U.S. Department of the Interior

U.S. Geological Survey

Pamphlet to accompany

Scientific Investigations Map 3244

Flood-Inundation Maps for the Saluda River from 

Old Easley Bridge Road to Saluda Lake Dam 

near Greenville, South Carolina
Cover. Photograph of Saluda Lake Dam and Saluda Dam Road (S-63) crossing the Saluda River near Greenville, South Carolina. 

Photograph by Wladmir Guimaraes, U.S. Geological Survey.
Flood-Inundation Maps for the Saluda River from 

Old Easley Bridge Road to Saluda Lake Dam 

near Greenville, South Carolina

By Stephen T. Benedict, Andral W. Caldwell, and Jimmy M. Clark 

Pamphlet to accompany 

Scientific Investigations Map 3244

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Benedict, S.T., Caldwell, A.W., and Clark, J.M., 2013, Flood-inundation maps for the Saluda River from Old Easley 

Bridge Road to Saluda Lake Dam near Greenville, South Carolina: U.S. Geological Survey Scientific Investigations 

Map 3244, 15 sheets, 7-p. pamphlet.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Study Area Description........................................................................................................................3

Previous Studies ...................................................................................................................................4

Constructing Water-Surface Profiles.........................................................................................................4

Hydrologic and Steady-Flow Data .....................................................................................................4

Topographic/Bathymetric Data ..........................................................................................................4

Energy Loss Factors .............................................................................................................................5

Model Calibration and Performance .................................................................................................5

Development of Water-Surface Profiles...........................................................................................5

Inundation Mapping ......................................................................................................................................6

Saluda River, South Carolina, Flood-Inundation Maps on the Internet .......................................6

Disclaimer for Flood-Inundation Maps .............................................................................................6

Uncertainties and Limitations for Use of Flood-Inundation Maps................................................6

Summary..........................................................................................................................................................7

References Cited............................................................................................................................................7

Figure

1. Map showing locations of study reach for the Saluda River, U.S. Geological Survey 

streamgage, and National Weather Service forecast point .................................................2

Tables

1. Site information for the U.S. Geological Survey streamgage on the study reach, 

Saluda River near Greenville, South Carolina..........................................................................3

2. Estimates of peak streamflow for a 1.0-percent annual exceedance 

probability for selected locations on the Saluda River ..........................................................4

3. Stages, water-surface elevations, and corresponding streamflow estimates 

based on rating no. 11 at the U.S. Geological Survey streamgage 

station 02162500, Saluda River near Greenville, South Carolina ..........................................5
iv

Sheets 

[Sheets and additional materials are available online at http://pubs.usgs.gov/sim/3244/]

1–15. Maps showing flood-inundation for the Saluda River from Old Easley Bridge Road to 

Saluda Lake Dam near Greenville, South Carolina, corresponding to a stage at 

U.S. Geological Survey streamgage Saluda River near Greenville, 

South Carolina (02162500)—

 1. Stage of 6.0 feet and an elevation of 803.2 feet

 2. Stage of 7.0 feet and an elevation of 804.2 feet

 3. Stage of 8.0 feet and an elevation of 805.2 feet

 4. Stage of 9.0 feet and an elevation of 806.2 feet

 5. Stage of 10.0 feet and an elevation of 807.2 feet

 6. Stage of 11.0 feet and an elevation of 808.2 feet

 7. Stage of 12.0 feet and an elevation of 809.2 feet

 8. Stage of 13.0 feet and an elevation of 810.2 feet

 9. Stage of 14.0 feet and an elevation of 811.2 feet

 10. Stage of 15.0 feet and an elevation of 812.2 feet

 11. Stage of 16.0 feet and an elevation of 813.2 feet

 12. Stage of 17.0 feet and an elevation of 814.2 feet

 13. Stage of 18.0 feet and an elevation of 815.2 feet

 14. Stage of 19.0 feet and an elevation of 816.2 feet

 15. Stage of 20.0 feet and an elevation of 817.2 feet
v

Conversion Factors and Datums

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2

) 0.0929 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Elevation, as used in this report, refers to the distance above NAVD 88.

Stage, as used in this report, is the height of the water surface above an arbitrary datum 

established at the gage (gage datum).

