Small enough to be manageable, but large enough to be meaningful best describes the thirty-plus years of scientific insights that have emerged from the ecosystem science conducted along the lower Cosumnes River. In partnership with a consortium of agencies and non-governmental organization that serve as the land owners and land managers within the Cosumnes River Preserve, scientists have participated in a long-running, multi-disciplinary endeavor to better understand the natural flow regime, floodplain dynamics, and process-based restoration as it benefits riparian forests and wildlife, ephemeral aquatic ecosystems, and other components of a tightly coupled hydrological system that benefits from access to floodplains. Singularly, it has been the experimental nature of levee failures, levee breaches, and levee setbacks along the lower Cosumnes River corridor that have provided three decades of insights about natural flood frequencies, floodplain inundation, geomorphic dynamism, hydrochorous dispersal and establishment, carbon sequestration, groundwater recharge, freshwater primary productivity, food web structure and dynamics, native fish and bird population recovery, as well as coupled natural-human systems. These insights, showing that dynamic fluvial processes are necessary to create and maintain floodplain riparian ecosystems, now serve as the basis for many restoration efforts throughout California’s Sacramento-San Joaquin River watershed and beyond.