Physical activity and social connectedness interventions in outdoor spaces among children and youth: a rapid review. / Interventions pour favoriser l'activité physique et l'appartenance sociale chez les enfants et les jeunes dans des espaces extérieurs : revue rapide de la littérature.

INTRODUCTION: The rise in sedentary behaviour, coupled with the decline in overall mental health among Canadian children and youth in recent decades, demonstrates a clear need for applied research that focusses on developing and evaluating cross-disciplinary interventions. Outdoor spaces provide opportunities for physical activity and social connectedness, making them an ideal setting to address these critical health concerns among children and youth. METHODS: We conducted a rapid review of peer-reviewed (n = 3096) and grey literature (n = 7) to identify physical activity and/or social connectedness outdoor space interventions targeted at children and youth (19 years and under) in Australia and New Zealand, Canada, Europe and the United States. We determined if interventions were effective by analyzing their research design, confidence intervals and reported limitations, and then conducted a narrative synthesis of the effective interventions. RESULTS: We found 104 unique studies, of which 70 (67%) were determined to be effective. Overall, 55 interventions targeted physical activity outcomes, 10 targeted social connectedness outcomes and 5 targeted both. Play (n = 47) and contact with nature (n = 25) were dominant themes across interventions, with most taking place in a school or park. We report on the identifying features, limitations and implications of these interventions. CONCLUSION: The incorporation of natural and play-focussed elements into outdoor spaces may be effective ways to improve physical activity and social connectedness. There is a considerable need for more Canadian-specific research. Novel methods, such as incorporating smartphone technology into the design and evaluation of these interventions, warrant consideration.

Flow in bedrock canyons.

Bedrock erosion in rivers sets the pace of landscape evolution, influences the evolution of orogens and determines the size, shape and relief of mountains. A variety of models link fluid flow and sediment transport processes to bedrock incision in canyons. The model components that represent sediment transport processes are increasingly well developed. In contrast, the model components being used to represent fluid flow are largely untested because there are no observations of the flow structure in bedrock canyons. Here we present a 524-kilometre, continuous centreline, acoustic Doppler current profiler survey of the Fraser Canyon in western Canada, which includes 42 individual bedrock canyons. Our observations of three-dimensional flow structure reveal that, as water enters the canyons, a high-velocity core follows the bed surface, causing a velocity inversion (high velocities near the bed and low velocities at the surface). The plunging water then upwells along the canyon walls, resulting in counter-rotating, along-stream coherent flow structures that diverge near the bed. The resulting flow structure promotes deep scour in the bedrock channel floor and undercutting of the canyon walls. This provides a mechanism for channel widening and ensures that the base of the walls is swept clear of the debris that is often deposited there, keeping the walls nearly vertical. These observations reveal that the flow structure in bedrock canyons is more complex than assumed in the models presently used. Fluid flow models that capture the essence of the three-dimensional flow field, using simple phenomenological rules that are computationally tractable, are required to capture the dynamic coupling between flow, bedrock erosion and solid-Earth dynamics.