Mississippi Valley Division Engineer Research and Development Center

Lake Providence to Old River 

Geomorphology Assessment

MRG&P Report No. 32 • April 2020

Mississippi River Geomorphology & 

Potamology (MRG&P) Program 

MRG&P Report No. 32 

April 2020 

Lake Providence to Old River Geomorphology 

Assessment

Waleska Echevarria-Doyle and David S. Biedenharn

Coastal and Hydraulics Laboratory

U.S. Army Engineer Research and Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

Charlie D. Little Jr.

Mendrop Engineering Resources, LLC

3530 Manor Drive, Suite 2

Vicksburg, MS 39180

Final report

Approved for public release; distribution is unlimited. 

Prepared for U.S. Army Corps of Engineers, Mississippi Valley Division

Mississippi River Geomorphology & Potamology Program

1400 Walnut Street

Vicksburg, MS 39180

Under Project No. 470711
MRG&P Report No. 32 ii

Abstract

This report integrates information from previous geomorphic studies 

coupled with new analysis to provide a comprehensive geomorphic 

characterization of the Lake Providence (River Mile [RM] 487.2 Above 

Head of Passes [AHP]) to Old River Control Complex, (RM 317 AHP) 

reach from the early-1800s to present. Individual components of this 

study included the following: historical geomorphic studies, development 

of an events timeline, specific gage records, stage and flow duration 

trends, trends in water surface slopes, bed material studies, suspended 

sediment data, channel geometry data, and effects of channel 

improvement features (cutoffs, dikes, revetment, and dredging). These 

individual assessments were consolidated to develop an overall 

assessment of how the study reach has evolved since the early-1800s. 

DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. 

Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. 

All product names and trademarks cited are the property of their respective owners. The findings of this report are not to 

be construed as an official Department of the Army position unless so designated by other authorized documents.

DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.
MRG&P Report No. 32 iii

Contents

Abstract................................................................................................................................................... ii

Figures and Tables.................................................................................................................................iv

Preface....................................................................................................................................................vi

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

1.1 Background.................................................................................................................... 1

1.2 Objective ........................................................................................................................ 1

1.3 Approach........................................................................................................................ 2

2 Geomorphic Changes Early-1800s to Present............................................................................3

2.1 Event timeline................................................................................................................ 3

2.2 Pre-cutoff Period (early-1800s to 1929)...................................................................... 4

2.2.1 Early-1800s to 1880s ................................................................................................. 4

2.2.2 Late-1880s to 1929 ................................................................................................... 8

2.3 Cutoff Period (1929 – 1942)......................................................................................12

2.4 Post-cutoff Period (1943 – present) ..........................................................................14

2.4.1 Channel improvements (revetments, dikes, and dredging) ....................................15

2.4.2 Flow regime in the Post-cutoff Period ......................................................................18

2.4.3 Specific gage records ...............................................................................................19

2.4.4 Water surface slope trends ......................................................................................23

2.4.5 Stage duration changes............................................................................................31

2.4.6 Bed material characteristics ....................................................................................40

2.4.7 Channel geometry trends .........................................................................................55

2.4.8 Suspended sediment trends ....................................................................................57

3 Summary .......................................................................................................................................59

3.1 Pre-cutoff Period (early-1800s to 1929)....................................................................59

3.2 Cutoff Period (1929–1942)........................................................................................60

3.3 Post-cutoff Period (1943 to Present) .........................................................................61

3.3.1 Channel improvements features ..............................................................................61

3.3.2 Channel stability ........................................................................................................61

3.3.3 Bed material trends ..................................................................................................62

3.3.4 Sediment load trends ...............................................................................................63

4 Recommendations.......................................................................................................................64

References............................................................................................................................................68

Unit Conversion Factors......................................................................................................................70

Acronyms and Abbreviations..............................................................................................................71

Report Documentation Page
MRG&P Report No. 32 iv

Figures and Tables

Figures

Figure 2-1. Change in Mississippi River top bank width between 1820 and 1973 (adapted 

from Winkley [1994])................................................................................................................................. 7

