Estimation of Scour and Channel Stability for Selected Highway Crossings of Streams in Louisiana

LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT Water Resources Technical Report No. 67C

ON AND D TI EV TA E R L O O P P S M STATE OF LOUISIANA N E N

A T

R T

DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT DOTD F

OFFICE OF PUBLIC WORKS AND INTERMODAL N

A P E PUBLIC WORKS AND WATER RESOURCES DIVISION D in cooperation with the U.S. GEOLOGICAL SURVEY 2003 STATE OF LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT PUBLIC WORKS AND WATER RESOURCES DIVISION WATER RESOURCES SECTION In cooperation with the U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY

WATER RESOURCES TECHNICAL REPORT NO. 67C

Estimation of Scour and Channel Stability for Selected Highway Crossings of Streams in Louisiana

By J. Josh Gilbert and Elliot J. Green U.S. GEOLOGICAL SURVEY

Published by the

LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT Baton Rouge, Louisiana

2003 STATE OF LOUISIANA M.J. “MIKE”F FOSTER,LO JR., GovernorU O IS E JU I T N S A DEPARTMENTO OF TRANSPORTATION AND DEVELOPMENTT I N A KAM K. MOVASSAGHI, Secretary I PUBLICN WORKS AND FLOOD CONTROL DIRECTORATEC

T A Curtis G. Patterson, Director U E

S HYDRAULICS SECTION Jack C. Manno, Hydraulics Engineer Adminstrator

C Cooperative project with the U.S.O DEPARTMENT OF THE INTERIORE NBRUCE BABBITT, SecretaryNC U.S. GEOLOGICALFIDE SURVEY Charles G. Groat, Director

Any use of trade, product, or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey or the Louisiana Department of Transportation and Development.

For additional information contact:

Zahir “Bo” Bolourchi, P.E. Jack C. Manno Charles R. Demas Chief, Water Resources Section Hydraulics Engineer Administrator District Chief Louisiana Department of Louisiana Department of Transportation U.S. Geological Survey Transportation and Development and Development 3535 S. Sherwood Forest Blvd., Suite 120 P.O. Box 94245 Hydraulics Section - Room 300 Baton Rouge, LA 70816 Baton Rouge, LA 70804-9245 P.O. Box 94245 E-mail: [email protected] E-mail: Baton Rouge, LA 70804-9245 Telephone: (225)298-5481 [email protected] E-mail: [email protected] Fax: (225) 298-5490 Telephone: (225) 379-1434 Telephone: (225) 379-1306 Home page: www.dlabrg.er.usgs.gov Fax: (225) 379-1523 Fax: (225) 379-1707 Home page: www.dotd.state.la.us/ Home page: www.dotd.state.la.us/hydr/ water/direct.html hydr.html CONTENTS

Abstract ...... 1 Introduction...... 1 Purpose and Scope...... 1 Approach ...... 2 Acknowledgments ...... 3 Evaluation of Selected Highway Crossings of Streams...... 3 Mississippi River Basin...... 3 Interstate Highway 20 Crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi)...... 6 Pier Scour ...... 8 Channel Stability...... 8 U.S. Highway 65 Crossing of the Mississippi River at Vidalia...... 8 Pier Scour ...... 8 Channel Stability...... 12 U.S. Highway 190 Crossing of the Mississippi River at Baton Rouge...... 12 Pier Scour ...... 12 Channel Stability...... 15 Interstate Highway 10 Crossing of the Mississippi River near Baton Rouge...... 15 Pier Scour ...... 15 Channel Stability...... 15 Louisiana Highway 70 Crossing of the Mississippi River at Donaldsonville ...... 18 Pier Scour ...... 18 Channel Stability...... 18 Louisiana Highway 3213 Crossing of the Mississippi River at Gramercy...... 21 Pier Scour ...... 21 Channel Stability...... 21 Interstate Highway 310 Crossing of the Mississippi River at Luling ...... 21 Pier Scour ...... 25 Channel Stability...... 25 U.S. Highway 90 Crossing (Huey P. Long bridge) of the Mississippi River at New Orleans ...... 25 Pier Scour ...... 25 Channel Stability...... 28 U.S. Highway 90 Crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans...... 28 Pier Scour ...... 28 Channel Stability...... 32 Interstate Highway 10 Crossing of the Inner Harbor Navigation Canal at New Orleans...... 32 Pier Scour ...... 34 Channel Stability...... 34 Ouachita River Basin...... 34 Interstate Highway 20 Crossing of the Ouachita River at Monroe...... 34 Pier Scour ...... 34 Channel Stability...... 38

i U.S. Highway 165 Crossing of the Ouachita River at Columbia...... 38 Pier Scour...... 38 Channel Stability ...... 40 Tensas River Basin ...... 40 U.S. Highway 80 Crossing of the Tensas River at Tendal...... 40 Pier Scour...... 40 Channel Stability ...... 43 Interstate Highway 20 Crossing (west, middle, and east) of the Tensas River near Tendal...... 43 Pier Scour...... 48 Channel Stability ...... 48 Louisiana Highway 128 Crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight ...... 52 Pier Scour...... 52 Channel Stability ...... 52 Louisiana Highway 15 Crossing of the Tensas River at Clayton...... 52 Pier Scour...... 55 Channel Stability ...... 55 Black River Basin ...... 55 U.S. Highway 84 Crossing of the Black River at Jonesville...... 55 Pier Scour...... 58 Channel Stability ...... 58 Calcasieu River Basin...... 58 Louisiana Highway 8 Crossing of the Calcasieu River near Slagle...... 61 Pier Scour...... 61 Channel Stability ...... 64 Louisiana Highway 28 Crossing of the Calcasieu River near Hicks-LaCamp ...... 64 Pier Scour...... 64 Channel Stability ...... 64 Louisiana Highway 121 Crossing of the Calcasieu River near Hineston ...... 67 Pier Scour...... 67 Channel Stability ...... 70 Louisiana Highway 113 Crossing of the Calcasieu River near Glenmora...... 70 Pier Scour...... 70 Channel Stability ...... 73 Louisiana Highway 10 Crossing of the Calcasieu River near Oakdale...... 73 Pier Scour...... 73 Channel Stability ...... 76 Louisiana Highway 26 Crossing of the Calcasieu River near Oberlin...... 76 Pier Scour...... 76 Channel Stability ...... 79 U.S. Highway 190 Crossing of the Calcasieu River near Kinder ...... 79 Pier Scour...... 79 Channel Stability ...... 80 U.S. Highway 171 Crossing of the Calcasieu River near Moss Bluff ...... 80 Pier Scour...... 84 Channel Stability ...... 84 Interstate Highway 10 Crossing of the Calcasieu River at Lake Charles...... 84 Pier Scour...... 87

ii Channel Stability ...... 87 Interstate Highway 210 Crossing of the Calcasieu River near Lake Charles...... 87 Pier Scour...... 90 Channel Stability ...... 90 Sabine River Basin...... 90 Louisiana Highway 12 Crossing of the Sabine River near Starks...... 90 Pier Scour...... 93 Channel Stability ...... 93 Interstate Highway 10 Crossing of the Sabine River near Vinton ...... 95 Pier Scour...... 95 Channel Stability ...... 95 Atchafalaya River Basin ...... 95 Louisiana Highway 1 Crossing of the Atchafalaya River at Simmesport...... 99 Pier Scour...... 99 Channel Stability ...... 99 U.S. Highway 190 Crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs...... 102 Pier Scour...... 102 Channel Stability ...... 102 Interstate Highway 10 Crossing of the Atchafalaya River near Henderson...... 106 Pier Scour...... 106 Channel Stability ...... 106 Interstate Highway 10 Crossing of the Whiskey Bay Pilot Channel near Henderson- Grosse Tete...... 110 Pier Scour...... 110 Channel Stability ...... 110 Summary...... 112 Selected References...... 112

FIGURES 1. Map showing location of sites evaluated for scour and channel stability at selected highway crossings of streams in Louisiana ...... 5 2-3. Interstate Highway 20 crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi), Louisiana 2. Aerial photograph...... 7 3. Bridge schematic, comparative cross sections, and scour estimates ...... 9 4-5. U.S. Highway 65 crossing of the Mississippi River at Vidalia, Louisiana 4. Aerial photograph...... 10 5. Bridge schematic, comparative cross sections, and scour estimates...... 11 6-7. U.S. Highway 190 crossing of the Mississippi River at Baton Rouge, Louisiana 6. Aerial photograph...... 13 7. Bridge schematic, comparative cross sections, and scour estimates...... 14 8-9. Interstate Highway 10 crossing of the Mississippi River near Baton Rouge, Louisiana 8. Aerial photograph...... 16 9. Bridge schematic, comparative cross sections, and scour estimates...... 17 10-11. Louisiana Highway 70 crossing of the Mississippi River at Donaldsonville, Louisiana 10. Aerial photograph...... 19 11. Bridge schematic, comparative cross sections, and scour estimates...... 20

iii 12-13. Louisiana Highway 3213 crossing of the Mississippi River at Gramercy, Louisiana 12. Aerial photograph...... 22 13. Bridge schematic, comparative cross sections, and scour estimates...... 23 14-15. Interstate Highway 310 crossing of the Mississippi River at Luling, Louisiana 14. Aerial photograph...... 24 15. Bridge schematic, comparative cross sections, and scour estimates...... 26 16-17. U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans, Louisiana 16. Aerial photograph...... 27 17. Bridge schematic, comparative cross sections, and scour estimates...... 29 18-19. U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans, Louisiana 18. Aerial photograph...... 30 19. Bridge schematic, comparative cross sections, and scour estimates...... 31 20-21. Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans, Louisiana 20. Aerial photograph...... 33 21. Bridge schematic, comparative cross sections, and scour estimates...... 35 22-23. Interstate Highway 20 crossing of the Ouachita River at Monroe, Louisiana 22. Aerial photograph...... 36 23. Bridge schematic, comparative cross sections, and scour estimates...... 37 24-25. U.S. Highway 165 crossing of the Ouachita River at Columbia, Louisiana 24. Aerial photograph...... 39 25. Bridge schematic, comparative cross sections, and scour estimates...... 41 26-27. U.S. Highway 80 crossing of the Tensas River at Tendal, Louisiana 26. Aerial photograph...... 42 27. Bridge schematic, cross section, and scour estimates ...... 44 28-30. Interstate Highway 20 crossing of the Tensas River near Tendal, Louisiana 28. Aerial photograph (west)...... 45 29. Aerial photograph (middle)...... 46 30. Aerial photograph (east)...... 47 31-33. Interstate Highway 20 crossing of the Tensas River near Tendal, Louisiana 31. Bridge schematic, cross section, and scour estimates (west) ...... 49 32. Bridge schematic, cross section, and scour estimates (middle) ...... 50 33. Bridge schematic, cross section, and scour estimates (east) ...... 51 34-35. Louisiana Highway 128 crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight, Louisiana 34. Aerial photograph...... 53 35. Bridge schematic, cross section, and scour estimates ...... 54 36-37. Louisiana Highway 15 crossing of the Tensas River at Clayton, Louisiana 36. Aerial photograph...... 56 37. Bridge schematic, comparative cross sections, and scour estimates...... 57 38-39. U.S. Highway 84 crossing of the Black River at Jonesville, Louisiana 38. Aerial photograph...... 59 39. Bridge schematic, comparative cross sections, and scour estimates...... 60 40-41. Louisiana Highway 8 crossing of the Calcasieu River near Slagle, Louisiana 40. Aerial photograph...... 62 41. Bridge schematic, cross section, and scour estimates ...... 63

iv 42-43. Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp, Louisiana 42. Aerial photograph...... 65 43. Bridge schematic, cross section, and scour estimates ...... 66 44-45. Louisiana Highway 121 crossing of the Calcasieu River near Hineston, Louisiana 44. Aerial photograph...... 68 45. Bridge schematic, cross section, and scour estimates ...... 69 46-47. Louisiana Highway 113 crossing of the Calcasieu River near Glenmora, Louisiana 46. Aerial photograph...... 71 47. Bridge schematic, cross section, and scour estimates ...... 72 48-49. Louisiana Highway 10 crossing of the Calcasieu River near Oakdale, Louisiana 48. Aerial photograph...... 74 49. Bridge schematic, comparative cross sections, and scour estimates...... 75 50-51. Louisiana Highway 26 crossing of the Calcasieu River near Oberlin, Louisiana 50. Aerial photograph...... 77 51. Bridge schematic, comparative cross sections, and scour estimates...... 78 52-53. U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana 52. Aerial photograph...... 81 53. Bridge schematic, comparative cross sections, and scour estimates...... 82 54-55. U.S. Highway 171 crossing of the Calcasieu River near Moss Bluff, Louisiana 54. Aerial photograph...... 83 55. Bridge schematic, comparative cross sections, and scour estimates...... 85 56-57. Interstate Highway 10 crossing of the Calcasieu River at Lake Charles, Louisiana 56. Aerial photograph...... 86 57. Bridge schematic, comparative cross sections, and scour estimates...... 88 58-59. Interstate Highway 210 crossing of the Calcasieu River near Lake Charles, Louisiana 58. Aerial photograph...... 89 59. Bridge schematic, comparative cross sections, and scour estimates...... 91 60-61. Louisiana Highway 12 crossing of the Sabine River near Starks, Louisiana 60. Aerial photograph...... 92 61. Bridge schematic, comparative cross sections, and scour estimates...... 94 62-63. Interstate Highway 10 crossing of the Sabine River near Vinton, Louisiana 62. Aerial photograph...... 96 63. Bridge schematic, comparative cross sections, and scour estimates...... 98 64-65. Louisiana Highway 1 crossing of the Atchafalaya River at Simmesport, Louisiana 64. Aerial photograph...... 100 65. Bridge schematic, comparative cross sections, and scour estimates...... 101 66-68. U.S. Highway 190 crossing of the Atchafalaya River near Krotz Springs, Louisiana 66. Aerial photograph (eastbound and westbound)...... 103 67. Bridge schematic, comparative cross sections, and scour estimates (eastbound)...... 104 68. Bridge schematic, comparative cross sections, and scour estimates (westbound)...... 105 69-70. Interstate Highway 10 crossing of the Atchafalaya River near Henderson, Louisiana 69. Aerial photograph...... 107 70. Bridge schematic, comparative cross sections, and scour estimates...... 108 71-72. Interstate Highway 10 crossing of Whiskey Bay Pilot Channel near Henderson-Gross Tete, Louisiana 71. Aerial photograph...... 109 72. Bridge schematic, comparative cross sections, and scour estimates...... 111

v TABLES 1. Sites evaluated for scour and channel stability at selected highway crossings of streams in Louisiana ...... 4 2-34. Scour data for: 2. Interstate Highway 20 crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi), Louisiana...... 6 3. U.S. Highway 65 crossing of the Mississippi River at Vidalia, Louisiana ...... 12 4. U.S. Highway 190 crossing of the Mississippi River at Baton Rouge, Louisiana ...... 12 5. Interstate Highway 10 crossing of the Mississippi River near Baton Rouge, Louisiana ...... 15 6. Louisiana Highway 70 crossing of the Mississippi River at Donaldsonville, Louisiana ...... 18 7. Louisiana Highway 3213 crossing of the Mississippi River at Gramercy, Louisiana...... 21 8. Interstate Highway 310 crossing of the Mississippi River at Luling, Louisiana...... 25 9. U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans, Louisiana...... 28 10. U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans, Louisiana...... 32 11. Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans, Louisiana...... 32 12. Interstate Highway 20 crossing of the Ouachita River at Monroe, Louisiana...... 38 13. U.S. Highway 165 crossing of the Ouachita River at Columbia, Louisiana...... 40 14. U.S. Highway 80 crossing of the Tensas River at Tendal, Louisiana...... 43 15. Interstate Highway 20 crossing (west, middle, and east) of the Tensas River near Tendal, Louisiana ...... 48 16. Louisiana Highway 128 crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight, Louisiana...... 52 17. Louisiana Highway 15 crossing of the Tensas River at Clayton, Louisiana...... 55 18. U.S. Highway 84 crossing of the Black River at Jonesville, Louisiana...... 58 19. Louisiana Highway 8 crossing of the Calcasieu River near Slagle, Louisiana...... 61 20. Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp, Louisiana...... 64 21. Louisiana Highway 121 crossing of the Calcasieu River near Hineston, Louisiana...... 67 22. Louisiana Highway 113 crossing of the Calcasieu River near Glenmora, Louisiana...... 70 23. Louisiana Highway 10 crossing of the Calcasieu River near Oakdale, Louisiana...... 73 24. Louisiana Highway 26 crossing of the Calcasieu River near Oberlin, Louisiana...... 76 25. U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana...... 79 26. U.S. Highway 171 crossing of the Calcasieu River near Moss Bluff, Louisiana...... 84 27. Interstate Highway 10 crossing of the Calcasieu River at Lake Charles, Louisiana...... 87 28. Interstate Highway 210 crossing of the Calcasieu River near Lake Charles, Louisiana...... 90 29. Louisiana Highway 12 crossing of the Sabine River near Starks, Louisiana...... 93 30. Interstate Highway 10 crossing of the Sabine River near Vinton, Louisiana ...... 97 31. Louisiana Highway 1 crossing of the Atchafalaya River at Simmesport, Louisiana...... 99 32. U.S. Highway 190 crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs, Louisiana...... 102 33. Interstate Highway 10 crossing of the Atchafalaya River near Henderson, Louisiana...... 106 34. Interstate Highway 10 crossing of the Whiskey Bay Pilot Channel near Henderson-Grosse Tete, Louisiana...... 110

vi CONVERSION FACTORS AND DATUMS

Multiply By To obtain

foot (ft) 0.3048 meter (m) foot per second (ft/s) 0.3048 meter per second (m/s) foot per foot (ft/ft) 0.3048 meter per meter (m/m) foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) inch per year (in/yr) 25.4 millimeters per year (mm/yr) acre-foot (acre-ft) 1,233 cubic meter (m3) mile (mi) 1.609 kilometer (km) square mile (mi2) 2.590 square kilometer (km2)

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Horizontal coordinate information in this report is referenced to the North American Datum of 1983.

vii viii Estimation of Scour and Channel Stability for Selected Highway Crossings of Streams in Louisiana

By J. Josh Gilbert and Elliot J. Green

ABSTRACT Maximum pier and contraction scour from a 500-year flood were estimated at 36 bridges that cross streams in northeastern and southern (excluding the Florida Parishes area) Louisiana. The selected highway crossings were located over the Mississippi, Ouachita, Tensas, Black, Calcasieu, Sabine, and Atchafalaya Rivers; Inner Harbor Navigation Canal; and Whiskey Bay Pilot Channel. Of the sites investigated, the maximum estimated pier scour ranged from 4 to 77 feet. Estimates of contraction scour generally were not substantial in magnitude or were not applicable due to site characteristics at all but four sites. For sites along the Mississippi River, the maximum estimated pier scour was 77 feet at U.S Highway 190. Contraction scour estimation is not applicable for conditions at the sites along the Mississippi River where levees limit flood-plain flow. For sites along the Ouachita and Tensas Rivers, the maximum estimated pier scour was 19 feet. The Black River at U.S. Highway 84 had pier scour estimates ranging from 5 to 22 feet. For sites along the Calcasieu River, the maximum estimated pier scour was 24 feet at Interstate Highway 10. Of the two Sabine River sites, the maximum pier scour estimate was 33 feet at Louisiana Highway 12. At the Interstate Highway 10 crossing of the Atchafalaya River, the maximum pier scour estimate was 57 feet.

