Prepared in cooperation with the

ARKANSAS STATE HIGHWAY AND TRANSPORTATION DEPARTMENT

SIMULATIONS OF FLOODFLOWS ON THE WHITE 

RIVER IN THE VICINITY OF U.S. HIGHWAY 79 NEAR 

CLARENDON, ARKANSAS

Water-Resources Investigations Report 02-4256

U.S. Department of the Interior

U.S. Geological Survey
Photographs on Front Cover:

A - Tugboat pushing a barge on the White River 1/4 mile upstream from the U.S. Highway 79 

crossing.

B - Vehicle traffic on the U.S. Highway 79 White River bridge.

C - Roc Roe Bayou, 1/2 mile upstream from the confluence of the White River.

A B

C
SIMULATIONS OF FLOODFLOWS ON THE WHITE 

RIVER IN THE VICINITY OF U.S. HIGHWAY 79 NEAR 

CLARENDON, ARKANSAS

By Jaysson E. Funkhouser and C. Shane Barks

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4256

Prepared in cooperation with the

ARKANSAS STATE HIGHWAY AND TRANSPORTATION 

DEPARTMENT 

Little Rock, Arkansas

2003

The use of firm, trade, and brand names in this report is for identification purposes only and does not

constitute endorsement by the U.S. Geological Survey.
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Branch of Information Services

401 Hardin Road Box 25286

Little Rock, Arkansas 72211 Denver Federal Center

Denver, Colorado 80225

The use of firm, trade, and brand names in this report is for identification purposes only and does not

constitute endorsement by the U.S. Geological Survey.
Contents III

CONTENTS

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

Introduction..........................................................................................................................................................2

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

Acknowledgments.......................................................................................................................................3

Description of Study Area....................................................................................................................................4

Existing Conditions.....................................................................................................................................5

Natural Conditions ......................................................................................................................................5

Proposed Conditions ...................................................................................................................................5

Hydrology ...................................................................................................................................................6

Modeling Approach .............................................................................................................................................6

Model Description.......................................................................................................................................6

Model Implementation................................................................................................................................7

Computational Grid .......................................................................................................................... 7

Boundary Conditions ........................................................................................................................ 8

Model Parameters ............................................................................................................................. 9

Model Calibration .......................................................................................................................................9

Sensitivity Analysis.....................................................................................................................................9

Simulation of Floodflows................................................................................................................................... 10

5-Year Flood.............................................................................................................................................. 10

Existing Conditions......................................................................................................................... 10

Natural Conditions........................................................................................................................... 10

Proposed Conditions—Alternative 1 ............................................................................................... 12

Proposed Conditions—Alternative 2 ............................................................................................... 17

Proposed Conditions—Alternative 3 ............................................................................................... 17

Proposed Conditions—Alternative 4 ............................................................................................... 20

Comparison of Simulation Results for Proposed Alternatives and Existing Conditions................. 20

100-Year Flood.......................................................................................................................................... 22

Existing Conditions.......................................................................................................................... 22

Natural Conditions........................................................................................................................... 23

Proposed Conditions—Alternative 1 ............................................................................................... 23

Proposed Conditions—Alternative 2 ............................................................................................... 28

Proposed Conditions—Alternative 3 ............................................................................................... 28

Proposed Conditions—Alternative 4 ............................................................................................... 31

Comparison of Simulation Results for Proposed Alternatives and Existing Conditions................. 31

Summary ............................................................................................................................................................ 35

References.......................................................................................................................................................... 36
IV Contents

ILLUSTRATIONS

Figures 1-4. Maps showing:

1. Location of study area .................................................................................................................. 2

2. Location of existing and proposed roadway alignments............................................................... 3

3. White River flood plain upper and lower model boundaries and U.S. Highway 79 model area

in the study area ..................................................................................................................... 4

4. Computational grid generated for the model area........................................................................ 7

5. Graph showing verification of the 10-meter digital elevation model data with the most

downstream surveyed cross section........................................................................................... 8

6-41. Maps showing:

6. Simulated water-surface elevations for the 5-year floodflow through the existing U.S.

Highway 79 roadway alignment............................................................................................11

7. Depth-averaged velocity contours for the 5-year floodflow through the existing U.S.

Highway 79 roadway alignment............................................................................................11

8. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through

the existing U.S. Highway 79 roadway alignment ................................................................12

9. Simulated water-surface elevations for the 5-year floodflow for natural conditions

through the White River flood plain at the U.S. Highway 79 crossing.................................13

10. Depth-averaged velocity contours for the 5-year floodflow for natural conditions

through the White River flood plain at the U.S. Highway 79 crossing.................................13

11. Distribution of depth-averaged point velocity vectors for the 5-year floodflow for natural

conditions through the White River flood plain at the U.S. Highway 79 crossing ...............14

12. Simulated water-surface elevations for the 5-year floodflow through the proposed

Alternative 1 U.S. Highway 79 roadway alignment..............................................................14

13. Depth-averaged velocity contours for the 5-year floodflow through the proposed 

Alternative 1 U.S. Highway 79 roadway alignment..............................................................15

14. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through

the proposed Alternative 1 U.S. Highway 79 roadway alignment ........................................15

15. Simulated water-surface elevations for the 5-year floodflow through the proposed

Alternative 2 U.S. Highway 79 roadway alignment..............................................................17

16. Depth-averaged velocity contours for the 5-year floodflow through the proposed

Alternative 2 U.S. Highway 79 roadway alignment..............................................................18

17. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through

the proposed Alternative 2 U.S. Highway 79 openings ........................................................18

18. Simulated water-surface elevations for the 5-year floodflow through the proposed

Alternative 3 U.S. Highway 79 alignment ............................................................................19

19. Depth-averaged velocity contours for the 5-year floodflow through the proposed

Alternative 3 U.S. Highway 79 roadway alignment..............................................................19

20. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through

the proposed Alternative 3 U.S. Highway 79 roadway alignment ........................................20

21. Simulated water-surface elevations for the 5-year floodflow through the proposed 

Alternative 4 U.S. Highway 79 roadway alignment..............................................................21

22. Depth-averaged velocity contours for the 5-year floodflow through the proposed

Alternative 4 U.S. Highway 79 roadway alignment..............................................................21

23. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the

proposed Alternative 4 U.S. Highway 79 roadway alignment ..............................................22

24. Simulated water-surface elevations for the 100-year floodflow through the existing U.S.

Highway 79 roadway alignment............................................................................................25

25. Depth-averaged velocity contours for the 100-year floodflow through the existing U.S.

Highway 79 roadway alignment............................................................................................25
Contents V

26. Distribution of depth-averaged point velocity vectors for the 100-year floodflow through

the existing U.S. Highway 79 openings ................................................................................ 26

27. Simulated water-surface elevations for the 100-year floodflow for natural conditions

through the White River flood plain at the U.S. Highway 79 crossing................................. 26

28. Depth-averaged velocity contours for the 100-year floodflow for natural conditions

through the White River flood plain at the U.S. Highway 79 crossing................................. 27

29. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for 

natural conditions through the White River flood plain at the U.S. Highway 79 crossing ... 27

30. Simulated water-surface elevations for the 100-year floodflow through the proposed

Alternative 1 U.S. Highway 79 roadway alignment.............................................................. 28

31. Depth-averaged velocity contours for the 100-year floodflow through the proposed

Alternative 1 U.S. Highway 79 roadway alignment.............................................................. 29

32. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the

proposed Alternative 1 U.S. Highway 79 openings .............................................................. 29

33. Simulated water-surface elevations for the 100-year floodflow through the proposed

Alternative 2 U.S. Highway 79 roadway alignment.............................................................. 30

34. Depth-averaged velocity contours for the 100-year floodflow through the proposed

Alternative 2 U.S. Highway 79 roadway alignment.............................................................. 30

35. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the

proposed Alternative 2 U.S. Highway 79 openings .............................................................. 31

36. Simulated water-surface elevations for the 100-year floodflow through the proposed

Alternative 3 U.S. Highway 79 roadway alignment.............................................................. 32

37. Depth-averaged velocity contours for the 100-year floodflow through the proposed

Alternative 3 U.S. Highway 79 roadway alignment.............................................................. 32

38. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the

proposed Alternative 3 U.S. Highway 79 openings .............................................................. 33

39. Simulated water-surface elevations for the 100-year floodflow through the proposed

Alternative 4 U.S. Highway 79 roadway alignment.............................................................. 33

40. Depth-averaged velocity contours for the 100-year floodflow through the proposed

Alternative 4 U.S. Highway 79 roadway alignment.............................................................. 34

41. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the

proposed Alternative 4 U.S. Highway 79 openings .............................................................. 34

TABLES

Table 1. Existing and alternative proposed bridge widths ..................................................................................6

2. Known and simulated water-surface elevation for the model calibration.............................................9

3. Hydraulic data for the White River flood plain U.S. Highway 79 roadway alignment for simulated 

floodflows having a 5-year recurrence interval .............................................................................16

4. Comparison of backwater and velocity data for each alternative for simulated floodflows having

a 5-year recurrence interval ...........................................................................................................23

5. Hydraulic data for the White River flood plain U.S. Highway 79 roadway alignment for simulated

floodflows having a 100-year recurrence interval .........................................................................24

6. Comparison of backwater and velocity data for each alternative to existing conditions for simulated

floodflows having a 100-year recurrence interval .........................................................................35
VI Contents

In this report vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 

1929).

CONVERSION FACTORS, ABBREVIATIONS, AND VERTICAL DATUM

Multiply By To obtain

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2)

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

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per day (ft/d) 0.3048 meter per day (m/d)

square foot per second (ft2/s) 0.0929 square meter per second (m2/s)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)
Abstract 1

SIMULATIONS OF FLOODFLOWS ON THE WHITE 

RIVER IN THE VICINITY OF U.S. HIGHWAY 79 NEAR 

CLARENDON, ARKANSAS

By Jaysson E. Funkhouser and C. Shane Barks

ABSTRACT

A two-dimensional finite-element surfacewater model was used to study the effects of the 

proposed modification to the U.S. Highway 79 

corridor on flooding on the White River near Clarendon, Arkansas. The effects of floodflows were 

simulated for the following scenarios: existing, 

natural, and four proposed bridging alternatives. 

