SYMP 14-1
Ecological convergence of hydrological systems in urban landscapes
The effects of impervious surface on hydrological systems is one of the most obvious and common impacts of urbanization on ecosystems. Reductions in infiltration and increases in the amount and energy of surface runoff associated with impervious surface lead to physical degradation of stream channels and associated riparian zones. This degradation catalyzes a series of biological and chemical changes that reduce a wide range of ecosystem services. This “urban stream syndrome” has been observed in cities across the world and has motivated a variety of restoration responses. These responses range from installation of large stormwater detention basins to extensive geomorphic stream channel restorations to small scale rain gardens and green roofs. Design plays a critical role in all these efforts, affecting the environmental performance and societal satisfaction of different features. In this talk, I will review the science underlying the urban stream syndrome and give examples of restoration efforts associated with the National Science Foundation funded urban long term ecological research (LTER) project in Baltimore, MD; the Baltimore Ecosystem Study, emphasizing opportunities for interactions with designers to increase both environmental performance and societal satisfaction.
Results/Conclusions
Urban stream syndrome converts riparian zones from sinks to sources of nutrient pollution in urban watersheds. Incised streams lead to deeper water tables and drier, more aerobic riparian soils that fosters release of accumulated nutrients and decreases microbial conversion of reactive nitrogen to nitrogen gas. Some of this lost riparian nutrient removal function is restored by the installation of stormwater detention features that have the capacity to support anaerobic microbial processes and other nutrient retention mechanisms. Stream restorations that reduce incision and create connections to riparian zones and floodplain wetlands also restore some of this lost function. The ultimate success of these restoration activities depends fundamentally on societal acceptance of the disturbance associated with their installation and their effects on housing values, pests and aesthetics all of which fundamentally on design. There is thus great potential for productive interactions between ecologists and designers in managing hydrological systems in urban landscapes.