As part of the hydrological cycle, freshwater runs off the land and into the ocean – fueling ocean ecosystems with food and nutrients as well as affecting currents and stratification in coastal waters. Changes in the volume and timing of this runoff, as well as in the particulate and dissolved load, have a profound effect on coastal and estuarine waters with impacts on fisheries, ecosystems, wildlife and human health. John Largier's research focuses on west-coast estuaries and river plumes, notably addressing estuaries with seasonal inflow (little runoff during long dry summers) and estuaries with wave-built sand barriers across their mouths. Runoff Oceanography focuses on addressing the role of land runoff in shaping estuaries (e.g., bar-built and low-inflow estuaries) and nearshore waters (i.e. , river plumes); emphasis on flow features and processes that exert control on estuarine habitats and coastal pollution.