As global climate change causes sea levels to rise and weather events to become more extreme, the occurrence of severe floods will become more common around the world. The large populations living in deltaic or riverine floodplain regions will be particularly severely affected, especially those living at the lowest levels of income.
There is increasing awareness worldwide that traditional flood-mitigation strategies that alter the environment and create concentrations of risk, such as levee- and dike-building, only increase the likelihood of catastrophic concentrations when eventual failure inevitably occurs. The greater the degree of artifical protection, and the confidence that builds in the communities living behind it, the more disastrous are the consequences when an unexpected failure occurs. New Orleans learned this lesson the hard way in 2005, when 80% of the city flooded due to numerous failures of the levee system in Hurricane Katrina's aftermath.