The greatest step forward in mankind's early history, I think, was when they chose to settle and cultivate crops. As farming activities expand and develop, people need more water sources. From that, perhaps, the idea was born to dam river water and then divert it into canals or ditches that were dug to drain water to the lowlands where water was needed to grow crops and build new settlements.
As an agrarian society, people in my area before the modern era seem to have used wood and bamboos to dam the river water which they would divert into irrigation canals. They seem to build the construction of dams and floodgates in the dry season to make the work easier.
In modern times, such dams are called diversion dams, like this small dam located in my district.
But what I noticed there, on both banks of the river also had to build stone walls several tens of meters away to hold both banks of the river from collapsing which would also threaten the dam. It was probably the result of uncontrolled gravel mining.
However, those are the things that crossed my mind when I took pictures of the dam in a river known as the Krueng Jreu river in Aceh.
This is my entry for the #monomad challenge.