All of the scenarios were modeled with floods having the 5- and 100-year recurrence intervals 

(115,100 and 216,000 cubic feet per second). The 

simulated existing conditions included a 3,200-

foot White River bridge located on the east side of 

the study area near Clarendon, Arkansas; a 3,700-

foot First Old River bridge located 0.5 mile west of 

the White River bridge opening; and a 1,430-foot 

Roc Roe Bayou bridge located 1.6 mile west of the 

First Old River bridge. The simulated hypothetical 

natural conditions involved removing the U.S. 

Highway 79 and the Union Pacific Railroad 

embankments along the entire length of the flood 

plain. The primary purpose of model simulations 

for natural conditions was to calculate backwater 

data for the existing and proposed conditions. The 

four simulated hypothetical proposed alternatives 

involved a 1.8-mile White River bridge located on 

the east side of the study area near Clarendon, 

Arkansas, either a 1,400-foot relief bridge (Alternative 1) or a 1,545 relief bridge (Alternatives 2-4) 

located 0.25 mile west of the White River bridge 

opening, and three different Roc Roe Bayou 

bridge openings ranging from 1,540-3,475 feet in 

length located 0.9 mile west of the relief bridge 

(Alternatives 1-4).

Simulation of the 5-year floodflow for the 

existing bridge openings indicates that about 57 

percent (65,600 cubic feet per second) of flow was 

conveyed by the White River bridge, about 26 percent (29,900 cubic feet per second) by the First 

Old River bridge, and about 17 percent (19,600 

cubic feet per second) by the Roc Roe Bayou 

bridge. Maximum depth-averaged point velocities 

for the White River, First Old River, and Roc Roe 

Bayou bridges were 3.6, 1.6, and 3.3 feet per second, respectively. For the 100-year floodflow, the 

simulation indicates that about 56 percent 

(123,100 cubic feet per second) of flow was conveyed by the White River bridge, about 26 percent 

(56,200 cubic feet per second) by the First Old 

River bridge, and about 19 percent (41,000 cubic 

feet per second) by the Roc Roe Bayou bridge. The 

maximum depth-averaged point velocities for the 

White River, First Old River, and Roc Roe Bayou 

bridges were 4.2, 2.2, and 4.1 feet per second, 

respectively. 

Simulation of the 5-year floodflow for the 

proposed U.S. Highway 79 alignment alternatives 

indicates that 76-78 percent (87,100-89,900 cubic 

feet per second) of the flow was conveyed by the 

proposed White River bridge, 6-7 percent (7,000-

7,500 cubic feet per second) by the proposed relief 

bridge, and 13-16 percent (14,600-18,600 cubic 

feet per second) by the proposed Roc Roe Bayou 

bridge. For the 100-year floodflow, simulations 

predicted that 70-72 percent (151,200-155,600 

cubic feet per second) of the flow was conveyed by 

the proposed White River bridge, 9-10 percent 

(19,800-20,700 cubic feet per second) by the proposed relief bridge, and 14-20 percent (30,700-

43,000 cubic feet per second) by the proposed Roc 

Roe Bayou bridge. 
2 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

INTRODUCTION

The hydraulic performance of bridges during 

floods is a major concern when the opening and grade 

of drainage structures are designed. In the case of multiple bridge openings, it is important to know the distribution of discharge and velocity through the bridges for 

an efficient hydraulic design. U.S. Highway 79, which 

crosses the White River flood plain in southeastern 

Arkansas (fig. 1), is such a case. 

U.S. Highway 79 is a two-lane highway constructed during the late 1920’s and early 1930’s. The 

town of Clarendon is on the east bank of the White 

River (fig. 2). Because of a substantial increase in traffic volume and the age and deterioration of the roadway, the Arkansas State Highway and Transportation 

Department (AHTD) made the decision to replace the 

roadway and bridges that cross the White River and its 

flood plain. 

Two National Wildlife Refuges are located near 

the U.S. Highway 79 crossing of the White River. The 

Cache River National Wildlife Refuge is located to the 

north and the White River National Wildlife Refuge is 

located to the south (fig. 1). The AHTD and U.S. Fish 

and Wildlife Service (USFWS) are concerned about the 

effects that velocities and velocity distributions generated by the proposed bridges will have on the environment. To deal with these concerns, the AHTD proposed 

combining the two bridges that cross the White River 

and the First Old River, adding a relief bridge in the 

White River flood plain, and lengthening the bridge 

that crosses Roc Roe Bayou by 110 ft (fig. 2). In addition, the AHTD and USFWS also are concerned about 

potential high point velocities in the Roc Roe Bayou 

bridge opening and any possibility for scour near 

bridge abutments. 

Figure 1. Location of study area.

Little Rock Clarendon

40

40

79

79

79

79

40

40

30

Cache

River

National

Wildlife

Refuge

White

River

National

Wildlife

Refuge

LITTLE CLARENDON ROCK

Prairie

County

Monroe

County

STUDY

AREA

Mississippi

River

Arkansas

River

White

River

White

River

Cache River

0

0 25 KILOMETERS

25 MILES

92o 91o

35o

34o

EXPLANATION

CACHE RIVER NATIONAL

WILDLIFE REFUGE

WHITE RIVER NATIONAL

WILDLIFE REFUGE
Introduction 3

Figure 2. Location of existing and proposed roadway alignments.

Clarendon

WHITE

WHITE

RIVER

RIVER

First

Old River

Passmore

Lake

Hart

Lake

East

Bayou

Roc

Roe Bayou

Brushy

Lake

EXISTING ROC ROE

BAYOU BRIDGE

PROPOSED

ALTERNATIVE 1

RELIEF

BRIDGE

PROPOSED

WHITE RIVER

BRIDGE

PROPOSED

ALTERNATIVE 1

ROC ROE

BAYOU BRIDGE

PROPOSED

ALTERNATIVE 4

ROC ROE

BAYOU BRIDGE

PROPOSED

ALTERNATIVE 3

ROC ROE

BAYOU BRIDGE

PROPOSED

ALTERNATIVES 2-4

RELIEF

BRIDGE

PROPOSED

ALTERNATIVE 2

ROC ROE

BAYOU BRIDGE

EXISTING

FIRST OLD RIVER

AND

WHITE RIVER

BRIDGES

EXPLANATION

Existing U.S. Highway 79 roadway

alignment

Proposed U.S. Highway 79 roadway

alignment

0

0

0.5

0.5

1 MILE

1 KILOMETER

91 22’ o 91 17’ o

34 41’ o

34 40’ o

A large portion of the White River breaches its 

banks and flows along its flood plain during flood 

events. The U.S. Army Corps of Engineers (USACE) 

computed a discharge of 439,648 ft3/s at the streamgage on the White River at Clarendon during a major 

flood event in April 1927. Of the total discharge, 

130,088 ft3

/s flowed through the main channel of the 

White River and 309,560 ft3

/s flowed through the relief 

bridges (U.S. Army Corps of Engineers, written commun., 1927). Because of the complexity of the site and 

the two-dimensional nature of the flow, a two-dimensional flood study was needed to accurately describe 

the discharge distribution, velocity, and velocity distribution through the White River bridge openings. To 

address this need, the U.S. Geological Survey (USGS), 

in cooperation with the AHTD, conducted simulations 

of floodflows of the White River in the vicinity of U.S. 

Highway 79 near Clarendon, Arkansas.

Purpose and Scope

The purpose of this report is to present the results 

of floodflow simulations from a two-dimensional surface-water model. These simulations illustrate the 

hydraulic effects that the proposed bridges will have on 

the White River flood plain in the vicinity of Clarendon, Arkansas. The simulation results will aid the 

AHTD in the design of U.S. Highway 79 bridges crossing the White River flood plain.

This report presents results of a two-dimensional 

surface-water model for floodflows having 5- and 100-

year recurrence intervals for existing, natural, and proposed conditions. Discharge, discharge distribution, 

velocity, and velocity distribution are given for various 

locations of interest throughout the study area. Backwater data are given at the approach section approximately 1 mi upstream from U.S. Highway 79. Other 

topics discussed include the evaluation of hydrology, 

modeling approach, model description, model calibration, and simulation of floodflows.

Acknowledgments

The assistance of Henry Langston and the personnel of the Environmental Division of the AHTD is 

greatly appreciated. The assistance of Ms. Janice Fulford of the USGS, Office of Surface Water and Mr. Karl 

Winters of the USGS, Mississippi District were instrumental in the success of this project. Also, gratitude is 

expressed to the USFWS for granting the USGS access 

to the wildlife refuges for the flood plain survey.
4 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

DESCRIPTION OF STUDY AREA

The study area is located in eastern Prairie 

County and western Monroe County near Clarendon, 

Arkansas (fig 1). The White River drains 25,555 mi2

(Sullavan, 1974) at the U.S. Highway 79 bridge. The 

USACE has operated a gaging station on the White 

River at Clarendon (gaging station 07077800) since 

1927 and on the White River at Aberdeen (gaging station 07077810) since 1932. The gaging station at Clarendon is located on the Union Pacific Railroad bridge 

approximately 500 ft downstream from the U.S. Highway 79 White River bridge (fig. 3). The gaging station 

at Aberdeen is located on the right bank of the White 

River about 8 river mi downstream from the U.S. Highway 79 crossing.

