“A Twenty-First-Century Catastrophe” - The Ripple Effect: The Fate of Freshwater in the Twenty-First Century - page 179

—from a congressional report on flood control, 1966
A flood can be local, or it can affect entire river basins and cover several states. It can
arrive slowly and gently, or it can appear with sudden, terrifying violence. There are riv-
erine floods, in which heavy precipitation causes rivers to overrun their channels; es-
tuarine floods, caused by storms or tidal surges; coastal floods, which result from hur-
ricanes or tsunamis; catastrophic floods, which are caused by significant events, such as
the breach of a levee; and muddy floods, which are generated by agricultural runoff. The
most destructive are flash floods, in which water rises to dangerous levels within hours,
and these are typically caused by dam failure, collapsing ice jams, or an intense down-
pour.
Many factors contribute to flooding, but two key elements are the intensity and dur-
ation of rainstorms. The less ground cover or wetland available to absorb rising waters,
the more likely a river is to flood destructively.
Ground cover—grass, bushes, trees—can help sop up rising water, as can spongy
wetlands, the “kidney of the environment.” Wetlands absorb rainfall and waves and help
to mitigate the impact of flooding (they also absorb carbon, a greenhouse gas).
In the United States, some wetlands are regulated by states and some by the federal
government, under the Clean Water Act. But wetlands are transitional zones that lie
between wet or swampy areas and dry upland areas; delineating the boundary between
regulated wetland and nonregulated lands has proven contentious and led to numerous
court cases (a subject I will return to presently).
An estimated 60 percent of the world's wetlands —and 90 percent of Europe's wet-
lands—have been destroyed over the past century, according to ScienceDaily. When
wetlands are filled in and built upon, the displaced water will try to reassert itself. Often
the result is flooding, erosion, and wet basements filled with mold.
Floods hold a special, dark grip on the human imagination. People from many soci-
eties and religions have envisaged the end of the world arriving in the form of a “great
lood,” or “deluge,” as told in the story of Noah's Ark in the topic of Genesis, or in Ovid's
Metamorphoses,or the Babylonian EpicofGilgamesh. he single deadliest natural dis-
aster ever recorded was a series of terrible flash floods in central China in 1931. After
a prolonged drought, heavy snowstorms arrived, along with rains, causing the Yellow,
Yangtze, and Huai Rivers to overflow, killing an estimated 2.5 to 3.5 million people.
Between 1991 and 1999, loods in the United States killed 850 people and caused
over $89 billion in property damage, according to the Sierra Club. The deadliest natural
disaster in American history was the looding of Galveston , Texas, by a hurricane in
September 1900, which killed about eight thousand people. The Okeechobee hurricane
of 1928 killed about four thousand people in Florida, the Bahamas, and Puerto Rico.