U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1191

Prepared in cooperation with the City of Newport News

Simulated Changes in Salinity in the York and Chickahominy 

Rivers from Projected Sea-Level Rise in Chesapeake Bay
Cover photograph: St. Michaels Marina, Chesapeake Bay, Maryland.
Simulated Changes in Salinity in the York 

and Chickahominy Rivers from Projected 

Sea-Level Rise in Chesapeake Bay

By Karen C. Rice, Mark R. Bennett, and Jian Shen

Prepared in cooperation with the City of Newport News

Open-File Report 2011–1191

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Rice, K.C., Bennett, M.R., and Shen, Jian, 2011, Simulated changes in salinity in the York and Chickahominy Rivers 

from projected sea-level rise in Chesapeake Bay: U.S. Geological Survey Open-File Report 2011–1191, 31 p.

ISBN 978-1-4113-3235-5
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Climate Variability and Change and Sea-Level Rise ......................................................................2

Drinking-Water Utilities and Climate Change ..................................................................................3

Study Area..............................................................................................................................................5

Sea-Level Rise in Chesapeake Bay ...................................................................................................5

Sea-Level Rise Scenarios ...................................................................................................................6

Hydrodynamic Models .................................................................................................................................7

Model Limitations..................................................................................................................................7

York River Model ...................................................................................................................................7

Chickahominy River Model .................................................................................................................9

Model Results.................................................................................................................................................9

York River ............................................................................................................................................10

Chickahominy River ...........................................................................................................................11

Summary........................................................................................................................................................21

Acknowledgments.......................................................................................................................................21

References....................................................................................................................................................22

Appendix........................................................................................................................................................25

Figures

1. Graph showing smoothed reconstructions of large-scale surface temperature 

variations from proxy records and the instrumental record of global mean 

surface temperature ....................................................................................................................2

2. Graph showing variations in global sea-level elevation over the last 

400,000 years resulting from four natural glacial and interglacial cycles...........................3

3. Graph showing past and projected global average sea level ..............................................3

4. Map showing location of York, Chickahominy, and James Rivers, Virginia .......................4

5. Graph showing historic sea-level rise at Sewells Point, Virginia, 1927–2006 ....................6

6. Graph showing chloride concentration at Walkers Dam on the Chickahominy 

River, 1999–2004 ............................................................................................................................6

7. Map showing large domain model of Chesapeake Bay ........................................................8

8. Map showing nested-grid model of the York River.................................................................9

9. Map showing nested-grid model of the James and Chickahominy Rivers ......................10

10. Graphs showing time series of surface and bottom simulated salinity at the 

head of the York estuary for three sea-level rise scenarios, 1998–2008 ...........................12

11. Graphs showing cross sections (A–A’ on figure 4) of average simulated 

salinity at the head of the York estuary for July and August...............................................13
iv

12. Graphs showing cross sections (A–A’ on figure 4) of average simulated 

salinity at the head of the York estuary for September and October.................................14

13. Graphs showing cross sections (A–A’ on figure 4) of average simulated 

salinity at the head of the York estuary for November and December..............................15

14. Graphs showing effect of simulated sea-level rise scenarios on 31-day 

mean salinity along the York River...........................................................................................16

15. Graphs showing time series of simulated surface and bottom salinity at 

Walkers Dam on the Chickahominy River for three sea-level rise scenarios, 

1998–2008 .....................................................................................................................................17

16. Graphs showing cross sections (B–B’ on figure 4) of average simulated 

salinity downstream of Walkers Dam on the Chickahominy River for 

July and August ..........................................................................................................................18

17. Graphs showing cross sections (B–B’ on figure 4) of average simulated 

salinity downstream of Walkers Dam on the Chickahominy River for 

September and October ............................................................................................................19

18. Graphs showing cross sections (B–B’ on figure 4) of average simulated 

salinity downstream of Walkers Dam on the Chickahominy River for 

November and December.........................................................................................................20

19. Graphs showing effect of simulated sea-level rise scenarios on 

31-day mean salinity along the Chickahominy River ............................................................20

Tables

1. Rates of relative sea-level rise for selected long-term tidal gages on the

Atlantic coast of the United States............................................................................................5

2. Mean annual discharge for the James River near Richmond ............................................11

3. Number of days that salinity is predicted to exceed 0.1 parts per thousand 

at the head of the York estuary from June 1 to December 31 .............................................11

4. Number of days that salinity is predicted to exceed 0.1 parts per thousand 

at Walkers Dam on the Chickahominy River from June 1 to December 31 ......................16

5. Number of days that water from sea-level rise is predicted to overtop 

Walkers Dam on the Chickahominy River from June 1 to December 31...........................16
v

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

millimeter per year (mm/yr) 0.03937 inch per year (in/yr)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

kilometer (km) 0.5400 mile, nautical (nmi) 

meter (m) 1.094 yard (yd) 

Area

square kilometer (km2

) 0.6214 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

cubic meter per second (m3

/s) 264.2 gallon (gal)

cubic meter (m3

) 0.0002642 million gallons (Mgal) 

Flow rate

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

Conversion Factors

SI to Inch/Pound

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F–32)/1.8

Acronyms and Additional Abbreviations

TDS Total dissolved solids

GMSL Global mean sea level

IPCC Intergovernmental Panel on Climate Change

mg/L Milligrams per liter

ppt Parts per thousand

river km River kilometer 

HEM-3D Three-Dimensional Hydrodynamic-Eutrophication Model

DEQ Virginia Department of Environmental Quality

VIMS Virginia Institute of Marine Science

NOAA National Oceanic and Atmospheric Administration

Abstract

As a result of climate change and variability, sea level is 

rising throughout the world, but the rate along the east coast of 

the United States is higher than the global mean rate. The U.S. 

Geological Survey, in cooperation with the City of Newport 

News, Virginia, conducted a study to evaluate the effects 

of possible future sea-level rise on the salinity front in two 

tributaries to Chesapeake Bay, the York River, and the Chickahominy/James River estuaries. Numerical modeling was used 

to represent sea-level rise and the resulting hydrologic effects. 

Estuarine models for the two tributaries were developed and 

model simulations were made by use of the Three-Dimensional Hydrodynamic-Eutrophication Model (HEM-3D), 

developed by the Virginia Institute of Marine Science. HEM3D was used to simulate tides, tidal currents, and salinity for 

Chesapeake Bay, the York River and the Chickahominy/James 

River. The three sea-level rise scenarios that were evaluated 

showed an increase of 30, 50, and 100 centimeters (cm). 

Model results for both estuaries indicated that high 

freshwater river flow was effective in pushing the salinity 

back toward Chesapeake Bay. Model results indicated that 

increases in mean salinity will greatly alter the existing waterquality gradients between brackish water and freshwater. This 

will be particularly important for the freshwater part of the 

Chickahominy River, where a drinking-water-supply intake 

for the City of Newport News is located. 

Significant changes in the salinity gradients for the York 

River and Chickahominy/James River estuaries were predicted 

for the three sea-level rise scenarios. When a 50-cm sea-level 

rise scenario on the York River during a typical year (2005) 

was used, the model simulation showed a salinity of 15 parts 

per thousand (ppt) at river kilometer (km) 39. During a 

dry year (2002), the same salinity (15 ppt) was simulated at 

river km 45, which means that saltwater was shown to migrate 

6 km farther upstream during a dry year than a typical year.

The same was true of the Chickahominy River for a 

50-cm sea-level rise scenario but to a greater extent; a salinity 

of 4 ppt was simulated at river km 13 during a typical year 

and at river km 28 during a dry year, indicating that saltwater 

migrated 15 km farther upstream during a dry year.

Near a drinking-water intake on the Chickahominy River, 

for a dry year, salinity is predicted to more than double for all 

three sea-level rise scenarios, relative to a typical year. During 

a typical year at this location, salinity is predicted to increase 

to 0.006, 0.07, and more than 2 ppt for the 30-, 50-, and 100-

cm rise scenarios, respectively. 

Introduction

Society faces many environmental problems and challenges, but the recent threat of climate change and variability has become a prominent focus for both government and 

industry. Some of the consequences of climate change and 

variability are water availability for municipal and industrial 

use, water demand for irrigation, changes in water quality, threats to stormwater and wastewater infrastructure, and 

changes in sea level. An Intergovernmental Panel on Climate 

Change (IPCC) assessment report concludes, “Observational 

records and climate projections provide abundant evidence 

that freshwater resources are vulnerable and have the potential 

to be strongly impacted by climate change, with wide-ranging 

consequences for human societies and ecosystems” (Bates and 

others, 2008). 

The purpose of this study was to utilize a hydrodynamic 

simulation model to evaluate possible future changes in 

salinity in the York River and Chickahominy/James River 

estuaries resulting from projected sea-level rise. The scope 

of this report is to describe the models used and present 

the results of the model simulations for the York and 

Chickahominy/James Rivers.

