Northeast Region—Urban Landscapes Capability Team

Urban Hydrology—Science Capabilities of the

U.S. Geological Survey

Urbanization affects streamflow characteristics, coastal flooding, and groundwater recharge. Increasing impervious areas, streamflow 

diversions, and groundwater pumpage are some of the ways that the natural water cycle is affected by urbanization. Assessment of the 

relations among these factors and changes in land use helps water-resource managers with issues such as stormwater management 

and vulnerability to flood and drought. Scientists with the U.S. Geological Survey (USGS) have the expertise to monitor and model 

urban hydrologic systems. Streamflow and groundwater data are available in national databases, and analyses of these data, 

including identification of long-term streamflow trends and the efficacy of management practices, are published in USGS reports.

Expertise and Resources

The USGS scientists of the Northeast Region Urban Landscapes Capability Team share expertise and resources to provide and interpret data on a wide 

range of urban-related issues at local, regional, and national levels. These 

scientists use state-of-the-art monitoring, modeling, and laboratory methods 

to better understand hydrologic processes and their impacts on aquatic organisms and human life in urban environments. Examples of these efforts include 

operating continuous streamflow monitoring stations coupled with alert systems 

in flash-flood prone areas to provide the public with real-time warnings about 

flooding (http://waterwatch.usgs.gov/), generating data critical to refining inundation and storm surge forecasting models and maps, and providing emergency 

personnel with early warning of coastal flooding (http://water.usgs.gov/floods/

swath/). Assessing the interactions between surface water and groundwater 

using advanced monitoring technologies and modeling applications informs 

urban planners and stakeholders about water resources. See http://ny.water.usgs.

gov/projects/SOTA/ and Provost and others (2009) for more details.

Urban Streams

The USGS currently operates a network of over 8,000 streamgages 

(http://waterdata.usgs.gov/nwis/rt) as part of its cooperative water program, 

which is used by local, state, and Federal cooperators; stakeholders; and other 

government agencies. Increases in stormwater runoff from impervious surfaces 

(roads, parking lots, and roofs) increase peak flows during rain events, which 

can degrade stream channel stability. Advanced monitoring equipment, such as 

noncontact radar-stage sensors and acoustic Doppler velocimeters, are used to 

understand rapidly-changing hydrodynamic conditions in streams and estuaries 

in real time (http://ny.cf.er.usgs.gov/nyprojectsearch/projects/LK00-FKD-0300.

html). The USGS modeling program, Stochastic Empirical Loading and Dilution Model (also known as SELDM), was created in cooperation with the Federal Highway Administration to determine the risk of adverse effects of storm 

runoff, the potential need for mitigation measures, and the effectiveness of 

management measures for reducing these risks (https://pubs.er.usgs.gov/publication/tm4C3). Information about how stream and coastal flooding are affected 

by land use helps municipal officials manage their current and future vulnerability to floods. Scientists with the USGS also work with urban planners and 

community groups to study the effects of stream restoration such as daylighting 

(uncovering buried streams) and dam removal.

Groundwater in Urban Areas

The USGS operates an extensive network of groundwater wells that can be 

used to assess groundwater level and quality and aquifer properties. Urbanization can affect groundwater resources in many ways. Impervious surfaces in an 

Cement-lined stream in Queens County, New 

York. Photograph from U.S. Geological Survey.

Urban hydrology qualifies and quantifies effects of A, impervious surfaces, B, groundwater sourcing, C, stream response 

time and sewage overflow, and D, waterway impairment.

U.S. Department of the Interior

U.S. Geological Survey

Banner photograph: Washington, D.C., skyline by Ad Meskens,

Creative Commons Attribution-Share Alike 3.0 Unported license

https://commons.wikimedia.org/wiki/File:Washington_dc_skyline.jpg.

Fact Sheet 2016–3023

April 2016
Conceptual model showing how 

a discharge hydrograph is altered 

by increases in impervious areas 

throughout a watershed. Water runs 

off faster from streets and roofs than 

from natural vegetated areas. The 

construction of parking lots, artificial 

channels, and storm sewers reduce 

the time required for a given amount 

of water to run off into neighboring 

streams. Effects of decreasing lag 

time are higher in-stream velocities, 

increased erosion, higher instantaneous discharge, and increased 

potential for flash flooding. Image 

modified from Leopold, 1968.