Figure 2-2. LMR valley flows before levees (Winkley 1977)................................................................... 8

Figure 2-3. Average levee heights and peaks stages at Natchez, MS (Winkley 1977). ....................11

Figure 2-4. Specific gage records at Lake Providence and Vicksburg in the Pre-cutoff 

Period for 1,500,000 cfs.........................................................................................................................12

Figure 2-5. Specific gage records along the LMR (Winkley 1977).......................................................14

Figure 2-6. Revetment and dike construction timeline in the study reach.........................................15

Figure 2-7. Total linear feet of revetments and dikes in study reach (by 10-mile 

increments)...............................................................................................................................................16

Figure 2-8. Accumulated annual average bank caving volumes from the Arkansas River to 

the ORCC (Winkley 1973)........................................................................................................................ 17

Figure 2-9. Relationship between total linear feet of dikes and maintenance dredging in 

the New Orleans, Vicksburg, and Memphis Districts............................................................................18

Figure 2-10. Average annual discharges at Vicksburg. ........................................................................19

Figure 2-11. Specific gage record at Lake Providence, LA...................................................................21

Figure 2-12. Specific gage record at Vicksburg, MS.............................................................................21

Figure 2-13. Specific gage record at St. Joseph, LA..............................................................................22

Figure 2-14. Specific gage record at Natchez, MS................................................................................23

Figure 2-15. Average annual water surface slopes for the Lake Providence to Vicksburg 

reach.......................................................................................................................................................... 24

Figure 2-16. Water surface slope trends in the Vicksburg to St. Joseph reach. ................................26

Figure 2-17. Water surface slope trends in the St. Joseph reach to Natchez.....................................28

Figure 2-18. Water surface slope trends in the Vicksburg to Natchez Reach....................................29

Figure 2-19. Lake Providence stage duration curve using time periods in Table 2-14.....................33

Figure 2-20. Flow-adjusted stage duration curves at Lake Providence..............................................34

Figure 2-21. Vicksburg stage duration curve using time periods in Table 2-14.................................35

Figure 2-22. Flow-adjusted duration curves at Vicksburg....................................................................35

Figure 2-23. St. Joseph Stage duration curve using time periods in Table 2-14...............................36

Figure 2-24. Flow-adjusted duration curve at St. Joseph..................................................................... 37

Figure 2-25. Natchez stage duration curve using time periods in Table 2-14...................................38

Figure 2-26. Flow-adjusted duration curves at Natchez. .....................................................................38

Figure 2-27. Bed Material trends at the Vicksburg gaging station. .....................................................42

Figure 2-28. Box and whisker plot for the Vicksburg bed material data.............................................42

Figure 2-29. Bed material trends at the Natchez gaging station. .......................................................43

Figure 2-30. Box and whisker plot for the Natchez bed material data. ..............................................43

Figure 2-31. Downstream trends in D50 in November 2013 – Study reach outlined in red 

(Gaines and Priestas 2016). ...................................................................................................................45
MRG&P Report No. 32 v 

Figure 2-32. Downstream trends in bed material grain size distributions in the LMR in (a) 

1932, (b) 1989, and (c) 2013 – Study reach outlined in red (Gaines and Priestas 2016)..............46

Figure 2-33. Selected bed material gradation curve in the research study. ......................................48

Figure 2-34. Box and whisker plots of D50, D16, and D84 for the 14 potamology reaches.................49

Figure 2-35. Cumulative volume change curves for the Vicksburg District. Study reach 

outlined in red........................................................................................................................................... 57

Tables

Table 2-1. List of natural meander cutoffs in study reach between 1776 and 1884

(modified from Winkley [1977]). ............................................................................................................... 6

Table 2-2. Geomorphic reach characteristics (adapted from Schumm et al. [1994]). ....................... 9

