Rivers have always been intimately connected to human life, and river valleys have been the birthplaces of the world's great civilizations. The Nile River is the scene of the oldest and perhaps the most remarkable of ancient civilizations, that of Egypt. The Nile's yearly floods brought rich sediments to the soil, and the people learned to divert the floodwaters for agriculture and drain the swamps. Chinese civilization got its start in the lower valley of the Huang He, where many floods and extreme weather forced people to develop the technology necessary for life to continue successfully there. In the valley of the Tigris and Euphrates rivers, Sumerian civilization developed as people fought to clear jungle swamps and manage floodwaters. The same was true of the Indus civilization, which arose in the valleys of the Ganges and Indus rivers in India and Pakistan. While rivers offered opportunities...