© 2020 The Authors River design is often conceptually approached aiming at either physical channel stability or ecological functionality. We present a novel concept within an open-source software called River Architect that addresses both these goals and estimates costs. River Architect is flexible for site- and application-specific characteristics, with modules for the analysis and design of habitat-enhancing and channel-stabilising feature groups. Ecological assets are assessed as a function of a novel metric that incorporates the seasonal and discharge-dependent preferred habitat area of target species. Calculations of cost estimates and ecological efficiency are illustrated by an example in a gravel-cobble-bed river.