The study area includes a 17-mi reach, a 1.5-mi 

reach, and a 9-mi reach of the White River, Cache 

River, and Roc Roe Bayou, respectively (fig. 3). The 

17-mi reach of the White River consists of a 9-mi reach 

upstream from U.S. Highway 79 and a 8-mi reach 

downstream. The White River flood plain is approximately 5.5 mi wide in the northern part of the study 

area, 3.5 mi wide at the U.S. Highway 79 crossing, and 

approximately 4.5 mi wide in the southern part of the 

study area. The White River flows in a southeasterly 

direction, and the Cache River and Roc Roe Bayou 

flow in a southerly direction. The confluence of the 

Cache River with the White River is located approximately 1 mi upstream from the existing U.S. Highway 

79 White River bridge. The confluence of Roc Roe 

Bayou with the White River is located approximately 7 

mi downstream from the existing U.S. Highway 79 

White River bridge.

Figure 3. White River flood plain upper and lower model boundaries and U.S. Highway 79 model area in the study area.

Clarendon

79

79

Aberdeen

Roc Roe

Bayou

White

White

Cache River

River

River

Slaughters

Lake

0 1 MILE

0 1 KILOMETER

34 42’30” o

34 40’ o

34 37’30” o

34 35’ o

91 22’30” o 91 20’ o

91 17’30” o

EXPLANATION

White River flood plain

Upper model boundary

Lower model boundary

Streamgage

Union Pacific Railroad

U.S. HIGHWAY 79

MODEL AREA

(Figures 6-41)
Description of Study Area 5

The average slope of the basin in the study area 

is 0.36 ft/mi. The basin is mostly characterized as flat, 

swampy, and heavily wooded with dense vegetation 

throughout. However, 20 percent of the study area consists of cotton and rice fields. The basin includes 

numerous small, braided, meandering channels, many 

of which contain small beaver dams that make the 

channels ineffective for conveying flow. At the eastern 

boundary of the study area, the flood plain is open and 

is currently being used for row cropping, with a shallow 

sloping bank (less than 0.1 ft/ft). The western boundary 

is a combination of land used for row crops and land 

that is heavily wooded, with a steep sloping bank 

(greater than 2 ft/ft). 

Floodflows for several scenarios were simulated 

in this report. The scenarios were existing conditions, 

natural conditions, and four proposed alternatives. Natural conditions and proposed conditions simulated 

hypothetical modifications to existing conditions.

Existing Conditions

U.S. Highway 79 uses three separate bridges to 

cross the White River flood plain-one 3,200-ft bridge 

over the White River near Clarendon, one 3,700-ft 

bridge over the First Old River located 0.5 mi west of 

the White River bridge opening, and one 1,430-ft 

bridge over Roc Roe Bayou located 1.6 mi west of the 

First Old River (fig. 2). The embankments between the 

bridges were constructed from soil material dug from 

the borrow pits that run adjacent to the embankments. 

These pits range in depth from 3 to 10 ft. Downstream 

from U.S. Highway 79, the Union Pacific Railroad 

crosses the White River flood plain with a series of five 

embankments and five bridges.

Natural Conditions

Natural conditions involved the hypothetical 

removal of all existing U.S. Highway 79 and Union 

Pacific Railroad embankments and bridges from the 

study area. Model simulations for natural conditions 

were run to aid in the calculation of the backwater 

caused by the existing and proposed U.S. Highway 79 

roadway alignments.

Proposed Conditions

Proposed conditions involve the hypothetical 

construction of the bridges planned by the AHTD. The 

AHTD plans to construct a new roadway alignment for 

a 4.8-mi stretch of U.S. Highway 79 near Clarendon, 

Arkansas. The proposed new alignment will be located 

approximately 425 ft downstream from the existing 

highway (fig. 2). The AHTD has designed four alternate roadway alignments with varying bridge lengths 

(fig 2).

Alternative 1 (table 1) consists of three bridges: 

a 1.8-mi White River bridge, a 1,400-ft relief bridge 

located approximately 0.25 mi west of the White River 

bridge, and a 1,540-ft Roc Roe Bayou bridge crossing 

approximately 0.9 mi west of the relief bridge. Flood 

plain vegetation was added in areas upstream from, 

downstream from, and across the Roc Roe Bayou opening. Riprap was added to the west opening of the White 

River Bridge and both ends of the relief and Roc Roe 

Bayou bridge openings. The Union Pacific Railroad 

White River flood plain crossing was not altered for the 

proposed conditions.

Alternative 2 (table 1) consists of three bridges: 

a 1.8-mi White River bridge, a 1,545-ft relief bridge 

located approximately 0.25 mi west of the White River 

bridge, and a 2,475-ft Roc Roe Bayou bridge crossing 

approximately 0.9 mi west of the relief bridge. The 

additional 935 ft for the Roc Roe Bayou bridge crossing was added to the eastern end of the bridge. Flood 

plain vegetation was added in areas upstream from, 

downstream from, and across the Roc Roe Bayou opening. Riprap was added to the west opening of the White 

River bridge and to both ends of the relief and Roc Roe 

Bayou bridge openings. The Union Pacific Railroad 

White River flood plain crossing was not altered for the 

proposed conditions.

Alternative 3 (table 1) consists of three bridges: 

a 1.8-mi White River bridge, a 1,545-ft relief bridge 

located approximately 0.25 mi west of the White River 

bridge, and a 3,475-ft Roc Roe Bayou bridge crossing 

approximately 0.9 mi west of the relief bridge. The 

additional 1,935 ft for the Roc Roe Bayou bridge crossing was added the western (1,000 ft) and eastern (935 

ft) ends of the bridge. Flood plain vegetation was added 

in areas upstream from, downstream from, and across 

the Roc Roe Bayou opening. Riprap was added to the 

west opening of the White River bridge and both ends 

of the relief and Roc Roe Bayou bridge openings. The 

Union Pacific Railroad White River flood plain crossing was not altered for the proposed conditions.
6 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Table 1. Existing and alternative proposed bridge widths

[ft, feet; mi, mile, NA, not applicable]

Existing Alternative 1 Alternative 2 Alternative 3 Alternative 4

White River Bridge 3,200 ft 1.8 mi 1.8 mi 1.8 mi 1.8 mi

First Old River Bridge 3,700 ft NA NA NA NA

Relief Bridge NA 1,400 ft 1,545 ft 1,545 ft 1,545 ft

Roc Roe Bayou Bridge 1,430 ft 1,540 ft 2,475 ft 3,475 ft 3,475 ft

Alternative 4 (table 1) consists of three bridges: a 

1.8-mi White River bridge, a 1,545-ft relief bridge 

located approximately 0.25 mi west of the White River 

bridge, and a 3,475-ft Roc Roe Bayou bridge crossing 

approximately 0.9 mi west of the relief bridge. The 

additional 1,935 ft for the Roc Roe Bayou bridge crossing was added to the eastern end of the bridge. Flood 

plain vegetation was added in areas upstream from, 

downstream from, and across the Roc Roe Bayou opening. Riprap was added to the west opening of the White 

River Bridge and both ends of the relief and Roc Roe 

Bayou bridge openings. The Union Pacific Railroad 

White River flood plain crossing was not altered for the 

proposed conditions.

Hydrology

Flood frequencies in the White River Basin were 

estimated using techniques outlined by the Interagency 

Advisory Committee on Water Data (1982). Peak 

floodflows for floods having 5- and 100-year recurrence intervals were estimated for combined flooding 

on the White River and Roc Roe Bayou using the regulated period of record from 1973 to 1994 flow data collected from the USACE White River gaging station at 

Clarendon, Arkansas. During the time between the 

mid-1960’s to 1973, several dams were constructed on 

the upper White River Basin. The estimated 5- and 100-

year floodflows at the White River gaging station are 

115,100 ft3/s and 216,000 ft3/s, respectively. Because 

large flood magnitudes were simulated in this report, 

sustained peak discharges are probable. Therefore, 

steady-flow conditions were simulated.

MODELING APPROACH

Floodflow simulations for this report were based 

on a two-dimensional surface-water model. First, a 

computational grid representing the flow system for the 

existing conditions was constructed and appropriate 

boundary conditions and model parameters were 

selected. Next, the model was calibrated to existing 

conditions and a sensitivity analysis performed on 

selected model parameters. Finally, simulations were 

performed for the 5- and 100-year floodflows calibrated to existing conditions, then simulations for the 

natural conditions and the proposed conditions were 

performed.

The computational grid was constructed for the 

33.5-mi2

 model area in the White River flood plain 

between the upper and lower model boundaries (fig. 3). 

The model area within the White River flood plain 

extends from about 2.7 mi upstream from the proposed 

U.S. Highway 79 roadway alignment. Simulation 

results from the model are presented in figures 6-41 for 

about a 13-mi2

 part of the model area, referred to as the 

U.S. Highway 79 model area in figure 3.

Model Description

The Finite-Element Surface-Water Modeling 

System for Two-Dimensional flow in a Horizontal 

Plane (FESWMS-2DH) (Froehlich, 1989) was selected 

as an appropriate model for simulating two-dimensional flows within the study area. The model uses the 

Galerkin finite-element method to solve three partialdifferential equations representing conservation of 

mass and momentum (Lee and Froehlich, 1989). The 

model area is divided into triangular and quadrilateral 

sections (elements) of variable size, and input data are 

selected to describe the physical features of the model 
Modeling Approach 7

area. A depth-averaged velocity is computed at each 

computational point (node) in the model domain.

Input data requirements can be separated into 

three major categories: 

1. Geographical information. Land-surface 

elevations for each element, and dimensions and locations of each element (as defined by the computational 

grid).

2. Boundary conditions. Water-surface elevation or flow conditions at the model boundaries; also 

any net inflows and outflows to each element. Appropriate boundary conditions are needed to implement an 

accurate model.

3. Model parameters. Resistance coefficients 

for each element, possibly as a variable function of 

depth or velocity; also kinematic eddy viscosity.

An explanation of the theory of the model is 

beyond the scope of this report; however, a detailed 

explanation of the theory is provided in the research 

report by Lee and Froehlich (1989).