The regional distribution of salinity in the York River and 

Chickahominy/James River estuaries from projected sea-level 

rise is a critical element needed by water managers and others 

Simulated Changes in Salinity in the York and 

Chickahominy Rivers from Projected Sea-Level Rise in 

Chesapeake Bay

By Karen C. Rice1, Mark R. Bennett1, and Jian Shen2

1

 U.S. Geological Survey, Virginia Water Science Center, Richmond, Va.

2

 Department of Physical Sciences, Virginia Institute of Marine Science, 

Gloucester Point, Va.
2 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

concerned with protecting the Chesapeake Bay and its estuaries. In 2009, the U.S. Geological Survey (USGS), in cooperation with the City of Newport News, Virginia (Va.), began a 

study to investigate the potential effects of future sea-level rise 

on salinity change in two estuaries in southeastern Virginia. 

The two estuaries, the York River and the Chickahominy/

James River, discharge into Chesapeake Bay. This report provides information about the sea-level rise study and the results 

of model simulations of changes in salinity.

Climate Variability and Change and 

Sea-Level Rise 

Earth has a long history of climate variability and change, 

which includes periods of cooling and warming, and sea-level 

rise. Earth’s historical surface-temperature variations, derived 

from a variety of sources, show that there has been a warming 

trend since the early 1800s (fig. 1). A recent ice core collected 

from the Vostok site in Antarctica extends our knowledge of 

Earth’s climate to 420,000 years before present. According to 

data from the Vostok ice core, temperature has varied about 

12 degrees Celsius (oC) in fairly regular ±100,000-year cycles 

over this much longer record (Petit and others, 2000). Warmer 

air temperature leads to many environmental changes, including warmer ocean water, an increase in tropical storm intensity, sea-level rise, ocean and coastal changes, and changes in 

precipitation patterns.

Like the fluctuations in Earth’s climate, sea level also 

has fluctuated over the past 400,000 years (fig. 2). Evidence suggests that sea level was about 4 to 6 meters (m) 

higher than present during the last interglacial warm period 

125,000 years ago and 120 m lower during the last Ice Age, 

about 21,000 years ago (see reviews in Muhs and others, 2004, 

and Overpeck and others, 2006). More recently, during the 

current warming period, global mean sea level (GMSL) has 

risen about 0.25 m since measuring commenced in 1870 and is 

projected to rise an additional 0.5 m by the year 2100 (fig. 3). 

Specific environmental effects of future global climate 

variability and change remain uncertain; in particular, there is 

large uncertainty in whether the changes will occur gradually 

or abruptly. A certainty, however, is that as air temperature 

rises, polar ice caps and glaciers melt, and sea level rises from 

the influx of melt water. Increased air and water temperature 

will cause thermal expansion of the oceans, which also will 

contribute to sea-level rise. 

Sea-level rise can affect coastal and estuarine areas in 

several ways, including causing increased shoreline erosion, 

inundation of low-lying coastal areas, increased damage from 

storms and flooding, changes in the existence and distribution 

of wetlands and associated biota, and encroachment of saline 

water into estuaries and coastal aquifers. If estuarine salinity 

were to move far enough upstream into freshwater rivers, it is 

likely to affect municipal drinking-water supplies, as well as 

alter habitat for plant and animal communities.

Figure 1. Smoothed reconstructions of large-scale surface temperature variations 

(Northern Hemisphere mean or global mean) from proxy records and the instrumental 

record (beginning in 1856) of global mean surface temperature. Darker gray shading 

indicates greater generalized uncertainty (National Research Council, 2006).

EXPLANATION

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1.0

–1.2

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1.0

–1.2

Temperature anomaly, in degrees Celsius

Year

900 1,100 1,300 1,500 1,700 1,900

Borehole temperatures (Huang and

others, 2000)

Multiproxy (Mann and Jones, 2003)

Multiproxy (Hegerl and others, 2006)

Instrumental record (Jones and

others, 2001)

Glacier lengths (Oerlemans, 2005)

Multiproxy (Moberg and others, 2005)

Tree rings (Esper and others, 2002)
As climate patterns continue to change, natural variability also will continue. Any projected change in average river 

runoff, air temperature, and sea level will occur in addition 

to ongoing natural variability. In many cases, the amplitude 

of the natural variability can be quite large compared to the 

changes projected to result from global warming (Miller 

and Yates, 2006). Furthermore, relatively short instrumental 

records may not provide an adequate picture of the full range 

of natural climate variability. The longer-term view provided 

by geologic evidence, such as ice-core data, and recent climate 

research based on tree rings, are crucial when evaluating 

change and the rates of change (for example, fig. 1).

Drinking-Water Utilities and Climate Change

Surface-temperature variations and sea-level rise have 

implications for water-resources management. The engineering and economic approaches that underlie virtually all historical water planning in the United States, however, assume that 

climatic and hydrologic processes are nearly stationary. Effective management of existing water-resources infrastructure 

depends on adaption to current realities, including physical 

condition of infrastructure, competing demands, public values, 

population, and climate, none that are static. Establishing a 

reasonable range for variability will be a key element and 

challenge for water-supply management.

Personnel at public drinking-water utilities have spent 

most of the past decade identifying the specific water-quality 

and quantity changes that likely will be experienced, and the 

changes or threshold-level events that may be experienced, as 

a result of global change. Sustainability, resilience, and adaptability have emerged and coalesced as both goals and solutions 

for the drinking-water sector. To adequately simulate the effect 

that climate change could have on a specific region, a model 

must be scaled down from those used on a global scale.

The technical term for the degree of saltiness of surface 

waters is “salinity.” Water is considered to be fresh when 

salinity is less than 500 milligrams per liter (mg/L) total dissolved solids (TDS); 500 mg/L is equivalent to 0.5 parts per 

thousand (ppt, the salinity unit used in this report). The U.S. 

Environmental Protection Agency’s secondary standard for 

drinking water for TDS is 500 mg/L (http://water.epa.gov/

drink/contaminants/index.cfm; accessed 7/21/2011). When 

salinity is between 0.5 and 30 ppt, water is considered to be 

brackish. 

Newport News Waterworks is a regional drinking-water 

utility located on the Virginia Lower Peninsula, which is 

bounded on the north and south by the brackish tidal estuaries 

of the York and James Rivers, respectively (fig. 4). Newport 

News Waterworks serves about 415,000 people, including 

eight Federal installations. The water-treatment facilities for 

this sector and a growing multijurisdictional service area are 

located on the Virginia Lower Peninsula. 

A Newport News Waterworks public water-supply intake 

is located in a lake upstream of Walkers Dam, a tidal-barrier 

dam on the Chickahominy River estuary (fig. 4). The quantity and quality of water available for utility withdrawal from 

this location are dependent on climate variability, which can 

cause changes in river flow, lake stage, and salinity levels.

About 30 to 70 percent of the region’s drinking-water supply 

originates as transfers from the lake at Walkers Dam. When 

inflow to the various supply reservoirs is severely diminished 

during droughts, withdrawals from the lake at Walkers Dam 

are crucial.A consequence of reduced freshwater flows during 

droughts is increased salinity levels in the estuary. Historical 

water-quality data confirm that when freshwater flow is diminished in the James and Chickahominy Rivers, saline water 

moves upstream to Walkers Dam (Ron Harris, Newport News 

Waterworks, written commun., 2010). Therefore, any increase 

Introduction 3

0

–20

–40

–60

–80

–100

–120

Global sea level, in meters

–140

Thousands of years before present

–400 –300 –200 –100 0

Figure 2. Variations in global sea-level elevation over the 

last 400,000 years resulting from four natural glacial and 

interglacial cycles. Reprinted from Quaternary Science 

Reviews (Huybrechts, 2002).

