Flash Flooding occurs within 6 hours of the rain event.

Flooding is a longer term event and may last a week or more.

River Flooding

Flooding along rivers is a natural and inevitable part of life. Some floods occur seasonally when winter or spring rains, coupled with melting snows, fill river basins with too much water, too quickly. Torrential rains from decaying hurricanes or tropical systems can also produce river flooding.

Coastal Flood

Winds generated from tropical storms and hurricanes or intense offshore low pressure systems can drive ocean water inland and cause significant flooding. Escape routes can be cut off and blocked by high water. Coastal flooding can also be produced by sea waves call tsunamis, sometimes referred to as tidal waves. These waves are produced by earthquakes or volcanic activity.

Urban Flood

As land is converted from fields or woodlands to roads and parking lots, it loses its ability to absorb rainfall. Urbanization increases runoff 2 to 6 times over, what would occur on natural terrain. During periods of urban flooding, streets can become swift moving rivers, while basements can become death traps as they fill with water.

Stage 1 of a Quickly Developing Flash Flood

Stage 2 of a Quickly Developing Flash Flood

Final Stage of Developing Flash Flood

Flash Flooding in Arroyos/Washes

An arroyo is a water-carved gully or normally dry creek bed. Arroyos can fill with fast-moving water very quickly. Flash flooding at this arroyo in Arizona took only 58 seconds to develop.

Floating ice can accumulate at a natural or manmade obstruction and stop the flow of water.