Pre-Hispanic flood-management in the Pampa de Mocan

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A field with plants growing, behind an ancient canal
A modern-day floodwater field, located behind an ancient canal. [Image: Caramanica et al., PNAS]

For thousands of years, areas along the north coast of Peru have been subject to huge flooding as a result of El Niño, a periodic warming in the atmosphere of the Pacific Ocean, which causes torrential rainfall in the eastern Pacific. El Niño events are unpredictable, occurring anywhere from every 6-7 years to every 10-20 years, and are generally seen as a disruptive force, but recent archaeological work in the Pampa de Mocan, a coastal desert plain in northern Peru, indicates that this was not always the case.

The Proyecto Arqueo-Ambiental de la Pampa de Mocan (PAAPM) was established in 2012 to determine the function and age of a series of linear features running across the area, identified in aerial photos from the 1940s. The research, recently published in Proceedings of the National Academy of Sciences of the United States of America (https://doi.org/10.1073/pnas.2006519117), involved a combination of excavation, pedestrian survey and surface collection, palaeobotanical sampling and analysis, and modern-plant collection, which revealed that El Niño events played a key role in the area’s development in the pre-Hispanic past.

The study focused on a 1,707ha area in the north-eastern part of the Pampa de Mocan, above the limits of modern agriculture and the highest present-day irrigation canal. It was previously thought that the environmental conditions here were too challenging for any pre-Hispanic agricultural activity, but PAAPM identified habitation sites, agricultural tools like clod-breakers, and evidence of field and irrigation systems that had been used and modified over a 2,000-year period.

The north coast of Peru is a relatively flat area, with rivers running across it from the Andes mountains down to the Pacific Ocean, making it susceptible to extreme flooding during El Niño. However, using a flexible irrigation system, ancient farmers in the Pampa de Mocan were able to prepare for these sudden floodwaters and use them for agricultural production. Canals were constructed in the area from the Early Horizon Period (1100 BC) up to the Late Intermediate Period (c.AD 1460). These canals had multiple functions, carrying river water at some points in their use-lives and diverting floodwater at others, followed by a third life as agricultural fields once they were no longer used to channel water.

Discussions about the management of natural disasters are especially relevant in the present day, with most modern strategies focused on predicting and detecting events and mitigating their effects. The research from the Pampa de Mocan reveals that pre-Hispanic farmers in this region had a different approach, using opportunistic agricultural techniques to turn El Niño from a catastrophe into an advantage, and allowing them to utilise the Pampa de Mocan as both a productive agricultural area and a risk-management strategy.

A wide landscape shot with plants on the ground and mountains in the distance
Flooding can cause blooming events, as is shown here after the 2017 El Niño event. [Image: Caramanica et al., PNAS]

This article appeared in issue 104 of Current World ArchaeologyClick here for more information about subscribing to the magazine.

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