They moved to the plains because they live in the foothills at first. The hills were dry, so they moved to the plains hoping for more food or water supply. There was a ton of water to plant their crops, but the water flooded, so they made complex irrigation systems. So they main reason they moved from the foothills to the plains was because they needed water for their crops.
Early Mesopotamians were largely settled around the Tigris and Euphrates rivers. From these, and other rivers, they constructed a large and complex network of irrigation ditches.
The rivers in the northern plains maintain water flow during the summer primarily due to snowmelt from the nearby mountains and glaciers, which occurs in late spring and early summer. Additionally, these rivers are fed by seasonal monsoon rains that provide a significant amount of water. Groundwater recharge and tributaries from surrounding areas also contribute to the rivers' flow, ensuring they remain viable even during the hotter months.
These two rivers were what let the early Mesopotamians settle into one area. They provided water for agriculture, fish as a food supply, and later, a route for establishing commerce.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.
They all developed in areas around rivers, with some geographical protection from outside invaders.