INTRODUCTION

The design, construction, and maintenance of highway crossings over streams and flood plains require a balance of design variables such as bridge and embankment lengths, pier spacing, and pile penetration. The Federal Highway Administration requires that all state highway agencies evaluate bridges in the Federal aid system for scour susceptibility. The U.S. Geological Survey (USGS), in cooperation with the Louisiana Department of Transportation and Development (DOTD), has completed three major studies between 1992 and 2002 designed to evaluate scour potential and channel stability at selected bridges that cross streams in Louisiana. The first study evaluated 13 bridges that cross the Red River in the northwestern part of the State (Gilbert and Ensminger, 1996, 1999a). The second study evaluated selected bridges that cross streams in the Florida Parishes area of the State (Gilbert and Ensminger, 1999b). The third study, which is the focus of this report, evaluated selected bridges that cross streams in the northeastern and southern (excluding the Florida Parishes area) parts of the State.

Purpose and Scope

This report describes estimated maximum pier and contraction scour and channel stability at 36 bridges. The selected highway crossings were located over the Mississippi, Ouachita, Tensas, Black, Calcasieu, Sabine, and Atchafalaya Rivers; Inner Harbor Navigation Canal; and Whiskey Bay Pilot Channel. Maximum scour estimates were computed using methods outlined by the Federal Highway Administration to evaluate potential scour and channel stability. General hydrologic, hydraulic, hydrographic, and bathymetric information for these evaluations was obtained from existing information from DOTD, U.S. Army Corps of Engineers (USACE), and the

1 USGS. The 500-year flood was estimated from streamflow-gaging station records at the site, streamflow- gaging station records transferred to the site, or by a region of influence regression model. The existing information at some sites was not adequate to provide contraction scour estimates with reasonable confidence, so contraction scour estimates were not always performed. Contraction scour estimation is not applicable for conditions at some sites along the Mississippi River where levees limit flood-plain flow. All bridge, pier, and pile geometries examined in this report were derived from DOTD bridge plans, unless alternate or additional information sources are specified on a site specific basis. The report includes tabulated scour data, a photograph, and a cross section for the bridge sites evaluated. Values listed in tables are rounded from computations. Summing the rounded values in the tables may not agree by the smallest significant digit.

Approach

General hydrologic, topographic, and hydrographic information was assembled from available information in USGS, USACE, or DOTD files. The 500-year flood was determined from statistical analysis of streamflow-gaging station records. If sufficient streamflow-gaging station records were available at a site, these records were used to estimate the 500-year flood. At locations where streamflow data were not available, the 500-year flood estimate was adjusted based on values established at the nearest appropriate location along the stream, or a region of influence regressional model (RIRM) (Ensminger, 1998) was used. The distribution of flow within the bridge openings was computed using the one- dimensional Water Surface Profile (WSPRO) flow model (Shearman and others, 1986). Estimates of maximum pier and contraction scour were based on Federal Highway Administration guidelines presented in Hydraulic Engineering Circulars (HEC) 18 (Richardson and others, 1995) and 20 (Lagasse and others, 1991). Local scour at the pier locations (pier scour) was calculated using the Colorado State University equation (modified from Richardson and others, 1995, eq. 2).

0.65 0.43 ys ⁄ y1 = 2.0×× K1 K2 × K3 × K4 × ()ay⁄ 1 × ()Fr (1)

yd =,GSE– ys (2)

where ys = estimated depth of pier scour, in ft; y1 = flow depth directly upstream of the pier, in ft; K1 = dimensionless correction factor for pier nose shape; K2 = dimensionless correction factor for skew; K3 = dimensionless correction factor for bed form; K4 = dimensionless correction factor for bed armoring; a = width of pier, in ft; Fr = Froude number; yd = channel-bed elevation of the computed scour hole, in ft above NGVD of 1929; and GSE = observed existing ground-surface (channel-bed) elevation, in ft above NGVD of 1929.

The value for y1 at each pier was based upon the difference between the computed water-surface elevation and the appropriate ground-surface elevation. The minimum channel-bed elevation historically observed at that location, or the potential channel-bed elevation, may be chosen as the most appropriate ground-surface elevation. The values for K1, K2, K3, and K4 were taken from values recommended by Richardson and others (1995, p. 36-39) for pier geometry as represented on DOTD bridge plans and

2 anticipated bed conditions. The Froude number at the pier location was based upon the value of depth and velocity, which was computed using WSPRO.

In estimation of contraction scour, the average depth in the section or subsection was used. The scour estimate computed from the average depth was applied to the actual depths at pier and abutment locations for determination of the cumulative scour depth.

67⁄ k y2 Q2 W1 1 ----- = ⎛⎞------⎛⎞------(3) ⎝⎠ ⎝⎠ y1 Q1 W2

ys = y2 - yo = (average scour depth) where: y1 = average depth in the upstream main channel, in ft; y2 = average depth in the contracted section, in ft; yo = existing depth in the contracted section before scour, in ft; 3 Q1 = flow in the upstream channel, in ft /s; 3 Q2 = flow in the contracted channel, in ft /s; W1 = bottom width of the upstream main channel, in ft; W2 = bottom width of the main channel in the contracted section; in ft; k1 = exponent based on mode of bed material transport 0.69 for all sites evaluated.

Acknowledgments

The assistance of Jack C. Manno, Hydraulics Engineer Administrator, and Fred Cifreo, Hydraulics Engineer Supervisor, of the Louisiana Department of Transportation and Development, and John Miller of the U.S. Army Corps of Engineers, New Orleans District, in providing hydrographic survey information on the streams is gratefully acknowledged.

EVALUATION OF SELECTED HIGHWAY CROSSINGS OF STREAMS

The sites evaluated for scour and channel stability are highway crossings located in Louisiana or on the border of Louisiana with Mississippi or with Texas. Of the streams discussed in this report, only the Tensas and Calcasieu Rivers have their originating headwater areas within Louisiana. The Black and Atchafalaya River designations originate in Louisiana, but their origins are confluences of other streams. The sites evaluated are listed in table 1 and shown in figure 1.

Mississippi River Basin

The Mississippi River originates in Minnesota and is the largest river in the United States. The Missis- sippi River and its tributaries drain 31 states and parts of Canada. Such a large river system has a large natural flood plain that periodically becomes inundated. To maintain access to the river channel and utilize the flood plain, flood protection levees have been constructed at many locations along the river. With minor exceptions, both sides of the river are constrained by levees, which cause flood plain and channel widths to be nearly equal for the lower 300-mile reach to the Gulf of Mexico. In addition to protection levees, diversion of flood water from the river is effective in lowering flood peaks. The Old River flood control structure is located in south- central Louisiana about 300 mi upstream from the mouth of the river. This structure is the largest flood control

3 Table 1. Sites evaluated for scour and channel stability at selected highway crossings of streams in Louisiana

Site number Site name and location (fig. 1) Mississippi River Basin 1 Interstate Highway 20 crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi) 2 U.S. Highway 65 crossing of the Mississippi River at Vidalia 3 U.S. Highway 190 crossing of the Mississippi River at Baton Rouge 4 Interstate Highway 10 crossing of the Mississippi River near Baton Rouge 5 Louisiana Highway 70 crossing of the Mississippi River at Donaldsonville 6 Louisiana Highway 3213 crossing of the Mississippi River at Gramercy 7 Interstate Highway 310 crossing of the Mississippi River at Luling 8 U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans 9 U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans 10 Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans Ouachita River Basin 11 Interstate Highway 20 crossing of the Ouachita River at Monroe 12 U.S. Highway 165 crossing of the Ouachita River at Columbia Tensas River Basin 13 U.S. Highway 80 crossing of the Tensas River at Tendal 14a Interstate Highway 20 crossing (west) of the Tensas River near Tendal 14b Interstate Highway 20 crossing (middle) of the Tensas River near Tendal 14c Interstate Highway 20 crossing (east) of the Tensas River near Tendal 15 Louisiana Highway 128 crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight 16 Louisiana Highway 15 crossing of the Tensas River at Clayton Black River Basin 17 U.S. Highway 84 crossing of the Black River at Jonesville Calcasieu River Basin 18 Louisiana Highway 8 crossing of the Calcasieu River near Slagle 19 Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp 20 Louisiana Highway 121 crossing of the Calcasieu River near Hineston 21 Louisiana Highway 113 crossing of the Calcasieu River near Glenmora 22 Louisiana Highway 10 crossing of the Calcasieu River near Oakdale 23 Louisiana Highway 26 crossing of the Calcasieu River near Oberlin 24 U.S. Highway 190 crossing of the Calcasieu River near Kinder 25 U.S. Highway 171 crossing of the Calcasieu River near Moss Bluff 26 Interstate Highway 10 crossing of the Calcasieu River at Lake Charles 27 Interstate Highway 210 crossing of the Calcasieu River near Lake Charles Sabine River Basin 28 Louisiana Highway 12 crossing of the Sabine River near Starks 29 Interstate Highway 10 crossing of the Sabine River near Vinton Atchafalaya River Basin 30 Louisiana Highway 1 crossing of the Atchafalaya River at Simmesport 31 U.S. Highway 190 crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs 32 Interstate Highway 10 crossing of the Atchafalaya River near Henderson 33 Interstate Highway 10 crossing of the Whiskey Bay Pilot Channel near Henderson-Grosse Tete

4 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

91 94 93 92 ARKANSAS 33 3 125 71 2 165 1

167 LL 37 UN ONI CL IB O T 65 R EAN 2 ST r O A RRO ES 79 R LL E W R ve M E R USEHOO CA i A C R WEBSTER BOSSIER iver 220 COLNLIN 11 R Tendal 80 13 20 OUACHITA a MONROE 20 CADDO 147 t 79 B 137 Vicksburg, MS 49 I NVILELE 14(a,b,c) RICHLAND JACKSON c 165 Tallulah 1 u hi s S M I 34 O D NA 1 71 a 37 Oa

e FRANKLIN Newlight v EXPLANATION 12 T DE SOTO RED i er R 84 RIVER Columbia 15 TENSAS 32 WINN CAL WD ELL 128 5 LOCATION OF HIGHWAY CROSSING 15 AND SITE NUMBER 84

171 16 C AAT HOULA 71 L SALALE SABINE 165 Jonesville 17 Clayton 0 50 MILES Red NATCIHTOCHSE GARNT 84 Vidalia 2 0 50 KILOMETERS Riv 6 28

Ri ecvr

re p k IA

D p a R l i O RAPIDES B s 8 18 28 ONC 19 C Slagle s i Hineston MISISPISSIP 121 is

Hicks 112

20 M is 90 LaCamp r Simmesport er

VE ONRN e 21 AVOYELLES 31 v 10 21 iv Glenmora 55

165 30 67 Ri T R S 113 EAST

TEXAS WE A P ST. IA FELIC T WASH 190 O IC IANA I GN TO N Oakdale A e 26 22 IN ENL HELENA 1 F N n T ALL NE E G i

I ieua 71 CO 25 P 171 b A Krotz UP EAST ATOBN a B AE U EVAN H REGARD 23 Oberlin GELINE Springs E RUOGE O S E ST. TAMMA YN lc s ST. ANL DR Y 3 A 190 BATON L INIV GS OT N 41 W. 190 190 Ca ROUGE 24 31 59 109 12 49 A BAT ON 12 Kinder t c ROUGE h 32 W 33 a his f 4 26 a Starks Moss Bluff k Grosse 10 CALCASI UE E E ONRSJ FF l e 190 210 a y ACADIA 10 y B Tete DAVIS a 11 Inner Harbor a 10 Vinton 25 R y IB 55 LAKE 26 Henderson P 28 i E 10 Navigation Cana l v i R IL AS NCE I S N l O 10 OP NTCHARTRAIN 10 90 LAF ST. e ot V Gramercy. AYET M RA T IN r E 90 27 T ST E C L 5 TH E 70 310 h N LAKE 3213 H TI 13 e a S 10 29 167 n ST. JO T

27 n CHARLES AP J 30 E J A M S B S61 E NEW ORLEANS l 3127 T F S 14 IBE IRA C . 47 T 6 H F . 182 A CAMERON ASS MU PTION R E 8 B 35 Donaldsonville LE R E 1 S S 9 R 90 O N D ST. 7 46A R VERMILOI N 82 N MRTA IN Luling P S .T AM RY LA 90 QU EM 20 M I 39 i N A ss ES 89 24 82 O issipp RL UF CHE i

TERR OEB NNE Riv Gu 57 l 56 23 f of Mex e r ico 1

Source: Office of Planning and Programming, Louisiana Department of Transportation and Development

Figure 1. Location of sites evaluated for scour and channel stability at selected highway crossings of streams in Louisiana.

5 diversion on the Mississippi River, and it can divert about one third of the flood flow. Flow is diverted into the Lower Old River, which flows west about 6 mi and joins the Red River. The confluence of the Lower Old River and the Red River near Simmesport, Louisiana, is the origin of the Atchafalaya River. The drainage area of the Mississippi River at the diversion by the Lower Old River flood control structure is about 1.13 million square miles, but due to the effects of the diversion, the drainage area downstream of the diversion is indeterminate. The same indeterminate drainage-area conditions apply for the Lower Old River and Atchafalaya River, because they receive water diverted from the Mississippi River.

The Morganza Spillway flood control structure can divert flow from the Mississippi River at river mile 280. The Bonnet Carré Spillway flood control structure, which has a design capacity of 250,000 ft3/s, can divert flow from the Mississippi River at river mile 128. For the purpose of this evaluation, the flow and diversions are as follows: Old River flood control structure 600,000 ft3/s, Morganza Spillway flood control structure 600,000 ft3/s, and Bonnet Carré Spillway 250,000 ft3/s (U.S. Army Corps of Engineers, 2001). Based on this flow distribution, sites at Baton Rouge are evaluated at 1,500,000 ft3/s, and sites at New Orleans are evaluated at 1,250,000 ft3/s.

Interstate Highway 20 Crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi) The estimate of the 500-year flood used for the hydraulic analysis is 2,060,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 103 ft above NGVD of 1929 (table 2). The width of the channel at the 500-year flood is approximately 6,000 ft; about 3,000 ft includes the main spans of the bridge (fig. 2). The downstream boundary condition for hydraulic computations using WSPRO was a water-surface elevation of 98 ft, based on calibration to the flood of 1973. Simulations of the 500-year flood indicate velocities ranging from 2.0 to 12.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 2.

Table 2. Scour data for Interstate Highway 20 crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi), Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 103 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3, 1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans; * = pile tip elevation; NA, not applicable]

Scour Footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 162+93 21 Round 1.0 26 4.0 26 NA -5 -70 158+70 51 Round 1.0 44 8.0 46 NA 5 -70 150+00 2 Round 1.0 44 9.0 53 NA -51 -90 145+77 19 Round 1.0 33 10.0 45 NA -26 -85 141+51 47 Round 1.0 20 12.0 33 NA 14 -50* 137+25 59 Round 1.0 20 9.0 28 NA 31 -30* 132+99 85 Round 1.0 20 5.0 20 NA 65 0*

LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

DI RECT ION OF FLOW Vicksburg, Miss.

S 20 I

S S I

M Tallulah

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last modified: 2/5/01

Figure 2. Aerial photograph of the Interstate Highway 20 crossing of the Mississippi River near Tallullah (at Vicksburg, Mississippi), Louisiana. Pier Scour

For evaluation of pier scour at Interstate Highway 20, values for y1 at each pier were based on the DOTD hydrographic survey of 1993. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum estimated scour depth was approximately 53 ft for the pier at DOTD station 150+00 (table 2, fig. 3). The channel-bed elevation for this computed scour hole is about 51 ft below NGVD of 1929. Bridge plans indicate riprap protection at all piers. Willow mattress protection is indicated for the piers at DOTD stations 145+77 and 150+00. This protection will reduce the pier scour values indicated in table 2. The pier locations for the Interstate Highway 20 bridge are similar to those of the U.S Highway 80 and railroad bridge immediately upstream (fig. 2). There is the possibility that scour holes at the bridge piers could overlap for the two structures, increasing the potential scour depth.

Channel Stability

Cross-section information is shown in figure 3 for the years 1967, scaled from bridge plans, and 1993, from DOTD surveys. These surveys show minor changes in the channel bed in the center channel areas. The thalweg in both surveys is near the east bank, with an elevation of approximately 40 ft below NGVD of 1929. The 1967 survey was scaled from the bridge plans, which has some effect on its accuracy. The 1967 survey does not reflect the installation of willow mattresses and riprap, which may be an influence on higher bed elevations indicated in 1993. The 1993 survey represents the lowest bed elevations of the DOTD surveys of 1993 and 1994 post- construction surveys.

U.S. Highway 65 Crossing of the Mississippi River at Vidalia

The estimate of the 500-year flood used for the hydraulic analysis is 2,400,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 82.9 ft above NGVD of 1929 (table 3). The width of the channel (fig. 4) at the bridge for the 500-year flood simulation is approximately 3,500 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.0007 ft/ft, which is the same slope determined from the calibration simulations at this site. Simulations of the 500-year flood indicate velocities ranging from 4.0 to 13.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 3.

Pier Scour

For the evaluation of pier scour, values for water depths at each pier (y1), were based on the DOTD hydrographic survey of 1993. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 56 ft for the pier at DOTD station 37+86 (table 3, fig. 5). The channel-bed elevation of the computed scour hole is about 99 ft below NGVD of 1929. Bridge plans indicate a willow mattress at this pier which will limit actual scour.

8 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 650 600 EXPLANATION 550 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: 500 SCOUR ELEVATION 1967 DOTD 450 WATER-SURFACE 400 1993 DOTD ELEVATION FOR 500- YEAR FLOOD 350 MISSISSIPPI 300 LOUISIANA 250

9 200 150

BELOW NGVD OF 1929 OF NGVD BELOW 100 50 ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION, 0 -50 -100 WEST BANK EAST BANK -150 130+00 135+00 140+00 145+00 150+00 155+00 160+00 165+00

DOTD STATION, IN FEET

Figure 3. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 20 crossing of the Mississippi River near Tallulah (at Vicksburg, Mississippi), Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

W O F

VIDALIA IO 65

IR ECT N OF L D

R E V I R

I P P I S I S S S I M

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 4. Aerial photograph of the U.S. Highway 65 crossing of the Mississippi River at Vidalia Louisiana.

