StreamLab: Full-scale Experiments in River Science (Invited)

Experimental studies of river processes can provide control of essential variables and support detailed technical measurements. Practical constraints often drive experiments toward a reduced scale, but essential features of natural systems are difficult or impossible to scale. These include processes involving aquatic organisms and their interactions with their physical surroundings, as well as features such bed forms and channel pattern that arise from interactions among processes operating across a range of spatial scales. A sound understanding of both local mechanisms and broader interactions is needed to develop predictive models in river science. The solution is to conduct experiments at full scale while maintaining experimental control and using instrumentation that can resolve both local and full-scale processes. Important advances in automated measurement technology play a key role in making such an approach feasible, but considerable conceptual, technical, and organizational challenges remain to be addressed. This paper reports on some of these challenges and opportunities based on experience with StreamLab: a program of full-scale experiments on linked physical/chemical/biological processes initiated by The National Center for Earth-surface Dynamics (NCED) and the St. Anthony Falls Laboratory (SAFL). The essential features of StreamLab are an explicit multi-disciplinary focus, experimental control at the field scale, and the use of advanced technology to support detailed observations typical of small-scale lab experiments. StreamLab has three elements: Indoor StreamLab (ISL), Outdoor StreamLab (OSL), and Virtual StreamLab (VSL). ISL is based on a large rectangular laboratory channel and includes smaller facilities that can be used to isolate individual mechanisms. OSL includes two basins in which full-scale channels can develop with natural riparian vegetation and in-stream biota. VSL extends the StreamLab concept to full-scale, turbulence-resolving, predictive numerical models of flow-bed and flow-organism interactions. The different components of StreamLab have an essential symbiosis. ISL and OSL provide the high-resolution, field-scale observations needed to validate VSL. VSL provides the capability to extrapolate detailed flow information beyond regions of direct observation, supporting testing of reach-scale hypotheses and models. VSL also extends experimental capacity, supporting virtual experiments in a number and range much broader than could be accomplished in a physical flume.