What is the Difference Between Flood and Flash Flood?

The main difference between a flood and a flash flood lies in the duration and the rate at which the water rises.

• Flood: A flood is an overflow of water onto normally dry land, often caused by rising water in an existing waterway, such as a river, stream, or drainage ditch. Floods can last for days or weeks and are typically caused by a gradual increase in water levels. They are more likely to occur in densely populated areas or near rivers, streams, and dams.
• Flash Flood: A flash flood is a flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours. Flash floods are characterized by raging torrents after heavy rains that rip through river urban streets or mountain canyons, sweeping everything before them. They can occur within minutes or a few hours of excessive rainfall and can also occur even if no rain has fallen, for instance, after a levee or dam has failed, or after a sudden release of water by a debris or ice jam. Flash floods are more life-threatening than floods due to their rapid onset and the potential for people to be trapped in flooded areas.

In summary, a flood is a longer-term event with a gradual rise in water levels, while a flash flood is a shorter-term event with a rapid rise in water levels, often caused by heavy rainfall within a few hours.

Comparative Table: Flood vs Flash Flood

The main difference between a flood and a flash flood lies in their duration, development, and location. Here is a table summarizing the differences:

In summary, a flood is a long-term event that covers normally dry areas and usually develops more slowly, while a flash flood is a short-term event that covers low-lying areas and develops rapidly. Floods are often caused by multiple factors, including rising water levels in rivers or creeks, while flash floods are typically caused by excessive rainfall that overwhelms storm sewers or ground conditions. Both types of flooding can cause extensive damage, but flash floods can be particularly dangerous due to their fast-moving water and the potential for vehicles and people to be swept away.