10 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 800

EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 600 ELEVATION: SCOUR ELEVATION 1940 DOTD WATER-SURFACE 1993 DOTD ELEVATION FOR 500- YEAR FLOOD 400

MISSISSIPPI LOUISIANA 200 11 BELOW NGVD OF 1929 OF NGVD BELOW 0 ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION, WEST BANK EAST BANK

-200 65+00 60+00 55+00 50+00 45+00 40+00 35+00 30+00 25+00 20+00

DOTD STATION, IN FEET

Figure 5. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 65 crossing of the Mississippi River at Vidalia, Louisiana. Table 3. Scour data for U.S. Highway 65 crossing of the Mississippi River at Vidalia, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 82.9 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack, K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Bottom of Scour footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 29+11 15 Round 1.0 30 8.0 41 NA -26 -60 37+86 -43 Round 1.0 30 13.0 56 NA -99 -120 46+61 13 Round 1.0 30 9.0 42 NA -29 -120

Channel Stability

Cross-section information is shown in figure 5 for the years 1940 and 1993. These surveys indicate significant changes in elevations at the west bank, but little change in the thalweg. The thalweg elevations observed were approximately the same elevation of about 50 ft below NGVD of 1929. The changes in elevation at the west bank indicate a decrease in elevation of approximately 50 ft in 1993, resulting in a larger and wider cross section than the 1940 conditions. Bed material was removed on the west bank by dredging as specified in the bridge plans and shown by results from the DOTD survey of 1993.

U.S. Highway 190 Crossing of the Mississippi River at Baton Rouge The estimate of the 500-year flood used for the hydraulic analysis is 1,500,000 ft3/s. The water- surface elevation used for the 500-year estimate is 45.6 ft above NGVD of 1929. The width of the channel (fig. 6) at the 500-year flood is approximately 3,000 ft. Simulations indicate velocities ranging from 4.0 to 11.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 4.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1992. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO. The maximum computed scour depth is approximately 77 ft for the pier at DOTD station 73+68 (table 4, fig. 7). The channel-bed elevation of the computed scour hole is 135 ft below NGVD of 1929.

Table 4. Scour data for U.S. Highway 190 crossing of the Mississippi River at Baton Rouge, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 45.6 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; bottom of footing scaled from DOTD bridge plans; NA, not applicable]

Bottom of Scour footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 65+20 -4 Round 1.0 31 4.0 30 NA -33 -183 73+68 -58 Round 1.0 62 10.0 77 NA -135 -157 80+18 -30 Round 1.0 56 7.0 59 NA -89 -181

12 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

R R TIO F

I EC N

190 190

BATON ROUGE

ISI

Photograph source: Louisiana Department of Transportation and Development, 11/6/87 Figure 6. Aerial photograph of the U.S. Highway 190 crossing of the Mississippi River at Baton Rouge, Louisiana.

13 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 560

480 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 400 ELEVATION SCOUR ELEVATION 1940 DOTD WATER-SURFACE 320 ELEVATION FOR 500- 1992 DOTD YEAR FLOOD 240

160

0 14

BELOW NGVD OF 1929 OF NGVD BELOW -80

ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION, -160

-240 WEST BANK EAST BANK -320

-400 60+00 70+00 80+00 90+00

DOTD STATION, IN FEET

Figure 7. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 190 crossing of the Mississippi River at Baton Rouge, Louisiana. Channel Stability

Cross-section information is shown in figure 7 for the years 1940 and 1992. These surveys do not indicate significant changes in the main channel part, but increased bed elevations of about 30 ft are indicated in the channel near the east bank. A part of this bed change may possibly be man-made. There are effects from dredging in the channel near the west bank and a pipeline crossing that is riprap protected the channel near the east bank. Levees on both banks confine the channel along this reach of the river (fig. 6).

Interstate Highway 10 Crossing of the Mississippi River near Baton Rouge

The 500-year flood estimate used for the hydraulic analysis is 1,500,000 ft3/s. The water- surface elevation used for the 500-year estimate is 44.3 ft above NGVD of 1929 (table 5). The width of the channel (fig. 8) at the 500-year flood is approximately 3,000 ft. Simulations indicate velocities of 4.0 to 9.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 5.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1994 for evaluations of pier scour at Interstate Highway 10. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using the WSPRO model. The maximum computed scour depth is approximately 34 ft for the pier at DOTD station 387+63 (table 5, fig. 9). The channel-bed elevation of the computed scour hole is about 78 ft below NGVD of 1929. None of the predicted scour depths produce bed elevations that are below the design bottom of footing elevations.

Table 5. Scour data for Interstate Highway 10 crossing of the Mississippi River near Baton Rouge, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 44.3 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3, 1.1; ft, feet; ft/s, foot per second; bottom of footing scaled from DOTD bridge plans; NA, not applicable]

Bottom of Scour footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 402+48 17 Round 1.0 14 4.0 15 NA 2 NA 398+20 -14 Round 1.0 14 8.0 22 NA -36 -105 393+57 -24 Round 1.0 25 6.0 29 NA -53 -110 387+63 -44 Round 1.0 30 6.0 34 NA -78 -155 375+28 -18 Round 1.0 30 4.0 27 NA -45 -120

Channel Stability

Cross-section information is shown in figure 9 for the years 1968, 1975, and 1994. The 1975 and 1994 surveys do not indicate significant changes in the shape of the cross-section. The 1968 DOTD bed elevation data was scaled from a reduced copy of the bridge plans. Some of the differences noted between the 1968 data and the 1975 and 1994 data may be due to the errors in scaling the source drawing. The 1975 USACE cross section is close to the bridge but not along the exact alignment as the DOTD cross section. The increased bed elevations near station 375+00 and near the pier result from industrial development along the bank.

15 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

BATON ROUGE

DIRECTI NO OF F OL W

MSIISSIP S PI RIVRE

Photograph source: Louisiana Department of Transportation and Development, 9/7/95

Figure 8. Aerial photograph of the Interstate Highway 10 crossing of the Mississippi River near Baton Rouge, Louisiana.

16 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 480

EXPLANATION 400 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 1968 DOTD WATER-SURFACE 1975 USACE 320 ELEVATION FOR 500- 1994 DOTD YEAR FLOOD 240

160

80 17 0

-80

-160 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, -240 365+00 370+00 375+00 380+00 385+00 390+00 395+00 400+00 405+00 410+00

DOTD STATION, IN FEET

Figure 9. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 10 crossing of the Mississippi River near Baton Rouge, Louisiana. The 1994 DOTD cross section is similar to the 1975 cross section. Bed elevation differences in the main channel of about 15 ft are within the expected difference considering seasonal variation in data collection and different cross section locations. The willow mattresses and heavy riprap armoring indicated on the bridge plans at the piers should limit scour to values less than the estimates in table 5.

Louisiana Highway 70 Crossing of the Mississippi River at Donaldsonville The 500-year flood estimate used in the hydraulic analysis was 1,500,000 ft3/s. The water- surface elevation used for the 500-year estimate is 34.7 ft above NGVD of 1929 (table 6). The width of the channel (fig. 10) at the 500-year flood estimate is approximately 3,200 ft. Simulations indicate velocities ranging from 5.0 to 9 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 6.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1991 for evaluations of pier scour at Louisiana Highway 70. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO.

The pier footings become partially exposed when the estimated bed elevations are considered. The width of the pier used in computations is 40 ft, an average of the pier width and footing width. This approximate width produces an over-estimation of the scour, but the bottom of the footings are not exposed. Timber fenders protect the piers in the navigation area of the channel, which can reduce the amount of scour. The abrupt increase in width at the top of the footing may also disrupt the downward component of pier scour currents, reducing the actual amount of scour.

The maximum computed scour depth is approximately 52 ft for the piers at DOTD stations 3971+75 and 3980+00 (table 6, fig. 11). The channel-bed elevation of the computed scour hole is about 109 ft below NGVD of 1929. None of the predicted scour depths produce bed elevations that are below the design bottom of footing elevations.

Table 6. Scour data for Louisiana Highway 70 crossing of the Mississippi River at Donaldsonville, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 34.7 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3, 1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Bottom of Scour footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 3963+75 -48 Round 1.0 40 5.0 42 NA -90 -130 3971+75 -57 Round 1.0 40 8.0 52 NA -109 -130 3980+00 -57 Round 1.0 40 8.0 52 NA -109 -130

Channel Stability

The bridge crossing is located in one of the straight sections of channel along this reach of the river. Cross-section information is shown in figure 11 for the years 1961, 1975, 1989, and 1991. These surveys show minor changes in the bed elevation which may have been caused by seasonal differences at the time of the survey. The 1961 survey was scaled from a reduced bridge plan drawing, and is subject to the errors in that process.

18 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

N N O

Donaldsonville R E

DIRE RIV

70 70

Photograph source: Louisiana Department of Transportation and Development, 8/20/91

Figure 10. Aerial photograph of the Louisiana Highway 70 crossing of the Mississippi River at Donaldsonville, Louisiana.

19 3990+00 EAST BANK 3985+00 3980+00 DOTD STATION, IN FEET DOTD STATION, ESTIMATED MAXIMUM ESTIMATED WATER-SURFACE ELEVATION FOR 500- FOR ELEVATION SCOUR ELEVATION YEAR FLOOD 3970+00 3975+00 DOTD DOTD DOTD DOTD EXPLANATION 1991 1989 1975 1961 3965+00 WEST BANK GROUND-SURFACE GROUND-SURFACE ELEVATION: LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM COOPERATIVE RESOURCES WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA 3960+00 0

700 600 500 400 300 200 100 -100 -200 -300 -400

BELOW NGVD OF 1929 OF NGVD BELOW ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION, Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 70 crossing of the cross sections, and scour estimates at the Louisiana Highway 70 Bridge schematic, comparative 11. Figure Mississippi River at Donaldsonville, Louisiana.

20 Louisiana Highway 3213 Crossing of the Mississippi River at Gramercy

The 500-year flood estimate used in the hydraulic analysis was 1,500,000 ft3/s. The water-surface elevation used for the 500-year estimate is 29.0 ft above NGVD of 1929. The width of the channel (fig. 12) at the 500-year flood estimate is approximately 2,900 ft. Simulations indicate velocities ranging from 4.0 to 10.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 7.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1997 for evaluations of pier scour at Louisiana Highway 3213. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO.

The maximum computed scour depth is approximately 50 ft for the pier at DOTD station 230+18 (table 7, fig. 13), which corresponds to a channel-bed elevation of the computed scour hole of 108 ft below NGVD of 1929. None of the predicted scour depths produce bed elevations that are below the pile tip elevations.

Table 7. Scour data for Louisiana Highway 3213 crossing of the Mississippi River at Gramercy, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 29.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3, 1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Channel Stability

The bridge crossing is located in a reach where the channel is straight for several channel widths upstream from the crossing (fig. 12), and bends to the right about one channel width downstream from the bridge crossing along this reach of the river. Cross-section information is shown in figure 13 for the years 1981 and 1997. At the thalweg, the 1997 elevation is about 20 ft lower than the 1981 elevation. However, the general shape of the cross section is the same when the two years are compared. The lower elevations indicated from the 1997 survey compared to those from the 1981 survey may result from the mobile character of the sand bed parts of the river.

Interstate Highway 310 Crossing of the Mississippi River at Luling

The 500-year flood estimate used in the hydraulic analysis is 1,250,000 ft3/s. This discharge is the discharge from upstream sites with diversion through the Morganza and Bonnet Carré Spillways. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate was 15.0 ft above NGVD of 1929 (table 8) with a channel width of approximately 3,100 ft (fig. 14). Simulations indicate velocities ranging from 4.0 to 10.0 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 8.

21 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

Gramercy

3125 ER RV P I O LW 3213 OF F I SISP I N MS S I EC TI DOIR

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 12. Aerial photograph of the Louisiana Highway 3213 crossing of the Mississippi River at Gramercy, Louisiana.

22 255+00 ESTIMATED MAXIMUM ESTIMATED SCOUR ELEVATION WATER-SURFACE FOR 500 - ELEVATION YEAR FLOOD 250+00 NORTH BANK NORTH DOTD DOTD EXPLANATION 1981 1997 245+00 GROUND-SURFACE ELEVATION: 240+00 235+00 (Pile tip elev.=-190 ft below ft (Pile tip elev.=-190 NGVD of 1929, DOTD) DOTD STATION, IN FEET DOTD STATION, 230+00 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM RESOURCES COOPERATIVE WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA 225+00 220+00 SOUTH BANK SOUTH 0 50 -50

100 150 200

-150 -100 ELEVATION, IN FEET ABOVE OR BELOW SEA LEVEL SEA BELOW OR ABOVE FEET IN ELEVATION, crossing 3213 Highway Louisiana the at estimates scour and sections, cross comparative schematic, Bridge 13. Figure of the Mississippi River at Gramercy, Louisiana. Gramercy, at River Mississippi the of

23 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

Luling

310

DIRECTN IO OFO FL W

MSIISSIPIS P VERRI

310

Photograph source: Louisiana Department of Transportation and Development, 9/28/94

Figure 14. Aerial photograph of the Interstate Highway 310 crossing of the Mississippi River at Luling, Louisiana.

24 Pier Scour

Values for y1 at each pier were based on the DOTD hydrographic survey of 1991. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity, which was computed using the WSPRO model.

The maximum computed scour depth was approximately 53 ft for the pier at DOTD station 261+70 (table 8). The channel-bed elevation for this computed scour hole is about 117 ft below NGVD of 1929. Predicted scour depths are not below the pile tip elevations at any of the piers.

Table 8. Scour data for Interstate Highway 310 crossing of the Mississippi River at Luling, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 15.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 249+35 -26 Round 1.0 35 5.0 35 NA -61 -166 261+70 -64 Round 1.0 43 8.0 53 NA -117 -185 266+65 -50 Round 1.0 27 6.0 33 NA -83 -149 269+25 -39 Round 1.0 20 6.0 27 NA -66 -109 271+90 -8 Round 1.0 17 4.0 18 NA -26 -100

Channel Stability

Cross-section information is shown in figure 15 for the years 1973, 1975, 1990, and 1991. The surveys indicate some shifting in the location and elevation of the thalweg, but the most recent elevations are above the 1973 elevations. The bridge crossing is located in a relatively straight reach of the river (fig. 14) where levees to confine flood flows are constructed on each bank. Values of velocity at the pier locations are listed in table 8.

U.S. Highway 90 Crossing (Huey P. Long bridge) of the Mississippi River at New Orleans

The 500-year flood estimate used in the hydraulic analysis was 1,250,000 ft3/s. The water- surface elevation used for the 500-year estimate is 10.6 ft above NGVD of 1929 (table 9). The width of the channel (fig. 16) at the 500-year flood is approximately 2,300 ft. Simulations indicate velocities range from 5.0 to 8.0 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 9.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1991 for evaluations of pier scour. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using the WSPRO model.

25 270+00 SOUTH BANK 260+00 DOTD STATION, IN FEET DOTD STATION, ESTIMATED MAXIMUM ESTIMATED WATER-SURFACE ELEVATION FOR 500- FOR ELEVATION SCOUR ELEVATION YEAR FLOOD 250+00 EXPLANATION 1973 DOTD 1975 USACE 1990 DOTD 1991 DOTD LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM COOPERATIVE RESOURCES WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA GROUND-SURFACE ELEVATION: NORTH BANK 0 240+00 60

-60

120 180 240 -240 -180 -120 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, . Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 310 crossing of the 15. Bridge schematic, comparative cross sections, and scour estimates Figure Mississippi River at Luling, Louisiana.

26 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

NEW ORLEANS 90

V RI ER

90 I PPI FLOW S F O N ISSIS IO M

DIRECT

Photograph source: Louisiana Department of Transportation and Development, 10/6/92

Figure 16. Aerial photograph of the U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans, Louisiana.

27 The maximum computed scour depth is approximately 73 ft for the pier at DOTD station 113+20 (table 9). The channel-bed elevation of the computed scour hole is about 140 ft below NGVD of 1929. None of the estimated scour depths produce bed elevations that are below the bottom of the footings. Willow mattresses and riprap protection at the piers will limit the actual depth of pier scour.

Table 9. Scour data for U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 10.6 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans; NA, not applicable]

Scour Footing Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 105+28 -61 Round 1.0 70 8.0 72 NA -133 -170 113+20 -67 Round 1.0 70 8.0 73 NA -140 -169 118+49 -67 Round 1.0 50 8.0 58 NA -126 -169 123+81 -33 Round 1.0 50 5.0 44 NA -77 -168

Channel Stability

Cross-section information is shown in figure 17 for the years 1936, 1975, and 1991. The two more recent surveys indicate a decrease in the elevation of the thalweg from the original 1936 survey. The 1936 bed elevations were scaled from a reduced copy of DOTD bridge plans and could have some error from that process. With that in consideration, the general shape of the cross section is consistent, and differences between 1975 and 1991 elevations across the section are generally less than 15 ft. Some shifting of the thalweg is apparent when comparing the 1975 and 1991 surveys. The bridge crosses the river at a relatively straight reach about 1 mi upstream of a turn to the right. Flood flows are confined by levees on each bank (fig. 16).

U.S. Highway 90 Crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans

The 500-year flood estimate used for hydraulic analysis is 1,250,000 ft3/s. The water- surface elevation used for the 500-year estimate is 9.0 ft above NGVD of 1929 (table 10). The width of the channel (fig. 18) at the 500-year flood estimate is approximately 2,500 ft. Simulations indicate velocities ranging from 5.0 to 10.0 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 10.

Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1991. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of velocity, which is computed using the WSPRO model. The maximum computed scour depth is approximately 50 ft for the pier at DOTD station 125+78 (table 10, fig. 19). The channel-bed elevation of the computed scour hole is about 107 ft below NGVD of 1929. None of the estimated scour depths produce bed elevations that are below the bottom of the footings. Willow mats and riprap protection at the piers will limit the actual pier scour depths.

28 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 800

700 EXPLANATION GROUND-SURFACE 600 ELEVATION: ESTIMATED MAXIMUM SCOUR ELEVATION 1936 DOTD 500 1975 DOTD WATER-SURFACE 1991 DOTD ELEVATION FOR 500- 400 YEAR FLOOD

300

200

100 29 0 BELOW NGVD OF 1929 OF NGVD BELOW -100 ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION,

-200 SOUTH BANK NORTH BANK

-300 100+00 105+00 110+00 115+00 120+00 125+00

DOTD STATION, IN FEET

Figure 17. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 90 crossing (Huey P. Long bridge) of the Mississippi River at New Orleans, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

ER V

NEW RI ORLEANS

F FL

SS O IIP

ON I

MSS C

E TI

Photograph source: Louisiana Department of Transportation and Development, 1/24/95 Figure 18. Aerial photograph of the U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans, Louisiana.

