Dams and Levees: A Risky Solution For Flooding
Flooding is one disaster that can impact a community very quickly. Typically, flooding happens with heavy rain, excessive snow melting, or when ocean waves break onshore. In a similar vein, flash flooding is essentially a fast-moving flood. This occurs when heavy rain falls quicker than the ground can absorb it. This kind of flooding can also be exacerbated when excess water overflows the banks of streams and rivers.
One way to help control flooding is through dams and levees. For dams, they work by storing flood water during storms and other weather events, and gradually release it into the stream or river over the course of several days through a spillway pipe. This helps with water regulation and preventing flooding in communities downstream of dams.
Levees are built parallel to the water to prevent flooding in communities on land. They achieve this with floodwalls made of concrete or steel at the peak, or crown, of the levee on top of its embankment. This helps keep rising water on one side of the embankment from reaching the communities on the other side.
While dams and levees certainly add a level of protection when it comes to flooding, they pose their own flooding risks as well. Dams can deteriorate and break, causing a surge of water downstream. One such case occurred in 1889 in Johnstown, Penn. where a 30-to-40-foot wall of water rushed through the town and killed 2,200 people within minutes and left many homeless. Another instance occurred in 1972 when a coal slurry dam in Buffalo Creek Hollow, W. Va. deteriorated and collapsed, killing 125 people. Dams can also overflow and cause additional flooding as well.
Levees can fail when the expected flood water overtops the embankment, rushing towards the community on the other side. One notorious occurrence was in 2005 in New Orleans after Hurricane Katrina came onshore. The resulting flood water was too excessive for the levees to handle, causing many to breakdown or overflow and flood the city. In 1993, levees also were overtopped along the Mississippi River, causing devastating floods.
On the one hand you feel a sense of safety, but it’s important to understand the risks that accompany living near a dam or levee. Having an evacuation plan in place for flash flooding, whether from dam or levee failures or Mother Nature, will help guide you should the worst-case scenario occur. Also, consider getting flood insurance if property damage is a worry for you. Remember, never drive on flooded roadways, “Turn Around, Don’t Drown!”
Source: NOAA, FEMA
Image by Russ McElroy from Pixabay