Figure 3. Past and projected global average sea level. The 

gray shaded area shows the estimates of sea-level change 

from 1800 to 1870 when measurements were not available. The 

red line is a reconstruction of sea-level change measured by 

tidal gages with the surrounding shaded area depicting the 

uncertainty. The green line shows sea-level change as measured 

by satellite. The purple shaded area represents the range of 

Global Circulation Model projections for a medium-growth 

emissions scenario (Intergovernmental Panel on Climate Change 

SRES A1B). For reference, 100 millimeters is about 4 inches. From 

Intergovernmental Panel on Climate Change (2007).
4 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

James

Chi ckahominy

CHESAPEAKE BAY

York

River

River

Pamunkey

River

VIRGINIA

NORTH CAROLINA

VIRGINIA

MARYLAND

River

River

Mattaponi

VIRGINIA

Appomattox

River

02042500

SUSSEX

SUFFOLK

SURRY

CAROLINE

ESSEX

SOUTHAMPTON

HANOVER

DINWIDDIE

CHESAPEAKE

ISLE OF WIGHT

YORK

KING WILLIAM

GREENSVILLE

RICHMOND

GLOUCESTER

VIRGINIA BEACH

PRINCE GEORGE

MIDDLESEX

LANCASTER

JAMES CITY

CHARLES CITY

MATHEWS

WESTMORELAND

Hampton

HENRICO

KING & QUEEN

CHESTERFIELD

NORTHUMBERLAND

NEWPORT NEWS

Norfolk

Richmond

Portsmouth

POQUOSON

Petersburg

Hopewell

Franklin

Emporia

Williamsburg

Hampton Roads

West

Point

Yorktown

Sewells Point

01674500

01673000

02037500

77°30' 77° 76°30' 76°

38°

37°30'

37°

0 10 20 MILES

0 10 20 KILOMETERS

WALKERS

DAM

NEW KENT A

B

A ́

B ́

Figure 4. Location of York, Chickahominy, and James Rivers, Virginia.
Introduction 5

in the occurrence or duration of salinity at the location of the 

intake could affect the safe yield and sustainability of the 

surface-water system. 

In addition to the effects of reduced freshwater flows on 

water quality, utilities need to be aware of the effects of potential sea-level rise on water quality. In general, sea-level rise 

can cause saline water to migrate upstream to points where 

freshwater existed previously (National Research Council, 

1987; Poff and others, 2002; Climate Change Science Program, 2009). A salinity migration may cause loss of salt-sensitive habitat that would affect surface-water and groundwater 

drinking-water supplies, as well as habitat loss for a variety of 

plants and animals.

One way to assess potential future changes in environmental systems is to develop accurate science-based models of 

present-day environmental system behavior. Once present-day 

processes can be simulated, the models can be used to investigate a plausible range of future changes. Changes in environmental processes typically are interrelated with each other and 

a variety of other factors, resulting in complex feedback loops. 

Study Area

The study area includes two tributaries to Chesapeake 

Bay, the York River and the Chickahominy/James River 

(fig. 4). The York River is the fifth largest tributary basin 

that discharges to Chesapeake Bay and is formed at West 

Point, Va., by the confluence of the Mattaponi and Pamunkey 

Rivers. The York River flows southeastward and discharges 

to the bay between the York-James and Middle Peninsulas of 

Virginia. The Chickahominy River is located south of West 

Point and flows southward to join the James River, which 

flows southeastward and discharges to the bay south of the 

Lower Peninsula.

Sea-Level Rise in Chesapeake Bay

Global mean sea level has risen 10 to 15 cm over the 

last 100 years (Ayers and others, 1994) and the rate from 

1993 to 2003 has been reported at 3.1 millimeters per year 

(mm/yr; Intergovernmental Panel on Climate Change, 2007). 

The measured rate of rise along the east coast of the United 

States (table 1) relative to land surface has been greater than 

the GMSL rise because of local land subsidence (Hull and 

Titus, 1986). 

Relative sea-level rise refers to the change in sea level 

relative to the elevation of the adjacent land, which can also 

subside or rise as a result of natural and human-induced factors. Relative sea-level changes include both global sea-level 

rise and changes in the vertical elevation of the land surface. 

Land surface of southeastern Virginia is sinking because of 

isostatic rebound to the north from the most recent glaciation. 

In addition, land subsidence from groundwater withdrawal in 

southeastern Virginia has been documented (Pope and 

Burbey, 2004). In this report, “sea-level rise” refers to relative 

sea-level rise.

In the mid-to-upper Chesapeake Bay region, local 

sea-level rise averages between 3.1 and 3.5 mm/yr. Farther 

south in the lower Chesapeake Bay region, local sea-level 

rise is higher, averaging 3.6 to 7.0 mm/yr (Boon and others, 

2008). The highest rate of sea-level rise for the east coast, 

4.42 mm/yr, is reported for Hampton Roads, Va. (table 1). At 

Sewells Point, Va., a tidal gage indicates that average sea level 

has risen at a rate of about 4.44 mm/yr from 1927 through 

2006 (fig. 5). 

The magnitude of the effects of climate change and 

variability in Chesapeake Bay will be influenced in large part 

through changes of physical processes, such as precipitation, 

wind, tides, and freshwater river discharge to the bay. The 

Table 1. Rates of relative sea-level rise for selected long-term 

tidal gages on the Atlantic coast of the United States. 

[For comparison, the global average rate of sea-level rise is 1.7 millimeters per 

year (mm/yr; from Williams and others, 2009); ±, plus or minus]

Station Rate of sea-level 

rise (mm/yr)

Time span of 

record

Eastport, Maine 2.12 ± 0.13 1929–1999

Portland, Maine 1.91 ± 0.09 1912–1999

Seavey Island, Maine 1.75 ± 0.17 1926–1999

Boston, Massachusetts 2.65 ± 0.10 1921–1999

Woods Hole, Massachusetts 2.59 ± 0.12 1932–1999

Providence, Rhode Island 1.88 ± 0.17 1938–1999

Newport, Rhode Island 2.57 ± 0.11 1930–1999

New London, Connecticut 2.13 ± 0.15 1938–1999

Montauk, New York 2.58 ± 0.19 1947–1999

Willets Point, New York 2.41 ± 0.15 1931–1999

The Battery, New York 2.77 ± 0.05 1905–1999

Sandy Hook, New Jersey 3.88 ± 0.15 1932–1999

Atlantic City, New Jersey 3.98 ± 0.11 1911–1999

Philadelphia, Pennsylvania 2.75 ± 0.12 1900–1999

Lewes, Delaware 3.16 ± 0.16 1919–1999

Baltimore, Maryland 3.12 ± 0.08 1902–1999

Annapolis, Maryland 3.53 ± 0.13 1928–1999

Solomons Island, Maryland 3.29 ± 0.17 1937–1999

Washington, D.C. 3.13 ± 0.21 1931–1999

Hampton Roads, Virginia 4.42 ± 0.16 1927–1999

Portsmouth, Virginia 3.76 ± 0.23 1935–1999

Wilmington, North Carolina 2.22 ± 0.25 1935–1999

Charleston, South Carolina 3.28 ± 0.14 1921–1999

Fort Pulaski, Georgia 3.05 ± 0.20 1935–1999

Fernandina Beach, Florida 2.04 ± 0.12 1897–1999

Mayport, Florida 2.43 ± 0.18 1928–1999

Miami, Florida 2.39 ± 0.22 1931–1999

Key West, Florida 2.27 ± 0.09 1913–1999
6 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

physical processes will mediate change through dynamics that 

amplify or suppress rates and magnitudes of change. A recent 

article by Najjar and others (2010) reviews the potential effect 

of climate change on Chesapeake Bay. On the basis of current 

understanding, they find that: (1) sea level will rise 0.7 to 

1.6 m by the end of the 21st century; (2) precipitation amount 

is likely to increase in the winter and spring; (3) precipitation intensity is likely to increase; and (4) droughts are likely 

to increase in both frequency and duration. The Hampton 

Roads Planning District Commission confirms that climate 

change could affect water resources significantly in the region 

(MacFarlane and Walberg, 2010).

Estuaries are vertically stratified, with denser more saline 

water lying below less dense and less saline water. Because 

of interactions of tides and freshwater inflow, this difference 

in density produces a two-layered flow situation, a common 

characteristic of estuaries. The denser saline bottom water 

enters the estuary from Chesapeake Bay and flows upstream, 

whereas the less dense surface waters, dominated by freshwater discharge, flow downstream toward the bay. Salinity 

variations throughout Chesapeake Bay have been shown to be 

strongly tied to river discharge (Schubel and Pritchard, 1986). 

In turn, Chesapeake Bay estuaries exhibit large seasonal 

variations in salinity (represented by chloride concentration 

in fig. 6). 

Simple models are able to accurately predict monthly 

average salinity throughout the mainstem of the bay from the 

flow of the Susquehanna River (Gibson and Najjar, 2000). 

A clear signal of salinity change in Chesapeake Bay from 

sea-level rise was detected by Hilton and others (2008), and a 

recent study indicates that salinity in the bay has the potential 

to increase by 2 ppt (Najjar and others, 2010). No detailed 

studies of potential effects of salinity-front migration as a 

result of sea-level rise have been performed on any tributaries that discharge to the bay. When and where the saline water 

displaces the freshwater is of great interest to a wide variety of 

stakeholders. 

Salinity variability in Chesapeake Bay estuaries is monitored by a number of organizations, including the Virginia 

Department of Environmental Quality (DEQ), the Virginia 

Institute of Marine Science (VIMS), the City of Newport 

News, and the Chesapeake Bay Program. DEQ has been 

collecting specific conductance and salinity data at multiple 

locations and at varying depths in the York River estuary 

since 1979, and VIMS has collected salinity data at 6-minute 

intervals at the mouth of the York River estuary since 1986. 

