These drone sentries should be relatively inexpensive, costing less than some professional drones. It's more resilient than some warning systems, too. Where river monitoring stations frequently collapse in floods and other natural catastrophes, the drones can fly above the chaos as long as they have a charge.

Unlike many research projects, there's already a customer. Vietnam's Disaster Management Authority has picked the drone network to help monitor extreme weather and get in touch with emergency services. Whether or not other countries follow suit is less than certain. The US Interior Department, for instance, recently grounded its Chinese-made drones over security fears. It may take a lot of persuasion (and non-Chinese drones) before you see drones keeping watch over American waterways.