Application of the principles and tools of hydraulics to predict and manage natural flows has been admiringly successful, yet with the advent of concepts such as environmental sustainability and resilience it has been necessary to introduce a biogeochemical component to hydraulic designs. Wetlands, land formation, nutrient availability are all dependent on the distribution of flow and turbulence in natural flows, and any manipulation of hydraulic behavior can sensitively influence related ecosystems. In this paper, the evolution of modern environmental hydraulics is outlined first, followed by a technical discussion on river diversions to splay sediment-laden freshwater flow over marshes to help land and wetland building. The latter is exemplified using a project conducted by the US Army Corps of Engineers (USACE) in the lower Mississippi river to improve the resilience of Louisiana coast against such forcing as land subsidence, storm surges and climate change. Some relevant hydraulic principles are discussed and compared with observations made in the USACE study.