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The Urban Stream Syndrome: Current Knowledge and the Search for a Cure


The term “urban stream syndrome” describes the consistently observed
ecological degradation of streams draining urban land. This paper
reviews recent literature to describe symptoms of the syndrome, explores
mechanisms driving the syndrome, and identifies appropriate goals and
methods for ecological restoration of urban streams. Symptoms of the
urban stream syndrome include a flashier hydrograph, elevated
concentrations of nutrients and contaminants, altered channelmorphology,
and reduced biotic richness, with increased dominance of tolerant
species. More research is needed before generalizations can be made
about urban effects on stream ecosystem processes, but reduced nutrient
uptake has been consistently reported. The mechanisms driving the
syndrome are complex and interactive, but most impacts can be ascribed
to a few major large-scale sources, primarily urban stormwater runoff
delivered to streams by hydraulically efficient drainage systems. Other
stressors, such as combined or sanitary sewer overflows, wastewater
treatment plant effluents, and legacy pollutants (long-lived pollutants
from earlier land uses) can obscure the effects of stormwater runoff.
Most research on urban impacts to streams has concentrated on
correlations between instream ecological metrics and total catchment
imperviousness. Recent research shows that some of the variance in such
relationships can be explained by the distance between the stream reach
and urban land, or by the hydraulic efficiency of stormwater drainage.
The mechanisms behind such patterns require experimentation at the
catchment scale to identify the best management approaches to
conservation and restoration of streams in urban catchments. Remediation
of stormwater impacts is most likely to be achieved through widespread
application of innovative approaches to drainage design. Because humans
dominate urban ecosystems, research on urban stream ecology will require
a broadening of stream ecological research to integrate with social,
behavioral, and economic research.