Acronyms

AHPS Advanced Hydrologic Prediction Service

DFIRM Digital Flood Insurance Rate Map

FEMA Federal Emergency Management Agency

FIS Flood Insurance Study

GIS geographic information system

LiDAR light detection and ranging

NWS National Weather Service

RMSE Root Mean Square Error

USGS U.S. Geological Survey

Acknowledgments

The authors wish to thank South Carolina Electric and Gas for funding the operation and 

maintenance of the gage used for this study. Special thanks are given to Sara Brown of the 

U.S Army Corps of Engineers for her technical guidance and support and to the National 

Weather Service for their continued support to the USGS flood-inundation mapping initiative. 

Flood-Inundation Maps for the Saluda River from 

Old Easley Bridge Road to Saluda Lake Dam 

near Greenville, South Carolina

By Stephen T. Benedict, Andral W. Caldwell, and Jimmy M. Clark 

Abstract

Digital flood-inundation maps for a 3.95-mile reach of 

the Saluda River from approximately 815 feet downstream 

from Old Easley Bridge Road to approximately 150 feet 

downstream from Saluda Lake Dam near Greenville, South 

Carolina, were developed by the U.S. Geological Survey 

(USGS). The inundation maps, which can be accessed through 

the USGS Flood Inundation Mapping Science Web site at 

http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding 

to selected water levels (stages) at the USGS streamgage 

at Saluda River near Greenville, South Carolina (station 

02162500). Current conditions at the USGS streamgage 

may be obtained through the National Water Information System Web site at http://waterdata.usgs.gov/sc/nwis/

uv/?site_no=02162500&PARAmeter_cd=00065,00060,00062. 

The National Weather Service (NWS) forecasts flood hydrographs at many places that are often collocated with USGS 

streamgages. Forecasted peak-stage information is available 

on the Internet at the NWS Advanced Hydrologic Prediction Service (AHPS) flood-warning system Web site (http://

water.weather.gov/ahps/) and may be used in conjunction with 

the maps developed in this study to show predicted areas of 

flood inundation. 

In this study, flood profiles were computed for the stream 

reach by means of a one-dimensional step-backwater model. 

The model was calibrated using the most current stagestreamflow relations at USGS streamgage station 02162500, 

Saluda River near Greenville, South Carolina. The hydraulic 

model was then used to determine water-surface profiles for 

flood stages at 1.0-foot intervals referenced to the streamgage 

datum and ranging from approximately bankfull to 2 feet 

higher than the highest recorded water level at the streamgage.

The simulated water-surface profiles were then exported to a 

geographic information system, ArcGIS, and combined with 

a digital elevation model (derived from Light Detection and 

Ranging [LiDAR] data with a 0.6-foot vertical Root Mean 

Square Error [RMSE] and a 3.0-foot horizontal RMSE), using 

HEC–GeoRAS tools in order to delineate the area flooded at 

each water level.

The availability of these maps, along with real-time stage 

data from the USGS streamgage station 02162500 and forecasted stream stages from the NWS, can provide emergency 

management personnel and residents with information that is 

critical during flood-response and flood-recovery activities, 

such as evacuations, road closures, and disaster declarations.

Introduction

The Saluda River flows generally southeastward along 

the boundary between Greenville and Pickens Counties near 

the outskirts of the city limits of Greenville and Easley, South 

Carolina (SC) (fig. 1). Greenville and Pickens Counties have 

a combined population of about 580,000 and the nearby 

urban communities of Greenville and Easley have estimated 

populations of 58,400 and 20,000, respectively (U.S. Census 

Bureau, 2012a). Historical records at the U.S. Geological 

Survey (USGS) streamgage station 02162500, Saluda River 

near Greenville, SC (fig. 1) indicate that the Saluda River 

experienced large floods in 1949, 1961, 1964, 1965, 1995, 

and most recently in 2004. The 2004 floodwaters inundated 

yards and the crawl spaces of several homes located along 

the study reach (Pat Tanner, National Weather Service, oral 

commun., September 25, 2012). In the neighboring Reedy 

River basin, damage costs for the 2004 flood in downtown 

Greenville were reported to be $5.8 million (Burrus and Pelissier, 2011). Flood plains along the Saluda River study reach 

are moderately developed and contain a mix of residential and 

commercial structures.