Model Implementation

There are several steps involved in the implementation of FESWMS-2DH. First, a finite-element 

grid representing the flow system must be constructed 

and tested. Once a stable grid has been constructed, 

boundary conditions, such as water-surface elevation 

and flow, must be determined. Finally, several model 

parameters and options must be considered to determine which model will produce the most accurate 

results for floodflow simulations.

Computational Grid

The use of FESWMS-2DH requires that the 

model area be divided into elements that form a grid 

(fig. 4). In the case of a triangular and quadrilateral 

grid, nodes are located at the corners, mid-sides, and 

center of the elements and are assigned coordinates and 

elevations. A finite-element grid should be carefully 

designed so that mass is conserved within the system. 

Figure 4. Computational grid generated for the model area.

FLOW

N

0

0

1 MILE

1 KILOMETER

EXPLANATION

Existing U.S. Highway 79

roadway alignment

Proposed Alternative 1

U.S. Highway 79

roadway alignment

Existing Union Pacific

Railroad alignment

Bridge Abutments

Roc Roe

Bayou

Cache

River

White

River
8 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

The finite-element grid needs to be more refined 

(smaller elements) in areas where changes in velocity 

or bathymetry are substantial than in areas where 

changes are gradual. Because of the size of the grid 

needed for this report, the model did not fully conserve 

the mass (discharge) within the system. The sum of the 

discharge distribution through the bridge openings, 

presented later in this report, did not equal 100 percent 

for all scenarios simulated. Usually, +/- 3 percent error 

is considered acceptable for the type of model simulations performed for this report, and model results were 

within this range with the exception of Alternative 1, 

which was +/- 5 percent.

The software package Surface-Water Modeling 

System (SMS) (Brigham Young University, 1999) was 

used to construct the computational grid representing 

the flow system in this report. The grid was constructed 

using an automated grid generator in SMS, surveying 

data supplied by the AHTD and USGS, and a 10-m digital elevation model (DEM). SMS uses vertex triangulation methods in which vertices (nodes) are distributed 

through the model domain and then connected appropriately by a triangulation algorithm. Nodes were created using the 10-m DEM data. DEM data were 

generated from topographic maps having 5-ft contour 

intervals and were verified by surveying five cross sections in the White River flood plain using total station 

and GPS units. Surveying data verified the accuracy of 

DEM data and no adjustments to the DEM data were 

necessary (fig. 5). The finite-element grid used for 

modeling the existing and natural conditions for this 

report consisted of nearly 11,000 elements and almost 

36,000 nodes; the grid for the proposed condition consisted of nearly 11,000 elements and almost 40,000 

nodes.

Boundary Conditions

Boundary conditions are established around the 

perimeter of a finite-element grid and identified as 

either closed or open. Closed boundaries represent 

obstructions, such as shorelines, embankments, and 

levees, that do not allow flow to pass through. The locations of the closed boundaries representing the shorelines in this report were estimated using the ground 

elevations obtained from the DEM’s. For the simulations in this report, all solid boundaries were set up for 

tangential slip condition, which forces all flow adjacent 

to the solid boundaries to flow parallel to the boundaries. Flows also can be allowed to pass over solid 

Figure 5. Verification of the 10-meter digital elevation model data with the most downstream surveyed cross section.

, , , , ,
Modeling Approach 9

boundaries to simulate weir flows over embankments. 

However, because both the existing and proposed conditions have embankments that are higher than the 100-

year floodflow, no weir flows were used for the simulations in this report.

Open boundaries represent boundaries that allow 

flow to enter or leave the finite-element grid. In this 

report, open boundaries are located at the upstream and 

downstream boundaries of the model area. The open 

boundary conditions at the upstream boundary are the 

discharges for the different flows being simulated. The 

open boundary conditions for the downstream boundary of the model area are water-surface elevations 

obtained from the gaging station at Aberdeen, Arkansas. The downstream boundary conditions from the 

gaging station are 168.5 and 173.2 ft for the 5- and 100-

year flood, respectively. 

Model Parameters

Several model parameters and options were considered and varied throughout the modeling process to 

ensure that the best simulation of floodflows was 

achieved. Manning’s roughness coefficient and kinematic eddy viscosity were the two primary model 

parameters that were varied. Default values for all other 

modeling parameters were used for floodflow simulations. These parameters included the following: water 

density, air density, dimensionless turbulence coefficient, relaxation factor, depth tolerance, and coefficients used to compute the momentum correction 

coefficient. Additionally, a low-order numerical integration technique was performed for each simulation. 

Wind effects were ignored and a constant density was 

assumed (assumed that flow was well mixed vertically). Any unsteady effects of the floodflow were 

ignored. Some of the modeling options that were considered were (1) steady-state or time-dependent solution, (2) elements being “turned on” and “off” during a 

run or elements being left “on” (Froehlich, 1989), and 

(3) varying the number of iterations to be performed to 

reach a converged solution.

Model Calibration

Calibration is the process of adjusting model 

input parameters until a reasonable match is produced 

between simulated results and actual known data for 

the study area. Grid configuration, the selection of 

Manning’s roughness coefficients, and the selection of 

kinematic eddy viscosities were based on engineering 

judgment and experience. Water-surface elevations 

were available for the 5- and 100-year floodflows at the 

USACE Aberdeen and Clarendon gaging stations by 

using the rating curves developed for the Clarendon 

and Aberdeen gages. Simulated water-surface elevations for each floodflow were calibrated to match the 

water-surface elevations at the Clarendon gaging station. Simulated water-surface elevations at the Clarendon gaging station from the calibrated model closely 

matched measured water-surface elevations (table 2). If 

default values for model parameters do not need to be 

adjusted to reach a solution comparable to the recorded 

data for the independent event, the model is commonly 

considered calibrated for a limited range of discharges. 

The model could not be validated because a separate 

recorded event was not available to simulate. 

Sensitivity Analysis

Sensitivity analysis evaluates the response of the 

model to incremental changes in parameters. The evaluation provides information about the uncertainty in 

model results and the level of confidence in use of 

model results. Manning’s roughness coefficients and 

base kinematic eddy viscosity (equations 4-19, Froehlich, 1989) were adjusted from the original values 

used in the calibrated model. Changes in Manning’s 

roughness coefficients had substantial effects on the 

model results of the water-surface elevation across the 

flood plain (about 0.5 ft). Changes in base kinematic 

eddy viscosity also had substantial effects on the watersurface elevation across the flood plain. For each floodflow simulation, a beginning kinematic eddy viscosity 

of 250 ft2

/s was used. Once a convergence solution was 

reached for the targeted boundary conditions, the kinematic eddy viscosity was lowered in a series of steps by 

decreasing the kinematic eddy viscosity values by onehalf. For kinematic eddy viscosities between 250 ft2/s 

Table 2. Known and simulated water-surface elevation for 

the model calibration

[WSE, water-surface elevation above NGVD of 1929]

Aberdeen

assigned

WSE

(feet)

Clarendon

known

 WSE

(feet)

Clarendon

simulated

WSE

(feet)

5-year floodflow 168.53 170.78 170.82

100-year floodflow 173.21 175.48 175.50
10 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

and 40 ft2/s, substantial changes in water-surface elevations (about 0.4 ft) occurred at the upstream boundaries. However, for kinematic eddy viscosities between 

40 ft2/s and 7 ft2/s, changes in the water-surface elevations were less (less than 0.15 ft) at the upstream 

boundaries. 

SIMULATION OF FLOODFLOWS

Floodflows for the 5- and 100-year floods were 

simulated for the existing, natural, and proposed conditions. The AHTD and USFWS have concerns about the 

backwater and velocity distributions caused by the proposed bridges during all flow conditions because the 

bridges are located in the National Wildlife Refuges. 

For each of the four proposed alternatives, average upstream and downstream water-surface elevations 

as well as the water-surface elevation along the proposed U.S. Highway 79 alignment were estimated by 

taking the average of the water-surface elevations at a 

group of nodes on a line at the location of interest. 

Approach elevations were selected from a group of 

nodes on a line that stretched from the left bank to the 

right bank approximately 1 mi upstream from the simulated roadway alignment. Backwater then was estimated by subtracting the average water-surface 

elevations determined for the natural conditions from 

the average water-surface approach elevations determined for the existing and proposed conditions. Average bridge opening velocities were calculated by taking 

the average depth-averaged velocities at a group of 

nodes on a line that crossed the entire bridge opening 

from the left bridge abutment to the right bridge abutment.

5-Year Flood

Floodflows were simulated for the White River 

5-year flood for the existing, natural, and proposed 

conditions. The estimated 5-year floodflow was 

115,100 ft3

/s and has a 20 percent chance of being 

equaled or exceeded in any given year. During the 5-

year flood, flow model simulations show that the floodwaters would breach the main channel of both the 

White River and Roc Roe Bayou and submerge the 

entire width of the flood plain in the study area. The 

average water depth computed for a series of nodes 

along a cross section at the upper model boundary was 

about 11 ft; the average water depth computed for a 

series of nodes along a cross section at the lower model 

boundary was about 10 ft. For the 5-year floodflow, the 

main channel of the White River ranges in depth from 

25 to 60 ft, and the main channel of Roc Roe Bayou 

ranges in depth from 18 to 29 ft. Water-surface elevations for the 5-year flood event range from 171.9 ft 

above NGVD of 1929 at the upper model boundary to 

168.5 ft above NGVD of 1929 at the lower model 

boundary.