The City of Newport News has monitored specific conductance and chloride concentrations along the Chickahominy 

River at about 10 locations (some sites have been discontinued 

and others added) since 1997. The Chesapeake Bay Program 

(http://www.chesapeakebay.net/) has overseen the majority of 

the salinity monitoring in and around the bay since 1984.

Sea-Level Rise Scenarios

This report does not provide a forecast of future rates 

of sea-level rise. Rather, the implications of three reasonable 

estimates of sea-level rise scenarios over the next century were 

evaluated. A recent U.S. report (Climate Change Science Program, 2009) synthesized an enormous amount of climatic and 

oceanic modeling and proposed three sea-level rise scenarios 

for the 21st century for the mid-Atlantic region. The scenarios 

were developed from a combination of the 20th century sealevel rise rate and either a 2- or 7-mm/yr increase in global sea 

level, and are as follows:

• Scenario 1: The 20th century rate, which is generally 

3 to 4 mm/yr in the mid-Atlantic region (30 to 40 cm 

total by the year 2100);

• Scenario 2: The 20th century rate plus 2 mm/yr acceleration (up to 50 cm total by 2100); and

• Scenario 3: The 20th century rate plus 7 mm/yr acceleration (up to 100 cm total by 2100).

Scenario 1 assesses the effect if future sea-level rise 

occurs at the same rate as was observed over the 20th century 

at a particular location. Scenarios 1 and 2 are within the range 

Figure 5. Historic sea-level rise at Sewells Point, 

Virginia, 1927–2006 (National Oceanic and Atmospheric 

Administration, 2010).

190019101920193019401950196019701980199020002010

0.45

0.50

0.30

0.15

0

–0.15

–0.30

–0.45

–0.60

Sea-level change, in meters

Year

Sewells Point, Virginia 4.44 +/– mm/yr

Monthly mean sea level with the 

average cycle removed

Linear trend

Upper 95% confidence interval

Lower 95% confidence interval

Source: NOAA

1/1/1999 1/1/2000 1/1/2001 1/1/2002 1/2/2003 1/2/2004

Chloride concentration, in milligrams per liter

0

50

100

150

200

250

300

350

500

450

400

Figure 6. Chloride concentration at Walkers Dam on 

the Chickahominy River, 1999–2004.
Hydrodynamic Models 7

of those reported by IPCC (2007). Scenario 3 exceeds the 

IPCC scenario range by up to 40 cm by 2100. Higher estimates on the basis of possible warmer air temperature have 

been suggested by Chand and others (2009), although no consensus on the likely upper bound of GMSL currently exists. 

The three sea-level rise scenarios bracket the current 

scientific research relating to mid-Atlantic sea-level rise. As 

such, rises of 30, 50, and 100 cm were selected for the modeling component of this study, and they are referred to as the 

30-cm, 50-cm, and 100-cm scenarios, respectively. Temporal 

variability is an important consideration, because years with 

lower-than-normal river flow (drought conditions) will allow 

the salinity front to migrate farther upstream as sea level rises. 

Years with higher-than-normal river flow, however, will counteract upstream salinity movement.

Hydrodynamic Models 

The Virginia Institute of Marine Science developed a 

numerical model for Chesapeake Bay and parts of its Virginia 

tributaries. The model has been applied to a wide range of 

environmental studies in the Chesapeake Bay system and 

other estuarine systems (Hamrick, 1992; Sisson and others, 

1997; Shen and Haas, 2004; Shen and Lin, 2006). The simulator used to develop the Chesapeake Bay model is called the 

Three-Dimensional Hydrodynamic-Eutrophication Model 

(HEM-3D). The Environmental Fluid Dynamics Code makes 

up the hydrodynamic part of the HEM-3D model (Hamrick, 

1992; Park and others, 1995) and resembles the widely used 

Blumberg Mellor model (Blumberg and Mellor, 1987) in both 

the physics and the computational schemes. The full hydrodynamic shallow-wave equations are solved in three dimensions. 

The model is capable of simulating density and topographically induced circulation; tidal and wind-driven flows; and 

spatial and temporal distributions of salinity, temperature, 

suspended-sediment concentration, and conservative tracers. 

The model solves the three-dimensional continuity and freesurface equations of motion. The Mellor and Yamada level 

2.5 turbulence closure scheme was implemented in the model 

(Mellor and Yamada, 1982; Galperin and others, 1988). The 

model uses stretched (or sigma) vertical coordinates and Cartesian (or curvilinear) orthogonal horizontal coordinates. 

The modeling done for this project built upon previously developed models of the York and James Rivers and 

the Chesapeake Bay. A nested-grid modeling approach was 

used to simulate salinity with sufficient resolution while not 

sacrificing computational efficiency. HEM-3D was used to 

simulate tides, tidal currents, and salinity for Chesapeake Bay, 

creating boundary conditions for the York and James Rivers. 

To reduce the influence of the boundary conditions on the interior model domain, a large domain model that encompasses 

both the Chesapeake Bay mainstem and tributaries was used 

to simulate salinity changes from sea-level rise in Chesapeake 

Bay. The model uses a high-resolution grid placed in the main 

channel of the bay and relatively coarse grids in the tributaries 

(fig. 7). This grid configuration allows the model to simulate 

estuarine dynamics accurately and provide boundary conditions for high-resolution models developed for the York River 

and the Chickahominy/James River. The Chesapeake Bay 

model consists of 8,932 horizontal grids with 20 vertical layers. The period of simulation for the purpose of this study was 

10 years, from 1998 through 2007.

Model Limitations

The modeling scenarios do not consider future changes 

in freshwater flows in the York, James, or Chickahominy 

Rivers. Generally, scientists estimate that the eastern United 

States will receive more precipitation because of climate 

change (Brekke and others, 2009) and that individual storms 

in the Chesapeake Bay area will become more intense (Najjar and others, 2010). In addition, the modeling scenarios do 

not consider future increases in the salinity of the ocean or at 

the mouth of Chesapeake Bay, both of which are expected to 

occur with climate change (MacFarlane and Walberg, 2010).

Because of the nested modeling approach, any errors that 

occur in the Chesapeake Bay model propagate to the York 

and Chickahominy/James Rivers. Given that there are no 

daily observations at the mouth of the Chesapeake Bay and 

that wind forcing at one station was used for both the entire 

York and Chickahominy/James Rivers, some discrepancies 

between the predicted and observed salinity occur for parts of 

the simulations. A sensitivity analysis of the Chickahominy 

River model was performed (appendix). The sensitivity 

analysis indicated that the model was most sensitive to a 

decrease in river discharge and change of salinity concentration at the open boundary. The model also is sensitive to wind 

and change of bottom roughness. Testing an increase in river 

discharge or an increase in boundary salinity, however, were 

some of the alternatives not attempted.

York River Model

The existing York River model (Shen and Haas, 2004), 

which includes the Pamunkey and Mattaponi Rivers that form 

the York River, was modified for this study. The model, modified by deepening the bathymetry of the river, includes 3,839 

horizontal grid cells with 8 vertical layers. The grid scale 

ranges from 250 to 800 m in the York River and was explicitly linked to the coarse-grid tributary part of the Chesapeake 

Bay model (fig. 8). The hourly time-series outputs of salinity 

and tide (surface elevation) from the bay model near the York 

River mouth were used to force the York River model. The 

timestep used for the York River model was 30 seconds. For 

freshwater discharge, the upstream boundaries of the model 

were the USGS stream gages on the Mattaponi (USGS gage 

01674500) and Pamunkey (USGS gage 01673000) Rivers. 

Hourly wind data at Sewells Point from 1998 to 2003, and 

data at Yorktown from 2004 to 2007, were used as wind forcing (fig. 4). Monthly salinity data used for model calibration 

were obtained from the Chesapeake Bay Program.
8 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

0 20 40 MILES

0 20 40 KILOMETERS

N

Figure 7. Large domain model of Chesapeake Bay. The locations of the linkages of the 

Chesapeake Bay model with the York River and James River models are denoted by the bold 

red line at the mouth of each river.
Model Results 9

Chickahominy River Model

The existing model for the James River consists of a 

high-resolution model grid with 4,715 horizontal grid cells and 

8 vertical layers (Shen and others, 1999; Shen and Lin, 2006). 

