An ancient desert wall in northern Peru was built to protect precious farmlands and canals from the ravages of El Niño floods, according to new research.

Many archaeologists had suggested that the wall, known as the Muralla La Cumbre and located near Trujillo, was built by the Chimú people to protect their lands from invasions by the Incas, with whom they had a long-standing enmity. But the latest research affirms a theory that the earthen wall, which stretches 6 miles (10 kilometers) across the desert, was built to hold back devastating floods during the wettest phases of northern Peru’s weather cycle. 

These phases are now known as El Niño — Spanish for “The Boy,” a reference to the child Jesus — because they bring heavy rain to the region around Christmastime every few years. 

Although El Niño brings drought to some other parts of the world, it brings heavy rains to Ecuador and northern Peru. El Niño floods are thought to have occurred there for thousands of years, and they would have been a serious danger to the Chimú, Gabriel Prieto, an archaeologist at the University of Florida, told Live Science.

“The annual rainfall there in a regular year is very low — almost no rain at all,” he said. “So when the rainfall was very high, that caused a lot of damage.”

The Chimor kingdom of the Chimú people emerged around A.D. 900 in the territories once occupied by the Moche people; as a result, the Moche period is sometimes called “Early Chimú.”

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