Existing Conditions

The 5-year floodflow was simulated with the 

existing land use and roadway alignment in place. The 

simulation also included the Union Pacific Railroad 

embankment and bridge configuration that was in place 

prior to 1995, because the stage and discharge data 

used to calculate the flood frequency were collected 

prior to 1995. Simulation of the 5-year floodflow for 

the existing conditions indicates that about 57 percent 

(65,600 ft3/s) of flow was conveyed by the White River 

bridge, about 26 percent (29,900 ft3

/s) by the First Old 

River bridge, and about 17 percent (19,600 ft3

/s) by the 

Roc Roe Bayou bridge. The maximum depth-averaged 

point velocities for the White River and First Old River 

bridges were 3.6 and 1.6 ft/s, respectively. Average 

water depths were 12 and 10 ft at the White River and 

First Old River bridges, respectively. The maximum 

depth-averaged point velocity predicted at the Roc Roe 

Bayou bridge was 3.3 ft/s with an average water depth 

of 8 ft. The average water-surface elevation at the upper 

model boundary was 171.9 ft, the average water-surface elevation along the U.S. Highway 79 roadway 

alignment was 171.5 ft, and the average water-surface 

elevation at lower model boundary was set at 168.5 ft 

(predetermined from a developed rating curve at the 

Aberdeen gaging station). Average water depths at the 

upper model boundary, U.S. Highway 79 roadway 

alignment, and the lower model boundary were 11 ft, 

10 ft, and 10 ft, respectively. Simulated water-surface 

elevations for the 5-year floodflow for the existing conditions are shown on figure 6, the corresponding depthaveraged velocity contours are shown on figure 7, and 

the corresponding distribution of depth-averaged point 

velocity vectors near the existing U.S. Highway 79 

roadway alignment is shown on figure 8. 

Natural Conditions

Simulation of the 5-year floodflow for the natural conditions, that is, without U.S. Highway 79 or 
Simulation of Floodflows 11

Figure 6. Simulated water-surface elevations for the 5-year floodflow through the existing U.S. Highway 79 roadway 

alignment.

Figure 7. Depth-averaged velocity contours for the 5-year floodflow through the existing U.S. Highway 79 roadway alignment.

Roc

Roe

Bayou

White

White

River

River

First

Old

River

UNION PACIFIC RAILROAD

171.1

171.3

171.5

171.5

171.3

171.1

171.0

170.8

170.6

171.0

170.8

170.6

170.4

171.5

171.7

171.3

171.1

171.0

170.8

170.6

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

Roc

Roe

Bayou

White River

River

First

Old

White

River

UNION

PACIFICPACIFIC

RAILROADRAILROAD

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

34 41’ o

34 40’ o

91 22’30” o 91 20’ o
12 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 8. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the existing U.S. Highway 79 

roadway alignment.

0 7

VELOCITY, IN FEET

PER SECOND

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

Union Pacific Railroad bridges and embankments, indicates maximum depth-averaged point velocities for an 

area near the location of the existing White River, First 

Old River and Roc Roe Bayou bridges were 2.9, 0.7, 

and 1.2 ft/s, respectively. Average water depths near the 

location of the existing bridge openings were 11, 9, and 

7 ft for the White River, First Old River, and Roc Roe 

Bayou bridges, respectively. The average water-surface 

elevation at the upper model boundary was 171.4 ft; the 

average water-surface elevation near the location of the 

existing U.S. Highway 79 roadway alignment was 

170.9 ft; the average water-surface elevation at the 

lower model boundary was set at 168.5 ft (predetermined from a developed rating curve at the Aberdeen 

gaging station). Average water depths at the upper 

model boundary, near the location of the existing U.S. 

Highway 79 roadway alignment, and at the lower 

model boundary were 10, 8, and 10 ft, respectively. The 

simulated water-surface elevations for the 5-year floodflow for natural conditions are shown on figure 9, the 

corresponding depth-averaged velocity contours are 

shown on figure 10, and the corresponding distribution 

of depth-averaged point velocity vectors near the location of the existing roadway bridges is shown on figure 

11.

Proposed Conditions—Alternative 1

Simulation of the 5-year floodflow for the proposed Alternative 1 U.S. Highway 79 roadway alignment indicates that about 78 percent (89,900 ft3/s) of 

the flow was conveyed by the proposed White River 

bridge, about 6 percent (7,400 ft3

/s) by the proposed 

1,400-ft relief bridge, and about 13 percent (14,600 ft3/

s) by the proposed Roc Roe Bayou bridge (table 3). 

Although average velocities for Alternative 1 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

bridge opening increase moderately compared to existing conditions (table 3). Water-surface elevations range 

from 171.0 ft to 171.4 ft through the bridge openings 

(fig. 12), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 13-14, table 3). 

The average backwater caused by the simulated 

proposed Alternative 1 U.S. Highway 79 bridges was 
Simulation of Floodflows 13

Figure 9. Simulated water-surface elevations for the 5-year floodflow for natural conditions through the White River flood plain 

at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway for natural conditions).

Figure 10. Depth-averaged velocity contours for the 5-year floodflow for natural conditions through the White River flood plain 

at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway for natural conditions).

Roc

Roe

Bayou

UNION PACIFIC RAILROAD 0

0

0.5

0.5

1 MILE

1 KILOMETER

79

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

79

White River

First

River

Old

River

White

171.2

171.0

170.9

170.7

170.6

170.4

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

Roc

Roe

Bayou

White River

River

FirstOld

White

River

UNION PACIFIC

RAILROADRAILROAD

79

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0
14 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 11. Distribution of depth-averaged point velocity vectors for the 5-year floodflow for natural conditions through the 

White River flood plain at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway for 

natural conditions).

Figure 12. Simulated water-surface elevations for the 5-year floodflow through the proposed Alternative 1 U.S. Highway 79 

roadway alignment.

N

0 7

VELOCITY, IN FEET

PER SECOND

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

River

River

First

Old

White

White

River

171.7

171.5

171.4

171.0

170.6

171.4

171.2

171.0

170.8

170.6

170.4

170.4

171.5

171.2

171.0

170.8

170.6

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.0
Simulation of Floodflows 15

Figure 13. Depth-averaged velocity contours for the 5-year floodflow through the proposed Alternative 1 U.S. Highway 79 

roadway alignment.

Figure 14. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the proposed Alternative 1 

U.S. Highway 79 roadway alignment.

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White

River

UNION

Proposed Highway 79Proposed Highway 79

PACIFIC

RAILROADRAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

0 7

VELOCITY, IN FEET

PER SECOND

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER
16 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Table 3. Hydraulic data for the White River flood plain U.S. Highway 79 roadway alignment for simulated floodflows having a 5-

year recurrence interval

WHITE RIVER FLOOD PLAIN CROSSING

5-YEAR FLOOD EVENT

Simulated conditions

and U.S. Highway 79

bridge opening

Discharge

distribution

(cubic feet

per second)

Discharge

distribution

(percent)

Backwater

at

approach

section

(feet)

Average

velocity

through

bridge

openings

(feet per

second)

Maximum

velocity

through

bridge

openings

(feet per

second)

Location

of

maximum

velocity

(feet per second)

Average

depth

of water

through

bridge

opening

(feet)

Existing

White River Bridge 65,600 57 1.0 3.6 Main channel 12

First Old River Bridge 29,900 26 0.4 0.8 1.6 Right bridge abutment 10

Roc Roe Bayou Bridge 19,600 17 1.6 3.3 Main channel 8

Natural

White River Bridge area1

1

Locations near existing openings. Bridges and embankments removed for the hypothetical natural conditions.

0.6 2.9 Main channel 11

First Old River Bridge area1 not applicable not applicable 0.5 0.7 Main channel 9

Roc Roe Bayou Bridge area1 0.6 1.2 Main channel 7

Proposed Alternative 1

White River Bridge 89,900 78 0.9 4.6 Main channel 10

1,400-Foot Relief Bridge 7,400 6 0.5 0.8 1.7 Right bridge abutment 5

Roc Roe Bayou Bridge

(1,540 Foot Bridge)

14,600 13 1.0 2.9 Main channel 6

Proposed Alternative 2

White River Bridge 89,900 78 0.8 4.5 Main channel 12

1,545-Foot Relief Bridge 7,500 7 0.2 1.1 2.0 Right bridge abutment 5

Roc Roe Bayou Bridge

(2,475 Foot Bridge)

16,200 14 1.2 2.3 Main channel 7

Proposed Alternative 3

White River Bridge 89,900 78 0.8 4.4 Main channel 12

1,545-Foot Relief Bridge 7,500 7 0.2 1.1 2.0 Right bridge abutment 5

Roc Roe Bayou Bridge

(3,475 Foot Bridge)

16,600 14 0.9 2.2 Main channel 6

Proposed Alternative 4

White River Bridge 87,100 76 0.8 4.3 Main channel 12

1,545-Foot Relief Bridge 7,000 6 0.2 1.0 1.9 Right bridge abutment 5

Roc Roe Bayou Bridge

(3,475 Foot Bridge)

18,600 16 1.0 2.0 Main channel 7
Simulation of Floodflows 17

0.5 ft for the 5-year floodflow. A complete tabulation of 

the hydraulic data for the 5-year floodflow for the 

bridges for proposed Alternative 1 is in table 3. 

Proposed Conditions—Alternative 2

Simulation of the 5-year floodflow for the proposed Alternative 2 U.S. Highway 79 roadway alignment indicates that about 78 percent (89,900 ft3/s) of 

the flow was conveyed by the proposed White River 

bridge, about 7 percent (7,500 ft3

/s) by the proposed 

1,545-ft relief bridge, and about 14 percent (16,200 ft3

/

s) by the proposed Roc Roe Bayou bridge (table 3). 

Although average velocities for Alternative 2 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

bridge opening increase moderately compared to existing conditions (table 3). Water-surface elevations range 

from 171.0 ft to 171.4 ft through the bridge openings 

(fig. 15), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 16-17, table 3).

The average backwater caused by the proposed 

Alternative 2 U.S. Highway 79 bridges was 0.2 ft for 

the 5-year floodflow. A complete tabulation of the 

hydraulic data for the 5-year floodflow for the bridges 

for proposed Alternative 2 is listed in table 3. 