Prior to this study, local government officials have relied 

on several information sources (all of which are available 

on the Internet) to make decisions on how to best alert the 

public and mitigate flood damages. One source is the Federal 

Emergency Management Agency (FEMA) Flood Insurance 

Study (FIS) Digital Flood Insurance Rate Maps (DFIRMs) for 

Greenville and Pickens Counties, dated December 2, 2004, 

and April 16, 2008, respectively (Federal Emergency Management Agency, 2004, 2008). A second source of information is 

the USGS streamgage, Saluda River near Greenville, South 

Carolina (station 02162500), from which current or historical 

water levels (stage) are available for this streamgage. A third 
2 Flood-Inundation Maps for the Saluda River from Old Easley Bridge Road to Saluda Lake Dam near Greenville, SC

Figure 1. Locations of study reach for the Saluda River, U.S. Geological Survey streamgage, and National Weather Service 

forecast point.

Saluda

Lake

124

123

Georges Creek

Saluda River

ANDERSON

GREENVILLE

PICKENS

SOUTH CAROLINA

Columbia

Area of Interest

Base from ESRI® Data & Maps, 2010

Universal Transverse Mercator projection, zone 17

North American Datum, 1983

Central_Meridian: -81.000000

EXPLANATION

Model extent

U.S. Geological Survey Streamgage and identifier

 and National Weather Service forecast point

ANDERSON

GREENVILLE

PICKENS

Greenville Easley

Old Easley Bridge Rd (S- 8 5)

Saluda Dam Rd (S-63)

02162500

02162500

0 0.25 0.5 0.75 1 MILES

0 250 500 750 1,000 METERS

BLUE RIDGE

PIEDMONT

Brushy

Creek

Saluda River

Reedy River

Long Branch
Introduction 3

source is the National Weather Service (NWS) forecasts 

of flood hydrographs showing peak stage at the USGS 

streamgage through the NWS Advanced Hydrologic Production Service (AHPS) Web site (http://water.weather.gov/ahps/).

Although USGS current stage and NWS forecast stage 

data are particularly useful for residents in the immediate 

vicinity of a streamgage, the data are of limited use to residents farther upstream or downstream because the watersurface elevation is not constant along the entire stream 

channel. Additionally, FEMA and State emergency management mitigation teams or property owners typically lack 

information related to water depth at locations other than near 

USGS streamgages or NWS flood-forecast points. To provide 

information on floods in areas upstream and downstream 

from the USGS streamgage, the USGS conducted a study to 

produce digital flood-inundation maps for a 3.95-mile (mi) 

reach of the Saluda River. These digital flood-inundation maps 

show an estimate of the modeled flood-water extent and depth 

on the land surface and are tied to USGS and NWS floodforecast sites to help officials to make timely operational and 

public safety decisions during floods. The flood-inundation 

maps show estimated flood-inundated areas overlain on highresolution, aerial imagery of the study area for each of the 

water-surface profiles generated by the HEC–RAS hydraulic 

model (U.S. Army Corps of Engineers, Hydrologic Engineering Center, 2010).

Purpose and Scope

The purpose of this report is to describe the development of a series of estimated flood-inundation maps for the 

Saluda River near Greenville, SC. The maps and other useful 

flood information are available on the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/

flood_inundation/ and the previously mentioned NWS AHPS 

Web site. Internet users can select estimated inundation maps 

that correspond closely to (1) current stages at the USGS 

streamgage (02162500), (2) the NWS forecasted peak stage, 

or (3) other desired stream stages.

The scope of the study was limited to a 3.95-mi reach of 

the Saluda River from approximately 815 feet (ft) downstream 

from Old Easley Bridge Road (Road S-85) to approximately 

150 ft downstream from Saluda Lake Dam (fig. 1). Tasks 

specific to development of the maps were (1) analysis of stage 

and flow data for station 02162500 (table 1), (2) collection of 

topographic data and geometric data (for bridges) throughout 

the study reach, (3) determination of energy-loss factors 

(roughness coefficients) in the stream channel and flood plain, 

(4) computation of water-surface profiles using the U.S. Army 

Corps of Engineers’ HEC–RAS computer program (U.S. Army 

Corps of Engineers, Hydrologic Engineering Center, 2010), 

(5) production of estimated flood-inundation maps at various 

stream stages using the U.S. Army Corps of Engineers’ HEC–

GeoRas software (U.S. Army Corps of Engineers, Hydrologic 

Engineering Center, 2009) within a geographic information 

system (ArcGIS), and (6) development of a Web site interface 

that links to USGS real-time streamgage information and 

NWS forecasted peak stage to facilitate the display of userselected flood-inundation maps on the Internet.

