Fast Facts on Levees, Dams and Floods

• Excerpted from Before the Deluge: Coping with Floods in a Changing Climate

A Flood of Damages

Number of people the UN estimates will live in the path of a potential damaging flood by 2050: 2 billion 

Increase over today’s figures: 100%

Annual number of “major floods” worldwide:

1950s to 1970s: 7-9

1980s: 20

1990s: 34

Number of damaging floods in Europe from 1989-2002: 100

Approximate number of people displaced: 500,000 

Cost of damages: $30 billion 

Amount spent by US government on flood-control schemes (mainly dams and levees), 1960-85: $38 billion

Average inflation-adjusted cost of flood damage every year from 1964 to 1993: $4.6 billion 

Increase in cost of flood damages during that time over previous 30-year period: Approximately 66%

Increase in length of embankments in Indian state of Bihar from 1952-98: 22 times 

Percent increase in flood-prone area in Bihar in that time: approx. 300 

Percent increase in flood damages in Bihar between the 1950s and 1970s: almost 400

Number of people in Bihar living inside embankments: 2 million

Regulated Rivers

Length of levees that separate US rivers from their floodplains: >40,000 km

Percent of floodplain lost in the Danube basin: 92

Percent lost in the Rhine, Elbe and Tiza basins: >80

Area of Louisiana’s coastal wetlands that has disappeared since 1930s: >4,900 sq. km. 

Height, in places, of the bed of China’s Yellow River above the surrounding flood plain: 20 meters

Levees and Dams: Technical Difficulties

Number of levee failures during “Great Flood” of 1993 in the Mississippi Basin: 1,576

As a percent of all levees in the flood zone: 68

Area inundated by reservoirs worldwide: >260,000 sq. km.

Percent of China’s 85,000 dams in need of urgent repairs: >33

Annual property-damage cost of dam failures in US in the mid-2000s: $100 million

Number of US dams now classified as “unsafe”: >3,500 

Total investment needed to bring them into safety compliance: >$30 billion

A Better Way

Percent of India’s monsoon run-off that could be captured and stored as groundwater: 25

Percent of that stored water that could be retrieved later for irrigation: 75

Estimated amount of water that 0. hectares of wetland can store: >6,000 cubic meters 

Estimated value of ,00 hectares of intact wetlands on the Charles River (Massachusetts) for flood protection alone: $17 million per year

Cost of moving 5,100 homes and businesses in Illinois and Missouri after the Great Flood: $66 million

Insurance payments used to repair and rebuild those structures in past floods: $191 million