The Chickahominy River model was developed for this study 

with 1,158 horizontal grids and 8 vertical layers (fig. 9). The 

James River model was explicitly linked to the Chickahominy 

River model. The resulting Chickahominy/James River 

model was forced by the outputs of tide and salinity from the 

Chesapeake Bay model. The time step for the Chickahominy/

James River model was 20 seconds. For freshwater discharge, 

the upstream boundaries of the model were the USGS stream 

gages on the James (USGS gage 02037500), Appomattox

(USGS gage 02040000), and Chickahominy (USGS gage 

02042500) Rivers. Hourly wind data at Sewells Point from 

1998 to 2003 and data at Yorktown from 2004 to 2007 were 

used as wind forcing (fig. 4). 

Model Results

Results of the model simulations are shown for a no-rise 

scenario and the three sea-level rise scenarios. Results are presented relative to a “typical” year for river discharge in southeastern Virginia. The discharge record for the James River 

near Richmond (USGS gage 02037500) for calendar years 

1990 through 2009 was used to determine a “typical” year, a 

Figure 8. Nested-grid model of the York River.

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

N
10 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

“wet” year, and a “dry” year. The annual mean discharge for 

this time interval indicated that a typical year was 2005, a wet 

year was 2003, and a dry year was 2002 (table 2).

York River 

Results from the York River simulations are presented for 

the location at the confluence of the Mattaponi and Pamunkey 

Rivers (fig. 4), referred to as the “head of the York estuary.” At 

this location, data were recorded showing the number of days 

from June 1 through December 31 that salinity was predicted 

to exceed 0.1 ppt (100 mg/L TDS). This 7-month (214-day) 

period was chosen, because river flow in the southeastern 

Virginia region tends to decline during the second half of the 

calendar year. This decline allows the model to simulate a 

“worst-case scenario” with respect to saltwater migration into 

the estuary. During both a typical and a dry year at this location, salinity is expected to exceed 0.1 ppt on each of the 214 

days (table 3). In contrast, during a wet year when river flow 

is higher, 0.1 ppt of salinity is simulated as being reached a 

fewer number of days for the no-rise scenario (183 days) and 

the 30- and 50-cm rise scenarios (201 and 211 days, respectively), but simulated to exceed 0.1 ppt for all of the 214 days 

for the 100-cm rise scenario (table 3).

The 10-year time-series simulated salinity data from the 

no-rise scenario and the three sea-level rise scenarios indicated 

that salinity is highest during a dry year (2002) and that salinity is projected to increase as sea level rises, at the surface of 

the water as well as at depth (fig. 10). In contrast, a wet year 

(2003) decreases the salinity substantially (fig. 10).

Cross sections of average salinity simulated at the head 

of the York estuary are shown for July and August (fig. 11), 

September and October (fig. 12), and November and December (fig. 13); the scale for salinity is not uniform for all panels 

in these figures. The cross section (A–A′) is viewed looking 

downstream (the left side of the section is the northeast side of 

the river).

0 10 20 Miles

0 10 20 Kilometers

0 2 4 Miles

0 2 4 Kilometers

N

James

Chickahominy

River

River

84.60 km

73.09 km

18.54 km River mouth

10.45 km

48.10 km

LE5.1

30.93 km

LE5.2

62.77 km

RET5.1

RET5.2

Figure 9. Nested-grid model of the James and Chickahominy Rivers. The location of the linkage of the James River and 

Chickahominy River models is denoted by the bold red line at the mouth of the Chickahominy River.
Model Results 11

Despite month, year, or amount of sea-level rise, the 

most saline water in all cases is in the deepest part of the 

channel and the least saline water is on the surface of the 

southwest side of the river (figs. 11, 12, 13). The southwest 

side of the river is dominated by discharge from the Pamunkey River, which has a larger drainage basin (3,812 square 

kilometers, km2

) than that of the Mattaponi River (2,362 km2). 

Nevertheless, with sea-level rise, salinity increases even in the 

southwest side of the river. Salinity is greatly reduced during a 

wet year (2003), even at depth. The primary difference among 

the three figures is that September and October show the most 

saline conditions, followed by July and August, with the least 

salinity in November and December.

Mean salinity for October is shown along the river moving upstream from the mouth to the head of the estuary for 

2002 (dry year; fig. 14A) and 2005 (typical year; fig. 14B). 

Figure 14 was created by running the model, and for each river 

km, recording the mean salinity for the 31 days of October at 

that point along the river. This process was followed for the 

no-rise scenario and each of the three sea-level rise scenarios. 

Salinity is similar at the mouth of the river for both 

years (fig. 14). Farther upstream, however, salinity is higher 

for a dry year (2002; fig. 14A) than for a typical year (2005; 

fig. 14B), again demonstrating the role of river flow in pushing the salinity back toward the bay. For the 50-cm sea-level 

rise scenario, salinity is 15 ppt at river km 39 for 2005, and 

the model predicted the same salinity at river km 45 for 2002, 

indicating a 6-km upstream migration. 

The increase in salinity for each sea-level rise scenario 

is somewhat uniform spatially, with the largest change at the 

head of the estuary. For both years, at the head of the York 

estuary (river km 52), a large increase in mean salinity is 

predicted for each sea-level rise scenario (fig. 14). This will 

greatly alter the existing water-quality gradients between the 

brackish water and freshwater. 

Chickahominy River 

Results for the Chickahominy River simulations are 

presented for just downstream of Walkers Dam (fig. 4), the 

approximate location of the municipal drinking-water intake 

for the City of Newport News. During a wet year at this location, salinity is not expected to exceed 0.1 ppt for any of the 

sea-level rise scenarios (table 4). During a typical year, salinity 

may exceed 0.1 ppt for fewer than 100 days (table 4). In contrast, during a dry year when river flow is lower, salinity may 

Table 2. Mean annual discharge for the James River 

near Richmond (for calendar years 1990 through 2009).

[USGS gage 02037500; records provided by Virginia Department 

of Environmental Quality, Water Division. m3/s, cubic meters per 

second; shaded dates are the years for which results are reported]

Chronological order Lowest-to-highest order

Year

Mean annual 

discharge,

m3

/s

Year

Mean annual 

discharge,

m3/s

1990 231 2002 102

1991 190 2001 103

1992 197 2008 116

1993 251 1999 124

1994 233 2000 133

1995 197 2007 161

1996 321 1997 181

1997 181 1991 190

1998 307 2006 191

1999 124 2005 194

2000 133 1992 197

2001 103 1995 197

2002 102 2009 204

2003 414 1990 231

2004 269 1994 233

2005 194 1993 251

2006 191 2004 269

2007 161 1998 307

2008 116 1996 321

2009 204 2003 414

Table 3. Number of days that salinity is predicted to 

exceed 0.1 parts per thousand at the head of the York 

estuary from June 1 to December 31 (total 214 days) of the 

year indicated for the no-rise scenario and the three sealevel rise scenarios.

[cm, centimeter]

Model 

scenario

Dry year 

2002

Wet year 

2003

Typical year 

2005

No rise 214 183 214

30-cm rise 214 201 214

50-cm rise 214 211 214

100-cm rise 214 214 214
12 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

0

2

4

6

8

10

12

14

16

A

0

2

4

6

8

10

12

14

16

18

B

0

2

4

6

8

10

12

14

16

1/2/19981/2/19991/2/20001/2/20011/2/20021/2/20031/2/20041/2/20051/2/20061/2/20071/2/2008

Salinity, in parts per thousand

C

0

2

4

6

8

10

12

14

16

18

20

1/2/19981/2/19991/2/2000

1/2/2001

1/2/20021/2/20031/2/20041/2/20051/2/20061/2/2007

1/2/2008

D

EXPLANATION

No rise

30-cm rise

EXPLANATION

50-cm rise

100-cm rise

EXPLANATION

No rise

30-cm rise

EXPLANATION

50-cm rise

100-cm rise

Figure 10. Time series of surface and bottom simulated salinity at the head of the York estuary for three 

sea-level rise scenarios, 1998–2008; A, no rise and 30-cm rise at surface; B, 50-cm rise and 100-cm rise at 

surface; C, no rise and 30-cm rise at bottom; and D, 50-cm rise and 100-cm rise at bottom.
Model Results 13

No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

–1 11.8 3.8

5

6

5.5

5

4.5

4

8

7.5

7

6.5

6

4.5

4

3.5

7.6

8.5

9.4

9.2

9

8.8

8.6

8.4

8.2

11

10.5

10

8

7.5

7.4

7.2

7

6.8

6.6

6.4

3.6

3.4

3.2

3

2.8

2.6

11.6

11.4

11.2

11

12

13.2

13

12.8

12.6

12.4

14.6

14.4

14.2

14

13.8

12

12

12

11

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

0

200400600800

1,0001,2001,4001,6001,8002,000

0

200400600

800

1,000

1,2001,4001,6001,800

2,000

0

200400600800

1,000

1,200

1,4001,6001,8002,000

Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters

Figure 11. Cross sections (A–A’ on figure 4) of average simulated salinity at the head of the York estuary for July and August. 

