Such was the finding of a study by the National Oceanic and Atmospheric Administration (NOAA) examining the record-breaking rainfall that landed on Louisiana in 2016, causing devastating flooding. Basically, because of global warming, when it rains, it pours more. In the Northeast, the most extreme storms generate approximately 27 percent more moisture than they did a century ago. As the country has heated up an average of 1.8 degrees Fahrenheit since 1901, it has also become about 4 percent wetter, with the eastern half of the United States growing soggiest. These are some of the key ways climate change increases flood risks.Ī warmer atmosphere holds and subsequently dumps more water. Ryan Soderlin/Omaha World-Herald via AP How Does Climate Change Lead to Flooding? coastal flooding has doubled in a matter of decades. According to the Climate Science Special Report (issued as part of the Fourth National Climate Assessment, which reports on climate change in America), more flooding in the United States is occurring in the Mississippi River Valley, Midwest, and Northeast, while U.S. In other words, while our warming world may not induce floods directly, it exacerbates many of the factors that do. However, as the IPCC (Intergovernmental Panel on Climate Change) noted in its special report on extremes, it is increasingly clear that climate change “has detectably influenced” several of the water-related variables that contribute to floods, such as rainfall and snowmelt. Not only do myriad weather- and human-related factors play into whether or not a flood occurs, but limited data on the floods of the past make it difficult to measure them against the climate-driven trends of floods today. Climate Change and FloodingĬonnecting climate change to floods can be a tricky endeavor. More and more, flooding factors are also linked to climate change. In cities, under-maintained infrastructure can lead to urban flooding. Increased urbanization, for example, adds pavement and other impermeable surfaces, alters natural drainage systems, and often leads to more homes being built on floodplains. There are weather events (heavy or prolonged rains, storm surge, sudden snowmelt), and then there are the human-driven elements, including how we manage our waterways (via dams, levees, and reservoirs) and the alterations we make to land. Many factors can go into the making of a flood. This happens when rainfall runoff is channeled from roads, parking lots, buildings, and other impervious surfaces to storm drains and sewers that cannot handle the volume. Also caused by dam or levee breaks or the sudden overflow of water due to a debris or ice jam, flash floods combine the innate hazards of a flood with speed and unpredictability and are responsible for the greatest number of flood-related fatalities.įlash floods, coastal floods, and river floods can occur in urban areas, but the term “ urban flooding” refers specifically to flooding that occurs when rainfall-not an overflowing body of water-overwhelms the local stormwater drainage capacity of a densely populated area. Flash floods can happen anywhere, although low-lying areas with poor drainage are particularly vulnerable. These quick-rising floods are most often caused by heavy rains over a short period (usually six hours or less). There are also increasing numbers of shallow, non-life-threatening floods caused by higher sea levels these high tide floods (also known as “nuisance” or “sunny day” floods) occur when the sea washes up and over roads and into storm drains as the daily tides roll in. Storm surge can produce widespread devastation.
More than 8.6 million Americans live in areas susceptible to coastal flooding, which happens when winds from a coastal storm, such as a hurricane or nor’easter, push a storm surge-a wall of water-from the ocean onto land. residents are at risk from flooding along rivers and streams. According to one study, approximately 41 million U.S. Most common in late winter and early spring, river flooding can result from heavy rainfall, rapidly melting snow, or ice jams. This occurs when a river or stream overflows its natural banks and inundates normally dry land. It’s caused by the overflow of inland waters (like rivers and streams) or tidal waters, or by an unusual accumulation of water from sources such as heavy rains or dam or levee breaches. Flooding Facts What is a flood?Ī flood is the accumulation of water over normally dry land. Here’s how climate change plays a role in flooding, and how we can better keep our heads above water. As global warming continues to exacerbate sea level rise and extreme weather, our nation’s floodplains are expected to grow by approximately 45 percent by century’s end. They have brought destruction to every state and nearly every county, and in many areas they are getting worse.
Floods are the most common (and among the most deadly) natural disasters in the United States.