30 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 600

500 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION SCOUR ELEVATION 400 1975 USACE WATER-SURFACE 1980 DOTD ELEVATION FOR 500- 1991 DOTD YEAR FLOOD 300

200

100 31

-100

WEST BANK EAST BANK -200 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION,

-300 113+20 120+00 130+00 140+00 147+60

DOTD STATION, IN FEET

Figure 19. Bridge schematic, comparative cross sections, and scour estiamtes at the U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans, Louisiana. Table 10. Scour data for U.S. Highway 90 crossing (Greater New Orleans bridge no. 2) of the Mississippi River at New Orleans, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 9.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing or pile tip elevations scaled from DOTD bridge plans]

Footing or Scour pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 125+78 -57 Round 1.0 50 6.0 50 0 -107 -180 141+53 5 Round 1.0 42 6.0 31 0 -26 -85

Channel Stability

Cross-section information is shown in figure 19 for the years 1975, 1980 and 1991. The 1980 cross section represents the lowest thalweg elevation among the three surveys. The change in bed elevation between the surveys near midchannel is about 25 ft. The horizontal location of the thalweg does not change significantly among the three surveys, and it is not near the main piers which are located out of the midchannel area. The 1980 bed elevations were scaled from a reduced copy of DOTD bridge plans and could have some error from that process. The USACE and DOTD cross-section data were collected at slightly different locations, but comparison of these data does not indicate any major changes in the minimum bed elevations at the site.

Interstate Highway 10 Crossing of the Inner Harbor Navigation Canal at New Orleans

The discharge used for hydraulic analysis was computed based on a conveyance weighted distribution of discharge between the Mississippi River main channel and the Inner Harbor Navigation Canal. Only the geometry of the canal was considered in this evaluation, even though it is not considered as a flood control feature. Losses through the navigation locks were not considered in this estimate, making the discharge estimate biased upward if the locks stayed open during the flood. The downstream water-surface elevation used for the simulations was estimated at 1.0 ft above NGVD of 1929 at Lake Pontchartrain and at the bridge (table 11). This represents a minimum normal elevation at the lake which will bias the velocity estimates upward. The combination of an upward biased discharge estimate, and a further upward bias in the velocity computations results in an over-estimation of scour depths (table 11). The width of the channel (fig. 20) at the estimated flood elevation is approximately 420 ft. The minimum channel-bed elevation for the cross section at the bridge is 37 ft below NGVD of 1929. Simulations indicate velocities ranging from 1.7 to 7.5 ft/s along the cross section at the bridge. Values of velocity at the pier locations are listed in table 11.

Table 11. Scour data for Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 1.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Scour Pile tip Ground elevation elevation elevation (ft above or (ft above (ft above Local or Contraction below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 1525+23 -10 Round 1.0 20 5.1 20 0 -30 -95 1528+23 -8 Round 1.0 20 5.7 21 0 -29 -100

32 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

rIn

arb

NEW

ORLEANS Na

10 10

Can

Photograph source: Louisiana Department of Transportation and Development, 5/6/94 Figure 20. Aerial photograph of the Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans, Louisiana.

33 Pier Scour

For evaluation of pier scour at Interstate Highway 10 crossing of Inner Harbor Navigation Canal, values for the depth of the pier were based on the DOTD hydrographic survey of 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity, which was computed using WSPRO.

The maximum computed scour depth was approximately 21 ft for the pier at DOTD station 1525+23. The channel-bed elevation of the computed scour hole is about 30 ft below NGVD of 1929 (fig. 21). The elevation of the pile tip for this pier is about 95 ft below NGVD of 1929.

Channel Stability

An aerial view of this bridge crossing is shown in figure 20. Cross-section information is shown in figure 21 for the years 1966, 1988, and 1994. These surveys do not show significant changes in the pattern or minimum elevations of the channel bed.

Ouachita River Basin

The Ouachita River Basin originates in Arkansas and drains parts of Arkansas and Louisiana. The drainage area is approximately 19,000 mi2 (Sloss, 1971, p. 73). The basin is bounded by the Tensas River Basin on the east and the Red River Basin on the west. At its mouth, the Ouachita River joins the mouth of the Tensas River and the mouth of Little River to form the origin of the Black River.

Interstate Highway 20 Crossing of the Ouachita River at Monroe The estimate of the 500-year flood used for the hydraulic analysis is 103,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 81.5 ft above NGVD of 1929 (table 12). The width of the flood plain at the 500-year flood is approximately 1,000 ft. The width of the channel (fig. 22) at the 500-year flood is approximately 820 ft. Simulations indicate velocities ranging from 1.6 to 4.0 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 12.

Pier Scour

The maximum computed scour depth was approximately 18 ft for the pier at DOTD station 88+55 (table 12, fig. 23). The channel-bed elevation for this computed scour hole is about 17 ft above NGVD of 1929.

34 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 320

280 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 240 1966 DOTD WATER-SURFACE 1988 DOTD ELEVATION FOR 500- 200 1994 DOTD YEAR FLOOD

160

120

35 40

-40

-80

-120 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, -160

-200 1523+00 1524+00 1525+00 1526+00 1527+00 1528+00 1529+00 1530+00

DOTD STATION, IN FEET

Figure 21. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 10 crossing of the Inner Harbor Navigation Canal at New Orleans, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

L 20 F

F F

TI N

RIVER

MONROE

Photograph source: Louisiana Department of Transportation and Development, 11/30/93

Figure 22. Aerial photograph of the Interstate Highway 20 crossing of the Ouachita River at Monroe, Louisiana.

36 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 240

220 EXPLANATION 200 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 1959 DOTD 180 WATER-SURFACE 1990 DOTD ELEVATION FOR 500- DOTD 160 1993 YEAR FLOOD

140

120

37 100

80 BELOW NGVD OF 1929 OF NGVD BELOW 60 ELEVATION, IN FEET ABOVE OR OR ABOVE FEET IN ELEVATION, 40

0 WEST BANK EAST BANK

-20 81+00 83+00 85+00 87+00 89+00 91+00 93+00

DOTD STATION, IN FEET

Figure 23. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 20 crossing of the Ouachita River at Monroe, Louisiana. Table 12. Scour data for Interstate Highway 20 crossing of the Ouachita River at Monroe, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 81.5 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Scour Pile tip Ground elevation elevation elevation Local or Contrac- (ft above (ft above (ft above Pier pier tion or below or below DOTD NGVD of width Velocity scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 83+97 50 Round 1.0 9 2.0 10 0 40 0 84+95 37 Round 1.0 14 4.0 17 0 20 -10 86+45 35 Round 1.0 14 4.0 17 0 18 -10 88+55 35 Round 1.0 14 4.0 18 0 17 -10 90+05 42 Round 1.0 14 3.0 15 0 27 0

Channel Stability Cross-section information is shown in figure 23 for the years 1959, 1990, and 1993. The riverbed elevation indicated on figure 23, based on surveys of 1959, 1990, and 1993, show only minor differences in the bed elevations with no trend indicated. The differences can be attributed to seasonal flow variations and minor lateral position of the data collection vessel when the riverbed was surveyed.

U.S. Highway 165 Crossing of the Ouachita River at Columbia The estimate of the 500-year flood used for the hydraulic analysis is 76,400 ft3/s. The computed water- surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 58.0 ft above NGVD of 1929 (table 13). The width of the flood plain at the 500-year flood is approximately 1,280 ft. The width of the channel (fig. 24) at the bridge for the 500-year flood simulation is approximately 900 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.00008 ft/ft, which is the same slope determined from the calibration simulations at this site. Simulations of the 500-year flood indicate velocities ranging from 1.1 to 5.1 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 13.

Pier Scour

For the evaluation of pier scour, values for water depths at each pier (y1), were based on the DOTD hydrographic survey of 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 17 ft for the pier at DOTD station 38+56 (table 13, fig. 25). The channel-bed elevation of the computed scour hole is about 8 ft below NGVD of 1929.

38 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

W O

FL O F N 165

TIO C E R DI

165 OU AC HITA

Columbia RIV RE

Photograph source: Louisiana Department of Transportation and Development, 11/25/91

Figure 24. Aerial photograph of the U.S. Highway 165 crossing of the Ouachita River at Columbia, Louisiana.

39 Table 13. Scour data for U.S. Highway 165 crossing of the Ouachita River at Columbia, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 58.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip and footing elevations scaled from DOTD bridge plans]

Footing Scour and pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 38+56 9 Round 1.0 13 4.4 17 0 -8 -40 40+29 19 Round 1.0 13 4.0 16 0 3 -40

Channel Stability

The channel cross section has changed very little from the west bank to mid-channel. There are increases in bed elevations of about 10 ft on the east bank based on comparison of the 1931 and 1991 data. The comparison of the 1991 and 1994 data indicate some minor changes in bed elevation. These minor changes may be due in part to small differences in the location of the cross sections and horizontal approximations made on the original hydrographic records at the time of the data collection.

Tensas River Basin

The Tensas River Basin, located in southeastern Arkansas and northeastern Louisiana, is an area of low topographic relief that lies west of the Mississippi River. The drainage area of the Tensas River is 2,520 mi2 at its mouth. (Sloss, 1971, p. 73). The basin has its headwaters in Arkansas and is bounded by the Mississippi River levee on the east, the Ouachita River Basin on the west, and the upper limits of the Atchafalaya River Basin on the south. The upper part of the basin can be affected by headwater flooding, and the lower part is affected by backwater from the Mississippi River and the Red River.

U.S. Highway 80 Crossing of the Tensas River at Tendal

The estimate of the 500-year flood used for the hydraulic analysis is 7,300 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 78.5 ft above NGVD of 1929 (table 14). The width of the flood plain at the 500-year flood is approximately 300 ft. The width of the channel (fig. 26) at the bridge for the 500-year flood simulation is also approximately 300 ft; without width reduction at the bridge, no contraction scour would be indicated. The downstream boundary condition for computations using the WSPRO model was a slope of 0.00005 ft/ft, which is the same slope determined from the calibration simulations at this site. A general calibration for the reach including U.S. Highway 80 and Interstate Highway 20 was based on the 1949 flood of 4,610 ft3/s, which is the peak of record. The calibration also generally matched the 1979 flood of 3,800 ft3/s. Roughness coefficients for the 500-year flood simulation were reduced by about 10 percent to account for geometric and roughness changes with the increased depth and flow. Simulations of the 500-year flood indicate velocities ranging from 0.7 to 1.6 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 14.

Pier Scour

For the evaluation of pier scour of the Tensas River at U. S. Highway 80, values for water depths at each pier (y1), were based on the DOTD hydrographic survey of 1952. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions.

40 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 220 EXPLANATION 200 GROUND-SURFACE ELEVATION: ESTIMATED MAXIMUM 1931 DOTD SCOUR ELEVATION 180 1991 DOTD WATER-SURFACE 1994 DOTD ELEVATION FOR 500- 160 YEAR FLOOD

140

120

100

41 60

0 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, -20 WEST BANK EAST BANK

-40

-60 30+00 35+00 40+00 45+00 50+00

DOTD STATION, IN FEET

Figure 25. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 165 crossing of the Ouachita River at Columbia, Louisiana.

R 80 E V I R S A S N E T

DIRECTION OF FLOW DIRECTION OF FLOW Tendal Tendal Source: Louisiana Oil Spill Coordinator’s (LOSCO), 20001009, Color Infrared Orthophoto, Office Source: Louisiana Oil Spill SW quadrant of Tendal Quadrangle, LA, 50:1 MrSID compressed, UTM 15 NAD83, LOSCO Tendal SW quadrant of (2000) [c3209138_sws_50] 20 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM RESOURCES COOPERATIVE WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA Aerial photograph of the U.S. Highway 80 crossing of the Tensas River at Tendal, Louisiana. Tendal, River at Tensas Aerial photograph of the U.S. Highway 80 crossing 26. Figure

42 The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 5 ft for the pier at DOTD station 352+17 (table 14, fig. 27). The channel-bed elevations of the computed scour holes are about 58 ft, 53 ft, and 55 ft above NGVD of 1929, respectively.

Table 14. Scour data for U.S. Highway 80 crossing of the Tensas River at Tendal, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 78.5 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans; NA, not applicable]

Ground Scour Footing elevation elevation elevation (ft above Local or Contraction (ft above (ft above DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 350+85 75 Abut 1.0 1 0 0 0 75 NA 351+17 63 Round 1.0 5 1.2 5 0 58 35 352+17 58 Round 1.0 5 1.6 5 0 53 32 353+18 60 Round 1.0 5 1.3 5 0 55 35 353+50 64 Round 1.0 1 1.0 2 0 62 35 353+82 67 Round 1.0 1 0.7 1 0 66 35 354+14 75 Abut 1.0 1 0 0 0 75 NA

Channel Stability

An aerial photograph of this bridge crossing is shown in figure 26. Cross-section information is shown in figure 27 for the year 1952. Because this bridge is not in the DOTD channel monitoring program, there are no comparative bed elevation data. Changes in bed elevations can have significant effects on the scour estimates.

Interstate Highway 20 Crossing (West, Middle, and East) of the Tensas River near Tendal

The estimate of the 500-year flood used for the hydraulic analysis is 7,300 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year estimate is 78.3 ft above NGVD of 1929 at the western crossing, 76.9 ft above NGVD of 1929 at the middle crossing, and 76.6 ft above NGVD of 1929 at the eastern crossing (table 15). The width of the flood plain at the 500-year flood is approximately 300 ft. The width of the channel through all three bridges at the 500-year flood is approximately 180 ft. Figures 28, 29 and 30 show the west, middle, and east bridge crossings. The downstream boundary condition for computations using the WSPRO model was a slope of 0.0005 ft/ft, which is the same slope, determined from the calibration simulations at this site. A general calibration for the reach including U.S. Highway 80 and Interstate Highway 20 was based on the 1949 flood of 4,610 ft3/s, which is the peak of record. The calibration also generally matched the 1979 flood of 3,800 ft3/s. Roughness coefficients for the 500-year flood simulation were reduced by about 10 percent to account for geometric and roughness changes with the increased depth and flow. Simulations indicate velocities ranging from 0.6 to 5.5 ft/s along the cross sections at each of the bridges. Values of velocity at pier locations are listed in table 15.

43 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 160

140 EXPLANATION ESTIMATED MAXIMUM GROUND-SURFACE SCOUR ELEVATION 120 ELEVATION: WATER-SURFACE 1952 DOTD ELEVATION FOR 500- 100 YEAR FLOOD

60 44

20 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE NGVD OF 1929 OF NGVD ABOVE FEET IN ELEVATION,

0 350+50 351+00 351+50 352+00 352+50 353+00 353+50 354+00 354+50

DOTD STATION, IN FEET

Figure 27. Bridge schematic, cross section, and scour estimates at U.S. Highway 80 crossing of the Tensas River at Tendal, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

Tendal

O C

FLOW

20 20

TENSAS

R I VER

Photograph source: Louisiana Department of Transportation and Development, 11/10/93

Figure 28. Aerial photograph of the Interstate Highway 20 crossing (west) of the Tensas River near Tendal, Louisiana.

45 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

IE RVR

Tendal S

EN AS T

IONFL OF T OW

EC IR D

Photograph source: Louisiana Department of Transportation and Development, 11/10/93

Figure 29. Aerial photograph of the Interstate Highway 20 crossing (middle) of the Tensas River near Tendal, Louisiana.

46 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

D C I RE

TI N OW OO

F F L

N Tendal S AS

20 20

Photograph source: Louisiana Department of Transportation and Development, 11/10/93

Figure 30. Aerial photograph of the Interstate Highway 20 crossing (east) of the Tensas River near Tendal, Louisiana.

47 Pier Scour

Values for y1 at each pier are based on the DOTD hydrographic survey of 1970. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO.

The maximum computed scour depth is approximately 5 ft for the pier at DOTD station 392+28 at the West Bridge, at 537+47 at the Middle Bridge, and at 592+57 at the East Bridge (table 15, figs. 31-33). The channel-bed elevation of the computed scour holes are about 40 ft below NGVD of 1929.

Table 15. Scour data for Interstate Highway 20 crossing (west, middle, and east) of the Tensas River near Tendal, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation are shown in the table in feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans; NA, not applicable]

West Bridge water surface = 78.3 above NGVD of 1929 391+08 66 Round 1.0 2 0.7 3 2 61 25 391+68 56 Round 1.0 2 1.6 3 2 51 25 392+28 49 Round 1.0 4 1.9 5 2 42 25 392+88 59 Round 1.0 2 1.5 3 2 54 25

Middle Bridge water surface = 76.9 above NGVD of 1929 536+26 61 Round 1.0 2 1.3 4 3 54 25 536+87 54 Round 1.0 2 1.8 3 3 48 25 537+47 48 Round 1.0 4 2.0 5 3 40 25 538+06 66 Round 1.0 2 0.7 2 3 61 25

East Bridge water surface = 76.6 above NGVD of 1929 591+27 61 Round 1.0 2 0.6 3 0 58 25 591+92 46 Round 1.0 2 1.6 3 0 43 25 592+57 45 Round 1.0 4 1.6 5 0 40 25 593+22 61 Round 1.0 2 0.6 2 0 59 25

Channel Stability

Aerial photographs of these bridge crossings are shown in figures 28-30. Cross-section information is shown in figures 31-33 for the year 1970. Because these bridges are not in the DOTD channel monitoring program, there are no comparative bed elevation data. Any undocumented bed elevation changes could affect scour-elevation estimates.

48 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 120

EXPLANATION

GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 100 WATER-SURFACE 1970 DOTD ELEVATION FOR 500- YEAR FLOOD

60 49 40 ELEVATION, IN FEET ABOVE NGVD OF 1929 OF NGVD ABOVE FEET IN ELEVATION,

EAST BANK WEST BANK

0 392+80 392+20 391+60 391+00

DOTD STATION, IN FEET Figure 31. Bridge schematic, cross section, and scour estimates at the Interstate Highway 20 crossing (west) of the Tensas River near Tendal Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 120

EXPLANATION

100 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 1970 DOTD WATER-SURFACE ELEVATION FOR 500- YEAR FLOOD

60 50

40 ELEVATION, IN FEET ABOVE NGVD OF 1929 OF NGVD ABOVE FEET IN ELEVATION,

WEST BANK EAST BANK

0 538+40 537+80 537+20 536+60 536+00

DOTD STATION, IN FEET

Figure 32. Bridge schematic, cross section, and scour estimates at the Interstate Highway 20 crossing (middle) of the Tensas River near Tendal, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 120

EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 100 ELEVATION: SCOUR ELEVATION WATER-SURFACE 1970 DOTD ELEVATION FOR 500- YEAR FLOOD

60 51

40 ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION,

EAST BANK WEST BANK

0 593+40 592+80 592+20 591+60 591+00

DOTD STATION, IN FEET

Figure 33. Bridge schematic, cross section, and scour estimates at the Interstate Highway 20 crossing (east) of the Tensas River, near Tendal, Louisiana. Louisiana Highway 128 Crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight

The estimate of the 500-year flood used for the hydraulic analysis is 10,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year estimate is 60 ft above NGVD of 1929 (table 16). The width of the flood plain at the 500-year flood is approximately 425 ft. The width of the channel (fig. 34) at the 500-year flood is approximately 400 ft. The downstream boundary condition for computations using the WSPRO model was a water-surface elevation of 59 ft above NGVD of 1929. This value is based on backwater conditions and historical flood peak elevations observed at the site. Simulations indicate velocities ranging from 0.3 to 1.1 ft/s along the cross section at the bridge. Values of velocity at pier locations are shown in table 16.