Proposed Conditions—Alternative 3

Simulation of the 5-year floodflow for the proposed Alternative 3 U.S. Highway 79 roadway alignment indicates that about 78 percent (89,900 ft3

/s) of 

the flow was conveyed by the proposed White River 

bridge, about 7 percent (7,500 ft3

/s) by the proposed 

1,545-ft relief bridge, and about 14 percent (16,600 ft3/

s) by the proposed Roc Roe Bayou bridge (table 3). 

Although average velocities for Alternative 3 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

bridge opening increase moderately compared to existing conditions (table 3). Water-surface elevations range 

from 171.0 ft to 171.4 ft through the bridge openings 

(fig. 18), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 19-20, table 3).

Figure 15. Simulated water-surface elevations for the 5-year floodflow through the proposed Alternative 2 U.S. Highway 79 

roadway alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

River

River

First

Old

White

White

River

171.5

171.4

171.2

171.0

170.8

170.6

170.4

170.8

171.0

171.4

171.2

170.4

170

17

.6

0.8

171.0

171.2

171.4

171.5

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.0
18 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 16. Depth-averaged velocity contours for the 5-year floodflow through the proposed Alternative 2 U.S. Highway 79 

roadway alignment.

Figure 17. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the proposed Alternative 2 

U.S. Highway 79 roadway alignment.

Roc

Roe

Bayou

White River

River

First

Old

White

River

UNION

Proposed Highway 79Proposed Highway 79

PACIFIC

RAILROADRAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

0 7

VELOCITY, IN FEET

PER SECOND
Simulation of Floodflows 19

Figure 18. Simulated water-surface elevations for the 5-year floodflow through the proposed Alternative 3 U.S. Highway 79 

roadway alignment.

Figure 19. Depth-averaged velocity contours for the 5-year floodflow through the proposed Alternative 3 U.S. Highway 79 

roadway alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

River

River

First

Old

White

White

River

171.7

171.4

171.2

171.0

170.8

170.6

170.4

170.8

171.0

171.2

171.4

170.4

170

170.

.6

8 171.0

171.2

171.4

171.5

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.0

Roc Roe

Bayou

White River

River

First

Old

White

River

UNION

Proposed Highway 79Proposed Highway 79

PACIFICPACIFIC

RAILROADRAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

0

0

0.5

0.5

1 MILE

1 KILOMETER
20 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 20. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the proposed Alternative 3 

U.S. Highway 79 roadway alignment.
Simulation of Floodflows 21

Figure 21. Simulated water-surface elevations for the 5-year floodflow through the proposed Alternative 4 U.S. Highway 79 

roadway alignment.

Figure 22. Depth-averaged velocity contours for the 5-year floodflow through the proposed Alternative 4 U.S. Highway 79 

roadway alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

River

River

First

Old

White

White

River

171.3

171.1

170.9

171.4

171.3

171.1

170.9

170.7

170.5

171.1

170.5

170.7

1

170.9

71

1

.1

71.3

171.4

171.6

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.0

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White

River

UNION

Proposed Highway 79Proposed Highway 79

PACIFIC

RAILROADRAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0
22 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 23. Distribution of depth-averaged point velocity vectors for the 5-year floodflow through the proposed Alternative 4 

U.S. Highway 79 roadway alignment.

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

0 7

VELOCITY, IN FEET

PER SECOND

second) across the Roc Roe Bayou bridge opening than 

for existing conditions. However, as table 3 illustrates, 

these differences are relatively small and the locations 

of the maximum depth averaged point velocity does not 

change between each alternative and existing bridge 

openings. A comparison of backwater and velocity for 

each alternative to existing conditions is shown in table 

4. 

100-Year Flood

The estimated 100-year floodflow is 216,000

ft3/s and has a 1 percent chance of being equaled or 

exceeded in any given year. Model simulations show 

that the entire White River flood plain in the study area 

becomes submerged during the 100-year floodflow. 

Average depths computed for a series of nodes along a 

cross section at the upper model boundary was about 15 

ft; the average water depth computed for a series of 

nodes along a cross section at the lower model boundary was about 14 ft. For the 100-year floodflow, the 

main channel of the White River ranges in depth from 

32 to 65 ft, and the main channel of Roc Roe Bayou 

ranges in depth from 20 to 33 ft. Water-surface elevations for the 100-year floodflow range from 176.9 ft 

above NGVD of 1929 at the upper model boundary to 

173.2 ft above NGVD of 1929 at the lower model 

boundary. 

Existing Conditions

The 100-year floodflow was simulated with the 

existing land use and roadway alignment in place. The 

simulation also included the Union Pacific Railroad 

embankment and bridge configuration that was in place 

prior to 1995, because stage and discharge data used to 

calculate the flood frequency were collected prior to 

1995. Simulation of the 100-year floodflow indicates 

that about 56 percent (123,100 ft3

/s) of flow was conveyed by the White River bridge, about 26 percent 

(56,200 ft3

/s) by the First Old River bridge, and about 

19 percent (41,000 ft3

/s) by the Roc Roe Bayou bridge 

(table 5). The maximum depth-averaged point velocities for the White River and First Old River bridges 

were 4.2 and 2.2 ft/s, respectively. Average water 

depths were 16 and 15 ft at the White River and First 

Old River bridges, respectively. The maximum depthaveraged point velocity at the Roc Roe Bayou bridge 

was 4.1 ft/s with an average water depth of 13 ft 
Simulation of Floodflows 23

Table 4. Comparison of backwater and velocity data for each alternative to existing conditions for simulated

floodflows having a 5-year recurrence interval

Alternative 1 Alternative 2 Alternative 3 Alternative 4

Change in backwater elevation

(in feet) +0.1 -0.2 -0.2 -0.2

Change in average velocity 

across White river bridge

(in feet per second)

-0.1 -0.2 -0.2 -0.2

Change in average velocity 

across Roc Roe Bayou bridge 

(in feet per second)

-0.6 -0.4 -0.7 -0.6

Change in maximum velocity 

across White River bridge (in 

feet per second)

+1.0 +0.9 +0.8 +0.8

Change in maximum velocity 

across Roc Roe Bayou bridge 

(in feet per second)

-0.4 -1.0 -1.1 -1.3

(table 5). The average water-surface elevation at the 

upper model boundary was 176.9 ft; the average watersurface elevation along the U.S. Highway 79 roadway 

alignment was 176.3 ft; and the average water-surface 

elevation at the lower model boundary was set at 173.2 

ft (predetermined from a developed rating curve at the 

Aberdeen gaging station). Average depths at the upper 

model boundary, the U.S. Highway 79 roadway alignment, and the lower model boundary were 15, 14, and 

14 ft, respectively. The simulated water-surface elevations for the 100-year floodflow for existing conditions 

are shown on figure 24, the corresponding depth-averaged velocity contours are shown on figure 25, and the 

corresponding distribution of depth-averaged velocity 

vectors near the existing U.S. Highway 79 bridges is 

shown on figure 26. 

Natural Conditions

Simulation of the 100-year floodflow for the natural conditions, that is, without U.S. Highway 79 or 

Union Pacific Railroad bridges and embankments, 

indicates maximum depth-averaged point velocities for 

an area near the location of the existing White River, 

First Old River, and Roc Roe Bayou bridges were 3.3, 

0.9, and 1.3 ft/s, respectively (table 5). Average water 

depths near the location of the existing bridge openings 

were 15, 16, and 11 ft for the White River, the First Old 

River, and Roc Roe Bayou bridges, respectively (table 

5). The average water-surface elevation at the upper 

model boundary was 176.2 ft, the average water-surface elevation near the location of the existing U.S. 

Highway 79 roadway alignment was 175.4 ft, and the 

average water-surface elevation at the lower model 

boundary was set at 173.2 ft (predetermined from a 

developed rating curve at the Aberdeen gaging station). 

Average water depths at the upper model boundary, 

near the location of the existing U.S. Highway 79 roadway alignment, and the lower model boundary were 15, 

14, and 14 ft, respectively. The simulated water-surface 

elevations for the 100-year flood for the natural conditions are shown on figure 27, the corresponding depthaveraged velocity contours are shown on figure 28, and 

the corresponding distribution of depth-averaged point 

velocity vectors near the location of the existing roadway bridges is shown on figure 29.

Proposed Conditions—Alternative 1

Simulation of the 100-year floodflow for the proposed Alternative 1 U.S. Highway 79 roadway alignment indicates that about 72 percent (155,500 ft3

/s) of 

the flow was conveyed by the proposed White River 

bridge, about 9 percent (19,900 ft3/s) by the proposed 

1,400-ft relief bridge, and about 14 percent (30,700

ft3/s) by the proposed Roc Roe Bayou bridge (table 5). 

Although average velocities for Alternative 1 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 
24 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Table 5. Hydraulic data for the White River flood plain U.S. Highway 79 roadway alignment for simulated floodflows having a 

100-year recurrence interval

WHITE RIVER FLOOD PLAIN CROSSING

100-YEAR FLOOD EVENT

Simulated conditions

and U.S. Highway 79

bridge opening

Discharge

distribution

(cubic feet

per second)

Discharge

distribution

(percent)

Backwater

at

approach

section

(feet)

Average

velocity

through

bridge

openings

(feet per

second)

Maximum

velocity

through

bridge

openings

(feet per

second)

Location

of

maximum

velocity

(feet per second)

Average

depth of

water

through

bridge

opening

(feet)

Existing

White River Bridge 123,100 56 1.4 4.2 Main channel 16

First Old River Bridge 56,200 26 0.8 1.2 2.2 Right bridge abutment 15

Roc Roe Bayou Bridge 41,000 19 2.3 4.1 Left bridge abutment 13

Natural

White River Bridge area1

1

Locations near existing bridge openings. Bridges and embankments removed for the hypothetical natural conditions.

