By Jonny Lupsha, Wondrium Staff Writer
Floods cause billions in damage each year in the United States alone. South Carolina has suffered so much costly flood damage in recent years that the state is spreading millions of loblolly seeds. Six inches of moving water can sweep you off your feet.
A statewide initiative began Thursday in South Carolina in which 3 million loblolly pine seeds will be planted across the state to diminish flood damage. The South Carolinian government said that the state has suffered more than $4 billion in damages since Hurricane Joaquin struck in 2015, and that an adult loblolly pine will absorb about 11,000 gallons of water.
In his video series The Science of Extreme Weather, Professor Eric Snodgrass, Director of Undergraduate Studies for the Department of Atmospheric Sciences at the University of Illinois at Urbana–Champaign, explained how the dangers of flash floods and moving water are very real.
Flooding in the United States
Some regions of the United States are more likely to flood than others, for a variety of climatological and geological reasons.
“The Gulf Coast and East Coast of the U.S. are subject to flooding events year round,” Professor Snodgrass said. “In fall, winter, and spring, powerful low-pressure systems—called Gulf lows, Hatteras lows, and nor’easters—frequently track along the coastline. These systems tend to be the strongest low-pressure systems in the United States.”
According to Professor Snodgrass, as the central pressure falls, heavy rain and snow will combine with high winds and cause coastal beach erosion, flash flood events, and widespread flooding. In the summer and fall, this same region must also contend with hurricanes. These systems and hurricanes help explain why states like South Carolina frequently find themselves battered to the tune of billions of dollars.
“The Southwestern part of the United States is mostly desert, yet even here, deadly flood events are quite frequent,” he said. “The Southwestern United States experiences a monsoonal circulation each summer and fall.”
This circulation comes from the warm and humid air that blows in from the Gulf of Mexico and the Pacific Ocean. This warm air cools as it passes over the mountains, causing condensation that brings large thunderstorms. The Pacific Northwest is also prone to flooding due to plumes of moisture that come from the Pacific Ocean.
Flooding and the Rocky Mountains
The dangers of flash flooding have also struck the Rocky Mountains. The Rocky Mountains are prone to flooding because they often experience summertime thunderstorms. These thunderstorms are caused by the direction of the slopes in the Rockies, which cause winds to drive air up the mountainsides.
“The Rocky Mountains get their name for a reason,” Professor Snodgrass said. “Unlike other mountain chains in the United States, most of these slopes are bare rock. Without soil and vegetation to catch and absorb the rainfall, the water will simply drain into the valley below.”
Geologically speaking, powerful floods on the Rockies happen frequently. Evidence for thousands of such floods is found in alluvial fans, which are deposits of debris that fan outward. Professor Snodgrass said that in 1976, just six inches of rainfall came down the slopes and caused a 19-foot wall of water to spill out of the canyon.
“The power of the water reshaped the valley, carving the river deeper into its sides,” Professor Snodgrass said. “The sheer force of the water moved huge boulders, the size of trucks, miles downstream. One hundred forty-four people died in just a few minutes.”