Pier Scour

For evaluation of pier scour values for y1 at each pier were based on the observed pile configuration cross section at the bridge and the distance to the ground surface from the deck of the bridge. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The geometric data collected at the bridge was combined and referenced to topographic map features. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO.

The maximum computed scour depth is approximately 10 ft for the pier located 245 ft from the reference point on the west bank abutment (table 16, fig. 35). The channel-bed elevation of the computed scour hole is 7 ft above NGVD of 1929.

Table 16. Scour data for Louisiana Highway 128 crossing of Tensas River (near Tensas River National Wildlife Refuge) near Newlight, Louisiana

[Water-surface elevation is 60.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations unknown; NA, not applicable]

Distance Ground Scour Pile tip from west elevation elevation elevation bank (ft above Local or Contraction (ft above (ft above abutment NGVD of Pier width Velocity pier scour scour NGVD of NGVD of (ft) 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 40 50 Round 1.0 4 0.3 2 0 48 NA 160 27 Round 1.0 6 0.9 5 0 22 NA 245 17 Round 1.0 16 1.0 10 0 7 NA 325 23 Round 1.0 4 1.0 4 0 19 NA 445 48 Round 1.0 4 0.3 2 0 46 NA

Channel Stability

There were not sufficient historic river bed elevation data available to evaluate previous conditions at the site. Bed changes that have occurred since construction can affect scour estimates.

Louisiana Highway 15 Crossing of the Tensas River at Clayton

The estimate of the 500-year flood used for the hydraulic analysis is 15,800 ft3/s. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 56.7 ft above NGVD of 1929 (table 17). The width of the flood plain at the 500-year flood is approximately 576 ft. The

52 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

TENSAS RIVER NATIONAL WILDLIFE REFUGE

Newlight

128 4

OF 128

ON I

D RE

TEN

Photograph source: Spot-Thematic Satellite Image provided by GIS Data Depot, May 1999

Figure 34. Aerial photograph of the Louisiana Highway 128 crossing of the Tensas River (near Tensas River National Wildlife Refuge) near Newlight, Louisiana.

53 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 90

EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 75 WATER-SURFACE 1970 DOTD ELEVATION FOR 500- PILE TIP ELEVATIONS UNKNOWN YEAR FLOOD

45 54

30 ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION,

WEST BANK EAST BANK 15

0 480 360 240 120 0 DISTANCE FROM WEST BANK ABUTMENT, IN FEET

Figure 35. Bridge schematic, cross section, and scour estimates at the Louisiana Highway 128 crossing of the Tensas River (near New Tensas River National Wildlife Refuge) near Newlight, Louisiana. width of the channel (fig. 36) at the bridge for the 500-year flood is approximately 344 ft. The downstream boundary condition for hydraulic computations using WSPRO was a slope of 0.00001 ft/ft, which is the same slope used in calibration simulations of this reach. Simulations indicate velocities ranging from 0.5 to 1.4 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 17.

Pier Scour

For evaluation of pier scour of the Tensas River at Louisiana Highway 15, values for y1 at each pier were based on the DOTD hydrographic survey of 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 19 ft for the pier at DOTD station 114+15 (table 17, fig. 37). The channel-bed elevation for this computed scour hole is about 6 ft above NGVD of 1929.

Table 17. Scour data for Louisiana Highway 15 crossing of the Tensas River at Clayton, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 56.7 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Pile tip Ground Scour elevation elevation elevation (ft above (ft above Local or Contraction (ft above or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 112+40 48 Square 1.0 2 0.5 2 0 46 -11 113+20 33 Square 1.0 2 0.9 3 0 30 -13 114+15 25 Square 1.0 32 1.2 19 0 6 -51 116+27 28 Square 1.0 32 1.1 18 0 10 -46

Channel Stability

Cross-section information is shown in figure 30 for the years 1967 and 1994. These surveys do not show substantial changes in the elevation of the channel bed.

Black River Basin

The Black River is formed by the confluence of the Ouachita, Tensas, and Little Rivers. The drainage area is 21,000 mi2 at the confluence of the three rivers and 24,500 mi2 at the mouth (Sloss p. 73, 85). The mouth of the river is only about 30 mi south of the confluence. The Black River flows into the Red River about 25 mi upstream of the mouth of the Red River, where the confluence of the Lower Old River and the Red River forms the Atchafalaya River.

U.S. Highway 84 Crossing of the Black River at Jonesville The estimate of the 500-year flood used for the hydraulic analysis is 86,000 ft3/s. Hydraulic computations were based on calibration of the WSPRO model to the flood of 1973 which had a peak water-surface elevation of 50.75 ft above NGVD of 1929 and a discharge of 62,000 ft3/s. The calibration

55 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

F FLO O O W TI N EC IR D 15

R Clayton RIV E TENS AS

Photograph source: Louisiana Department of Transportation and Development, 9/20/91

Figure 36. Aerial photograph of the Louisiana Highway 15 crossing of the Tensas River at Clayton, Louisiana.

56 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 220

200 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 180 ELEVATION: SCOUR ELEVATION 1967 DOTD 160 WATER-SURFACE 1994 DOTD ELEVATION FOR 500- YEAR FLOOD 140

120

100

57 20

-20

ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, SOUTH BANK NORTH BANK -40

-60 111+00 112+00 113+00 114+00 115+00 116+00 117+00 118+00

DOTD STATION, IN FEET

Figure 37. Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 15 crossing of the Tensas River at Clayton, Louisiana. simulations determined a downstream boundary condition water surface slope of 0.000007 ft/ft to be used in the 500-year flood simulations. The magnitude of this slope is consistent with backwater conditions previously documented at the site (Neely, 1976). The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 59.7 ft above NGVD of 1929 (table 18). The normal width of the channel (fig. 38) is 575 ft. The width of the flood plain at the 500-year flood is approximately 2,400 ft. Simulations indicate velocities ranging from 0.6 to 2.6 ft/s along the cross section. Values of velocity at pier locations are listed in table 18.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the DOTD bridge plans and the hydrographic survey of 1993. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier. The maximum computed scour depth was approximately 22 ft at DOTD station 102+20 (table 18, fig. 39). The channel-bed elevation for this computed scour hole is about 28 ft below NGVD of 1929. Limited information was available for the south overbank piers on the original bridge plans. The approximate conditions at the pier nearest the main channel on each bank were used to estimate scour for the overbank piers.

Table 18. Scour data for U.S. Highway 84 crossing of the Black River at Jonesville, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 59.7 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 95+54 51 Round 1.0 5.5 1.4 5 0 46 -34 98+05 31 Round 1.0 8 1.4 7 0 24 -40 100+57 3 Round 1.0 10 2.6 12 0 -9 -50 102+20 -6 Round 1.0 26 2.4 22 0 -28 -50 103+83 6 Round 1.0 10 2.4 12 0 -6 -50 106+33 47 Round 1.0 8 1.1 6 0 41 -50

Channel Stability

The results of surveys performed by DOTD in 1933, 1990, and 1993 are shown in figure 39. The two recent surveys do not indicate any large differences in the channel-bed elevation from the original survey. Some bed elevation reductions of less than 10 ft were observed near the piers. Some part of the increases in the bed elevation shown on the north bank may be due to the potential error in comparison of elevations observed from hydrographic surveys, and those scaled from reduced scale bridge plans.

Calcasieu River Basin

The Calcasieu River Basin is located in southwestern Louisiana. The Calcasieu River flows southwesterly into Calcasieu Lake. The basin consists of hills and prairies in the upper part and coastal wetlands along the lower part. The drainage area at the Intracoastal Waterway is 3,240 mi2 (Sloss, 1971, p. 109). The City of Lake Charles is about 35 mi from the Gulf of Mexico, just

58 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

R Jonesville IEV R

ACK L B

W O

ION OF FL T C

IRE D

Photograph source: Louisiana Department of Transportation and Development, 11/13/82

Figure 38. Aerial photograph of the U.S. Highway 84 crossing of the Black River at Jonesville, Louisiana.

59 108+50 SOUTH BANK 105+00 100+00 DOTD STATION, IN FEET DOTD STATION, ESTIMATED MAXIMUM ESTIMATED WATER-SURFACE SCOUR ELEVATION 500- FOR ELEVATION YEAR FLOOD LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM COOPERATIVE RESOURCES WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA EXPLANATION DOTD DOTD DOTD 1933 1990 1993 95+00 GROUND-SURFACE ELEVATION: NORTH BANK 0 91+50

100 200 300 -200 -100 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 84 crossing of the Black River at 39 Bridge schematic, comparative cross sections, and scour estimates Figure. Jonesville, Louisiana.

60 downstream of the confluence of the West Fork Calcasieu River. Tidal influences from the Gulf of Mexico affect the water level in the river through the Lake Charles area. Tidal effects during low water levels have been observed as far upstream as a USGS gaging station located near Oberlin, Louisiana.

Louisiana Highway 8 Crossing of the Calcasieu River near Slagle The estimate of the 500-year flood used for the hydraulic analysis was 25,200 ft3/s. There are two openings at the site; the main channel bridge was apportioned 41 percent of the total flow. The 500-year flood simulations were based on a downstream boundary condition water surface slope of 0.0005 ft/ft. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 247.0 ft above NGVD of 1929. This elevation is consistent with limited annual peak water elevations documented at the site (Neely, 1976). The width of the flood plain (fig. 40) at the 500-year flood is approximately 3,500 ft. Simulations indicate velocities ranging from 3.7 to 11.6 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 19.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the observed pile configuration and ground elevation at the bridge. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The geometric data collected at the bridge was combined and referenced to topographic map features. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier. The maximum computed scour depth was approximately 4 ft at the first and second piers from the east bank abutment (table 19, fig. 41). The channel-bed elevation for this computed scour hole is about 230 ft.

Table 19. Scour data for Louisiana Highway 8 crossing of the Calcasieu River near Slagle, Louisiana

[Water-surface elevation is 247.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; NA, not applicable]

Distance Ground Scour Pile tip from east elevation elevation elevation bank (ft above Local or Contraction (ft above (ft above abutment NGVD of Pier width Velocity pier scour scour NGVD of NGVD of (ft) 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 0 241 Round 1.0 1 0.0 0 0 241 NA 20 234 Round 1.0 1 10.2 4 0 230 NA 40 234 Round 1.0 1 11.1 4 0 230 NA 60 240 Round 1.0 1 6.3 3 0 237 NA 80 241 Round 1.0 1 5.5 3 0 238 NA 100 242 Round 1.0 1 5.1 3 0 239 NA 120 242 Round 1.0 1 4.5 2 0 240 NA 140 243 Round 1.0 1 3.9 2 0 241 NA 160 243 Round 1.0 1 3.9 2 0 241 NA 180 243 Round 1.0 1 4.0 2 0 241 NA 200 243 Round 1.0 1 4.0 2 0 241 NA 220 243 Round 1.0 1 4.0 2 0 241 NA 240 243 Round 1.0 1 4.0 2 0 241 NA 260 243 Round 1.0 1 4.0 2 0 241 NA 280 243 Round 1.0 1 3.7 2 0 241 NA 300 243 Round 1.0 1 0.0 0 0 243 NA

61 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

CALCA S DI IEU R EF FCTIO O RIVER N O L W

62 Slagle

121

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 40. Aerial photograph of the Louisiana Highway 8 crossing of the Calcasieu River near Slagle, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 300 290 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 280 ELEVATION: SCOUR ELEVATION 270 1997 DOTD WATER-SURFACE ELEVATION FOR 500- Bridge deck YEAR FLOOD 260 PILE TIP ELEVATION UNKNOWN

250

240

63 230

220 EAST BANK WEST BANK 210

200 ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION, 190

0 100 200 300

DISTANCE FROM EAST BANK ABUTMENT, IN FEET

Figure 41. Bridge schematic, cross section, and scour estimates at the Louisianan Highway 8 crossing of the Calcasieu River near Slagle, Louisiana. Channel Stability

There were no comparative channel-bed elevations available at this site. The conditions in the immediate areas of the bridge are similar to the natural flood-plain conditions observed in the area. No remnants of local scour were evident at the site. This may be an indication that floods occurring since the construction of the bridge have not induced any substantial channel changes.

Louisiana Highway 28 Crossing of the Calcasieu River near Hicks-LaCamp

The 500-year flood estimate of 41,900 ft3/s was used for the hydraulic analysis. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate was 195.1 ft above NGVD of 1929. The width of the flood plain (fig. 42) at the 500-year flood estimate ranges from 1,100 at the bridge to 3,700 ft in natural areas of the reach. The downstream boundary condition for computations using WSPRO was a slope of 0.0009 ft/ft, which is the same slope used in the calibration simulations. Simulations indicate velocities ranging from 4.7 to 12.7 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 20.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic survey of 1971. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed using WSPRO.

The maximum computed pier scour depth was approximately 6.0 ft for the pier at DOTD stations 1173+71 and 1174+16 (table 20, fig. 43). When added to the contraction scour estimate at these locations, the channel-bed elevation for these computed scour holes is about 171 ft above NGVD of 1929.

Table 20. Scour data for Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 195.1 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Channel Stability

Cross-section information is shown in figure 43 for the year 1975. The original bridge cross-section is the only survey because this bridge is not monitored by DOTD. The bed elevation at the bridge is generally uniform with about a 10 ft decrease in elevation for piers in the low-water channel. Any undocumented changes in the bed elevations may affect scour estimates.

64 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

C A L CA IE RI V ER US

Hicks

I R

I O

Lacamp

Photograph source: Louisiana Department of Transportation and Development, 3/20/92 Figure 42. Aerial photograph of the Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp, Louisiana.

65 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 270

EXPLANATION 250 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 1971 DOTD 230 WATER-SURFACE ELEVATION FOR 500- YEAR FLOOD 210

190

170 66 150

130 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION,

110

90 1171+00 1172+00 1173+00 1174+00 1175+00 1176+00 1177+00 1178+00 1179+00 1180+00 1181+00 1182+00 1183+00

DOTD STATION, IN FEET

Figure 43. Bridge schematic, cross section, and scour estimates at the Louisiana Highway 28 crossing of the Calcasieu River near Hicks-LaCamp, Louisiana. Louisiana Highway 121 Crossing of the Calcasieu River near Hineston

The estimate of the 500-year flood used for the hydraulic analysis was 89,300 ft3/s. There are overflow openings at the site, the main channel bridge was apportioned 40 percent of the total flow based on relative flow areas. The simulations were based on a downstream boundary condition water-surface slope of 0.0006 ft/ft. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 159.0 ft above NGVD of 1929 (table 21). The width of the flood plain at the 500-year flood is approximately 4,000 ft with channel widths (fig. 44) of approximately 400 ft. Simulations indicate velocities ranging from 3.5 to 16.4 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 21.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the observed pile configuration and ground elevation at the bridge. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The geometric data collected at the bridge was combined with topographic map features. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier. The maximum computed scour depth was approximately 5 ft at the piers located 280 ft, 300 ft, and 320 ft from the north bank abutment (table 21, fig. 45). The minimum channel-bed elevation for these computed scour holes is about 129 ft.

Table 21. Scour data for Louisiana Highway 121 crossing of the Calcasieu River near Hineston, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is159.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; NA, not applicable]

Ground Scour Footing Distance elevation elevation elevation from north (ft above Local or Contraction (ft above (ft above bank NGVD of Pier width Velocity pier scour scour NGVD of NGVD of abutment 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 20 156 Round 1.0 1 3.5 2 0 154 NA 40 154 Round 1.0 1 3.5 2 0 152 NA 60 153 Round 1.0 1 3.5 2 0 151 NA 80 153 Round 1.0 1 3.5 2 0 151 NA 100 152 Round 1.0 1 6.6 3 0 149 NA 120 151 Round 1.0 1 6.6 3 0 148 NA 140 150 Round 1.0 1 7.5 3 0 147 NA 160 148 Round 1.0 1 8.8 4 0 144 NA 180 146 Round 1.0 1 9.7 4 0 142 NA 200 143 Round 1.0 1 11.9 4 0 139 NA 220 147 Round 1.0 1 10.8 4 0 143 NA 240 151 Round 1.0 1 4.5 3 0 148 NA 260 155 Round 1.0 1 4.5 2 0 153 NA 280 145 Round 1.0 1 16.4 5 0 140 NA 300 134 Round 1.0 1 13.8 5 0 129 NA 320 135 Round 1.0 1 13.5 5 0 130 NA 340 140 Round 1.0 1 11.1 4 0 136 NA 360 145 Round 1.0 1 5.8 3 0 142 NA 380 150 Round 1.0 1 5.8 3 0 147 NA

67 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

121

C A I C L A US R E IVER Hineston

121 D RECT O I I

ON OF

FL W

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 44. Aerial photograph of the Louisiana Highway 121 crossing of the Calcasieu River near Hineston, Louisiana.

68 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

180 EXPLANATION 175 GROUND-SURFACE ELEVATION: 1997 DOTD ESTIMATED MAXIMUM 170 NOTE: Vertical datum is top of road SCOUR ELEVATION elevation of approximately WATER-SURFACE 165 160 ft above sea level. ELEVATION FOR 500- Pile Tip Elevation Unknown YEAR FLOOD 160

155

150 69

145

140

135 ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION, 130 NORTH BANK SOUTH BANK 125

120 0 100 200 300 400 DISTANCE FROM NORTH BANK ABUTMENT, IN FEET

Figure 45. Bridge schematic, cross section, and scour estimates at the Louisiana Highway 121 crossing of the Calcasieu River near Hineston, Louisiana. Channel Stability

There were no comparative riverbed elevations available at this site. The conditions in the immediate areas of the bridge are similar to the natural flood-plain conditions observed in the area. There are no remnants of scour, which may be an indication that floods occurring since the construction of the bridge have not induced any substantial scour or channel changes.

Louisiana Highway 113 Crossing of the Calcasieu River near Glenmora The estimate of the 500-year flood used for the hydraulic analysis is 96,400 ft3/s. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 128.1 ft above NGVD of 1929 (table 22). There are multiple openings at this site, and 44 percent of the total discharge passes through the main bridge opening. The normal width of the channel (fig. 46) is approximately 400 ft. The width of the flood plain at the 500-year flood is approximately 5,900 ft. The downstream boundary condition for hydraulic computations using WSPRO was a slope of 0.00020 ft/ft, which is the same slope used in calibration simulations of this reach. Simulations indicate velocities ranging from 4.2 to 13.7 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 22.