0.8 3.3 Main channel 15

First Old River Bridge area1 not applicable not applicable 0.7 0.9 Main channel 16

Roc Roe Bayou Bridge area1 0.6 1.3 Main channel 11

Proposed Alternative 1

White River Bridge 155,500 72 1.2 5.4 Main channel 17

1,400 Foot Relief Bridge 19,900 9 0.6 1.5 2.4 Right bridge abutment 10

Roc Roe Bayou Bridge

(1,540 Foot Bridge)

30,700 14 1.9 2.9 Left bridge abutment 12

Proposed Alternative 2

White River Bridge 155,600 72 1.1 5.4 Main channel 17

1,545 Foot Relief Bridge 20,700 10 0.4 1.5 2.5 Right bridge abutment 10

Roc Roe Bayou Bridge

(2,475 Foot Bridge)

36,500 17 1.6 2.4 Left bridge abutment 11

Proposed Alternative 3

White River Bridge 155,100 72 1.1 5.3 Main channel 16

1,545 Foot Relief Bridge 20,600 10 0.3 1.5 2.4 Right bridge abutment 10

Roc Roe Bayou Bridge

(3,475 Foot Bridge)

37,300 17 1.2 2.4 Left bridge abutment 10

Proposed Alternative 4

White River Bridge 151,200 70 1.1 5.1 Main channel 17

1,545 Foot Relief Bridge 19,800 9 0.3 1.4 2.2 Right bridge abutment 10

Roc Roe Bayou Bridge

(3,475 Foot Bridge)

43,000 20 1.3 2.1 Left bridge abutment 11
Simulation of Floodflows 25

Figure 24. Simulated water-surface elevations for the 100-year floodflow through the existing U.S. Highway 79 roadway 

alignment.

Figure 25. Depth-averaged velocity contours for the 100-year floodflow through the existing U.S. Highway 79 roadway 

alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White River River

First

Old

River

176.4

176.1

176.0

175.8

175.6 175.4

175.2

176.2

176.0

175.8

175.6

175.4

175.2

175.2

176.4

176.2

176.0

175.4

175.8

176.6

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

Roc

Roe

Bayou

White River

River

First Old

White River

UNION PACIFIC RAILROAD

RAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0
26 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 26. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for natural conditions through the 

existing U.S. Highway 79 openings.

Figure 27. Simulated water-surface elevations for the 100-year floodflow for natural conditions through the White River flood 

plain at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway for natural 

conditions).

0 7

VELOCITY, IN FEET

PER SECOND

79 N

79

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White

River River

First

Old

River

175.8

175.6

175.5

175.3

175.1

175.0

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1
Simulation of Floodflows 27

Figure 28. Depth-averaged velocity contours for the 100-year floodflow for natural conditions through the White River flood 

plain at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway for natural 

conditions).

Figure 29. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for natural conditions through the 

White River flood plain at the U.S. Highway 79 crossing (embankments are transparent as to illustrate flow through roadway 

for natural conditions).

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White River

UNION PACIFIC

PACIFIC RAILROAD

RAILROAD

79

79 34 41’ o

34 40’ o

91 22’30” o 91 20’ o

0 7

VELOCITY, IN FEET

PER SECOND

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79
28 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

bridge opening increase moderately compared to existing conditions (table 5). Water-surface elevations range 

from 175.6 ft to 175.9 ft through the bridge openings 

(fig. 30), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 31-32, table 5).

The average backwater caused by the proposed 

Alternative 1 U.S. Highway 79 bridges was 0.6 ft for 

the 100-year floodflow. A complete tabulation of the 

hydraulic data for the 100-year floodflow for the 

bridges for proposed Alternative 1 is listed in table 5. 

Proposed Conditions—Alternative 2

Simulation of the 100-year floodflow for the proposed Alternative 2 U.S. Highway 79 roadway alignment indicates that about 72 percent (155,600 ft3

/s) of 

the flow was conveyed by the proposed White River 

bridge, about 10 percent (20,700 ft3/s) by the proposed 

1,545-ft relief bridge, and about 17 percent (36,500 ft3/

s) by the proposed Roc Roe Bayou bridge (table 5). 

Although average velocities for Alternative 2 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

bridge opening increase moderately compared to existing conditions (table 5). Water-surface elevations range 

from 175.6 ft to 176.0 ft through the bridge openings 

(fig. 33), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 34-35, table 5).

The average backwater caused by the proposed 

Alternative 2 U.S. Highway 79 bridges was 0.4 ft for 

the 100-year floodflow. A complete tabulation of the 

hydraulic data for 100-year floodflow for the bridges 

for proposed Alternative 2 is listed in table 5. 

Proposed Conditions—Alternative 3

Simulation of the 100-year floodflow for the proposed Alternative 3 U.S. Highway 79 roadway alignment indicates that about 72 percent (155,100 ft3/s) of 

the flow was conveyed by the proposed White River 

bridge, about 10 percent (20,600 ft3/s) by the proposed 

1,545-ft relief bridge, and about 17 percent (37,300 ft3/

s) by the proposed Roc Roe Bayou bridge (table 5). 

Although average velocities for Alternative 3 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

Figure 30. Simulated water-surface elevations for the 100-year floodflow through the proposed Alternative 1 U.S. Highway 79 

roadway alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White

River

River

Riv

er

First

Old

175.0

175.2

175.4

175.6 17

1

5.8

75.9

176.1

176.3

175.9

175.8

175.6

175.4

175.2

176.1

175.9

175.8

175.4

176.3

176.5

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1
Simulation of Floodflows 29

Figure 31. Depth-averaged velocity contours for the 100-year floodflow through the proposed Alternative 1 U.S. Highway 79 

roadway alignment.

Figure 32. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the proposed Alternative 1 U.S. 

Highway 79 openings.

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White River

UNION

PROPOSED HIGHWAY 79PROPOSED HIGHWAY 79

PACIFIC RAILROAD

RAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

0 7

VELOCITY, IN FEET

PER SECOND

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER
30 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 33. Simulated water-surface elevations for the 100-year floodflow through the proposed Alternative 2 U.S. Highway 79 

roadway alignment.

Figure 34. Depth-averaged velocity contours for the 100-year floodflow through the proposed Alternative 2 U.S. Highway 79 

roadway alignment.

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White

River

River

Riv

er

First

Old

176.2

176.0

175.8

175.6

175.4

175.2

175.4

175.6

175.8

176.0

176.2

175.8

175.6 175.4

175.2

175.0

176.4

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc Roe

Bayou

White River

River

First

Old

White

River

UNION

PROPOSED HIGHWAY 79PROPOSED HIGHWAY 79

PACIFIC RAILROAD

RAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0
Simulation of Floodflows 31

Figure 35. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the proposed Alternative 2 U.S. 

Highway 79 openings.

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

0 7

VELOCITY, IN FEET

PER SECOND

bridge opening increase moderately compared to existing conditions (table 5). Water-surface elevations range 

from 175.7 ft to 175.9 ft through the bridge openings 

(fig. 36), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 37-38, table 5).

The average backwater caused by the proposed 

Alternative 3 U.S. Highway 79 bridges was 0.3 ft for 

the 100-year floodflow. A complete tabulation of the 

hydraulic data for the 100-year floodflow for the 

bridges for proposed Alternative 3 is listed in table 5. 

Proposed Conditions—Alternative 4

Simulation of the 100-year floodflow for the proposed Alternative 4 U.S. Highway 79 roadway alignment indicates that about 70 percent (151,200 ft3

/s) of 

the flow was conveyed by the proposed White River 

bridge, about 9 percent (19,800 ft3/s) by the proposed 

1,545-ft relief bridge, and about 20 percent (43,000

ft3/s) by the proposed Roc Roe Bayou bridge (table 5). 

Although average velocities for Alternative 4 through 

each bridge opening were very similar to velocities 

through the bridge openings for existing conditions, the 

maximum point velocities through the White River 

bridge opening increase moderately compared to existing conditions (table 5). Water-surface elevations range 

from 175.6 ft to 175.8 ft through the bridge openings 

(fig. 39), and the maximum depth averaged point velocities occur around the bridge abutments for each opening (figs. 40-41, table 5).

The average backwater caused by the proposed 

Alternative 4 U.S. Highway 79 bridges was 0.3 ft for 

the 100-year floodflow. A complete tabulation of the 

hydraulic data for the 100-year floodflow for the 

bridges for proposed Alternative 4 is listed in table 5. 

Comparison of Simulation Results for Proposed 

Alternatives and Existing Conditions

Simulation results indicate relatively little difference in 

the changes in backwater elevation and velocities 

among the four alternatives during the 100-year recurrence interval floodflows (table 5). All of the alternatives typically result in slightly lower backwater 

elevations (0.2 to 0.5 foot lower), average velocities 

(0.2 to 1.1 ft/s lower), and maximum velocities (about 

1 to 2 ft/s lower) across Roc Roe Bayou bridge and 

higher maximum velocities (about 1 ft/s) across the 

White River bridge, than for existing conditions. However, as table 5 illustrates, these differences are relatively small and the locations of the maximum depth 

averaged point velocity does not change between each 

alternative and existing bridge openings. A comparison 

of backwater and velocity for each alternative to existing conditions is shown in table 6.
32 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 36. Simulated water-surface elevations for the 100-year floodflow through the proposed Alternative 3 U.S. Highway 79 

roadway alignment.

Figure 37. Depth-averaged velocity contours for the 100-year floodflow through the proposed Alternative 3 U.S. Highway 79 

roadway alignment.

Roc

Roe Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White

River

River

Riv

er

First

Old

176.3

176.1

175.9

175.7

175.5

175.3

175.5

175.7

175.9

176.1

174.9

175

17

.1

5.3 175.5

17

1

5.7

75.9

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White River

UNION

PROPOSED HIGHWAY 79PROPOSED HIGHWAY 79

PACIFIC RAILROAD

RAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0
Simulation of Floodflows 33

Figure 38. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the proposed Alternative 3 U.S. 

Highway 79 openings.

Figure 39. Simulated water-surface elevations for the 100-year floodflow through the proposed Alternative 4 U.S. Highway 79 

roadway alignment.

