Stormwater-Stream Connectivity: Process, Context, and Tradeoffs
2014 Fall Cyberseminar Series
- Anne Jefferson / Kent State University
Streams in urban areas are often said to suffer from “urban stream syndrome” resulting in degraded geomorphology, biogeochemistry, and ecosystem function. Uncontrolled or poorly controlled stormwater is a root cause of many of the symptoms of urban stream syndrome, so understanding how stormwater management options affect in-stream processes is important for creating sustainable urban streams. Today’s approaches to stormwater control include green infrastructure distributed throughout the watershed and more centralized stormwater control ponds and wetlands located near the stream. How well do these approaches minimize risks to human health and infrastructure and protect aquatic ecosystems? In this talk, I’ll suggest that the answer depends on three factors: context; process; and tradeoffs. In terms of context, watersheds and stormwater management efforts are situated within a particular natural landscape (climate, soils, etc.); relative to urban development (age and style of development, type of infrastructure); and within the social context of environmental attitudes and economic constraints and incentives. Processes upslope of stormwater controls that affect water quantity and quality and processes within the controls themselves, such as mixing, infiltration and residence time, exert significant influence on how urban stream hydrology, water quality, and ecology responds to stormwater inputs. Where stormwater ponds and wetlands (SCMs) are large inputs to a stream, they can impart distinct water quality signals, and such SCMs are unlikely to restore pre-development stream water quantity and quality. Distributed green infrastructure shows promising reductions in peakflows and total stormwater volumes at the street-scale, but challenges remain in scaling up to enough projects to make a difference at the watershed scale and in ensuring that variability in construction and maintenance don’t reduce the effectiveness of the green infrastructure. Finally, there are tradeoffs in our choices around stormwater management infrastructure, in terms of the broader environmental benefits it can provide versus a more narrow focus on water quantity and quality. Using an ecosystem services framework, I show one approach to examining these tradeoffs. None of the current approaches to managing stormwater are a panacea, but with process-based, contextual studies that also examine limitations and tradeoffs, we can move the science and practice of stormwater management toward better outcomes and more sustainable urban streams.
CUAHSI's Fall 2014 Cyberseminar Series on Sustainable Urban Streams— Science to Support Evolving Management Objectives!
The management of urban streams and rivers has historically emphasized two critical ecosystem services: stormwater conveyance (flood protection) and wastewater disposal. Maximizing these services has generally resulted in major alteration of aquatic ecosystem structure and function, and reduced provision of other ecosystem services, such as aesthetics, recreation, food and biodiversity. Recent decades have seen a renewed appreciation of the value of these other services, an improved understanding of the processes by which streams are altered, and the development of engineering and design practices to manage these processes in ways that can provide multiple services.
Hosted by Seth Wenger, Director of Science of the River Basin Center at the University of Georgia