then maybe it could not have been. They may have thought the army vehicle was high enough or rugged enough to cross the creek.
The accident at Foot Hood is very tragic, and I believe that it could have been prevented with the proper precautions. That truck should have never been driven through a flooded area. If the vehicle was properly equipped to handle these types of road, those soldiers would still be alive.
Car accidents can always be prevented. In today's culture we do not place enough emphasis on maying attention to a single responsibility. It is very possible that this accident was caused because the driver was distracted by something. The driver may have been talking to someone else, or thinking about something else and not fully focusing on driving.
This truck accident may have been the result of inappropriate procedures handled by the passengers - not buckling in seatbelts, driving carelessly - or the road construction agencies - posting stop signs, allowing greater space between lanes, etc. In either case, the loss of life could have been foreseen and prevented. If this accident involved military antagonistic groups, then it would have been safer to provide a more secure vehicle for the soldiers.