Damming is one of the most high-profile forms of human intervention in the environment, and it is commonly found across the modern Korean landscape. Since the 1960s, under the name of “Comprehensive Water Resources Development,” South Korean state engineers have constructed more than a dozen large multi-purpose dams on rivers in the nation. The prevailing Korean narrative tends to regard the surge of large dam-building as the outcome of modern state authority. Rather than granting all agency to the state, this dissertation shifts focus to newly emerged water experts who rationalized the damming of the nation. These new experts with backgrounds in civil engineering embraced hydrology as part of their research agenda to lead a comprehensive dam construction plan from a perspective of national water circulation. By examining the work of these experts, I demonstrate that river engineering became crucial for Korean engineers to position themselves in the developing nation that stood between the colonial legacy on the one side and American hegemony on the other. By utilizing both colonial data and Western development models, hydrological engineers quantified rivers, a process that compressed complex understandings of and interactions with unruly rivers into a singular vision—rivers as a manageable national resource. This conceptual and physical infrastructure naturalized a form of life dedicated to industrial South Korea while marginalizing social and cultural lives in rural areas. I ultimately argue that the modern dammed riverscape of the nation is the product of engineers’ precarious and contested efforts to build their own professional identities and research programs in developing South Korea. This contextualization of river engineering allows us to examine the violence of river engineering not just from a lens of top-down state authority but from compromises, contestations, and negotiations over the legitimate forms of rivers, modern South Korea, and how they are related.