Hydrological control points of biogeochemical cycling in suburbanizing stream corridors

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Canada's population is increasingly housed in cities, requiring increased land-use conversion to urban and suburban environments. In southern Ontario, the current population of 13 million residents is expected to grow by 50 % by 2040, requiring expansion of existing cities and towns. With new suburban development, current land planners aim to create integrated Natural Heritage Systems of green space centered on existing and expanded stream corridors. These suburban corridors are designed to mimic natural systems, with increased stream meander bends and extensive riparian zones, the land adjacent to the stream often wetter than the upland environment. In natural systems these corridor features enhance connectivity between the stream and the terrestrial environment, leading to greater rates of biogeochemical processing and species production and diversity. Whether these modified suburban stream corridors function as their natural analogues remains to be tested. This research will address four main questions on the hydrological and biogeochemical functioning of suburban and suburbanizing stream corridors. (1) What are the hydrological interactions along the upland-riparian zone-stream continuum in suburban stream corridors, and how do these affect nutrient dynamics within the streams and riparian zone? (2) Do the created morphologic features of suburban streams (wide meander bends, constructed riffle-pool sequences) mimic natural systems in terms of both groundwater-surface water interactions and nutrient turnover? (3) How quickly are nutrients utilized in highly modified suburban streams, particularly in response to winter freeze-thaw cycles and extreme precipitation events? (4) Do different stormwater management pond designs affect downstream nutrient dynamics differently? The overall purpose of this research is to develop a conceptual working model for these impacted stream corridors, such that the model can be applied to future designs for the improved creation and restoration of healthy suburban aquatic systems. The proposed research will provide opportunities for three PhD students, five MSc students, and 11 undergraduate thesis students (plus many more field and lab assistants) to develop their intellectual and technical skills in the environmental sciences to advanced levels. These HQP will make meaningful contributions to the environmental protection of Canada both during their tenure in my research program and throughout their careers as environmental scientists.