Rains, overflowing rivers, ruptured dams, and melting water from snow and ice may all result in flooding that produces harmful economic and environmental effects. Tsunamis, earthquakes and even strong tidal flows may also result in floods. Widespread flooding and severe flash floods can produce significant casualties and pose a serious threat to both human and wildlife populations.
Flooding refers to an overflow of water that submerges land areas that are usually dry. Flooding is typically caused when rivers, lakes and streams overflow, but heavy and sustained rains may produce flash floods even in dry regions and areas where bodies of water are scarce. Riverine floods are a real threat to human populations located near rivers where flat terrain provides floodwater with an unobstructed path.
Factors that may affect the frequency and severity of flooding include climate and precipitation, elevation and surrounding terrain as well as the volume of land area located in or near a watershed. Flooding can result in loss of life, widespread structural damage, power outages and may even increase the likelihood the spread of waterborne diseases such as typhoid, giardia and cryptosporidium. The long-term effects of flooding may involve damage to ecosystems and contamination of water sources. Flooding may be beneficial in terms of recharging ground water and improving soil quality.