Table 2-3. Man-made meander cutoffs, 1929 – 1942 (adapted from Winkley [1977]). .................13

Table 2-4. Average annual bank caving volumes in the Lake Providence to Old River reach 

for the Pre- and Post-revetment Periods................................................................................................ 17

Table 2-5. Specific gage locations within the study reach. ..................................................................20

Table 2-6. Period of record and reach length data for the Lake Providence to Vicksburg 

reach..........................................................................................................................................................25

Table 2-7. Average annual water surface slopes for three time periods in the Lake 

Providence to Vicksburg reach................................................................................................................25

Table 2-8. Period of record and reach length data for the Vicksburg to St. Joseph reach................26

Table 2-9. Average annual water surface slopes for three time periods in the Vicksburg to 

St. Joseph reach....................................................................................................................................... 27

Table 2-10. Period of record and reach length data for the St. Joseph to Natchez reach. ...............28

Table 2-11. Average annual water surface slopes for three time periods in the St. Joseph 

to Natchez reach. .....................................................................................................................................28

Table 2-12. Period of record and reach length data for the Vicksburg to Natchez reach.................30

Table 2-13. Average annual water surface slopes for three time periods in the Vicksburg 

to Natchez reach. .....................................................................................................................................30

Table 2-14. Time periods used in the development of the stage duration curves. ........................... 31

Table 2-15. Selected years with similar average daily discharges. .....................................................32

Table 2-16. Stage duration changes for a range of flow conditions....................................................40

Table 2-17. Fourteen potamology reaches used in the bed material analysis...................................48

Table 2-18. Bed classification from 2005 and 2007 geo-referenced videos. ................................... 51
MRG&P Report No. 32 vi

Preface

This study was performed for the U.S. Army Corps of Engineers, 

Mississippi Valley Division, Mississippi River Geomorphology & 

Potamology Program, Project No. 470711. The MRG&P Program is part of 

the Mississippi River and Tributaries Program and is managed by the U.S. 

Army Corps of Engineers (USACE) Mississippi Valley Division (MVD) in 

Vicksburg, MS. The MRG&P Technical Director was Dr. James W. Lewis. 

The MVD Commander was MG Richard G. Kaiser. The MVD Director of 

Programs was Mr. Jim Bodron.

Direct supervision of the U.S. Army Engineer Research and Development 

Center (ERDC), Coastal and Hydraulics Laboratory (CHL) aspects of this 

effort were provided by Dr. Cary A. Talbot, Chief of the Flood and Storm 

Protection Division, and Mr. Keith W. Flowers, Chief of the River and 

Estuarine Engineering Branch. The Deputy Director of CHL was 

Mr. Jeffrey R. Eckstein, and the Director was Dr. Ty V. Wamsley.

The Commander of ERDC was COL Teresa A. Schlosser, and the Director 

of ERDC was Dr. David W. Pittman. 
MRG&P Report No. 32 1 

1 Introduction

1.1 Background 

The Mississippi River has been molded by anthropogenic and natural 

factors for thousands of years. Early efforts by the U.S. Army Corps of 

Engineers (USACE) to manage the river for navigation began in the early1800s, with the most comprehensive efforts occurring as a result of the 

Flood Control Act (FCA) of 1928 following the Flood of 1927. The 

Mississippi River & Tributaries (MR&T) project that was authorized from 

the FCA of 1928 has produced a massive, comprehensive system for flood 

control and channel stabilization that includes levees, channel 

modifications, and floodways, as well as tributary reservoirs and other 

basin improvements. The first official “Potamology Investigations” were 

initiated in the mid-1940s. These potamology studies continued as an 

integral component of the MR&T Program until the 1980s when the 

program ended. As a result of this, the USACE realized it had basically lost 

decades of continued potamology advancement along with a generation of 

experienced staff with that important knowledge. In response to this need, 

the Mississippi River Geomorphology and Potamology (MRG&P) program 

was created by the USACE Mississippi Valley Division (MVD) in 2014. 

