Sometimes this situation occurs because of extreme amounts of rainfall over short periods of time—such as during atmospheric rivers. But quickly-melting snowpack or the failure of built infrastructure (dams and levees) can also cause inland flooding.
Inland flooding can occur quickly (“flash flooding”) or can build slowly over the course of a storm. Importantly, inland flooding often occurs downstream of the precipitation event or melting snowpack. Urban flooding, a type of inland flooding, indicates flooding happening in well-populated areas and is exacerbated by elements of the built environment, such as concrete parking lots, paved roads, and other impermeable surfaces that lead to water overwhelming drainage systems. Inland flooding is also frequently exacerbated by aging infrastructure, such as levees that break or drainage systems that are too small for the need.
In many parts of the country, flooding is a natural phenomenon. Before humans created structures to prevent floods, our rivers frequently flooded, replenishing soil and distributing nutrients across their floodplains, while recharging groundwater stores in aquifers. This natural, cyclical flooding, however, was not conducive to permanent settlement along nature’s highways of water, so humans began to create physical barriers to flooding. Floods then and now pose series health concerns, including illness through food- and water-borne diseases, physical injury, and even death.
In the modern era, street closures due to flooding can hinder emergency vehicles’ access to those in need. The mental health effects of floods include mental stress and anxiety from the loss of work (due to the loss of businesses and other structures), relocation to temporary housing, and contemplation of permanent relocation. Individuals affected by major flooding may also experience post-traumatic stress and depression.
Floods can be massively costly. The loss of economic value has increased significantly as we build our cities on lands that have historically flooded. Businesses, critical infrastructure, and homes are rebuilt, while people’s livelihoods are paused for the rebuilding and agricultural lands are left fallow as they drain. And, as we are learning on a regular basis around the U.S., inland floods can lead to tragic losses of life.
Carbon pollution acts like a warm blanket, wrapped around Earth. Because our climate systems are complex, the atmospheric heat does more than just warm the planet—it changes weather patterns. California and the northwest of the U.S., for example, are likely to experience increasingly severe swings between droughts and floods—particularly through more and more severe atmospheric rivers—as a result of carbon pollution.
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