Salinity units (right axis) in parts per thousand.
14 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

–1 12.8

3.8

4.8

5.5

5

4.5

7.5

7

6.5

6

4.6

4

4.2

4.4

3.6

3.8

7.6

11

12

11.5

11

10.5

13

12.5

12

10.5

10

7.4

7.2

7

6.8

6.6

6.4

3.6

3.4

3.2

3

2.8

12.6

12.4

12.2

12

13.8

14

13.8

13.6

13.4

15.2

15

14.8

14.6

13.4

13.2

13

12.8

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

0

200400600800

1,0001,2001,4001,6001,8002,000

0

200400600

800

1,000

1,2001,4001,6001,800

2,000

0

200400600800

1,000

1,200

1,4001,6001,8002,000

Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters

Figure 12. Cross sections (A–A’ on figure 4) of average simulated salinity at the head of the York estuary for September 

and October. Salinity units (right axis) in parts per thousand.
Model Results 15

Figure 13. Cross sections (A–A’ on figure 4) of average simulated salinity at the head of the York estuary for November 

and December. Salinity units (right axis) in parts per thousand.

No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

–1

8.5 2

3

3.5

3

2

2.5

6

6.5

5.5

4.5

4

5

3.5

2

2.5

8

9

9.5

10

9.5

9

8.5

8

12

12.5

11

10.5

11.5

10

8.5

8

7.5

7.5

7

6.5

6

1.8

1.6

1.4

1.5

8

7.5

7

9.5

10

9.5

9

8.5

12

11.5

11

10.5

10

9

8.5

8

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

–1

–2

–3

–4

–5

0

200400600800

1,0001,2001,4001,6001,8002,000

0

200

400600

800

1,000

1,2001,4001,6001,8002,000

0

200400600800

1,000

1,2001,4001,6001,8002,000

Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters
16 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

exceed 0.1 ppt for all three of the sea-level rise scenarios, with 

the number of days increasing with increasing sea-level rise 

(table 4). In addition to elevated salinity at the dam, overtopping of the dam by increasing tide levels is a drinking watersupply concern (table 5). 

The time-series salinity data for the no-rise scenario and 

the three sea-level rise scenarios suggest that salinity increases 

most dramatically with the highest sea-level rise scenario 

(fig. 15) and less so with lower rises at both the surface and 

the bottom of the river. For example, on October 2, 2005 (typical year), salinity at the surface for no rise is 0.005 ppt, and 

is 0.005, 0.014, and 2.46 ppt for a 30-, 50-, and 100-cm rise, 

respectively. Salinity is highest during a dry year (2002) and 

decreases substantially during a wet year (2003; fig. 15). For 

example, on October 2, 2002 (dry year), salinity at the surface 

for no rise is 0.695 ppt, and is 2.07, 2.96, and 5.50 ppt for a 

30-, 50-, and 100-cm rise, respectively. This simulation is in 

contrast to October 2, 2003 (wet year), when salinity at the 

surface is 0.014 ppt for all sea-level rise scenarios and for the 

no-rise scenario. For a 100-cm rise during a dry year, surface salinity greater than 1 ppt would endure for an 8-month 

period. These data suggest that sea-level rise will significantly 

affect the drinking-water supply intake. 

Salinity distributions for cross section B–B′, just downstream of Walkers Dam, are shown for average salinity for 

July and August (fig. 16); September and October (fig. 17); 

and November and December (fig. 18); the scale for salinity 

is not uniform for all panels in these figures. The cross section 

(B–B′) is viewed looking upstream (the left side of the section 

is the northwest side of the river). 

Despite month, year, or amount of sea-level rise, the most 

saline water in all cases is in the deepest part of the channel and the least saline water is on the surface of the river 

(figs. 16, 17, 18). Salinity is greatly reduced during a wet year 

(2003), even at depth. In a dry year with a 100-cm sea-level 

rise, however, average September and October salinity would 

increase nearly tenfold from 0.5 ppt with no rise to 5 ppt with 

a 100-cm rise. The primary difference among the three figures 

is that September and October show the most saline conditions, followed by July and August, with the least salinity in 

November and December.

Model simulations show that river discharge acts as a barrier to upstream salinity migration (fig. 19). Mean salinity for 

October is shown along the river moving upstream from the 

mouth of Chickahominy River for 2002 (dry year; fig. 19A) 

and 2005 (typical year; fig. 19B). Salinity is 4 ppt higher at the 

mouth of the river for the dry year (2002) than for the typical 

5

10

15

20

25

No rise

30-cm rise

50-cm rise

100-cm rise

ARiver mouth

5

10

15

20

25

0 10 20 30 40 50 60

Distance upstream of river mouth, in kilometers

Salinity, in parts per thousand

B

100-cm rise

50-cm rise

30-cm rise

No rise

River mouth

Head of

the

estuary 

Head of

the

estuary 

Figure 14. Effect of simulated sea-level rise scenarios on 

31-day mean salinity along the York River; A, October 2002, 

dry-year scenario; B, October 2005, typical-year scenario.

Table 4. Number of days that salinity is predicted to exceed 

0.1 parts per thousand at Walkers Dam on the Chickahominy 

River from June 1 to December 31 (total 214 days) of the year 

indicated for the no-rise scenario and the three sea-level rise 

scenarios. 

[cm, centimeter]

Model 

scenario

Dry year

2002

Wet year

2003

Typical year 

2005

No rise 69 0 2

30-cm rise 106 0 11

50-cm rise 131 0 20

100-cm rise 194 0 71

Table 5. Number of days that water from sea-level rise 

is predicted to overtop Walkers Dam on the Chickahominy 

River from June 1 to December 31 (total 214 days) of the year 

indicated for the no-rise scenario and the three sea-level rise 

scenarios. 

[cm, centimeter]

Model 

scenario

Dry year

2002

Wet year 

2003

Typical year 

2005

No rise 1 22 17

30-cm rise 44 133 120

50-cm rise 138 190 195

100-cm rise 214 214 214
Model Results 17

0

0.5

1

1.5

2

2.5

3

3.5

A

0

1

2

3

4

5

6

7

B

0

0.5

1

1.5

2

2.5

3

3.5

1/2/19981/2/19991/2/20001/2/20011/2/20021/2/20031/2/20041/2/20051/2/20061/2/20071/2/2008

Salinity, in parts per thousand

C

0

1

2

3

4

5

6

7

1/2/19981/2/19991/2/2000

1/2/2001

1/2/20021/2/20031/2/20041/2/20051/2/20061/2/2007

1/2/2008

D

EXPLANATION

No rise

30-cm rise

EXPLANATION

50-cm rise

100-cm rise

EXPLANATION

No rise

30-cm rise

EXPLANATION

50-cm rise

100-cm rise

Figure 15. Time series of simulated surface and bottom salinity at Walkers Dam on the Chickahominy 

River for three sea-level rise scenarios, 1998–2008; A, no rise and 30-cm rise at surface; B, 50-cm rise and 

100-cm rise at surface; C, no rise and 30-cm rise at bottom; D, 50-cm rise and 100-cm rise at bottom.
18 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

–1

0.015

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Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters

Figure 16. Cross sections (B–B’ on fig. 4) of average simulated salinity downstream of Walkers Dam on the Chickahominy 

River for July and August. Salinity units (right axis) in parts per thousand.
Model Results 19

No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

–1 0.6

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250300250

400

Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters

Figure 17. Cross sections (B–B’ on fig. 4) of average simulated salinity downstream of Walkers Dam on the Chickahominy 

River for September and October. Salinity units (right axis) in parts per thousand.
20 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

year (2005) for the no-rise scenario and for the three sea-level 

rise scenarios. For the 50-cm sea-level rise scenario, salinity 

is 4 ppt at river km 13 for 2005; the model predicted the same 

salinity at river km 28 for 2002, indicating a 15-km upstream 

migration for a dry year relative to a typical year. Near Walkers Dam, for a dry year (2002) salinity is predicted to more 

than double for all three sea-level rise scenarios, relative to a 

typical year (fig. 19). During a typical year near Walkers Dam, 

salinity is predicted to increase to 0.006 ppt, 0.07 ppt, and 

more than 2 ppt for the 30-, 50-, and 100-cm rise scenarios, 

respectively (fig. 19B). 

No rise 30-cm rise 50-cm rise 100-cm rise

Dry year

(2002)

Wet year

(2003)

Typical year

(2005)

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0.03

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250300250

400

Distance, in meters Distance, in meters Distance, in meters

Depth, in meters Depth, in meters Depth, in meters Depth, in meters

Figure 18. Cross sections (B–B’ on fig. 4) of average simulated salinity downstream of Walkers Dam on the Chickahominy 

River for November and December. Salinity units (right axis) in parts per thousand.