MRG&P studies are designed to provide a comprehensive analysis of 

physical and anthropogenic factors that influence the flood conveyance 

capacity, navigability, and environmental quality of the Mississippi River. 

The purpose of the studies is to identify cause-effect and process-response 

relationships that result in short- and long-term changes in the hydrology, 

hydraulics, and morphology of the Mississippi River. Additional purposes 

are to develop improved design approaches and criteria for construction of 

channel improvement actions that will result in flood damage reductions, 

enhanced navigation, and environmental sustainability. The report 

presented herein represents one component of the MRG&P Program.

1.2 Objective 

Over the past few years, there have been numerous individual studies that 

addressed various geomorphic aspects of the river. This report represents 

an integration of these studies combined with new analyses to weave 

together a more comprehensive understanding of the geomorphic 

character for the specific study area between Lake Providence, LA (River 
MRG&P Report No. 32 2 

Mile [RM] 487.2 Above Head of Passes [AHP]), and the Old River Control 

Complex (ORCC) (RM 317 AHP). The study included the development of a 

timeline and analysis of specific gage records, stage duration curves, 

channel geometry trends, bed material data, and meander migration 

information within this reach.

1.3 Approach 

The approach used to perform a geomorphic assessment of the study reach 

include the following elements: (1) event timeline from early-1800s to 

present; (2) general description of the pre-cutoff period (early-1800s to 

1929) morphological trends; (3) description of the cutoff period (1932 – 

1942), and post-cutoff period (1943 – present) geomorphic changes; and 

(4) analysis of specific gage records, stage-duration curves, channel 

geometry trends, bed and suspended material data, and meander 

migration information within the reach. 
MRG&P Report No. 32 3 

2 Geomorphic Changes Early-1800s to 

Present

This chapter discusses the geomorphic changes in the study reach from the 

early-1800s to present. The first section is an event timeline that lists 

some of the major natural and anthropogenic factors that have occurred 

during the study period. The next three sections describe the major 

geomorphic characteristics during three broad time periods: (1) Pre-cutoff 

Period (prior to 1929); (2) the Cutoff Period (1929 – 1942); and (3) Postcutoff Period (1943 – present).

2.1 Event timeline 

A chronology of the major river engineering, hydrologic, and anthropogenic 

events within the study reach was developed for the study time period. The 

timeline is presented to add insight into the interpretation of the results 

from other analyses presented in this report.

• 1800 – Mid-1800s. Massive clearing of streambanks and riparian areas 

for wood-burning steamboats and agriculture.

• 1811 – 1812 – New Madrid earthquakes.

• 1849 – 1850 – Repeated flooding along the Mississippi River Valley.

• Flood of 1874 – Results in creation of Levee Commission. 

• 1879 – Mississippi River Commission (MRC) created.

• 1879 – 1928 – Levees-only policy adopted by MRC.

• 1884 – 1929 – MRC adopts policy to prevent natural neck cutoffs from 

forming. Natural chute cutoffs were allowed to continue during this 

period. Natural neck or meander cutoffs occur when the river flow 

breaches between the two bends of a meander creating a new channel 

alignment. Chute cutoffs occur as a result of recurring large flows 

across the inside of point bars. Also, chute cutoff can form upstream of 

a neck cutoff due to head cutting or degradation caused by the neck 

cutoff and downstream of a neck cutoff due to aggradation forming a 

middle bar (Winkley 1977).

• 1890 Flood

• Floods of 1913 

• 1927 Major Flood. For this timeline, a major flood is defined as an 

event with a peak discharge of approximately 1.9 million cfs or more 

recorded at the Vicksburg USGS gage 07289000. 
MRG&P Report No. 32 4 

• 1928 – FCA of 1928 results in creation of Mississippi River & 

Tributaries (MR&T) Project.

• 1929 – MRC allows the Yucatan cutoff to occur, which was the first 

natural neck cutoff allowed since 1884.