Pier Scour

For evaluation of pier scour, values at each pier were based on the DOTD hydrographic survey of 1978. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 8 ft for the pier at DOTD station 129+00 (table 22, fig. 47). The channel-bed elevation for this computed scour hole is about 112 ft above NGVD of 1929.

Table 22. Scour data for Louisiana Highway 113 crossing of the Calcasieu River near Glenmora, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 128.1 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Ground Scour Pile tip elevation elevation elevation (ft above Local or Contraction (ft above (ft above DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 126+00 125 Round 1.0 1.5 6.3 4 0 121 70 126+50 122 Round 1.0 1.5 5.6 4 0 118 70 127+00 120 Round 1.0 1.5 4.3 4 0 116 70 127+50 120 Round 1.0 1.5 4.3 4 0 116 65 128+00 120 Round 1.0 1.5 9.4 5 0 115 65 128+50 112 Round 1.0 1.5 13.6 7 0 105 65 129+00 120 Round 1.0 3 9.2 8 0 112 80 129+50 120 Round 1.0 1.5 10.5 5 0 115 70 130+00 112 Round 1.0 1.5 13.2 7 0 105 70 130+50 120 Round 1.0 1.5 9.8 5 0 115 70 131+00 123 Round 1.0 1.5 5.7 4 0 119 75 131+50 125 Round 1.0 1.5 5.7 4 0 121 75

70 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

EU I W

O N CALC O F FLO I Glenmora

CT E 113 DIR

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 46. Aerial photograph of the Louisiana Highway 113 crossing of the Calcasieu River near Glenmora, Louisiana.

71 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 220

200 EXPLANATION ESTIMATED MAXIMUM 180 GROUND-SURFACE SCOUR ELEVATION ELEVATION: WATER-SURFACE 160 1978 DOTD ELEVATION FOR 500- YEAR FLOOD 140

120

72 100

ELEVATION, IN FEET ABOVE NGVD OF 1929 IN FEET ELEVATION, 60 WEST BANK EAST BANK

40 125+00 126+00 127+00 128+00 129+00 130+00 131+00 132+00

DOTD STATION, IN FEET

Figure 47. Bridge schematic, cross section, and scour estimates at the Louisiana Highway 113 crossing of the Calcasieu River near Glenmora, Louisiana. Channel Stability

Cross-section information is shown in figure 47 for the year 1978. This survey shows bed elevations ranging from 112 to 125 ft above NGVD of 1929. An aerial photograph of this bridge crossing is shown in figure 46. Any undocumented changes in the bed elevations may affect the scour estimates.

Louisiana Highway 10 Crossing of the Calcasieu River near Oakdale The estimate of the 500-year flood used for the hydraulic analysis is 85,500 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 102.8 ft above NGVD of 1929 (table 23). The width of the flood plain at the 500-year flood simulation is approximately 5,000 ft. The width of the at the bridge opening (fig. 48) is approximately 1,200 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.0004 ft/ft, which is the same slope determined from the calibration simulations at this site. Simulations of the 500- year flood indicate velocities ranging from 2.8 to 9.6 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 23. There are two small relief openings near the edges of the flood plain at this site that were not considered in this analysis. Using the unadjusted full value of the 500-year flood for the main bridge will exaggerate the scour estimates. Even with the exaggerated bias, scour estimates were well above the pile tips. The contraction scour estimate was less than 1 ft and was not considered in any tabulations.

Pier Scour

For the evaluation of pier scour, values for water depths at each pier were based on the DOTD hydrographic survey of 1977. Values for K1=1.0, K2=1.0, and K3=1.1 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the values of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 7 ft for the pier at DOTD stations 153+33. 156+13, and 157+53 (table 23, fig. 49). The minimum estimated channel-bed elevations of the computed scour holes at these stations is about 85 ft, 74 ft, and 86 ft above NGVD of 1929.

Table 23. Scour data for Louisiana Highway 10 crossing of the Calcasieu River near Oakdale, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 102.8 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans] Ground Scour Footing elevation elevation elevation (ft above Local or Contraction (ft above (ft above DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 149+83 94 Round 1.0 2 2.8 3 0 91 50 150+53 94 Round 1.0 2 2.8 3 0 91 50 151+23 93 Round 1.0 2 2.8 3 0 90 50 151+93 94 Round 1.0 2 2.8 3 0 91 50 152+63 94 Round 1.0 2 4.8 4 0 90 50 153+33 92 Round 1.0 4 4.8 7 0 85 50 154+03 89 Round 1.0 2 6.2 5 0 84 50 154+73 84 Round 1.0 2 8.5 6 0 78 50 155+43 90 Round 1.0 2 6.5 5 0 85 50 156+13 81 Round 1.0 2 9.5 7 0 74 50 156+83 87 Round 1.0 2 7.4 6 0 81 50 157+53 93 Round 1.0 4 5.3 7 0 86 50 158+23 90 Round 1.0 2 5.0 5 0 85 50 158+93 86 Round 1.0 2 5.9 5 0 81 50 159+63 86 Round 1.0 2 6.0 5 0 81 50 160+33 86 Round 1.0 2 6.1 5 0 81 50 161+03 88 Round 1.0 2 3.6 4 0 84 50

73 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

R RIVE

L U SIE C N OF CAL A O F

10 Oakdale

Photograph source: Louisiana Department of Transportation and Development, 9/27/90

Figure 48. Aerial photograph of the Louisiana Highway 10 crossing of the Calcasieu River near Oakdale, Louisiana.

74 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 190

170 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: 150 SCOUR ELEVATION 1977 DOTD 1991 DOTD WATER-SURFACE 130 ELEVATION FOR 500- YEAR FLOOD 110

50 75 30

0 NORTH BANK SOUTH BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -10

-30

-50 149+00 150+00 151+00 152+00 153+00 154+00 155+00 156+00 157+00 158+00 159+00 160+00 161+00 162+00

DOTD STATION, IN FEET

Figure 49. Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 10 crossing of the Calcasieu River near Oakdale, Louisiana. Channel Stability

Cross-section information is shown in figure 49 for the years 1977 and 1991. Comparison of only these surveys indicates changes in elevations in the main channel portion of the cross section. The thalweg elevations observed from the limited main channel data indicate a minor decrease in elevation of approximately 5 ft. An aerial photograph of this bridge crossing is shown in figure 48.

Louisiana Highway 26 Crossing of the Calcasieu River near Oberlin

The estimate of the 500-year flood used for the hydraulic analysis is 94,300 ft3/s. The water- surface elevation used for the 500-year estimate is 67.3 ft above NGVD of 1929. There are sinuous and sometimes braided channels (fig. 50) in the flood plain. The width of the flood plain at the 500- year flood simulation is approximately 1,700 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.0003 ft/ft, which is the same slope determined from the calibration simulation based on historic flood data at the site. Simulations of the 500-year flood indicate velocities ranging from 2.2 to 5.4 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 24.

Pier Scour

Values for each pier are based on the DOTD hydrographic surveys of 1979 and 1991. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which is computed using WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth is approximately 6 ft for the pier at DOTD station 152+10 (table 24, fig. 51). The channel-bed elevation of the computed scour hole is 41 ft above NGVD of 1929.

Table 24. Scour data for Louisiana Highway 26 crossing of the Calcasieu River near Oberlin, Louisiana [DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 67.3 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack and K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Ground Scour Pile tip elevation elevation elevation (ft above Local or Contraction (ft above (ft above DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 150+00 54 Round 1.0 2 2.1 3 3 48 15 150+70 54 Round 1.0 2 2.2 3 3 48 15 151+40 54 Round 1.0 2 2.4 3 3 48 15 152+10 50 Round 1.0 4 4.1 6 3 41 10 152+80 41 Round 1.0 2 5.4 5 3 33 5 153+50 42 Round 1.0 2 5.4 5 3 34 5 154+20 42 Round 1.0 2 5.3 5 3 34 10 154+90 46 Round 1.0 4 2.4 5 3 38 10 155+60 50 Round 1.0 2 2.4 3 3 44 15 156+80 54 Round 1.0 2 2.2 3 3 48 15 157+00 54 Round 1.0 2 2.2 3 3 48 15 157+70 54 Round 1.0 2 2.2 3 3 48 15 158+40 54 Round 1.0 2 2.2 3 3 48 15

76 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

W LO F F O N IO T C E IR Oberlin D

CALC

A SIE U R VER 26 I

Photograph source: Digital Orthophoto Quarter Quadrangle, U.S. Geological Survey Identification number 30092184: accessed 5/29/01 at URL; http://www.atlas.lsu.edu

Figure 50. Aerial photograph of the Louisiana Highway 26 crossing of the Calcasieu River near Oberlin, Louisiana.

77 EAST BANK 157+00 158+40 160+60 Bridge deck DOTD STATION DOTD STATION 152+80 154+20 155+60 ESTIMATED MAXIMUM ESTIMATED WATER-SURFACE ELEVATION FOR 500- FOR ELEVATION SCOUR ELEVATION YEAR FLOOD EXPLANATION LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM RESOURCES COOPERATIVE WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA 1979 DOTD 1991 DOTD GROUND-SURFACE GROUND-SURFACE ELEVATION: WEST BANK 148+00 150+00 151+40 0

-60 120 180 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 OF NGVD BELOW OR ABOVE FEET IN ELEVATION, Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 26 crossing of the 51. Bridge schematic, comparative cross sections, and scour estimates Figure Calcasieu River near Oberlin, Louisiana.

78 Channel Stability

Cross-section information is shown in figure 51 for the years 1979 and 1991. The channel-bed elevations indicated that the limited 1991 bed-elevation data are lower than the 1979 data at DOTD stations 152+80 and 154+20. Bed elevations in 1991 at these locations, near the edge of the low water channel, are about the same as at the center of the channel. Elevations at the center of the channel show substantial change between 1979 and 1991. It is possible that this is an indication of only a minor change of the low water channel. Without greater amounts of monitoring data to verify changes, no trend should be implied. These surveys do not indicate substantial changes in the main channel. An aerial photograph of this bridge crossing is shown in figure 50.

U.S. Highway 190 Crossing of the Calcasieu River near Kinder

The estimate of the 500-year flood used for the hydraulic analysis is 168,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood was 38.8 ft above NGVD of 1929 (table 25). The width of the flood plain at the 500-year flood is approximately 7,000 ft. The width of the channel (fig. 52) at the 500-year flood is approximately 1,000 ft. The downstream boundary condition for hydraulic computations using WSPRO was a slope of 0.00015 ft/ft, which is the same slope used in calibration simulations of this reach. There are multiple bridges at this site. The main bridge opening was apportioned 79 percent of the total flow based on relative conveyance computations of the main channel opening and 2 relief openings. No significant contraction scour was estimated at the sites, and the main bridge abutments are protected with spur dikes. Simulations indicate velocities ranging from 4.0 to 9.2 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 25.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic surveys of 1977 and 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

Pier scour estimates are in addition to a contraction scour estimate of 15 ft. The maximum computed scour depth was approximately 7 ft for the piers at DOTD station 140+15, 140+83, and 142+95 (table 25, fig. 53). The minimum channel-bed elevation of the scour hole at DOTD stations 140+15 and 140+83 is 12 ft below NGVD of 1929.

Table 25. Scour data for U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 38.8 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

79 Table 25. Scour data for U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana—Continued

Ground Scour Pile tip elevation elevation elevation (ft above Local or Contraction (ft above (ft above DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 139+45 21 Round 1.0 2 4.2 4 15 2 -20 140+15 9 Round 1.0 2 9.0 7 15 -12 -30 140+83 9 Round 1.0 2 9.2 7 15 -12 -30 141+55 14 Round 1.0 2 8.1 6 15 -7 -30 142+25 21 Round 1.0 2 6.3 5 15 1 -20 142+95 26 Round 1.0 4 4.5 7 15 4 -20 143+65 25 Round 1.0 2 4.6 4 15 6 -20 144+35 21 Round 1.0 2 5.0 5 15 1 -20 145+05 21 Round 1.0 2 4.4 5 15 1 -20 145+75 25 Round 1.0 2 4.4 4 15 6 -20 146+45 25 Round 1.0 2 3.8 4 15 6 -20

Channel Stability

Cross-section information is shown in figure 53 based on the DOTD surveys of 1977, 1990, and 1994. The 1977 cross-section information was scaled from DOTD bridge plans. The 1990 and 1994 information was based on DOTD channel monitoring surveys. The channel bed conditions in 1990 indicate a lowering of the bed by as much as 10 ft. The 1994 data indicate conditions that are near the bed elevations in 1977. It is possible that the 1990 survey represents remnants of scour from the 25- to 50-year flood of July 1989 (101,000 ft3/s). An aerial photograph of this bridge crossing is shown in figure 52.

U.S. Highway 171 Crossing of the Calcasieu River near Moss Bluff The sites along the Calcasieu River are in a coastal plain environment. The flood flow estimates reflect attenuation of flood peaks due to increased storage and decreased channel slopes. Although there are changes in drainage area and basin slopes for the bridge crossings at U.S. Highway 171, Interstate Highway 10, and Interstate Highway 210, the flood frequency estimates at all three sites are similar enough to use the same value of the 500-year flood. The three “at site” values differ by only three percent from the average of the three estimates. The estimates are near the limits of extremes of the RIRM input variables, and grouping the three sites with a variability of three percent does not violate reasonable hydrologic practices. Although separate flood frequency computations yield different values of the 500-year flood, a single value produces scour estimates that are not significantly different from independent computations. The estimate of the 500-year flood used for the hydraulic analysis of U.S. Highway 171, Interstate Highway 10, and Interstate Highway 210 is 137,000 ft3/s. This single value (rather than slightly scattered values) is used for consistency at these three sites because the sites are relatively close to each other.

The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate for U.S. Highway 171 crossing is 9.3 ft above NGVD of 1929 (table 26). The width of the flood plain at the 500-year flood is approximately 7,000 ft. The width of the channel (fig. 54) is approximately 600 ft. The main span of the bridge is 900 ft, with elevated approaches. The total bridge opening is approximately 5,700 ft (DOTD bridge plans). The downstream boundary condition for computations using the WSPRO model was a slope of 0.00008 ft/ft, which is the same slope, determined from the calibration simulations at this site. Simulations of the 500-year flood indicate velocities ranging from 1.3 to 8.0 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 26.

80 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

IRE

TIO

W L

Kinder

190 190

C CA ASL

I E U

R IV

E R

Photo source: Louisiana Department of Transportation and Development, 10/19/92

Figure 52. Aerial photograph of the U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana.

81 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 120

EXPLANATION 100 GROUND-SURFACE ELEVATION: ESTIMATED MAXIMUM 80 1977 DOTD SCOUR ELEVATION 1990 DOTD WATER-SURFACE 1994 DOTD ELEVATION FOR 500- 60 YEAR FLOOD

0 82

-20

-40 WEST BANK EASTBANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -60 134+00 136+00 138+00 140+00 142+00 144+00 146+00 148+00

DOTD STATION, IN FEET

Figure 53. Bridge schematic, comparative cross sections and scour estimates at U.S. Highway 190 crossing of the Calcasieu River near Kinder, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGR AM

Moss Bluff

D RE C I

171 TI ON OF LOW F

RIV RE

U IE S A C L A C [

Source: Louisiana Oil Spill Coordinator’s Office (LOSCO), 19981229, Color Infrared Orthophoto, SW quadrant of Moss Bluff Quadrangle, LA, 50:1 MrSID compressed, LOSCO (1998) [c3009347_sws_50]

Figu4 re 5 . Aerial photo graph o f the U .S. High way 17 1 c ross ing of t he Calcasi eu R iv e r n ear Mo ss Bluff, Lo u is iana .

83 Pier Scour

For the evaluation of pier scour, values for water depths at each pier (y1), were based on the DOTD hydrographic survey of 1997. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier location is based upon the value of depth and velocity computed by the WSPRO model at a position in the cross section that corresponds to the location of each pier.

The maximum computed scour depth was approximately 13 ft for the pier at DOTD stations 291+15 and 293+15 (table 26, fig. 55). The lowest channel-bed elevation of the computed scour holes is about -37 ft below NGVD of 1929.

Table 26. Scour data for U.S. Highway 171 crossing of the Calcasieu River near Moss Bluff, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 9.3 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) Approach Piers 2 Round 1.0 2 1.6 3 0 -1 NA 287+65 2 Round 1.0 6 1.5 5 0 -3 -50 289+15 1 Round 1.0 6 1.5 5 0 -4 -90 291+15 -21 Round 1.0 7.5 6.0 13 0 -34 -90 293+15 -24 Round 1.0 7.5 5.7 13 0 -37 -90 295+15 2 Round 1.0 6 2.2 6 0 -4 -90 296+65 2 Round 1.0 6 2.2 6 0 -4 -50 Approach Piers 2 Round 1.0 2 1.7 3 0 -1 NA

Channel Stability

Cross-section information is shown in figure 55 for the years 1965 and 1997. No substantial channel migration is evident based on this limited survey information. The two bed elevations shown may adequately document a generally stable geometry at the site. An aerial photograph of this bridge crossing is shown in figure 54.

Interstate Highway 10 Crossing of the Calcasieu River at Lake Charles

The estimate of the 500-year flood used for the hydraulic analysis of the Interstate Highway 10 crossing is 137,000 ft3/s. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 9.0 ft above NGVD of 1929 (table 27). The width of the flood plain at the 500-year flood is approximately 6,550 ft. The width of the channel (fig. 56) at the bridge for the 500-year flood simulation is approximately 700 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.00009 ft/ft, which is the approximate slope from the calibration simulations at nearby U.S. Highway 171. Simulations of the 500-year flood indicate velocities ranging from 1.0 to 6.3 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 27.

84 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 130

EXPLANATION 120 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 100 1997 DOTD WATER-SURFACE 1965 DOTD ELEVATION FOR 500- YEAR FLOOD 80

20 85 0

-20

-40

ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -60

NORTH BANK SOUTH BANK -80

-100 287+15 287+65 289+15 291+15 293+15 295+15 296+65 297+15

DOTD STATION, IN FEET

Figure 55. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 171 crossing of Calcasieu River near Moss Bluff, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

F L F

T ON

RIO

LAKE CHARLES

Photograph source: Louisiana Department of Transportation and Development, 10/10/89

Figure 56. Aerial photograph of the Interstate Highway 10 crossing of the Calcasieu River at Lake Charles, Louisiana.

86 Pier Scour

The maximum computed scour depth was approximately 24 ft for the pier at DOTD station 594+54 (table 27, fig. 57). The channel-bed elevation of the computed scour hole is about 50 ft below NGVD of 1929.