Figure 19. Effect of simulated sea-level rise scenarios on 31-day mean salinity along the Chickahominy River; 

A, October 2002, dry-year scenario; B, October 2005, typical-year scenario.

0

4

2

8

6

10

12

No rise

30-cm rise

50-cm rise

100-cm rise

ARiver mouth

0 5 10 15 20 25 30 35 40

Distance upstream of river mouth, in kilometers

0 5 10 15 20 25 30 35 40

Distance upstream of river mouth, in kilometers

Salinity, in parts per thousand

B

100-cm rise

50-cm rise

30-cm rise

No rise River mouth

Head of

the

estuary 

Head of

the

estuary 
Summary 21

Summary

Earth has a long history of a changing climate and, as a 

result, changing sea levels. Currently, sea level is rising along 

the Atlantic coast of the eastern United States at a rate higher 

than the global rate. Sea-level rise can affect coastal and 

estuarine areas in several ways, including causing increased 

damage from storms and flooding, changes in the existence 

and distribution of wetlands, and encroachment of saline water 

into estuaries and coastal aquifers. Of particular importance 

to drinking-water utilities is saline water that has migrated far 

enough upstream to affect drinking-water supplies.

One of the first steps in becoming a climate-ready utility 

is to define and understand how future changes in climate 

could affect local and regional water resources. The U.S. Geological Survey, in cooperation with the City of Newport News, 

Virginia, undertook a study to evaluate the effects of potential future sea-level rise on two Virginia estuaries. The study 

focused on the York River and Chickahominy/James River 

estuaries, which delineate Virginia’s Lower Peninsula. For 

the magnitude of potential sea-level rise for the mid-Atlantic 

region, the study relied on the U.S. Climate Change Science 

Program, which synthesized an enormous amount of climatic 

and oceanic modeling to propose three future sea-level rise 

scenarios for the 21st century. The scenarios were developed 

from a combination of the 20th century relative sea-level rise 

rate and either a 2 or 7 millimeter per year (mm/yr) increase in 

global sea level:

• Scenario 1: The 20th century rate, which is generally 3 

to 4 mm/yr in the mid-Atlantic region (30 to 40 centimeters (cm) total by the year 2100);

• Scenario 2: The 20th century rate plus 2 mm/yr acceleration (up to 50 cm total by 2100); and

• Scenario 3: The 20th century rate plus 7 mm/yr acceleration (up to 100 cm total by 2100). 

This report refers to the three scenarios as the 30-cm, the 

50-cm, and the 100-cm rise, respectively. The scenarios do not 

consider any future changes in freshwater flows in the York 

and Chickahominy/James Rivers.

Simulations were made by use of the Three-Dimensional 

Hydrodynamic-Eutrophication Model (HEM-3D), developed by the Virginia Institute of Marine Science. HEM-3D 

was used to simulate tides, tidal currents, and salinity for the 

Chesapeake Bay to produce boundaries for simulating these 

parameters for the York River and the Chickahominy/James 

River. To address salinity change from potential sea-level rise, 

a nested-grid modeling approach was used to accurately simulate salinity with sufficient resolution while not sacrificing 

computational efficiency. A sensitivity analysis of the model 

indicated that the model was most sensitive to a decrease 

in river discharge and change of salinity concentration at 

the open boundary. The model also is sensitive to wind and 

change of bottom roughness.

Model results for both estuaries indicated that high 

freshwater river flow was effective in pushing the salinity back 

toward Chesapeake Bay. The results also indicated that large 

increases in mean salinity are predicted for each sea-level rise 

scenario. Model results for both estuaries indicated that the 

months of September and October have the most saline conditions, followed by July and August, with the least salinity in 

November and December. These results are consistent whether 

the year is wet, dry, or typical, and whether sea level does not 

rise, or rises 30, 50, or 100 cm. 

For the 50-cm sea-level rise scenario on the York River 

during a typical year, the model simulation showed a salinity 

of 15 ppt at river km 39. During a dry year, the same salinity 

(15 ppt) was simulated at river km 45, which means that saltwater was shown to migrate 6 km farther upstream. The same 

was true of the Chickahominy River for the 50-cm sea-level 

rise scenario but to a greater degree; a salinity of 4 ppt was 

simulated at river km 13 during a typical year and at river km 

28 during a dry year, indicating that saltwater migrated 15 km 

farther upstream during a dry year.

Increases in mean salinity will greatly alter the existing 

water-quality gradients between the brackish water and freshwater. This is particularly important for the Chickahominy 

River, where a drinking-water-supply intake for the City of 

Newport News is located. The methodologies developed as 

part of this study are transferable to other tributary basins to 

the bay. The results of this study can be expanded and refined 

to assess the effect of sea-level rise throughout the Chesapeake 

Bay estuary.

Acknowledgments

The authors express their appreciation to Ron Harris, 

Chief of Water Resources of the Newport News Waterworks, 

who supported and guided this project to its successful 

completion. We thank Bo Hong, Virginia Institute of Marine 

Science, for conducting much of the estuarine modeling and 

processing the model results. We also appreciate the colleague 

reviews provided by Eric Swain and Paul Conrads, U.S. 

Geological Survey, of an earlier draft of the report.
22 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

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N

WALKERS DAM

Riverside Camp Chickahominy Haven

Rt 5 Bridge

Salinity Verification for Chickahominy River 25

Appendix

The appendix includes sections on Model Performance, 

Salinity Verification for the Chickahominy River model, and 

Model Sensitivity for the Chickahominy/James River model.

Model Performance

Model performance was evaluated using over 10 years 

of salinity observation data collected by the Chesapeake Bay 

Program. Monthly salinity data collected at different depths 

were downloaded from the Chesapeake Bay Program website 

(http://www.chesapeakebay.net). Modeled surface and bottom 

salinity at selected locations along the main channel of each 

estuary were examined. The salinity variation inside the estuary is highly dependent upon the river discharge into the lower 

Chesapeake Bay. A strong seasonal variation was observed, 

with elevated salinity in summer and lower salinity in spring. 

The evaluation of the model was focused on the model performance and its ability to simulate spring-neap and seasonal 

salinity variations, particularly during dry and wet years. The 

model simulations for seasonal and long-term salinity changes 

were consistent with actual observations. The stratification/

destratification processes shown by the observed data are 

reflected in the modeled time series results and indicated that 

model simulations of the estuarine circulation are consistent.

Salinity Verification for 

Chickahominy River

Simulated salinity data along the Chickahominy River 

were compared to data from four existing salinity observation 

stations operated by Newport News Waterworks (fig. 1-1). The 

observation data were collected about 0.3 m below the water 

Figure 1-1. Locations of 

salinity observation stations in 

the Chickahominy River.
26 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

surface. Model results for the surface and bottom and observations for salinity are shown for salinity monitoring stations 

at the Rt. 5 Bridge (fig. 1-2), Chickahominy Haven (fig. 1-3), 

Riverside Camp (fig. 1-4), and Walkers Dam (fig. 1-5). The 

model estimated the salinity at both the Rt. 5 Bridge and 

Chickahominy Haven stations reasonably well but slightly 

over estimated the salinity in a few cases farther upstream, at 

Riverside Camp and Walkers Dam. 

Model Sensitivity

Hydrodynamic model performance is dependent upon, 

among other things, the model calibration to parameters that 

numerically approximate the underlying physical processes 

and the forcing conditions used for driving the model at the 

open boundary. Both the eddy viscosity and diffusivity are key 

parameters for a hydrodynamic model. The hydrodynamic part 

Figure 1-2. Comparison of simulated and observed 

salinity at Rt. 5 Bridge station.

Figure 1-4. Comparison of simulated and observed 

salinity at Riverside Camp station.

Figure 1-5. Comparison of simulated and observed 

salinity at Walkers Dam station.

Figure 1-3. Comparison of simulated and observed 

salinity at Chickahominy Haven station.
Model Sensitivity 27

of the model uses the Mellor and Yamada level 2.5 turbulence 

closure scheme (Mellor and Yamada, 1982; Galperin and 

others, 1988) and computes both eddy viscosity and diffusivity based on transport of turbulent length and intensity. For 

bottom roughness, the model uses the logarithmic profile to 

compute the bottom shear stress based on prescribed bottom roughness values. Constant bottom roughness values of 

0.2 centimeter (cm) for the York River and 0.15 cm for the 

James River were used in the models based on the calibrations 

to surface elevations. The model used U.S. Geological Survey 

discharge data at the river boundary and National Oceanic and 

Atmospheric Administration wind data at the surface boundary. For the open-boundary condition at the mouth of each 

river, the model used tide and salinity data resulting from simulations by a large-domain Chesapeake Bay model. Any deviation of the forcing data from the real conditions can result in 

discrepancies between model simulations and observations.

