Believe it or not, flash flooding is a thunderstorm's number 1 killer, taking the lives of about 140 people annually across the United States. By comparison, about 80 lives are lost to tornadoes. About half of all flood related deaths occur in automobiles as people try to cross roads covered by water. They figure the water isn't deep enough or their vehicles are too heavy to be carried away. However, a foot of water can float about 1500 pounds of vehicle.
Flash flooding is triggered in several ways.
In general, flash flooding occurs when the ground becomes saturated, and water runs directly into streets, storm drains, streams and creeks, and rivers. If the water is not carried away fast enough, it can back up into homes causing extensive damage. Topography is also a factor. Arkansas is hilly in the north and west, with water running quickly from higher elevations into valleys. Some valleys are fairly narrow, with nowhere for water to spread out.