Lag time

Hydrograph of streamflow

Rainfall

Center of storm related discharge

Center of storm precipitation 

Time

Rainfall Discharge

Original hydrograph

Center of storm related precipitation

Lag time reduced

stream becomes flashy

Hydrograph of streamflow

impacted by urbanization

Increased stream

velocity 

Center of storm related discharge

urban landscape alter groundwater recharge. Sanitary infrastructure 

alters the natural water budgets. Groundwater withdrawal for public 

supply removes water from storage and can decrease base flows 

to streams. Above-normal precipitation events, rising sea level, 

and climate change may exacerbate current infrastructure flooding issues by increasing groundwater levels. Conversely, droughts 

and supply withdrawals can lower groundwater levels and may 

lead to land subsidence or saltwater intrusion. To better understand 

complex aquifer systems and their potential response to changes 

in precipitation, urbanization, wastewater recharge, or withdrawal, 

the USGS has developed numerous groundwater flow models in 

urban areas using computer programs such as MODFLOW. Models 

such as these greatly improve the understanding of groundwater 

processes and groundwater response to stressors such as intensive 

supply pumping.

Carmans River

East Meadow Brook

Percentage of total streamflow

derived from base flow

Water year

(Water year is the 12-month period of October 1, for any given year through September 30, 

of the following year. The water year is designated by the calendar year in which it ends.)

90

100

80757065605550454035 85 90

80

70

60

50

40

30

Percentage of streamflow derived from base flow at two streams in 

Long Island, New York; East Meadow Brook at Freeport, N.Y., and 

Carmans River at Yaphank, N.Y. Decreased streamflow in East Meadow 

Brook, N.Y., is attributed to sewering in the urbanized watershed, which 

exacerbated the low streamflows during drought conditions in the 1960s. 

Streamflow at the Carmans River, which is in a rural setting that is not 

sewered, was sustained by base flow during the same period of record 

(Scorca, 1996).

Examples of USGS Urban Hydrologic Studies

http://pubs.usgs.gov/sir/2014/5058/

http://pubs.usgs.gov/fs/fs07603/

http://pubs.usgs.gov/sir/2014/5036/pdf/sir2014-5036.pdf

http://pubs.usgs.gov/of/2014/1184

http://pubs.usgs.gov/circ/1968/0554/report.pdf

http://pubs.usgs.gov/wri/1996/4187/report.pdf

Partnering Opportunities

As the Nation’s largest hydrologic, geologic, and biologic science and mapping agency, the USGS provides scientific understanding about natural resource conditions, issues, and problems. The 

diversity of our scientific expertise enables us to carry out largescale, multi-disciplinary investigations and provide impartial scientific information to resource managers, planners, and other cooperators. The USGS Northeast Region Urban Landscape Capability 

Team is committed to continuing and expanding urban hydrologic 

studies needed to manage water resources of the United States. The 

USGS has a long history of collaborative science with a diversity 

of partners including local, state, Federal, and Tribal agencies; 

nonprofit organizations; academic institutions; watershed groups; 

and other water resources entities. Opportunities for jointly funded 

programs are available through the Cooperative Water Program 

(http://water.usgs.gov/coop/).

References Cited

Granato, G.E., 2013, Stochastic empirical loading and dilution model 

(SELDM) version 1.0.0: U.S. Geological Survey Techniques and 

Methods, book 4, chap. C3, 112 p., accessed April 12, 2016, at 

http://pubs.usgs.gov/tm/04/c03/.

Leopold, L.B., 1968, Hydrology for urban land planning—A guidebook of 

the hydrologic effects of urban land use: U.S. Geological Survey Circular 

554, 18 p., accessed April 12, 2016, at http://pubs.usgs.gov/circ/1968/0554/

report.pdf.

Provost, A.M., Reilly, T.E., Harbaugh, A.W., and Pollock, D.W., 2009, U.S. 

Geological Survey groundwater modeling software—Making sense of a 

complex natural resource: U.S. Geological Survey Fact Sheet 2009–3105, 

4 p., accessed April 12, 2016, at http://pubs.usgs.gov/fs/2009/3105/

pdf/2009-3105.pdf.

Scorca, M.P. and Ku, H.F.H., 1997, Urbanization and recharge in the vicinity 

of East Meadow Brook, Nassau County, New York, Part 3—Ground-water 

levels and flow conditions, 1988–93: U.S. Geological Survey WaterResources Investigations Report 96–4265, 39 p., accessed April 12, 2016, 

at https://pubs.er.usgs.gov/publication/wri964265.

By Joseph M. Bell, Amy E. Simonson, and Irene J. Fisher

For more information about these USGS projects and about 

partnering opportunities, contact:

USGS Northeast Region Urban Landscapes Capability Team

Email: GS-NE_ULCT@usgs.gov

or contact your local USGS office

https://www.usgs.gov/contact_us

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20163023