To assess the model performance and model sensitivity 

with respect to model parameter and forcing conditions, four 

sensitivity tests were performed for the model simulation of 

the Chickahominy/James River for the year 2001. A model 

base case was formulated for the simulation run without 

changing parameters or boundary conditions, which is equivalent to model calibration. The four sensitivity tests were:

• Test 1: Decrease river discharge by 20 percent; 

• Test 2: Decrease salinity concentration at the open 

boundary by 15 percent; 

• Test 3: Increase bottom roughness by 100 percent;

• Test 4: Decrease wind forcing on the surface by 

100 percent.

Model sensitivity was evaluated with the Chickahominy/

James River model. Results of these sensitivity tests, however, 

should be representative for the model performance in all 

Chesapeake Bay tributaries. The model simulation started at 

day 300 in year 2000 with the forcings that were used for the 

model calibration and was run for 60 days. The forcings were 

changed starting January 1, 2001, and the model was run for 

one year. To test the sensitivity of bottom roughness, the value 

was changed and the model was run starting from day 300 of 

year 2000 and allowed to proceed 370 days. The results of the 

sensitivity tests were compared to those of the base case.

Sensitivity to River Discharge (Test 1)

To evaluate the model sensitivity to river discharge, 

time series of salinities at the “Chickahominy,” “LE5.1,” and 

“RET5.2” stations were compared (fig. 1-6A, B, C; see fig. 9 

in body of report for locations of the salinity stations). As 

expected, decreasing river discharge by 20 percent allowed the 

salinity to migrate farther into the estuary. The salinity at the 

Chickahominy station increased about 1.0–1.5 parts per thousand (ppt) at both the surface and bottom (fig. 1-7). Salinity 

is more sensitive to the decrease of river discharge along the 

main channel of the James River, where the maximum salinity 

change was about 5 ppt. The 2 ppt salinity contour moved 

upstream about 5 kilometers (km) relative to the base case 

(fig. 1-8 Base Case, and Test 1). The results of Test 1 suggest 

that the salinity distribution is very sensitive to river discharge. 

Sensitivity to Salinity Open-Boundary Condition 

(Test 2)

The accuracy of salinity simulations is highly dependent 

upon the salinity specification at the model open-boundary 

condition. The hourly model salinity boundary conditions 

were obtained from a large Chesapeake Bay model. The 

Chesapeake Bay model open boundary is located far away 

from the bay mouth and was specified using climatology 

salinity conditions, which are the long-term monthly mean 

salinity concentrations obtained from a global model output. 

The Chesapeake Bay model salinity calibration shows that the 

model is not very sensitive to the salinity specification at the 

open boundary. This may not be true, however, when simulating tributaries using the nested-grid modeling approach. To 

test this, a sensitivity analysis was conducted with the salinity 

concentration at the model open boundary condition reduced 

by 15 percent. The model is very sensitive to the salinity open 

boundary specification (fig. 1-6). With a 15-percent decrease 

in salinity concentration at the open boundary condition, the 

salinity decreased substantially along the James River. The 

maximum salinity difference was up to 4 ppt in the Chickahominy River, and it was more than 6 ppt within the channel 

of the James River (fig. 1-7). The salinity change along the 

James River is much greater than the 15 percent that was used 

for the change of salinity near the mouth. The mean salinity 

contour of 2 ppt moved downstream by approximately 10 km 

(figure 1-8A, and C). 

Sensitivity to Bottom Roughness (Test 3)

Bottom roughness is the only estimated parameter used 

during model calibration to surface elevation. A constant 

roughness of 0.2 cm was used in the James River model. The 

model sensitivity to a change in bottom roughness was conducted by doubling the value. The model is very sensitive to 

the bottom roughness and its effects on tidal propagation along 

the estuary (fig. 1-9 Base Case, and Test 1). With an increase 

of the bottom roughness, the model results underestimated 

tide in the estuary. The modeled salinity concentration should 

be very sensitive to the change of roughness in the James 

and Chickahominy Rivers. The salinity in the Chickahominy 

River could decrease by a maximum of 2 ppt if roughness is 

increased to 0.4 cm. The model is more sensitive to bottom 

roughness where the water depth is shallow.
28 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

Figure 1-6A. Comparison of model results between Base 

Case, Test 1 (decrease river discharge by 20 percent), and 

Test 2 (decrease salinity concentration at the open boundary 

by 15 percent) at the Chickahominy station; A, surface, 

B, bottom.

Figure 1-6B. Comparison of model results between Base 

Case, Test 1 (decrease river discharge by 20 percent), and 

Test 2 (decrease salinity concentration at the open boundary 

by 15 percent) at the LE5.1 station; A, surface, B, bottom. 

Figure 1-6C. Comparison of model results between Base 

Case, Test 1 (decrease river discharge by 20 percent), and 

Test 2 (decrease salinity concentration at the open boundary 

by 15 percent) at the RET5.2 station; A, surface, B, bottom. 
Model Sensitivity 29

Figure 1-7A. Time series of salinity differences between 

the Base Case and model sensitivity Tests 1 through 4 at the 

Chickahominy station at the surface; A, Test 1, B, Test 2, 

C, Test 3, and D, Test 4. 

Figure 1-7B. Time series of salinity differences between 

the Base Case and model sensitivity Tests 1 through 4 at the 

Chickahominy station at the bottom; A, Test 1, B, Test 2, 

C, Test 3, and D, Test 4. 

Figure 1-7C. Time series of salinity differences between 

the Base Case and model sensitivity Tests 1 through 4 at the 

RET5.2 station at the surface; A, Test 1, B, Test 2, C, Test 3, 

and D, Test 4.

Figure 1-7D. Time series of salinity difference between 

Base Case and model sensitivity Tests 1 through 4 at the 

RET5.2 station at the bottom; A, Test 1, B, Test 2, C, Test 3, 

and D, Test 4. 
30 Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay

Figure 1-7E. Time series of salinity differences 

between the Base Case and model sensitivity Tests 1 

through 4 at the LE5.1 station at the surface; A, Test 1, 

B, Test 2, C, Test 3, and D, Test 4. 

Figure 1-7F. Time series of salinity differences 

between the Base Case and model sensitivity Tests 1 

through 4 at the LE5.1 station at the bottom; A, Test 1, 

B, Test 2, C, Test 3, and D, Test 4.

Base Case

Test 1

Test 2

Test 3

Test 4

Figure 1-8. James River mean salinity distribution 

(June and July) for the Base Case and sensitivity 

Tests 1 through 4. Salinity units (right axis) in parts 

per thousand.
Model Sensitivity 31

Sensitivity to Wind Forcing (Test 4)

Wind acting on the surface generates vertical mixing near 

the surface, particularly for an upstream wind. In contrast, a 

downstream wind can increase estuarine circulation. Gong and 

others (2009) show that wind reduces estuarine circulation, 

thus reducing salinity intrusion. Results of Test 4 indicate that 

salinity intruded farther upstream because of the increase of 

estuarine circulation without wind (fig. 1-9). Salinity increased 

in both the tributary and the main channel of the James River. 

Figure 1-9A. Comparison of model results between the Base 

Case, Test 3 (doubling of the bottom roughness value), and Test 4 

(turning off wind forcing at surface) at the Chickahominy station; 

A, surface, B, bottom. 

Figure 1-9B. Comparison of model results between the Base 

Case, Test 3 (doubling of the bottom roughness value), and 

Test 4 (turning off wind forcing at surface) at the RET5.1 station; 

A, surface, B, bottom. 

Figure 1-9C. Comparison of model results between the 

Base Case, Test 3 (doubling of the bottom roughness), and 

Test 4 (turning off wind forcing at surface) at the LE5.2 station; 

A, surface, B, bottom. 

The difference was up to 3 ppt in the Chickahominy River and 

more than 5 ppt in the James River. 

The model sensitivity tests indicated that the numerical 

model performance highly depends on the model calibration 

and forcings used to drive the model. Large uncertainties 

are involved in these forcing data as a result of missing data, 

insufficient spatial coverage, and omission of local freshwater 

discharge, therefore discrepancies between model results and 

actual observations should be expected.

For additional information regarding this publication, contact:

Director

USGS Virginia Water Science Center

1730 East Parham Road

Richmond, VA 23228

(804) 261-2600

email: dc_va@usgs.gov

Or visit the USGS Virginia Water Science Center Web site at:

http://va.water.usgs.gov

Prepared by:

USGS Science Publishing Network

Raleigh Publishing Service Center

3916 Sunset Ridge Road

Raleigh, NC 27607


Rice, Bennett, and Shen—Simulated Changes in Salinity in the York and Chickahominy Rivers from Projected Sea-Level Rise in Chesapeake Bay—Open-File Report 2011–1191

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