https://phys.org/news/2018-07-environmental-mekong-delta-farmers.html

The delta, which sits at the southern tip of Vietnam and Cambodia, is characterized by seasonal flooding and nutrient-rich sediment deposits from the Mekong and Bassac Rivers as they flow toward the South China Sea. Historically, mosquitoes, malaria, waterborne diseases, and unpredictable flow patterns made the delta a difficult place to live.

The population began to expand after French colonists set up a series of canals in the 1800's, in an attempt to partially drain the delta. After the canals were installed, dikes and levees followed. Once people had more control of the water, they could make it work for them. Today, the Mekong Delta is a leading exporter of rice, shrimp, and other seafood.