Flooding hazards

Floods are the most common natural disaster except for fires.

Floods are caused by rain, snow melt, hurricanes, and often are tied with other hazards, including earthquakes and mudslides.

Floods deeper than two feet can put enough pressure on building walls to destroy them.

Flash floods

Flash floods give little warning and can reach full intensity in minutes.

Fast-moving walls of water more than 15 feet high can hit structures hard enough to destroy buildings and bridges.

Flash floods usually result from an intense storm, which can be miles away in mountainous terrain.

• Storm surges that can reach 10-20 feet high, and hit structures with great force.
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• Severe inland flooding, especially with slow-moving storms.

After-effects of floods

Floods not only can damage structures during the event, but can continue to have an impact long after.

• Flooding can erode the soil base, or trigger sinkholes and landslides that undermine a structure's foundation.
• Some soils expand or contract when wet. Structures built on these soils can be damaged as their foundations shift.

• Structures built of wood can rot and decay and set up for termite damage if not dried out quickly.
• Flood waters can carry chemicals and salts from farm or urban runoff that can start chemical changes in structural materials.

Why make communities more flood-resilient

Communities that are resilient to flood damage from other hazards, including earthquakes, terrorist attacks, and hurricanes. This also increases the economic worth of the structures, protecting a community's economy.