Causes
Floods occur when bodies of water flow onto land that is typically dry. The sources of this overflowing water vary, with common causes including:
- Storms and torrential rain: Storms can bring large amounts of precipitation over days or within minutes, as seen in flash floods.
- Overflowing rivers, lakes, and oceans: External sources like rain, snow melt, or blockages can cause water levels to rise, spilling over onto surrounding land. Tsunamis are an extreme example, where large waves crash ashore due to underwater earthquakes.
Consequences
When floods inundate inhabited areas, they have immediate and long-term effects. The immediate impact includes disruptions such as blocked transportation routes, which can isolate cities or cut off remote communities. Floodwaters can sweep away fragile buildings, damage electrical infrastructure, and affect agriculture by destroying crops and drowning livestock.
The long-term impact involves the challenge of water removal, which can leave affected areas submerged for extended periods. This poses significant sanitation hazards, as dirty water and overflowing sewage create breeding grounds for diseases like typhoid and cholera. Infrastructure repair may be delayed, and agricultural losses could influence future food security, forcing affected regions to rely on external sources for food.
Satellite data
Satellites are a common tool for flood monitoring, as radar data—which is unaffected by clouds—provides valuable insight into the situation on the ground. Optical imagery may also be used before and after the clouds pass to predict an approaching storm or identify areas potentially at risk of flooding, and to map the extent of the flood in the aftermath.
Floods are among the most common types of disaster requested for activations of the International Charter: Space and Major Disasters.