Why do Sumerians city states develop near the mouth of Tigris and Euphrates rivers?

Sumerian city-states developed near the mouth of the Tigris and Euphrates rivers due to the fertile alluvial plains created by the rivers' annual flooding, which provided rich soil for agriculture. The availability of water for irrigation was crucial for farming, supporting population growth and urbanization. Additionally, the rivers facilitated trade and communication, allowing city-states to thrive economically and culturally. This strategic location contributed to the rise of some of the world's earliest complex societies.