Methods used are generally cited from previously 

published reports (Bales and others, 2007; Whitehead and 

Ostheimer, 2009). Maps were produced for water levels 

referenced to the water-surface elevation (stage) at the 

USGS streamgage Saluda River near Greenville, SC (station 

02162500) and range from approximately bankfull to 2 ft 

above the maximum observed water level at the streamgage. 

Study Area Description

The Saluda River is in northwest South Carolina and 

drains part of the Blue Ridge and Piedmont Physiographic 

Provinces. The drainage area ranges from 302 square miles 

(mi2

) at the downstream study limit to 296 mi2 at the upstream 

study limit. The drainage area at the USGS streamgage station 

02162500 is 298 mi2

. The headwaters originate in Greenville 

and Pickens Counties, and the river flows generally southeastward along the boundary between Greenville and Pickens 

Counties. There are no major tributaries to the Saluda River 

that join the main stem as it flows near the outskirts of the city 

Table 1. Site information for the U.S. Geological Survey streamgage on the study reach, Saluda River near Greenville, South Carolina.

[mi2, square mile; °, degree, ′, minute; ′′, second; ft, feet]

Station name Station 

number

Drainage 

area 

(mi2

)

Latitude Longitude Period of record

Maximum 

recorded stage at 

gage and date

Saluda River near Greenville, 

South Carolina

02162500 1

 298 34°50′32′′ 82°28′51′′ Jan. 1942 to Sep. 1978, Oct. 1978 to 

Jan. 1990 (partial-record site), 

Feb. 1990 to current year (2012)

2

 19.38 ft

Oct. 7, 1949

1

 The previous published drainage area for the U.S. Geological Survey streamgage station 02162500 was 295 mi2, but was updated in July 2012 to the current 

value of 298 mi2.

2 The 1949 flow is based on an indirect flow computation. The upper end of the current rating (no. 11) is based on a high flow measurement from the 2004 

flood and does not pass directly through the 1949 indirect flow measurement. Rating no. 11 is considered a reliable rating for current conditions; therefore, a 

stage of 18 ft corresponds to the flow of 11,000 cubic feet per second for rating no. 11. 
4 Flood-Inundation Maps for the Saluda River from Old Easley Bridge Road to Saluda Lake Dam near Greenville, SC

limits of Greenville and Easley, SC. The basin terrain generally consists of rolling hills. The study reach is approximately 

3.95 mi long, has an average top-of-bank channel width of 

about 120 ft and an average channel slope of 4.1 feet per mile 

(ft/mi). The lower half of the study reach has a flatter channel 

slope of approximately 2.1 ft/mi. The land contiguous to the 

study reach is classified as a mixture of housing developments, forest, and pasture. The study area is located 7 mi west 

of Greenville, SC, and 5 mi east of Easley, SC (fig. 1). The 

population for Greenville has increased by 2.1 percent from 

April 1, 2010, to July 1, 2011, while the population of Easley 

has increased by 0.3 percent for the same time period (U.S. 

Census Bureau, 2012b). Along the study reach, there are four 

bridges and one railroad that cross the channel and the adjacent flood plain. 

Previous Studies

The current DFIRM for Greenville County was published 

December 2, 2004, and the DFIRM for Pickens County was 

published April 16, 2008 (Federal Emergency Management 

Agency, 2008). The DFIRMs were used to check the inundation extent for a streamflow that was close to the 1-percent 

annual exceedance probability. A HEC–RAS model of the 

Saluda River, which was used in the 2008 publication of 

the Pickens County DFIRM, was obtained from FEMA on 

August 21, 2012, and was used to help verify the results of the 

USGS HEC–RAS model along the Saluda River study reach 

for this investigation. The HEC–RAS model was a Limited 

Detailed Study model that was tied into a model that was 

published in the 1992 FIS (Maria Cox, South Carolina Department of Natural Resources, written commun., October 31, 

2012). The HEC–RAS model obtained from FEMA was based 

on 2002 topographic map data and assumed a constant flow of 

12,930 cubic feet per second (ft3

/s) over the same study reach 

for the USGS investigation (table 2).

Constructing Water-Surface Profiles

The water-surface profiles used to produce the 

15 flood-inundation maps in this study were computed using 

HEC–RAS, version 4.1.0 (U.S. Army Corps of Engineers, 

Hydrologic Engineering Center, 2010). HEC–RAS is a 

one-dimensional step-backwater model for simulation of 

water-surface profiles with steady-state (gradually varied) 

or unsteady-state flow computation options. The HEC–RAS 

analysis for this study was completed using the steady-state 

flow computation option.

