{{Short description|Formerly natural waterway flowing through heavily populated area}} [[File:Second River west of High jeh.JPG|thumb|right|Second River, an urban stream in Orange, New Jersey]] An '''urban stream''' is a waterway that flows through a densely populated, heavily developed area. Urbanized landscapes alter water flows into and within streams compared with pre-urbanized landscapes.<ref>{{Cite journal |last=Violin |first=Christy R. |date=September 2011 |title=Effects of urbanization and urban stream restoration on the physical and biological structure of stream ecosystems |url=https://www.jstor.org/stable/41416629 |journal=Ecological Applications |volume=21 |issue=6 |pages=1932–1949 |doi=10.1890/10-1551.1 |jstor=41416629 |pmid=21939035 |bibcode=2011EcoAp..21.1932V |url-access=subscription }}</ref> Urban streams are often impaired in characteristic ways. The combination of impairments is referred to as "urban stream syndrome," and it includes pollution from urban stormwater runoff and combined sewer overflows. Urban streams tend to be "flashier" meaning they have more frequent and larger high flow and flooding events. These alterations to the stream typically lead to changes in the communities of organisms, favoring organisms with high tolerances of the degraded conditions.<ref name="walsh">{{cite journal |last1=Walsh |first1=Christopher J. |last2=Roy |first2=Allison H. |last3=Feminella |first3=Jack W. |last4=Cottingham |first4=Peter D. |last5=Groffman |first5=Peter M. |last6=Morgan |first6=Raymond P. |date=2005 |title=The urban stream syndrome: current knowledge and the search for a cure |journal=Journal of the North American Benthological Society |volume=24 |issue=3 |pages=706–723 |doi=10.1899/04-028.1 |s2cid=30667397}}</ref><ref>{{cite journal |last1=Vietz |first1=Geoff J. |last2=Walsh |first2=Christopher J. |last3=Fletcher |first3=Tim D. |date=2016 |title=Urban hydrogeomorphology and the urban stream syndrome: Treating the symptoms and causes of geomorphic change |journal=Progress in Physical Geography: Earth and Environment |volume=40 |issue=3 |pages=480–492 |doi=10.1177/0309133315605048 |s2cid=131397867}}</ref>
== Catchment urbanization == [[File:Hobart Rivulet Underground.jpg|thumb|left|Some urban streams, such as the Hobart Rivulet in Tasmania, run underground for substantial distances]]
The catchment area, or drainage basin, of a stream collects water flowing over and through the underlying land. As a catchment area urbanizes, more and more of the land draining to that stream is covered in impervious surfaces like concrete, asphalt, and rooftops. These impervious surfaces do not allow rain and snow to be absorbed into the soil, so the water runs across the surfaces instead. Governments build infrastructure deliberately designed to alter the flow or course of this water in and on the urban landscape. The goal of these alterations is to prevent localized flooding by moving water through and out of the city as fast as possible after storms. These changes include installation of storm drains and storm sewers, as well as direct alterations called river engineering, which include: lining stream beds with concrete or other hardscape materials, or diverting streams into culverts and storm sewers. Some urban streams, such as the subterranean rivers of London, run completely underground.
== Urban Stream Syndrome == Urban stream syndrome (USS) describes a consistent pattern of observed ecological degradation of streams caused by urbanization. While the exact impact of urbanization on any given stream will differ substantially across regions depending on local geography and climate, there are some basic commonalities. Urban stream syndrome typically includes increased pollutant inputs, more sediment entering the water, alterations in the stream banks, changes to the biological community of the stream, and changes to the flow rate and discharge amount compared with non-urbanized streams.<ref>{{Cite journal |last=Booth |first=Derek B |date=2016 |title=Global perspectives on the urban stream syndrome |url=https://research-ebsco-com.ezproxymbc.helmlib.org/c/dsibx4/viewer/pdf/3pcf6sk4jb?route=details&auth-callid=d45a17a6-278f-489c-b486-756312b37a7b |journal=Freshwater Science |volume=35 |issue=1}}</ref>
=== Pollution === Keep in mind the status of water quality is difficult to assess in urban areas because of the complexity of the pollutions sources.<ref>{{Cite journal |last=Duda |first=Alfred M. |date=July 1982 |title=Water Quality in Urban Streams: What We Can Expect |url=http://www.jstor.org/stable/25041633 |journal=Water Pollution Control Federation |volume=54 |issue=7 |pages=1139–1147 |jstor=25041633}}</ref> This could be from mining and deforestation, but the main cause can be attributed to urban and suburban development. This is because such land use has a domino effect that can be felt tens of kilometers away. Consistent decrease to ecological health of streams can be from many things, but most can be directly or indirectly attributed to human infrastructure and action.
