Four Lost Cities: A Secret History of the Urban Age

by Annalee Newitz

The culprit behind this network failure was climate fluctuation. Penny writes that the late 14th and early 15th centuries presented Angkorites with incredible challenges. A multidecade drought led people to build many extra canals to siphon as much water as they could out of the mountains. But the drought abruptly ended with several years of unusually intense rainy seasons, which had two disastrous effects. First the rain overwhelmed a system designed to bring as much water as possible into the city, causing floods and the need to build those massive runoff canals into the Tonle Sap. Second, the monsoons rapidly eroded the dry, dusty landscape, sweeping tons of debris into the canal system. And that caused sediment to build up and block the water supply when it was needed. Adding to Angkor’s troubles, the floods were followed by another multidecade drought.