Flood

A flood is an overflow of water that submerges land that is usually dry, including tidal inflow along coasts. Floods matter for agriculture, civil engineering and public health, and take several forms: river flooding, groundwater flooding, coastal flooding and urban or flash flooding, with tidal flooding sometimes combining coastal and river processes in estuaries. Human activity has made floods more frequent and intense through deforestation, wetland removal and changes to waterways and levees, and climate change compounds this by intensifying the water cycle, raising sea levels and making extreme weather more common. Because flat, fertile floodplains and easy water access have long attracted settlement, a large share of the global population and major cities and farmland now sit in areas of significant flood risk.