Levee Breach Shows Importance of Natural Floodplains for Public Safety


On Monday, the US Army Corps of Engineers made the difficult decision to intentionally breach a levee on the middle Mississippi River. Dynamiting the Birds’ Point Levee routed floodwaters into 130,000 acres of agricultural land on the New Madrid Floodway in nearby Missouri and away from the 2,800 residents of Cairo, Illinois. Yesterday’s event activated a plan developed by the Corps in 1928 after the Great Mississippi Floods of 1927. The plan has been executed only once before in 1937. Though the circumstances seem dire for all stakeholders involved, perhaps this event can be an example of a transition from risk to opportunity.

The New Madrid floodway is a good example of non-structural flood management designed to significantly reduce risk to human life and property.  There is a trade-off, but the benefits of this floodway clearly outweigh the costs. Damages on the agricultural lands within the Missouri floodway are expected to reach around $314 million (Cassens Weiss 2011) compared to damages in Cairo which would be expected at $1.7 billion without the levee breach. Cairo houses 2,800 residents, and the floodway is mostly agricultural with less than 100 homes. The dynamite may also save Hickman Kentucky, home to 8,000 people, from flooding.

Consequences of flooding are no minor event whether land is urban or agricultural.  Flooding cities means first and foremost, loss of life, but also disrupting business, destroying homes, and damaging critical infrastructure. Flooding agriculture, particularly when crops are already planted, also has economic impacts and significantly affects the livelihoods of rural communities. Therefore critical decisions including land use decisions must be made before (not during) a crisis to both minimize damage and optimize benefits.

While a seemingly unusual or extreme decision, the New Madrid Floodway is quite similar to the Yolo Bypass in California’s Central Valley. California’s early settlers found an “inland sea” when they arrived, and towns developing along the Sacramento and San Joaquin Rivers after the Gold Rush faced frequent floods. The historic flood of 1862 destroyed 1/3 California’s taxable property and created an inland sea 250 miles long and 20 miles wide.  It bankrupted the state..  Realizing that the current pattern of building a levee just a bit higher than the last highwater event was not a sustainable strategy, California sought a more comprehensive approach to flood management.

In 1895, State engineers proposed a system of flood bypasses throughout the entire Central Valley as a solution to the flooding problem. Though not adopted in its entirety, many components of the plan were built. In the early 1930s, the Army Corps of Engineers constructed the Yolo Bypass, a floodway designed to route Sacramento River floodwaters away from Sacramento and into an unpopulated area. 

Roughly half the size of the New Madrid Floodway, the Yolo Bypass was designed to convey nearly the same size flood as New Madrid (about 500,000 cubic feet per second). Some farmers in both the New Madrid Floodway and the Yolo Bypass maintain flowage easements, recognizing the value of agriculture in both regions. Yet unlike the New Madrid Floodway, activation of which requires dynamite, the Yolo Bypass utilizes a weir to divert water in a controlled manner off of the Sacramento River into the bypass land. This management strategy not only offers safer and more controlled flooding, but it also allows for inundating the floodplain to provide ecological benefits. During wet periods, the Yolo Bypass collects and stores water to provide valuable habitat for a number of aquatic and terrestrial species, and birds for much of the year.

The best way to reduce flood risk is to give rivers more room to safely convey floods. With thoughtful planning, more projects like the New Madrid Floodway and the Yolo Bypass could be implemented to save lives, protect agriculture, and restore ecosystem. 

Source:
Cassens Weiss, D. 2011. Supreme Court Doesn’t Stop Levee Break that Would Flood Farmland, Save Town. ABA Journal. May 2, 2011. Retrieved from: http://www.abajournal.com/news/article/supreme_court_doesnt_stop_levee_break_that_would_flood_farmland_save_town/