79

79

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

0 7

VELOCITY, IN FEET

PER SECOND

Roc

Roe

Bayou

UNION PACIFIC RAILROAD

0

0

0.5

0.5

1 MILE

1 KILOMETER

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

White

White

River

River

Riv

er

First

Old

176.2

176.0

175.8

175.6

175.4

175.2

175.6

176.0

175.8

175.0

17

17

5.2

5.4

175

1

.6

75.8

79

79

EXPLANATION

WATER-SURFACE CONTOUR--Shows

elevation of water surface, in feet. Contour

interval is variable. Datum is National

Geodetic Vertical Datum of 1929

BRIDGE ABUTMENTS

171.1
34 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Figure 40. Depth-averaged velocity contours for the 100-year floodflow through the proposed Alternative 4 U.S. Highway 79 

roadway alignment.

Figure 41. Distribution of depth-averaged point velocity vectors for the 100-year floodflow for the proposed Alternative 4 U.S. 

Highway 79 openings.

0

0

0.5

0.5

1 MILE

1 KILOMETER

Roc

Roe

Bayou

White River

River

First

Old

White River

UNION

PROPOSED HIGHWAY 79PROPOSED HIGHWAY 79

PACIFIC RAILROAD

RAILROAD

34 41’ o

34 40’ o

91 22’30” o 91 20’ o

EXPLANATION

DEPTH AVERAGED

VELOCITY, IN FEET PER

SECOND

0.0 - 1.0

1.0 - 2.0

2.0 - 3.0

3.0 - 4.0

4.0 - 5.0

5.0 - 6.0

6.0 - 7.0

N

0

0

0.5

0.5

1 MILE

1 KILOMETER

79

79

0 7

VELOCITY, IN FEET

PER SECOND
Summary 35

Table 6. Comparison of backwater and velocity data for each alternative to existing conditions for simulated floodflows having 

a 100-year recurrence interval

Alternative 1 Alternative 2 Alternative 3 Alternative 4

Change in backwater elevation

(in feet) -0.2 -0.4 -0.5 -0.5

Change in average velocity 

across White River bridge

(in feet per second)

-0.2 -0.3 -0.3 -0.3

Change in average velocity 

across Roc Roe Bayou bridge 

(in feet per second)

-0.4 -0.7 -1.1 -1.0

Change in maximum velocity 

across White River bridge (in 

feet per second)

+1.2 +1.2 +1.1 +0.9

Change in maximum velocity 

across Roc Roe Bayou bridge 

(in feet per second)

-1.2 -1.7 -1.7 -2.0

SUMMARY

A two-dimensional finite-element surface-water 

model was used to study the effects of the proposed 

modification to the U.S. Highway corridor 79 on flooding on the White River near Clarendon, Arkansas. The 

effects of floodflow were simulated for the following: 

existing conditions, natural conditions, and four proposed bridging alternatives. All of the scenarios were 

modeled with floods having the 5- and 100-year recurrence intervals (115,100 and 216,000 ft3

/s). The simulated existing conditions included a 3,200-ft White 

River bridge located on the east side of the study area 

near Clarendon, Arkansas; a 3,700-ft First Old River 

bridge located 0.5 mi west of the White River bridge 

opening; and a 1,430-ft Roc Roe Bayou bridge located 

1.6 mi west of the First Old River bridge. The simulated 

hypothetical natural conditions involved removing the 

U.S. Highway 79 and the Union Pacific Railroad 

embankments along the entire length of the flood plain. 

The primary purpose of model simulations for natural 

conditions was to calculate backwater data for the 

existing and proposed conditions. The four simulated 

hypothetical proposed alternatives involved a 1.8-mi 

White River bridge located on the east side of the study 

area near Clarendon, Arkansas; and either an Alternative 1 with a 1,400-foot relief bridge or Alternatives 2-

4 with a 1,545 relief bridge located 0.25 mi west of the 

White River bridge opening; and three different Roc 

Roe Bayou bridge openings ranging from 1,540-3,475 

ft in length located 0.9 mi west of the relief bridge.

Simulation of the 5-year floodflow for the existing conditions indicates that about 57 percent (65,600 

ft3/s) of flow was conveyed by the White River bridge, 

about 26 percent (29,900 ft3

/s) by the First Old River 

bridge, and about 17 percent (19,600 ft3

/s) by the Roc 

Roe Bayou bridge. Maximum depth-averaged point 

velocities for the White River and First Old River 

bridges were 3.6 and 1.6 ft/s, respectively. Average 

depths were 12 and 10 ft for the White River and First 

Old River bridges, respectively. The maximum depthaveraged point velocity predicted for the Roc Roe 

Bayou bridge was 3.3 ft/s with an average depth of 8 ft. 

The average water-surface elevation at the upper 

boundary of the study area was 171.9 ft; the average 

water-surface elevation along U.S. Highway 79 was 

171.5 ft; and the average water-surface elevation at 

lower boundary of the study area was set at 168.5 ft. 

Average depths at the upper boundary, U.S. Highway 

79, and the lower boundary were 11 ft, 10 ft, and 10 ft, 

respectively.

Simulation of the 5-year floodflow for the proposed U.S. Highway 79 alignment alternatives indicates that 76-78 percent (87,100-89,900 ft3/s) of the 

flow was conveyed by the proposed White River 

bridge, 6-7 percent (7,000-7,500 ft3/s) by the proposed 

relief bridge, and 13-16 percent (14,600-18,600 ft3

/s) 

by the proposed Roc Roe Bayou bridge.
36 Simulations of Floodflows on the White River in the Vicinity of U.S. Highway 79 near Clarendon, Arkansas

Simulation results indicate relatively little difference in the change in backwater elevation and velocities among the four alternatives during the 5-year 

recurrence interval floodflows. Alternative 1 typically 

resulted in slightly higher backwater elevation (about 

0.1 foot), lower average velocity (0.1 to 0.6 ft/s), higher 

maximum velocity across the White River bridge opening (about 1 ft/s) and a lower maximum velocity across 

the Roc Roe Bayou bridge opening (about 0.4 ft/s) than 

for the existing bridge openings. Alternatives 2, 3, and 

4 typically result in slightly lower backwater elevation 

(about 0.2 ft), lower average velocities (0.2 to 0.7 ft/s), 

higher maximum velocities (0.8 to 0.9 ft/s) across the 

White River bridge opening, and lower maximum 

velocities (1.0 to 1.3 ft/s) across the Roc Roe Bayou 

bridge opening than for existing conditions. However, 

these differences are relatively small and the locations 

of the maximum depth averaged point velocity does not 

change between each alternative and existing bridge 

openings.

Simulation of the 100-year floodflow for existing conditions indicates that about 56 percent (123,100 

ft3

/s) of flow was conveyed by the White River bridge, 

about 26 percent (56,200 ft3/s) by the First Old River 

bridge, and about 19 percent (41,000 ft3

/s) by the Roc 

Roe Bayou bridge. The maximum depth-averaged 

point velocities for the White River and First Old River 

bridges were 4.2 and 2.2 ft/s, respectively. Average 

depths were 16 and 15 ft for the White River and First 

Old River bridges, respectively. The maximum depthaveraged point velocity predicted for the Roc Roe 

Bayou bridge was 4.1 ft/s with an average depth of 13 

ft. The average water-surface elevation at the upper 

boundary of the study area was 176.9 ft; the average 

water-surface elevation along U.S. Highway 79 was 

176.3 ft; and the average water-surface elevation at the 

lower boundary of the study area was set at 173.21 ft. 

Average depths at the upper boundary, U.S. Highway 

79, and the lower boundary were 15, 14, and 14 ft, 

respectively.

Simulation of the 100-year floodflow for the proposed U.S. Highway 79 alignment alternatives indicates that 70-72 percent (151,200-155,600 ft3

/s) of the 

flow was conveyed by the proposed White River 

bridge, 9-10 percent (19,800-20,700 ft3

/s) by the proposed relief bridge, and 14-20 percent (30,700-43,000 

ft3

/s) by the proposed Roc Roe Bayou bridge. Simulation results indicate relatively little difference in the 

changes in backwater elevation and velocities among 

the four alternatives during the 100-year recurrence 

interval floodflows. All of the alternatives typically 

result in slightly lower backwater elevations (0.2 to 0.5 

ft lower) and average velocities (0.2 to 1.1 ft/s lower) 

than for existing conditions. Maximum velocities 

across Roc Roe Bayou bridge decreased (1.2 to 2.0 ft/

s) and across White River bridge increased (0.9 to 1.2 

ft/s) when compared to existing conditions. However, 

these differences are relatively small and the locations 

of the maximum depth averaged point velocity does not 

change between each alternative and existing bridge 

openings.

REFERENCES

Froehlich, D.A., 1989, Finite element surface-water modeling system, Two dimensional flow in a horizontal 

plane-Users manual: U.S. Department of Transportation Publication No. FHWA-RD-88-187, 285 p.

Brigham Young University, 1999, SMS Surface-water modeling system—Reference manual—Version 6.0: Provo, 

Utah, Environmental Modeling Research Laboratory, 

340 p.

Hydrology Subcommittee of the Interagency Advisory Committee on Water Data, 1982, Guidelines for determining 

flood flow frequency: Hydrology Subcommittee, 183 p.

Lee, J.K., and Froehlich, D.A., 1989, Two-dimensional 

finite-element hydraulic modeling of bridge crossings—Research report: U.S. Department of Transportation Publication No. FHWA-RD-88-146, 256 p.

Sullavan, J.N., 1974, Drainage areas of streams in Arkansas: 

U.S. Geological Survey Open-File Report, 123 p.
Funkhouser, J.E., and Barks, C.S.—SIMULATIONS OF FLOODFLOWS ON THE WHITE RIVER IN THE VICINITY OF U.S. HIGHWAY 79 NEAR 

CLARENDON, ARKANSAS—U.S. Geological Survey Water-Resources Investigations Report 02-4256