Hydrologic and Steady-Flow Data

The study area hydrologic network consists of one 

streamgage, station 02162500 (fig. 1; table 1). Water level 

(stage) is measured continuously at this streamgage, and 

continuous records of streamflow are computed from the 

stage record. All water-surface elevations are referenced to 

the North American Vertical Datum of 1988 (NAVD 88). The 

streamgage is equipped with a satellite radio transmitter that 

allows data to be transmitted routinely and made available on 

the Internet within an hour of collection.

Steady-flow data consisted of flow regime, boundary 

conditions (normal depth), and peak discharge. The steadyflow data for the study reach were determined by using 

streamflow values with known stages obtained from actual 

field measurements of streamflow and stage-streamflow 

relations at USGS streamgage station 02162500. The Saluda 

Lake Dam, located at the upstream end of the study reach, has 

minimal influence on higher streamflows (U.S. Geological 

Survey, 2012) and, therefore, was assumed to have negligible influence on the higher flows used in this investigation. 

Additionally, because the upstream to downstream change in 

drainage area for the study reach is small (296 to 302 mi2

), 

constant flows were assumed throughout the reach.

Topographic/Bathymetric Data

Channel cross sections were developed from USGS field 

surveys that were conducted in May and June 2012. These 

cross sections provided detailed elevation data in the channel 

below the water surface, on the streambanks, and a short 

distance into the flood plain. A combination of survey techniques were used to collect these data. Channel elevation data 

below the water surface were collected using hydroacoustic 

instrumentation to measure depth. Flood-plain, top-of-bank, 

and water-surface elevation data at each cross section were 

determined by using a standard surveying instrument; elevations were determined by using closed level-loop surveying 

techniques from a reference datum established with a Trimble 

RTKGPS with a 3-millimeter (mm) horizontal accuracy and 

5-mm vertical accuracy in static mode (Trimble, 2012). Light 

Detection and Ranging (LiDAR) data with 0.6-ft vertical 

root-mean square error (RMSE) and 3-ft horizontal RMSE 

Table 2. Estimates of peak streamflow for a 1.0-percent annual 

exceedance probability for selected locations on the Saluda River 

(from Federal Emergency Management Agency, 2008).

[mi2, square miles; ft3/s, cubic feet per second; USGS, U.S. Geological Survey]

Location on Saluda River

Drainage 

area 

(mi2

)

Streamflow 

estimate 

(ft3/s)

Percentage 

of total 

discharge

Downstream study limit 

(815 feet downstream 

from Old Easley 

Bridge Road)

302 12,930 100

USGS streamgage station 

02162500

1

 298 12,930 100

Upstream study limit 

(150 feet downstream 

from Saluda Lake Dam)

296 12,930 100

1

 The previous published drainage area for the U.S. Geological Survey 

streamgage station 02162500 was 295 mi2, but was updated in July 2012 to 

the current value of 298 mi2.
Constructing Water-Surface Profiles 5

were used to provide digital elevation data for the portions 

of the cross sections that were above the water surface. The 

LiDAR data were collected in 2011 for the South Carolina 

LiDAR Consortium and accuracy tested at a 95-percent 

confidence level (South Carolina Department of Natural 

Resources, 2010).

Various manmade drainage structures (bridges and 

roadway embankments) in and along the stream affect or 

have the potential to affect water-surface elevations during 

flooding. There are five bridge crossings along the study reach 

(in downstream to upstream order): Old Easley Bridge Road 

(Road S-85), Route U.S. 123, Route S.C. 124, a railroad, and 

Saluda Dam Road (Road S-63). The railroad and Road S-63 

bridges located near the upper limits of the study reach are 

long bridges that span the flood plain and create no constriction of flow; therefore, these bridges were not modeled as flow 

contractions. Both of these bridges have piers in the channel, 

however, and the Manning’s roughness coefficients were 

increased (based on guidance from Arcement and Schneider 

[1989]) in the HEC–RAS model at these cross sections to 

account for losses associated with the piers. To properly 

account for these features at the remaining three bridges, 

structural dimensions were measured and surveyed in the 

field concurrently with the stream channel surveys and were 

modeled using standard HEC–RAS techniques for modeling 

bridges. A detailed description of the methods used to acquire 

and process the topographic and bathymetric data can be 

found in Bales and others (2007).

