Natural Disasters

Tornadoes, Flooding, and Avalanches

Tornado Facts

• Mainly occur east of Rocky Mountains in US– Spring/summer

• 800 tornadoes reported nationwide

• Speeds up to 250 MPH; damage paths 1-50 miles long

Tornadoes – What Causes Them?

• Develop in warm, moist air as they are met with cold fronts

• Creates atmospheric instability, which causes a spinning updraft

Supercell Thunderstorms

• Long line of thunderstorms whose updrafts/downdrafts are in perfect balance

• Deadly: Perfect conditions for many tornadoes

Wall Cloud

• Rain-free clouds that accompany tornado-producing thunderstorms

Waterspouts

• Tornadoes that form over water

The “F” Scale

• F0: Winds less than 73 MPH

• F1: 73-112 MPH

• F2: 113-157 MPH

• F3: 158-206 MPH

• F4: 207-260 MPH

• F5: 261-318 MPH

Floods

• Most often, caused by overflow of rivers/lakes for a variety of reasons

• Farmhouses, vehicles and farmland ruined

• Can contaminate water

Why Live Near Water?

• Humans value the proximity to water

• Land cost is cheaper near water; easier access to transportation

Flood Control

• Levees/Reservoirs

• In emergencies, sandbags

Benefits of Flooding

• Egypt benefits from silt/clay deposits; soil becomes very fertile

• Indus/Ganges in Bangladesh

• Humans thrive off of rich soil for crops

Deadliest Flood

• China Flood, 1931

• Est. deaths: 400,000-4,000,000

• Left 80,000,000 homeless

Three Gorges Dam

• Built to help control flooding and control China’s 3 main rivers