Floods & Droughts

What are the main causes of floods?

Thunderstorms, melting snow and glaciers, ice jams, and seasonal monsoons.

What is a predicted river flood?

Flooding along streams and rivers caused by accumulated rainwater on saturated ground.

What is a flash flood?

A sudden local flood that develops in less than 6 hours due to heavy rainfall.

How do humans increase flooding?

By increasing runoff through paved surfaces, deforestation, wetland removal, and improper waste disposal.

What is a 100-year flood?

A flood with a 1% chance of occurring in any given year.

What is a 10-year flood?

A flood with a 10% chance of occurring in any given year.

What is flood recurrence interval?

The average time between floods of a certain magnitude.

What are the four components of flood risk assessment?

Flood hazard, exposure, vulnerability, and performance.

What is drought?

A temporary period of abnormally dry weather that causes a hydrologic imbalance.

What is aridity?

A permanent climatic condition of dryness in a region.

What is the difference between drought and aridity?

Drought is temporary; aridity is permanent.

What is a meteorological drought?

Below-normal precipitation.

What is a hydrological drought?

Below-normal surface water and groundwater supplies.

What is an agricultural drought?

Insufficient water to grow crops.

What is a socioeconomic drought?

Insufficient water to meet the needs of people and communities.

What is the Percent of Normal drought index?

A comparison of current precipitation to normal precipitation.

What is the Palmer Drought Index?

A drought index developed by W. C. Palmer in 1965.

What does SWSI stand for?

Surface Water Supply Index.

What is xeriscaping?

Using low-water-use plants and landscaping to conserve water during droughts.

What are shade balls used for?

To reduce water loss, algae growth, and harmful chemical formation in reservoirs.