Riverine fish stranding is of significant concern due to its potentially devastating impacts on fish populations already at risk. Because stranding is dependent on a wide range of biotic and abiotic factors, it is difficult to accurately identify and parameterize fish stranding risks for various river topographies, fish species/lifestages and flow ramping scenarios. This article presents a literature review, new concepts and a novel Python3 algorithm for post‐processing two‐dimensional hydrodynamic numerical model results to identify spatially explicit locations where fish stranding is likely, such as but not limited to downstream of hydropeaking facilities. Compared to previous stranding algorithms, this one is novel in its use of graph theory to find optimal fish escape routes and for its embedding in the free, open‐source river analysis software River Architect. Guided by biological parameter selection and supplied with two‐dimensional hydrodynamic model rasters, River Architect's Stranding Risk module is suitable for characterization of existing pool stranding risks, alternative flow regime and topographic design evaluation and post‐project assessment of rivers during flow recessions.

The dynamics of fish stranding have not been academically investigated within the context of physical adjustments to rivers for habitat enhancement purposes. River projects may aim to help fish populations but instead may function as attractive nuisances reducing populations because of unaccounted‐for stranding risk. This study applies a novel algorithm to predict spatially explicit, meter‐resolution fish stranding risk at a river rehabilitation site in California to address three scientific questions. Postproject disconnected wetted area predictions were validated against water surface elevation measurements and time lapse photography of flow reductions and stranding events. A comparison of preproject, final design, and postproject topographies revealed that the occurrence and severity of stranding events is highly sensitive to side‐channel topographic structure and postproject morphodynamic change. Even with moderate flows, side‐channel exits tend to close off by bars built across them via bedload transport. Implications for river management practices and river rehabilitation project design are discussed.

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Radiatively-driven convection is a physical process that occurs in freshwater below the temperature of maximum density wherein volumetric heating of surface waters by solar radiation creates a diurnal, spatially distributed, destabilizing buoyancy flux that drives penetrative convection. While this process has typically been studied under ice-covered conditions, it can also occur in open water during springtime warming leading up to overturn, and in such systems, it may serve as the dominant process driving mixing of nutrients and biota. Despite the ecological significance and unique physical dynamics of radiativelydriven convection, little is understood regarding the spatial heterogeneity and three-dimensional structure of the process. The addition of wind shear also modifies radiatively-driven convection dynamics in open water conditions, yet observations have not yet been used to quantify the relative scales and importance of these separate forcings in driving mixing and turbulence. This study examines data collected with a buoyancy-driven autonomous underwater vehicle (aka glider) during a period of active radiatively-driven convection and low surface wind shear in early springtime in Lake Superior. Conductivity, temperature and depth (CTD) measurements reveal distinct convective plumes of anomalously warm downwelling water with width scales on the order of 100 m and temperature anomalies of ˜0.1 °C. Shear and temperature microstructure measurements indicate turbulence kinetic energy (TKE) dissipation rates exceeding 10-8 W/kg, orders of magnitude greater than laterally adjacent waters. This is the first known observation of lateral variability in TKE dissipation rates during radiatively-driven convection. Spatially and temporally averaged TKE budgets illustrate buildup, vertical transport, and dissipation of TKE, while the ˜3 hr lag between buoyancy forcing and dissipation is consistent with the Deardorff convective timescale. These observations demonstrate that radiatively-driven convection can dominate vertical mixing dynamics even in deep, open water systems.