A brown bullhead with lip tumors from the Presque Isle Bay Area of Concern, Erie, Pennsylvania. Bottom-feeding bullheads are indicators of environmental health. Vicki Blazer, USGS.
Urban development degrades streams by changing their hydrology, water quality and physical habitat. Contaminants, habitat loss and flashier flows disrupt biological communities — above all, sensitive aquatic species disappear. How algae, invertebrates and fish respond shows how streams should be managed as watersheds urbanize, and the U.S. Geological Survey leads studies of this in metropolitan areas nationwide.
What the USGS measures
The Northeast Region Urban Landscapes Capability Team pairs traditional water and bed-sediment samples with toxicity tests and bioassays to gauge how exposed and vulnerable stream organisms are, and assesses streams and lakes by surveying fish, invertebrate and algal communities and testing tissues for contaminants.
Altered flows, lost species
Natural flow swings build and maintain habitat, shape water chemistry, and cue life stages of aquatic animals. Urbanization changes the size, duration, frequency and timing of flows:
- More pavement, more runoff — higher peak flows that erode channels;
- Less soaking in, less groundwater recharge — lower flows in summer;
- The result: fewer fish species and sensitive invertebrates, and a shift toward tolerant species.
USGS studies document how widespread and severe streamflow modification is nationwide, and why keeping natural flows matters for stream health.
Chemical stressors
- Mixtures: runoff from industrial and suburban pavement carries pesticides, nutrients, chloride, metals, wastewater compounds and more, which can limit survival, growth and reproduction — even small amounts can reshape communities.
- Emerging contaminants: endocrine disruption and reproductive effects in fish have been linked to hormones, estrogenic pesticides and wastewater compounds.
- Mercury: bioaccumulated trace elements such as mercury affect reproduction and behavior in fish and the predators that eat them.
- Road salt: chloride has risen sharply in urbanizing watersheds across the Northeast, where deicers are used heavily, possibly threatening sensitive species.
- Sediment: stormwater carries contaminants into streambeds, raising toxicity; floods then stir them up and move them downstream into estuaries.
Ecological toxicity tests measure lethal and sublethal — reproductive, developmental and behavioral — effects of bed sediment on test organisms. Jacob K. Stanley, U.S. Army Corps of Engineers.
Examples of USGS studies
| Study | Focus |
|---|---|
| National Water Census, Delaware River Basin (2016) | how streamflow's magnitude, duration, frequency, timing and rate of change relate to aquatic life — to help balance human water needs and healthy streams |
| Northeast Stream Quality Assessment | effects of urbanization and agriculture on streams in New England, New York, and northern New Jersey and Pennsylvania |
| Environmental Health Program | contaminants of emerging concern — present but not commonly monitored — with methods to detect them at low concentrations and study their sources, fate and effects |
| Urbanization and stream ecosystems (National Water-Quality Assessment) | how urban intensity relates to physical, chemical and biological stream quality in 11 metropolitan areas |
Partnering
USGS ecosystem studies use standardized protocols, so results compare locally and nationally. State and local agencies can partner, with matching funds, through the Cooperative Water Program; Federal agencies, universities, nonprofits and others through other programs.
Sources
Based on Urban Development and Stream Ecosystem Health—Science Capabilities of the U.S. Geological Survey, by Pamela A. Reilly, Zoltan Szabo and James F. Coles, USGS Fact Sheet 2016–3026, U.S. Geological Survey (DOI), citing Blazer and others and the USGS; a work of the United States government in the public domain. The photographs come from the fact sheet's PDF.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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