Early civilizations began in river valleys primarily because the flooding of rivers created good farmland and rivers provided plenty of fresh water. These factors made river valleys particularly suitable for agriculture, which was essential for sustaining larger populations. The fertile soil created by annual flooding allowed for the cultivation of crops, leading to food surpluses that enabled societies to grow and develop.
Additionally, while rivers could offer some advantages in terms of hiding or resources for building (like wood from trees), the main drivers for the establishment of early civilizations were the agricultural and water resources provided by river valleys.