Energy Loss Factors

Field observations and aerial photographs were used to 

select initial (pre-calibration) Manning’s roughness coefficients (“n” values) for energy (friction) loss calculations. The 

final Manning’s n values used ranged from 0.048 to 0.062 for 

the main channel and from 0.06 to 0.16 for the overbank areas 

modeled in this analysis. 

Model Calibration and Performance

The HEC–RAS hydraulic model was calibrated to the 

most current (2012) stage-streamflow relation at streamgage 

station 02162500. The peak streamflow for the period of 

record at the streamgage occurred during the 1949 flood 

with an estimated flow of 11,000 ft3

/s (based on an indirect 

flow computation) with an estimated stage of about 19.38 ft. 

(NOTE: The upper end of the current rating [no. 11] is based 

on a high-flow measurement from the 2004 flood and does 

not pass directly through the 1949 indirect flow measurement. Rating no. 11 is considered a reliable rating for current 

conditions and, therefore, a stage of 18 ft corresponds to the 

flow of 11,000 ft3

/s for rating no. 11.) The model calibration 

was limited to flows that were approximately equal to or less 

than the upper bound of the measured data. Model calibration was accomplished by adjusting Manning’s n values and, 

in some cases, changing the channel cross section until the 

results of the hydraulic computations closely agreed with 

the known flood flow and stage values at the streamgage. 

Differences between measured and simulated water levels for 

specified flows were equal to or less than 0.10 ft. The South 

Carolina Department of Transportation will typically identify 

high-water marks associated with historical events on their 

bridge plans, and such data can be used for model verification. However, the bridge plans associated with bridges along 

the study reach had no historical high-water marks that could 

be correlated to the Saluda River streamgage. Because the 

streamgage was the only point for calibration along the study 

reach, the uncertainty associated with the model calibration 

will increase with distance from the gage. This should be kept 

in mind when reviewing results associated with this investigation. Details on techniques used in model development and 

calibration can be found in Bales and others (2007).

Development of Water-Surface Profiles

Profiles were developed for 15 stages at 1.0-ft intervals 

between 6.0 and 20.0 ft as referenced to the USGS streamgage 

station 02162500. Streamflows corresponding to the various 

stages were obtained from the most current stage-streamflow 

relation (rating no. 11) at the Saluda River streamgage. Streamflows for all profiles (table 3) at USGS streamgage station 

02162500 on the Saluda River were assumed to be constant 

because of the small change in drainage area over the reach.

Table 3. Stages, water-surface elevations, and corresponding 

streamflow estimates based on rating no. 11 at the U.S. Geological 

Survey streamgage station 02162500, Saluda River near Greenville, 

South Carolina.

[NAVD 88, North American Vertical Datum of 1988]

Stage, 

in feet above 

gage datum

Elevation, 

in feet, 

NAVD 88

Estimated 

streamflow, 

in cubic feet 

per second

Map 

sheet 

number

6.0 803.2 2,810 1

7.0 804.2 3,620 2

8.0 805.2 4,390 3

9.0 806.2 5,130 4

10.0 807.2 5,840 5

11.0 808.2 6,530 6

12.0 809.2 7,210 7

13.0 810.2 7,870 8

14.0 811.2 8,520 9

15.0 812.2 9,150 10

16.0 813.2 9,780 11

17.0 814.2 10,400 12

18.0 815.2 11,000 13

19.0 816.2 12,000 14

20.0 817.2 13,200 15
6 Flood-Inundation Maps for the Saluda River from Old Easley Bridge Road to Saluda Lake Dam near Greenville, SC

Inundation Mapping

Flood-inundation maps were created based on the Saluda 

River near Greenville, SC, streamgage station 02162500, 

which has been designated as an NWS flood-forecast point 

(GSLS1). The maps were created in a geographic information 

system by combining the water-surface profiles and digital 

elevation model data. Estimated flood-inundation boundaries 

for each simulated profile were developed with HEC–GeoRAS 

software (U.S. Army Corps of Engineers, Hydrologic Engineering Center, 2009). HEC–GeoRAS is a set of procedures, 

tools, and utilities for processing geospatial data in ArcGIS by 

using a graphical user interface (Whitehead and Ostheimer, 

2009). The interface allows the preparation of geometric data 

for import into HEC–RAS and processes simulation results 

exported from HEC–RAS (U.S. Army Corps of Engineers, 

Hydrologic Engineering Center, 2010). USGS personnel then 

modified the HEC–GeoRAS results to ensure a hydraulically reasonable transition of the boundary between modeled 

cross sections relative to the contour data for the land surface 

(Whitehead and Ostheimer, 2009). The maps show estimated 

flood-inundated areas overlain on high-resolution aerial 

imagery of the study area for each of the water-surface profiles 

that were generated by the hydraulic model.