Urban streams also suffer from chemical alterations due to pollutants and waste being uncleanly dumped back into rivers and lakes. An example of this is Onondaga Lake. Historically one of the most polluted freshwater lakes in the world, its salinity and toxic constituents like mercury rose to unsafe levels as large corporations begun to set up shop around the lake. High levels of salinity would be disastrous for any native freshwater marine life and pollutants like mercury are dangerous to most organisms.<ref>{{Cite journal |last1=Rowell |first1=H. Chandler |last2=Enache |first2=Mihaela D. |last3=Quinlan |first3=Roberto |last4=Smith |first4=Alison J. |last5=Bloomfield |first5=Jay A. |last6=Charles |first6=Donald F. |last7=Effler |first7=Steven W. |date=2016 |title=Quantitative paleolimnological inference models applied to a high-resolution biostratigraphic study of lake degradation and recovery, Onondaga Lake, New York (USA) |url= |journal=Journal of Paleolimnology |language=en |volume=55 |issue=3 |pages=241–258 |bibcode=2016JPall..55..241R |doi=10.1007/s10933-015-9877-8 |s2cid=130414481}}</ref>
Higher levels of urbanization typically mean a greater presence of urban stream syndrome.<ref>{{Cite journal |last1=Brown |first1=Larry R. |last2=Cuffney |first2=Thomas F. |last3=Coles |first3=James F. |last4=Fitzpatrick |first4=Faith |last5=McMahon |first5=Gerard |last6=Steuer |first6=Jeffrey |last7=Bell |first7=Amanda H. |last8=May |first8=Jason T. |date=2009 |title=Urban streams across the USA: lessons learned from studies in 9 metropolitan areas |url= |journal=Journal of the North American Benthological Society |volume=28 |issue=4 |pages=1051–1069 |bibcode=2009JNABS..28.1051B |doi=10.1899/08-153.1 |s2cid=85861111}}</ref>
=== Hydrology === Alterations in hydrology are a consistent feature of urban stream syndrome. As urbanization of a catchment area progresses, the decrease in the pervious surfaces leads to an increase in the surface runoff and rapid flows through storm sewers into streams. These rapid flows into the urban stream lead to flashy hydrographs, where stream levels rise rapidly in response to precipitation events. Other common shifts in hydrology driven by urbanization include lower baseflows. This can cause problems during flood discharges. For example, flood discharges in urban catchments were at least 250% higher in urban catchments than in forested catchments in New York and Texas during similar storms.<ref>{{Cite journal |last=Paul |first=Michael J |date=2001 |title=Streams in the Urban Landscape |url=http://www.jstor.org/stable/2678644 |journal=Annual Review of Ecology and Systematics |volume=32 |issue=1 |pages=335 |bibcode=2001AnRES..32..333P |doi=10.1146/annurev.ecolsys.32.081501.114040 |jstor=2678644 |url-access=subscription}}</ref>
==Stressors== These modifications have often reduced habitat for fish and other species, caused downstream flooding due to alterations of flood plains, and worsened water quality.<ref>{{cite report |url=https://www.epa.gov/nps/hydromodification-and-habitat-alteration-national-management-measures |title=National Management Measures to Control Nonpoint Source Pollution from Hydromodification |date=July 2007 |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, DC |id=EPA 841-B-07-002}}</ref> Water scarcity makes flow management in the rehabilitation of urban streams problematic.<ref>{{cite journal |last1=Lawrence |first1=Justin E. |last2=Pavia |first2=Christopher P. W. |last3=Kaing |first3=Sereyvicheth |last4=Bischel |first4=Heather N. |last5=Luthy |first5=Richard G. |last6=Resh |first6=Vincent H. |date=2014 |title=Recycled water for augmenting urban streams in mediterranean-climate regions: a potential approach for riparian ecosystem enhancement |journal=Hydrological Sciences Journal |volume=59 |issue=3–4 |pages=488–501 |bibcode=2014HydSJ..59..488L |doi=10.1080/02626667.2013.818221 |s2cid=129362661 |doi-access=free}}</ref>Toxicants, ionic concentrations, available nutrients, temperature (and light), and dissolved oxygen are key stressors to urban streams.<ref>{{cite journal |last1=Wenger |first1=Seth J. |last2=Roy |first2=Allison H. |last3=Jackson |first3=C. Rhett |last4=Bernhardt |first4=Emily S. |last5=Carter |first5=Timothy L. |last6=Filoso |first6=Solange |last7=Gibson |first7=Catherine A. |last8=Hession |first8=W. Cully |last9=Kaushal |first9=Sujay S. |last10=Martí |first10=Eugenia |last11=Meyer |first11=Judy L. |last12=Palmer |first12=Margaret A. |last13=Paul |first13=Michael J. |last14=Purcell |first14=Alison H. |last15=Ramírez |first15=Alonso |last16=Rosemond |first16=Amy D. |last17=Schofield |first17=Kate A. |last18=Sudduth |first18=Elizabeth B. |last19=Walsh |first19=Christopher J. |title=Twenty-six key research questions in urban stream ecology: an assessment of the state of the science |journal=Journal of the North American Benthological Society |date=December 2009 |volume=28 |issue=4 |pages=1080–1098 |doi=10.1899/08-186.1|s2cid=23296920 |hdl=10919/80380 |hdl-access=free }}</ref>
