UC Davis

Designing an environmental flow (eflow) regime tends to either involve simplistic empirical methods spanning thousands of streams at the regional scale or detailed multidisciplinary frameworks for individual, large, charismatic rivers and species. The purpose of this research was to develop an objective approach to specifying functional geo-hydro-eco relations for every stream reach in a region that considers natural variability across these dimensions. This approach substitutes functional archetypes for detailed local characterizations, where a functional archetype is an idealized 3D site representation of the geo-hydro-eco setting. Functional archetype design first requires broad geo-hydro characterization of a region’s stream network. Next, machine learning and scaling relations are used to extrapolate geo-hydro-eco conditions from a reasonable number of sites with local training data to the entire stream network. The open software program River Builder is used to design and render the 3D terrain archetype at the site scale, including spatially explicit sub-reach geometric patterning to reproduce diverse fluvial landforms. 2D hydraulic and ecohydraulic analysis generate functional relations between flow and ecological metrics. Once specified, eflows may then be iteratively modified and refined by stakeholders with user-friendly decision support tools based on key site-specific channel information that updates the channel archetype and subsequent analyses. This approach has been developed and piloted in California.