Saluda River, South Carolina, Flood-Inundation 

Maps on the Internet

A USGS Flood Inundation Mapping Science Web site 

has been established to provide a portal for USGS floodinundation information to the public at http://water.usgs.gov/

osw/flood_inundation/. That Web portal has a link (http://

wim.usgs.gov/FIMI/FloodInundationMapper.html) to interactive online map libraries that can be downloaded in several 

commonly used electronic file formats. Each stream reach 

displayed on the latter Web site contains links to USGS 

National Water Information System graphs of the current stage 

and streamflow at USGS streamgage 02162500, to which the 

inundation maps are referenced. A link also is provided to the 

NWS AHPS Web site (http://water.weather.gov/ahps/) so that 

users can obtain applicable information on forecasted peak 

stage. The estimated flood-inundation maps are displayed in 

sufficient detail to note the extent of flooding with respect to 

individual structures so that preparations for flooding and decisions for emergency response can be performed efficiently. 

Roadways and bridges were closely reviewed and are shown 

as shaded (partially or fully inundated and likely impassable) or not shaded (dry and passable) to facilitate emergency 

planning and use. Buildings that are shaded do not necessarily 

reflect full inundation but denote that bare earth surfaces in the 

vicinity of the buildings are inundated. When the water depth 

(as indicated in the Web Mapping Application by holding the 

cursor over an inundated area) in the vicinity of the building 

of interest exceeds any portion of that building’s height, the 

structure can be considered partially to fully submerged, 

depending on the depth given.

Disclaimer for Flood-Inundation Maps

Inundated areas shown should not be used for navigation, 

regulatory, permitting, or other legal purposes. The USGS 

provides these maps “as-is” for a quick reference, emergency 

planning tool but assumes no legal liability or responsibility 

resulting from the use of this information.

Uncertainties and Limitations for Use of 

Flood-Inundation Maps

Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty 

is associated with these maps. The flood boundaries shown 

were estimated based on water stages (water-surface elevations) and streamflows at selected USGS streamgages. Watersurface elevations along the stream reaches were estimated by 

steady-state hydraulic modeling, assuming unobstructed flow, 

and using streamflows and hydrologic conditions anticipated 

at the USGS streamgage. The hydraulic model reflects the 

land-cover characteristics and any bridge, dam, or other 

hydraulic structures existing as of August 2012. Unique meteorological factors (timing and distribution of precipitation) 

may cause actual streamflows along the modeled reach to vary 

from those assumed during a flood, which may lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded due to unanticipated conditions such as: changes in the streambed elevation 

or roughness, backwater into major tributaries along a main 

stem river, or backwater from localized debris or ice jams. The 

accuracy of the floodwater extent portrayed on these maps will 

vary with the accuracy of the digital elevation model used to 

simulate the land surface. Additional uncertainties and limitations pertinent to this study are described in the document 

accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used in 

conjunction with National Weather Service (NWS) river 

forecasts, the user should be aware of additional uncertainties 

that may be inherent or factored into NWS forecast procedures. The NWS uses forecast models to estimate the quantity 

and timing of water flowing through selected stream reaches 

in the United States. These forecast models (1) estimate the 

amount of runoff generated by precipitation and snowmelt, 

(2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface 

elevation) for the stream at a given location (AHPS forecast 

point) throughout the forecast period (every 6 hours and 3 to 

5 days out in many locations). For more information on AHPS 

forecasts, please see: http://water.weather.gov/ahps/pcpn_and_

river_forecasting.pdf.
References Cited 7

Summary

A series of estimated flood-inundation maps were 

developed by the U.S. Geological Survey (USGS) for a 3.95-

mile reach of the Saluda River from approximately 815 feet 

downstream from Old Easley Bridge Road to approximately 

150 feet downstream from Saluda Lake Dam near Greenville, 

South Carolina. These maps, available at a USGS Web portal, 

in conjunction with the real-time stage data from the USGS 

streamgage Saluda River near Greenville, South Carolina 

(station 02162500), and National Weather Service flood-stage 

forecasts, can help to guide the general public in taking individual safety precautions and can provide local officials with 

a tool to efficiently manage emergency flood operations and 

flood-mitigation efforts.