==Restoration efforts== Some communities have begun stream restoration projects in an attempt to correct the problems caused by alteration, using techniques such as daylighting and fixing stream bank erosion caused by heavy stormwater runoff.<ref>{{cite web|author=California Department of Water Resources|title=Urban Streams Restoration Program|url=http://www.watershedrestoration.water.ca.gov/urbanstreams/|access-date=2009-07-11|archive-date=2009-04-30|archive-url=https://web.archive.org/web/20090430234754/http://www.watershedrestoration.water.ca.gov/urbanstreams/|url-status=dead}}</ref><ref>{{cite news |first= Andrew C. |last= Revkin |title= Rolling Back Pavement to Expose Watery Havens |url= https://www.nytimes.com/2009/07/17/world/asia/17daylight.html?_r=1 |work= New York Times |date=16 July 2009|access-date=19 July 2009 }} </ref> Streamflow augmentation to restore habitat and aesthetics is also an option, and recycled water can be used for this purpose.<ref>{{cite journal |last1=Bischel |first1=Heather N. |last2=Lawrence |first2=Justin E. |last3=Halaburka |first3=Brian J. |last4=Plumlee |first4=Megan H. |last5=Bawazir |first5=A. Salim |last6=King |first6=J. Phillip |last7=McCray |first7=John E. |last8=Resh |first8=Vincent H. |last9=Luthy |first9=Richard G. |title=Renewing Urban Streams with Recycled Water for Streamflow Augmentation: Hydrologic, Water Quality, and Ecosystem Services Management |journal=Environmental Engineering Science |date=2013 |volume=30 |issue=8 |pages=455–479 |doi=10.1089/ees.2012.0201}}</ref><ref>{{cite journal |last1=Halaburka |first1=Brian J. |last2=Lawrence |first2=Justin E. |last3=Bischel |first3=Heather N. |last4=Hsiao |first4=Janet |last5=Plumlee |first5=Megan H. |last6=Resh |first6=Vincent H. |last7=Luthy |first7=Richard G. |title=Economic and Ecological Costs and Benefits of Streamflow Augmentation Using Recycled Water in a California Coastal Stream |journal=Environmental Science & Technology |date=2013 |volume=47 |issue=19 |pages=10735–10743 |doi=10.1021/es305011z|pmid= 23688175 |bibcode=2013EnST...4710735H}}</ref>
=== Treatment === Many water managers treat USS by directly addressing the symptoms, most commonly through channel reconfiguration that includes reshaping rock to address altered hydrology and sediment regimes. In spite of having ecological objectives, this approach has been criticized for addressing physical failures in the system without improving ecological conditions.<ref>{{cite journal |last1=Laub |first1=Brian G. |last2=Baker |first2=Daniel W. |last3=Bledsoe |first3=Brian P. |last4=Palmer |first4=Margaret A. |title=Range of variability of channel complexity in urban, restored and forested reference streams: Channel complexity and stream restoration |journal=Freshwater Biology |date=2012 |volume=57 |issue=5 |pages=1076–1095 |doi=10.1111/j.1365-2427.2012.02763.x}}</ref>
==See also== * Nationwide Urban Runoff Program (NURP) – US research program * Nonpoint source pollution * Subterranean river
==References== <references />
==Bibliography== * {{cite book |last1=Riley |first1=Ann L. |last2=Leopold |first2=Luna B. |title=Restoring Streams in Cities: A Guide for Planners, Policymakers, and Citizens |url=https://books.google.com/books?id=2NyTJHrDYpkC&q=Ann+Riley+restoring+streams |year=1998 |publisher=Island Press |location=Washington, DC |isbn=978-1-55963-042-9}}
==External links== * [https://www.epa.gov/urbanwaterspartners Urban Waters Program] – U.S. Environmental Protection Agency (EPA) * [https://web.archive.org/web/20060925154708/http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/7711/report/0 Ecosystem Effects of Urban Stream Restoration] – EPA * [https://www.geocities.ws/linwood/suds/ Suspended Sediment and Discharge in a West London River]
Category:Hydrology and urban planning Category:Water pollution Category:Environmental engineering Category:Water streams Category:Rivers Category:Hydrology Category:Fluvial landforms