Table 27. Scour data for Interstate Highway 10 crossing of the Calcasieu River at Lake Charles, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 9.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below NGVD of Pier width Velocity pier scour scour NGVD of NGVD of DOTD station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 588+24 15 Round 1.0 18 0 NA 0 NA -40 590+33 -24 Round 1.0 19 3.5 19 0 -43 -120 594+54 -26 Round 1.0 19 5.9 24 0 -50 -120 596+64 -1 Round 1.0 19 1.8 12 0 -13 -40 598+46 -3 Round 1.0 19 1.8 13 0 -16 -40 600+30 -3 Round 1.0 19 2.1 13 0 -16 -40 Overbank piers -4 Round 1.0 10 2.1 9 0 -13 NA

Channel Stability

Cross-section information is shown in figure 57 for the years 1952 and 1994. An aerial photograph of this bridge crossing is also shown. The crossing is on the northern edge of the lake, Lake Charles (fig. 50). The 1994 cross section shows slightly lower elevations than the original bridge plans in the channel areas and a part of one overbank. Comparing the two cross sections shows some vertical changes in the thalweg with the 1994 elevations being 4 to 6 ft lower.

Interstate Highway 210 Crossing of the Calcasieu River near Lake Charles

The estimate of the 500-year flood used for the hydraulic analysis is 137,000 ft3/s. Flow though shallow parts of the flood plain to the south of the main channel was neglected and all flow was routed through the ship channel. The width of the opening in the simulation to estimate pier scour corresponds to the 900 ft main span of the bridge. This approximation may result in pier scour being overestimated. The computed water-surface elevation resulting from hydraulic simulations using the 500-year flood estimate is 4.0 ft above NGVD of 1929 (table 28). At this elevation, the overbank areas of the flood plain are not inundated and flow is confined to the main channel. The width of the channel (fig. 58) at the 500-year flood is approximately 800 ft. The downstream boundary condition for computations using the WSPRO model was a slope of 0.00007 ft/ft, which is representative of flood slopes in this area. Simulations of the 500-year flood indicate velocities ranging from 1.3 to 6.8 ft/s along the cross section at the bridge. Values of velocity at pier locations are listed in table 28.

87 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 480

400 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 320 1952 DOTD WATER-SURFACE 1994 DOTD ELEVATION FOR 500- YEAR FLOOD 240

160

80 88

-80

WEST BANK EAST BANK

ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -160

574+00 579+00 584+00 589+00 594+00 599+00 604+00 609+00 DOTD STATION, IN FEET

Figure 57. Bridge schematic, comparative cross sections, and scour estimates at Interstate Highway 10 crossing of the Calcasieu River at Lake Charles, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

FLO

ION OF CT W DIRE

210

IVER I

CALCAS EU R Lake Charles LAKE CHARLES

Source: Louisiana Oil Spill Coordinator’s Office (LOSCO), 19981230, Color Infrared Orthophoto, NE quadrant of Westlake Quadrangle, LA, 50:1 MrSID compressed, LOSCO (1998) [c3009354_ses_50]

Figure 58. Aerial photograph of the Interstate Highway 210 crossing of the Calcasieu River near Lake Charles, Louisiana.

89 Pier Scour

The maximum computed scour depth was approximately 23 ft for the main channel piers at DOTD station 141+25 (table 28, fig. 59). Timber fenders to protect the piers may serve to reduce the pier scour potential at these piers (Abed and Richardson, 1993). The channel-bed elevation of the computed scour hole is about 49 ft below NGVD of 1929. The greatest scour estimate for the east bank overbank piers was 9 ft. In consideration of the variations in the marsh and overbank areas, this maximum value could be applied to all of the overbank piers.

Table 28. Scour data for Interstate Highway 210 crossing of the Calcasieu River near Lake Charles, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 4.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans; NA, not applicable]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below NGVD of Pier width Velocity pier scour scour NGVD of NGVD of DOTD station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) West bank 2.5 Round 1.0 10 1.3 6 0 -4 NA overbank piers 139+00 0 Round 1.0 17 1.3 9 0 -9 -88 141+25 -26 Round 1.0 17 6.5 23 0 -49 -93 145+75 -26 Round 1.0 17 5.3 21 0 -47 -93 148+00 0 Round 1.0 17 2.7 12 0 -12 -88 East bank 0 Round 1.0 10 2.9 9 0 -9 NA overbank piers

Channel Stability

Cross-section information is shown in figure 59 for the years 1959 and 1997. An aerial photograph of this bridge crossing is shown in figure 58. The DOTD hydrographic survey of 1997 shows only minor differences when compared to the 1959 bed elevations in the main channel.

Sabine River Basin

The Sabine River Basin is located in the western part of Louisiana. The basin is bounded by the State of Texas on the west and Calcasieu River Basin on the east. Approximately half of the length of the river shared by Texas and Louisiana is the Toledo Bend Reservoir. The reservoir was formed by a dam completed in 1966 west of Leesville, Louisiana. The drainage area of the Sabine River at the Intracoastal Waterway is 9,760 mi2. The Intracoastal Waterway interconnects the water bodies in the coastal regions of the State, which can make drainage area determinations uncertain south of the interconnection (Sloss, 1971).

Louisiana Highway 12 Crossing of the Sabine River near Starks

The Louisiana Highway 12 crossing of the Sabine River (fig. 60) consists of an earthen embankment with multiple bridge openings to convey the main channel and overbank flow. A gaging station has been maintained at this location since 1924. The maximum discharge of record was 121,000 ft3/s that occurred in May 1953. The

90 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 180

160 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 140 ELEVATION: SCOUR ELEVATION 1959 DOTD WATER-SURFACE 120 1997 DOTD ELEVATION FOR 500- YEAR FLOOD 100

91 20

-20

-40

-60 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION,

-80

-100 130+00 132+25 134+50 136+75 139+00 141+25 143+50 145+75 148+00 150+25 152+50 154+75 157+00

DOTD STATION, IN FEET

Figure 59. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 210 crossing of the Calcasieu River near Lake Charles, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

V I Starks R

E IN OW B FL SA F O N O TI C E IR D

Source: Louisiana Oil Spill Coordinator’s Office (LOSCO), 19990105, Color Infrared Orthophoto, SW quadrant of Starks Quadrangle, TX, 50:1 MrSID compressed, LOSCO (1999) [c3009343_sws_50]

Figure 60. Aerial photograph of the Louisiana Highway 12 crossing of the Sabine River near Starks, Louisiana.

92 site is about 100 mi downstream from the Toledo Bend Reservoir. This impoundment has a significant effect on the validity of flood frequency estimates, and the confidence limits of these estimates. Based on several approaches, and their results, the 500-year flood estimate of 255,000 ft3/s was obtained by using 1.2 * Q100 value (Richardson, 1991). The Q100 value was based on RIRM estimates (Ensminger, 1998). This estimate of the 500-year flood may result in scour being overestimated on the Sabine River sites examined. A complete analysis of the hydraulics of this multiple opening embankment crossing of the 4 mile-wide flood plain requires application of 2-dimensional flow models which is beyond the scope of this evaluation. Apportionment of the flow among the openings is based on the distribution of flow for the largest flow measurement at the site where 16 openings in the highway embankment were measured. The flow apportioned to the main channel bridge opening is 13 percent of the total measured discharge based on the flow distribution observed from the largest recorded discharges. The computed water-surface elevation resulting from hydraulic simulations of the natural conditions of the flood plain (no bridge constrictions) using the 500-year flood estimate is 26 ft above NGVD of 1929 (table 29). Simulations using WSPRO at the main bridge opening indicate velocities ranging from 2.5 to 9.6 ft/s along the cross section at the main channel bridge. Values of velocity at pier locations are listed in table 29.

Pier Scour

The maximum computed scour depth was approximately 33 ft for the pier at DOTD station 1099+50 (table 29, fig. 61). The pier at this location is 32 ft in width and is the support for the swing span of the bridge. Adjustments for wide piers, as outlined by Jones and Sheppard (1999), were applied at this pier. The channel-bed elevation of the computed scour hole is about 34 ft below NGVD of 1929. The pile tip elevation for this pier is approximately 38 ft below NGVD of 1929.

Table 29. Scour data for Louisiana Highway 12 crossing of the Sabine River near Starks, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 26.0 feet above NGVD of 1929; K2, dimensionless correction factors; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 1098+20 22 Round 1.0 2 2.5 2 0 +20 -38 1098+69 6 Round 1.0 6 7.4 11 0 -5 -38 1099+50 -1 Round 1.0 32 9.4 33 0 -34 -38 1100+31 8 Round 1.0 6 8.7 12 0 -4 -38 1100+82 25 Round 1.0 2 3.7 2 0 23 -38

Channel Stability

Cross section information is shown in figure 61 for the years 1938 and 1994. The depth of the channel bed within the main channel has increased since the 1938 survey. These surveys indicate some decrease of the channel-bed elevations at the main channel piers. Bed elevations of the 1994 survey could reflect remnants of previous pier scour. Bed elevations based on the USGS flood discharge measurement in May 1989 represent the same general main channel shape as the 1994 DOTD survey.

93 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 90 EXPLANATION ESTIMATED MAXIMUM GROUND-SURFACE 70 SCOUR ELEVATION ELEVATION 1938 DOTD WATER-SURFACE ELEVATION FOR 500- 50 1994 DOTD YEAR FLOOD

10 94 0 -10

-30

EAST BANK WEST BANK -50 ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION,

1098+00 1099+00 1100+00 1101+00

DOTD STATION, IN FEET

Figure 61. Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 12 crossing of the Sabine River near Starks, Louisiana. Interstate Highway 10 Crossing of the Sabine River near Vinton

The Louisiana Highway 12 crossing of the Sabine River (fig. 62) consists of an earthen embankment with multiple bridge openings to convey the main channel and overbank flow. The 500-year flood estimate is 262,000 ft3/s based on RIRM estimates (Ensminger, 1998). This estimate of the 500-year flood may result in scour being overestimated on the Sabine River sites examined. A more complete analysis of the hydraulics of this multiple opening embankment crossing of the 4-mile wide flood plain requires application of 2- dimensional flow models which is beyond the scope of this evaluation. Apportionment of the flow among the openings in the embankment is based only on the approximate area of each opening. The flow apportioned to the main channel bridge opening is 79 percent of the total discharge. The computed water-surface elevation resulting from hydraulic simulations of the main channel bridge opening using the 500-year flood estimate is 6.1 ft above NGVD of 1929 (table 30). The downstream boundary condition for the simulations was a slope of 0.00012. Simulations using WSPRO at the main bridge opening indicate velocities ranging from 2.1 to 11.6 ft/ s along the cross section at the main channel bridge. Values of velocity at pier locations are listed in table 30.

Pier Scour

For evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic survey of 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity, which was computed using WSPRO.

The maximum computed scour depth was approximately 31 ft and 30 ft for the piers at DOTD station 396+50 and 398+50, respectively (table 30, fig. 63). Contraction scour is estimated at 23 ft in the main channel and 8 to 9 ft in the overbank areas. The minimum channel-bed elevation of the computed scour holes including contraction scour is 81 ft below NGVD of 1929 at DOTD station 398+50. This estimated elevation is 8 ft below the pile tip elevation.

Channel Stability

Cross-section information is shown in figure 63 for the years 1949 and 1994. The 1994 survey indicates a lowering of the stream bed in the main channel when compared to the survey of 1949. The 1994 elevations are generally 10 ft lower than the 1949 elevations. The 1994 DOTD survey also indicates some widening of the channel. On the west bank, elevation changes greater than 10 ft are indicated in 1994 when compared to the original 1949 data.

Atchafalaya River Basin

The Atchafalaya River originates in south-central Louisiana at the confluence of the Red River and the Old River flood control structure distributary (Lower Old River) of the Mississippi River. The Old River flood control structure is the receiving water body for flow diversion from the Mississippi River. Because of this diversion, the drainage area of the Atchafalaya River is indeterminate. The basin extends in a north-south direction from its origin to the Gulf of Mexico. The Atchafalaya River is the largest of all distributaries of the Mississippi River. Flood protection works, composed primarily of levees, have been constructed for most of the length of the basin. The 500-year flood is approximated based on flow diversions at the Old River flood control structure and Morganza Spillway flood control structure and flows from the Red River and other inter- vening areas (U.S. Army Corps of Engineers, 2001). At Simmesport, the approximate flow is derived by com- bining 600,000 ft3/s from the Old River flood control structure and 350,000 ft3/s from the Red River for a total of 950,000 ft3/s.

Although there is flow in the Atchafalaya River, the west Atchafalaya and Morganza floodways at Krotz Springs and Henderson, no flood statistics are applicable. The flood of record is simulated as main channel flow at those locations.

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Table 30. Scour data for Interstate Highway 10 crossing of the Sabine River near Vinton, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 6.1 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3, 1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plan; NA, not applicable]

Scour Pile tip Ground elevation (ft elevation elevation above or (ft above (ft above Local or pier Contraction below or below DOTD NGVD of Pier width Velocity scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 381+99 3.0 Round 1.0 0.0 2.2 3.8 9 -6 NA 382+80 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 383+60 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 384+40 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 385+20 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 386+00 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 386+80 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 387+60 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 388+40 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 389+20 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 390+00 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 390+80 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 391+60 2.0 Round 1.0 3.5 2.2 4.0 9 -11 NA 392+40 2.0 Round 1.0 3.5 4.0 5 9 -12 NA 393+20 2.0 Round 1.0 3.5 4.0 5 9 -12 NA 394+00 0 Round 1.0 3.5 4.0 6 9 -15 NA 395+00 -26 Round 1.0 5.0 10.1 13 23 -62 -73 396+50 -23 Round 1.0 20 9.8 31 23 -77 -73 398+50 -28 Round 1.0 20 8.9 30 23 -81 -73 400+00 -3.0 Round 1.0 5.0 4.1 7 8 -18 -73 401+00 2.0 Round 1.0 3.5 4.1 5 8 -11 NA 401+80 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 402+60 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 403+40 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 404+20 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 405+00 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 405+80 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 406+60 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 407+40 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 408+20 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 409+80 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 410+60 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 411+40 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 412+20 2.0 Round 1.0 3.5 2.1 4 8 -10 NA 413+01 2.0 Round 1.0 3.5 2.1 4 8 -10 NA

97 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT- U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 100 EXPLANATION 80 GROUND-SUFACE ESTIMATED MAXIMUM ELEVATION SCOUR ELEVATION 1949 DOTD WATER-SURFACE 60 1994 DOTD ELEVATION FOR 500- YEAR FLOOD 40

-20 98

-40

-60 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -80

-100 380+00 390+00 400+00 410+00

DOTD STATION, IN FEET Figure 63. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 10 crossing of the Sabine River near Vinton, Louisiana. Louisiana Highway 1 Crossing of the Atchafalaya River at Simmesport

The Louisiana Highway 1 crossing of the Atchafalaya River (fig. 64) is the first highway crossing of the river from the origin where the Red River and the Lower Old River merge. Traditional flood frequency techniques cannot be utilized along the Atchafalaya River due to the flow controls at the originating channels. The flood discharge used for calibration is the flow recorded in 1973 of 781,000 ft3/s. The recorded water-surface elevation for this flow is 54.5 ft above NGVD of 1929 (U.S. Army Corps of Engineers, 1995). A 500-year flood estimate of 950,000 ft3/s is based on combined flow from the Red River and Old River flood control structure diversions. The computed water-surface elevation resulting from hydraulic simulations of the 500-year flood is 59.0 ft above NGVD of 1929 (table 31). This elevation is near crown elevation shown on topographic maps of some levees in the area. Simulations using WSPRO indicate velocities at piers ranging from 4.0 to 12.0 ft/s. Values of velocity at pier locations are listed in table 31.

Pier Scour

The maximum computed scour depth was approximately 26 ft for the pier at DOTD station 965+70 (table 31, fig. 65). The channel-bed elevation of the computed scour hole is about 48 ft below NGVD of 1929. The lowest elevation resulting from scour computations was 63 ft below NGVD of 1929 for the pier located at DOTD station 958+50.

Table 31. Scour data for Louisiana Highway 1 crossing of the Atchafalaya River at Simmesport, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 59.0 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; footing elevations scaled from DOTD bridge plans]

954+56 50 Round 1.0 9 4.0 11 13 26 -75

958+50 -26 Round 1.0 15 6.0 24 13 -63 -150

965+70 -9 Round 1.0 15 8.0 26 13 -48 -150

969+10 45 Round 1.0 9 5.0 12 13 20 -75

Channel Stability

Cross section information is shown in figure 65 for the years 1965, 1991 and 1993. These surveys do not indicate substantial changes in the channel-bed elevation or alignment.

99 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

RIVER LAYA AFA Simmesport CH AT

W O L F F O

O I T

R I

Photograph source: U.S. Department of the Interior, U.S. Geological Survey Maintainer: [email protected] Last Modified: 2/5/01

Figure 64. Aerial photogragh of the Louisiana Highway 1 crossing of the Atchafalaya River at Simmesport, Louisiana.

100 977+70 EAST BANK 973+70 969+70 965+70 962+10 958+50 DOTD STATION, IN FEET DOTD STATION, 954+50 ESTIMATED MAXIMUM ESTIMATED WATER-SURFACE ELEVATION FOR 500- FOR ELEVATION SCOUR ELEVATION YEAR FLOOD 951+50 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM COOPERATIVE RESOURCES WATER SURVEY GEOLOGICAL AND DEVELOPMENT-U.S. TRANSPORTATION OF DEPARTMENT LOUISIANA EXPLANATION 947+50 1965 DDTD 1991 DOTD 1993 DOTD WEST BANK ELEVATION GROUND-SURFACE 943+50 0

150 300 -300 -150

NGVD OF 1929 OF NGVD ELEVATION, IN FEET ABOVE OR BELOW BELOW OR ABOVE FEET IN ELEVATION, Bridge schematic, comparative cross sections, and scour estimates at the Louisiana Highway 1 crossing of the sections, and scour estimates at the Louisiana Highway 1 crossing 65. Bridge schematic, comparative cross Figure Louisiana. Atchafalaya River at Simmesport,

101 U.S. Highway 190 Crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs

There are two bridges for this highway crossing (fig. 66). The original structure is now used only for eastbound traffic; another bridge for westbound traffic was built immediately upstream of the original structure. Traditional flood frequency techniques cannot be utilized along the Atchafalaya River due to the flow controls at the originating channels. Any flow exchange between the West Atchafalaya Floodway and the Atchafalaya River is unknown, and simulation of that complex flow system is beyond the scope of this analysis. The flood discharge of 781,000 ft3/s used in this analysis is the flow recorded in 1973. The record discharge is simulated as only in the main channel, neglecting floodway flows. Although this assumption will overestimate scour for the given discharge, it may be a reasonable indication of a 500-year flood response with flow through the floodways and main channel. Simulations using WSPRO with a downstream boundary condition of a slope of 0.000065 ft/ft produces computed water-surface elevations that are near the peak water level of 38.9 ft recorded at Krotz Springs (U.S. Army Corps of Engineers, 1995). Simulations using WSPRO indicate velocities ranging from 3.0 to 9.7 ft/s. Values of velocity at pier locations are listed in table 32.