The maps were developed using the U.S. Army Corps of 

Engineers HEC–RAS and HEC–GeoRAS computer programs 

to compute water-surface profiles and to delineate estimated 

flood-inundation areas for selected stream stages. The maps 

show estimated flood-inundation areas overlain on highresolution aerial imagery of the study area for stream stages 

between 6.0 feet and 20.0 feet (gage datum) at the Saluda 

River near Greenville, South Carolina, streamgage (station 

02162500). 

References Cited

Arcement, G.J., and Schneider, V.R., 1989, Guide for selecting Manning’s roughness coefficients for natural channels 

and flood plains: U.S. Geological Survey Water-Supply 

Paper 2339, 38 p. 

Bales, J.D., Wagner, C.R., Tighe, K.C., and Terziotti, Silvia, 

2007, LiDAR-derived flood-inundation maps for realtime flood-mapping applications, Tar River Basin, North 

Carolina: U.S. Geological Survey Scientific Investigations 

Report 2007–5032, 42 p.

Burrus, S.A., and Pelissier, Joseph, 2011, The Greenville, 

South Carolina, flash flood of 29 July 2004: National 

Oceanic and Atmospheric Administration, National 

Weather Service, accessed November 29, 2012, at http://

www.erh.noaa.gov/gsp/localdat/cases/2004/29July_

ReedyFlood/29July_ReedyRiverFlood.html.

Federal Emergency Management Agency, 2004, Digital Flood 

Insurance Rate Map, Greenville County, December 2, 2004, 

accessed July 2012 at http://www.msc.fema.gov/.

Federal Emergency Management Agency, 2008, Digital Flood 

Insurance Rate Map, Pickens County, April 16, 2008, 

accessed July 2012 at http://www.msc.fema.gov/.

South Carolina Department of Natural Resources, 2010, 

LiDAR and related data products, accessed August 9, 2012, 

at http://www.dnr.sc.gov/GIS/lidar.html. 

Trimble, 2012, Trimble R5 GPS Reciever, accessed August 13, 

2012, at http://trl.trimble.com/docushare/dsweb/Get/

Document-468444/022543-491B_TrimbleR5_DS_0212_lr_

sec.pdf.

U.S. Army Corps of Engineers, Hydrologic Engineering 

Center, 2009, HEC–GeoRAS, GIS Tools for Support of 

HEC–RAS Using ArcGIS, User’s Manual, version 4.2 [variously paged]. 

U.S. Army Corps of Engineers, Hydrologic Engineering 

Center, 2010, HEC–RAS River Analysis System, Hydraulic 

Reference Manual, version 4.1 [variously paged].

U.S. Census Bureau, 2012a, State and County QuickFacts, 

Greenville, South Carolina, accessed June 25, 2012, at 

http://quickfacts.census.gov/qfd/states/45/4530850.html.

U.S. Census Bureau, 2012b, State and County QuickFacts, 

South Carolina, accessed August 29, 2012, at http://

quickfacts.census.gov/qfd/states/45000.html.

U.S. Geological Survey, 2012, Water-resources data for the 

United States, Water Year 2011: U.S. Geological Survey 

Water-Data Report WDR-US-2011, site 02162500, accessed 

February 4, 2013, at http://wdr.water.usgs.gov/wy2011/

pdfs/02162500.2011.pdf.

Whitehead, M.T., and Ostheimer, C.J., 2009, Development 

of a flood-warning system and flood-inundation mapping 

for the Blanchard River in Findlay, Ohio: U.S. Geological 

Survey Scientific Investigations Report 2008–5234, 9 p.
Publishing support provided by:

Raleigh Publishing Service Center

Manuscript approved for publication January 15, 2013

For more information concerning this publication, contact:

Director, South Carolina Water Science Center

U.S. Geological Survey

720 Gracern Road

Suite 129

Columbia, SC 29210

(803) 750–6100

Or visit the South Carolina Water Science Center Web site at:

http://sc.water.usgs.gov/ 

Benedict and others—Flood-Inundation Maps for the Saluda River from Old Easley Bridge Road to Saluda Lake Dam near Greenville, SC—Scientific Investigations Map 3244