Pier Scour

For the evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic survey of 1994. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity computed using WSPRO. The velocities computed at pier locations for the eastbound (downstream) bridge range from 3.8 to 9.3 ft/s with a maximum computed scour depth of 49 ft for the pier at DOTD station 86+28. The channel-bed elevation of the computed scour hole is about 97 ft below NGVD of 1929 (table 32, fig. 67). The velocities computed at pier locations for the westbound (upstream) bridge range from 8.1 to 9.7 ft/ s, with a maximum computed scour depth of 52 ft for the pier at DOTD station 87+60. The channel-bed elevation of the computed scour hole is about 107 ft below NGVD of 1929 (table 32, fig. 68).

Table 32. Scour data for U.S. Highway 190 crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 38.9 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) Eastbound (downstream) bridge 76+45 35 Round 1.0 34 3.8 22 0 13 -140 81+24 -43 Round 1.0 34 8.9 47 0 -82 -140 86+28 -48 Round 1.0 34 9.3 49 0 -97 -140 90+80 36 Round 1.0 34 4.1 22 0 14 -140 Westbound (upstream) bridge 80+54 -27 Round 1.0 36 8.1 46 0 -73 -140 87+60 -55 Round 1.0 36 9.7 52 0 -107 -140

Channel Stability

Cross section information for the eastbound (downstream) bridge is shown in figure 67 for the years 1968, 1991, and 1994. The 1991 and 1994 surveys indicate that the channel has become wider and deeper since the 1968 survey. There are no substantial channel changes indicated between the 1991 and 1994 surveys. Cross section information for the westbound (upstream) bridge is shown in figure 68 for the years 1973, 1991, and 1994. Both the 1991 and 1994 surveys indicate a wider channel when compared to the 1973 survey. Although there is some lateral movement of the channel, there are no substantial increases in depth near the main piers.

102 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

DIR

ECT

OO IO

FLO

190

190 A

HA T

L Krotz A Y Springs A

IVER R

Photograph source: Louisiana Department of Transportation and Development, 6/19/95

Figure 66. Aerial photograph of the U.S. Highway 190 crossing (eastbound and westbound) of the Atchafalaya River near Krotz Springs, Louisiana.

103 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVEPOLMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 320

280 EXPLANATION

GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION SCOUR ELEVATION 240 1968 WATER-SURFACE 1991 ELEVATION FOR 500- 200 1994 YEAR FLOOD

160

120

40 104

-40

WEST BANK ELEVATION, IN FEET ABOVE OR BELOW NGVD OF 1929 IN FEET ELEVATION, -80 EAST BANK

-120

-160 65+00 70+00 75+00 80+00 85+00 90+00 95+00 100+00 105+00

DOTD STATION, IN FEET

Figure 67. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 190 crossing (eastbound) of the Atchafalaya River near Krotz Springs, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 280

240 EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 200 ELEVATION: SCOUR ELEVATION 1973 DOTD WATER-SURFACE 160 1991 DOTD ELEVATION FOR 500- 1994 DOTD YEAR FLOOD 120

40 105 NGVD OF 1929 0

-40

ELEVATION, IN FEET ABOVE OR BELOW IN FEET ELEVATION, -80 WEST BANK EAST BANK

-120

-160 65+00 70+00 75+00 80+00 85+00 90+00 95+00 100+00 105+00

DOTD STATION, IN FEET

Figure 68. Bridge schematic, comparative cross sections, and scour estimates at the U.S. Highway 190 crossing (westbound) of the Atchafalaya River near Krotz Springs, Louisiana. Interstate Highway 10 Crossing of the Atchafalaya River near Henderson

Traditional flood frequency techniques cannot be utilized along the Atchafalaya River (fig. 69), due to the flow controls at the originating channels. Any flow exchange between the West Atchafalaya River and the Morganza Floodway is unknown, and simulation of that complex flow system is beyond the scope of this analysis. The flood discharge used in this analysis is the flow of 781,000 ft3/s recorded in 1973. The water-surface elevation used was 27.3 ft above NGVD of 1929 (table 33). The record discharge is simulated as only in the main channel neglecting floodway flows. Although this assumption will overestimate scour for the given discharge, it may be a reasonable indication of a 500-year flood response with flow through the floodways and main channel. A distributary channel, locally known as the Whiskey Bay Pilot Channel (fig. 70), forms from the main channel of the Atchafalaya River about 3 mi upstream of Interstate 10. A detailed simulation of the distribution of flows between the two channels requires hydraulic modeling that is beyond the scope of this project. For the purposes of estimating pier scour, the design discharge was apportioned to each opening based on flow area. Most of the highway crossing is elevated on piers, with relatively little earthen embankment constricting flow through the flood plain. In consideration of the small degree of encroachment and hydraulic approximations used, no contraction scour estimates were performed at this site.

Pier Scour

For the evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic survey of 1993. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity computed using WSPRO. The velocities used in scour computations are shown in table 33. The maximum computed scour depth was 57 ft for the pier at DOTD station 2233+71 (table 33, fig. 70). The channel-bed elevation of the computed scour hole is about 85 ft below NGVD of 1929.

Table 33. Scour data for Interstate Highway 10 crossing of the Atchafalaya River near Henderson, Louisiana

[DOTD, Louisiana Department of Transportation and Development; water-surface elevation is 27.3 feet above NGVD of 1929; K2, dimensionless correction factor for angle of flow attack; K3=1.1; ft, feet; ft/s, foot per second; pile tip elevations scaled from DOTD bridge plans]

Channel Stability

Cross section information is shown in figure 71 for the years 1972, 1990, and 1993. The surveys do not indicate lowering of the channel bed at any locations in the channel parts evaluated. Some increase in the channel-bed elevation is indicated in the vicinity of DOTD station 2233+71.

Interstate Highway 10 Crossing of the Whiskey Bay Pilot Channel near Henderson-Grosse Tete

Traditional flood frequency techniques cannot be utilized along the Atchafalaya River due to the flow controls at the originating channels. The flood discharge used in this analysis is the flow recorded in 1973 of 781,000 ft3/s. The water-surface elevation used was 27.3 ft above NGVD of 1929 (table 34). A distributary channel, locally known as the Whiskey Bay Pilot Channel, forms from the main channel of the Atchafalaya River about 3 mi upstream of Interstate 10. A detailed simulation of the distribution of flows between the two channels requires hydraulic modeling that is beyond the scope of this project. For the 106 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

T O N CTI I EO RE

F L FW

10 10

Henderson

AC T H F A YAL A

RI VER

Photograph source: Louisiana Department of Transportation and Development, 3/24/92

Figure 69. Aerial photograph of the Interstate Highway 10 crossing of the Atchafalaya River near Henderson, Louisiana.

107 LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM 500

EXPLANATION 400 GROUND-SURFACE ESTIMATED MAXIMUM ELEVATION: SCOUR ELEVATION 300 1972 DOTD 1990 DOTD WATER-SURFACE ELEVATION FOR 500- 1993 DOTD 200 YEAR FLOOD

100

0 108 NGVD OF 1929 -100

-200 WEST BANK EAST BANK ELEVATION, IN FEET ABOVE OR BELOW IN FEET ELEVATION, -300

-400 2225+00 2230+00 2235+00 2240+00 2245+00

DOTD STATION, IN FEET

Figure 70. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 10 crossing of the Atchafalaya River near Henderson, Louisiana. LOUISIANA DEPARTMENT OF TRANSPORTATION AND DEVELOPMENT-U.S. GEOLOGICAL SURVEY WATER RESOURCES COOPERATIVE PROGRAM

s h

yW i

ha elnn

O C

OFLO O

W Grosse Tete

Photo source: Louisiana Department of Transportation and Development, 3/24/92

Figure 71. Aerial photograph of the Interstate Highway 10 crossing of the Whiskey Bay Pilot Channel near Henderson-Grosse Tete, Louisiana.

110 purposes of estimating pier scour, the design discharge was apportioned to each opening based on flow area. Most of the highway crossing is elevated on piers, with relatively little earthen embankment constricting flow through the flood plain. In consideration of the small degree of encroachment, and hydraulic approximations used, no contraction scour estimates were performed at this site.

Pier Scour

For the evaluation of pier scour, values for y1 at each pier were based on the DOTD hydrographic survey of 1993. Values for K1=1.0, K2=1.0, K3=1.1, and K4=1.0 were based on DOTD bridge plans, site geometry, and anticipated bed conditions. The Froude number at the pier locations is based upon the value of depth and velocity computed using WSPRO. The velocities at the pier locations ranted from 1.6 to 5.7 ft/s. The maximum computed scour depth was 43 ft for the pier at DOTD station 2500+30 (table 34, fig. 72). The channel-bed elevation of the computed scour hole is about 97 ft below NGVD of 1929.

Table 34. Scour data for Interstate Highway 10 crossing of Whiskey Bay Pilot Channel near Henderson-Grosse Tete, Louisiana

Scour Pile tip Ground elevation elevation elevation (ft above (ft above (ft above Local or Contraction or below or below DOTD NGVD of Pier width Velocity pier scour scour NGVD of NGVD of station 1929) Pier shape K2 (ft) (ft/s) (ft) (ft) 1929) 1929) 2491+80 10 Round 1.0 38 1.6 20 0 -10 -140 2496+05 -41 Round 1.0 38 5.2 40 0 -81 -140 2500+30 -54 Round 1.0 38 5.7 43 0 -97 -140 2504+97 6 Round 1.0 38 1.8 22 0 -16 -140

Channel Stability

Cross section information is shown in figure 72 for the years 1967, 1989, and 1993. The surveys indicate lowering of the channel bed between stations 2500+30 and 2504+97 between the 1967 survey and the 1989 survey. This change in the geometry of the channel occurred during the construction of the highway crossing (Brice and Blodgett, 1978, p. 388). There is little change indicated between the 1989 and 1993 surveys.

110 LOU ISIAN A DEPARTM ENT O F TRAN S PORTATI OND AND EVELOPMENT-U.S. G EOLOGICAL SURV E Y WATER RE SOURO CES CO PERATIVE PROGR AM 400

EXPLANATION GROUND-SURFACE ESTIMATED MAXIMUM 300 ELEVATION SCOUR ELEVATION 1967 DOTD WATER-SURFACE 1989 DOTD ELEVATION FOR 500- 1993 DOTD YEAR FLOOD 200

100 NGVD OF 1929 0 111

ELEVATION, IN FEET ABOVE OR BELOW IN FEET ELEVATION, -100

-200 WEST BANK EAST BANK

2484+65 2498+18 2511+72

DOTD STATION, IN FEET

Figure 72. Bridge schematic, comparative cross sections, and scour estimates at the Interstate Highway 10 crossing of the Whiskey Bay Pilot Channel near Henderson-Grosse Tete, Louisiana. SUMMARY

Maximum pier and contraction scour estimates at 36 bridges that cross streams in northeastern and southern (excluding the Florida Parishes area) Louisiana were computed using methodologies outlined by the Federal Highway Administration and information in Louisiana Department of Transportation and Development (DOTD) and U.S. Geological Survey files. The selected highway crossings were located over the Mississippi, Ouachita, Tensas, Black, Calcasieu, Sabine, and Atchafalaya Rivers; Inner Harbor Navigation Canal; and Whiskey Bay Pilot Channel.

Maximum estimated scour elevation was not below the known as-built pile tip elevation shown on DOTD bridge plans for all but one site. Maximum scour estimates were less than 10 feet below the pile tip elevations scaled from DOTD bridge plans at two piers of the I-10 crossing of the Sabine River near Vinton. In some instances marine traffic fenders are in place, which may reduce the potential scour at the pier. The maximum estimated pier scour among the sites ranged from 4 to 77 feet. Estimates of contraction scour generally were not substantial in magnitude or were not applicable due to site characteristics at all but four sites. For sites along the Mississippi River, the maximum estimated pier scour was 77 ft at U.S Highway 190. Contraction scour estimation is not applicable for conditions at sites along the Mississippi River where levees limit flood-plain flow. For sites along the Ouachita and Tensas Rivers, the maximum estimated pier scour was 19 ft. The Black River at U.S. Highway 84 had pier scour estimates ranging from 5 to 22 ft. For sites along the Calcasieu River, the maximum estimated pier scour was 24 ft at Interstate Highway 10. Of the two Sabine River sites, the maximum pier scour estimate was 33 ft at Louisiana Highway 12. At the Interstate Highway 10 crossing of the Atchafalaya River, the maximum pier scour estimate was 57 ft.

SELECTED REFERENCES

Abed, L.M., and Richardson, E.V., 1993, Effects of fenders on local pier scour, in Shen, Su, and Wen, eds., 1993, Hydraulic Engineering 1993, v. 2--Proceedings of the 1993 ASCE Conference: New York, American Society of Civil Engineers, p. 1750-1753. Biedenharn, D.S., Combs, P.G., Hill, G.J., Pinkard, C.F., Jr., and Pinkston, C.B., 1989, Relationship between channel migration and radius of curvature on the Red River, in Wang, S.S.Y., ed., 1989, Sediment transport modeling--Proceedings of the International Symposium, New Orleans, La., Aug. 14-18, 1989: New York, American Society of Civil Engineers, p. 536-541. Brice, J.C., Blodgett, J.C., and others, 1978, Countermeasures for hydraulic problems at bridges: Washington, D.C., Federal Highway Administration, v. 2, p. 554 Ensminger, P.A., and Gilbert, J.J., 1995, Peak-stage data for selected streams in coastal Louisiana, 1905-88: Louisiana Department of Transportation and Development Water Resources Basic Records Report no. 20, 50 p. Ensminger, P.A., 1998, Floods in Louisiana, magnitude and frequency (5th ed.): Louisiana Department of Transportation and Development Water Resources Technical Report no. 60, 333 p. Federal Emergency Management Agency, 1993 (revised), Flood Insurance Study--East Baton Rouge Parish, Louisiana: Washington, D.C., Federal Emergency Management Agency [variously paged]. Gilbert, J.J., and Ensminger, P.A., 1996, Estimation of pier scour and channel stability for highway crossings of the Red River in Louisiana: U.S. Geological Survey Open-File Report 96-574, 65 p. ----- 1999a, Estimation of pier scour and channel stability for highway crossings of the Red River in Louisiana: Louisiana Department of Transportation and Development Water Resources Technical Report no. 67A, 64 p.

112 ----- 1999b, Estimation of scour and channel stability for selected highway crossings of rivers in the Florida Parishes, Southeastern Louisiana: Louisiana Department of Transportation and Development Water Resources Technical Report no. 67B, 86 p.

Gilbert, J.J., and Froehlich, D.C., 1987, Simulation of the effect of U.S. Highway 90 on Pearl River floods of April 1980 and April 1983 near Slidell, Louisiana: U.S. Geological Survey Water-Resources Investigations Report 85-4286, 47 p.

Hodge, S.A., and Tasker, G.D., 1995, Magnitude and frequency of floods in Arkansas: U.S. Geological Survey Water-Resources Investigation Report 95-4224, 52 p. Jones, J.S., and Sheppard, D.M., 1999, Scour at wide bridge piers, in Proceedings of the American Society of Civil Engineers: accessed September 2001, at URL http://www.ewrinstitute.org/ewriproducts.htm. Lagasse, P.F., Schall, J.D., Johnson, F., Richardson, E.V., Richardson, J.R., and Chang, F., 1991, Stream stability at highway structures: U.S. Department of Transportation, Federal Highway Administration, FHWA-IP-90-014, Hydraulic Engineering Circular no. 20, 195 p. Lee, F.N., 1985, Floods in Louisiana, magnitude and frequency (4th ed.): Louisiana Department of Transportation and Development Water Resources Technical Report no. 36, 30 p. Lee, F.N., and Arcement, G.J., Jr., 1981, Hydrologic analysis of Pearl River floods, April 1979 and April 1980, in Louisiana and Mississippi: Louisiana Department of Transportation and Development, Office of Highways Research Study no. 81-1-SS, 37 p. Martien, R.F., 1978, Water-quality characteristics of the Red River in Louisiana: Louisiana Department of Transportation and Development, Office of Public Works Water Resources Technical Report no. 16, p.2. Nanson, G.C., and Hickin, E.J., 1986, A statistical analysis of bank erosion and channel migration in Western Canada: Geological Society of America, Bulletin 97, p. 497-504. Neely, B.L., Jr., 1976, Floods in Louisiana, magnitude and frequency (3d ed.): Louisiana Department of Highways, 340 p. Neill, C.R., and Yaremko, E.K., 1989, Identifying causes and predicting effects of bank erosion, in Ports, M.A., ed., Hydraulic Engineering--Proceedings of the 1989 National Conference on Hydraulic Engineering, (New Orleans, La., Aug. 14-18, 1989): New York, American Society of Civil Engineers, p. 101-105. Richardson, E.V., Harrison, L.J., and Davis, S.R., 1991, Evaluating scour at bridges: U.S. Department of Transportation, Federal Highway Administration, FHWA-IP-90-017, Hydraulic Engineering Circular no. 18, 105 p. Richardson, E.V., Harrison, L.J., Richardson, J.R, and Davis, S.R., 1993 (revised), Evaluating scour at bridges: U.S. Department of Transportation, Federal Highway Administration, FHWA-IP-90-017, Hydraulic Engineering Circular no. 18, 105 p. ----- 1995, Evaluating scour at bridges (3d ed.): U.S. Department of Transportation, Federal Highway Administration, FHWA-IP-90-017, Hydraulic Engineering Circular no. 18, 105 p. Shearman, J.O., Kirby, W.H., Schneider, V.R., and Flippo, H.N., 1986, Bridge waterways analysis: U.S. Department of Transportation, Federal Highway Administration, Research Report, FHWA-RD-86- 108, 112 p.

113 Sloss, Raymond, 1971, Drainage area of Louisiana streams: Louisiana Department of Public Works Basic Records Report no. 6, 117 p. Tasker, G.D., and Slade, R.M., Jr., 1994, An interactive regional regression approach to estimating flood quantiles in Fontane, D.G., and Tuvel, H.N., Water Policy and Management, Solving Problems-- Proceedings of the 21st annual conference of the Water Resources Planning and Management Division: New York, American Society of Civil Engineers, p. 782-785. Thorne, C.R., 1989, Bank processes on the Red River between Index, Arkansas, and Shreveport, Louisiana: Preliminary draft of final technical report to European Research Office of U.S. Army, London, England. U.S. Geological Survey, 1982, Guidelines for determining flood flow frequency: Reston, Va., Office of Water Data Coordination, Interagency Advisory Committee on Water Data, Bulletin 17B of the Hydrology Subcommittee, 162 p. U.S. Army Corps of Engineers, New Orleans District, 1995, Stages and discharges of the Mississippi River and tributaries and other watersheds in the New Orleans District: U.S. Army Engineer District, New Orleans Corps of Engineers, 268 p. ----- 2001, Water control, Bonnet Carre’ Spillway brochure: accessed November 3, 2001, at URL http://www.mvn.usace.army.mil/pao/bcarre/bcarre.htm

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