• 1930 – 1934 – Low-water period. For this timeline, a low-water period 

is defined as a period with peak discharges of approximately 1.6 million 

cfs or less recorded at the Vicksburg USGS gage 07289000.

• 1932 – 1942 – Cutoff Period (15 meander cutoffs between just south of 

Natchez, MS, and just north of Helena, AR).

• 1937 Major Flood

• 1940s – Studies indicate potential of Atchafalaya capturing Mississippi 

River Flow.

• 1940-1944 – Low-water period.

• 1950s – Mid 1990s – Major bank stabilization period.

• Mid 1960s – early 2000s – Major dike construction period. 

• 1952 – 1972 – Low-water period.

• 1963 ORCC Low Sill Structure in operation.

• 1973 – Major flood

• 1975 Flood

• 1984 – 1988 – Low-water period.

• 1986 – ORCC Auxiliary Structure in operation. 

• 1990 – ORCC Hydropower Unit in operation.

• 1993 – Major flood on upper Mississippi River.

• Mid 1990s – Dike-notching program begins.

• 1997 – Flood

• 2000 – Extreme low-water year. The published maximum daily average 

discharge at the Vicksburg USGS gage 07298000 is 787,000 cfs. 

• 2008 Flood

• 2011 Major flood

• 2012-2014 – Low-water period.

2.2 Pre-cutoff Period (early-1800s to 1929) 

The Pre-cutoff phase is divided into two general time periods: (1) early1800s to late-1870s and (2) late-1870s to 1929. A general description of 

the morphologic trends in these two time periods is provided below.

2.2.1 Early-1800s to 1880s

The early-1800s was a period of rapid expansion into the Lower 

Mississippi River Valley, and navigation along the waterways was the key 
MRG&P Report No. 32 5 

to the growth of this region. Unfortunately, the Mississippi River was 

experiencing dramatic geomorphic changes as a result of both natural and 

anthropogenic factors during this initial period of expansion. The first 

factor was the series of New Madrid earthquakes that occurred for almost 

2 years during the 1811 to 1812 period. Winkley (1994) mentions that an 

increase in meander rates and number of middle bars was observed after 

the earthquakes when comparing post-1811-1812 New Madrid Earthquakes surveys with the 1765 survey. Additionally, these earthquakes 

resulted in massive bank instabilities throughout the river and caused 

excessive sediment supply, bar growth, and navigation problems (Winkley 

1977). The system became overloaded with sediment and trees from caving 

banks, and numerous bars and islands were reported to have disappeared 

during the earthquakes. 

The early-1800s saw the introduction of the wood-burning steamboats 

along the Mississippi River. These steamboats required massive amounts of 

fuel (wood), which was supplied from the numerous woodyards that sprang 

up along the river during this period. This resulted in thousands of acres of 

streambanks being cleared, which, when combined with the land clearing 

along the natural levees for agriculture, significantly contributed to 

accelerated bank erosion and sediment supply to the system (Winkley 1977).

Six natural meander cutoffs occurred in the study reach between 1776 and 

1884, shortening the river by approximately 78 miles (Table 2-1). Although 

specific dates are listed in Table 2-1, it should be recognized that these 

cutoffs typically did not develop instantaneously but rather generally took 

many years to completely develop. Meanwhile, the river was obtaining 

additional length elsewhere through meander growth, such that, according 

to Winkley (1977), the overall river lengths for the entire Lower Mississippi 

River in 1765 (the first map of the Lower Mississippi River) and 1884 were 

nearly the same.
MRG&P Report No. 32 6 

Table 2-1. List of natural meander cutoffs in study reach between 1776 and 1884 (modified 

from Winkley [1977]). 

Natural Cutoff 1962 AHP River Mile 

Year Cutoff 

Occurred 

River Length Reduction by 

Cutoff (miles) 

Terrapin Neck 462 1866 16

Yazoo 442 1799 12

Centennial Lake 438 1876 6

Davis or Palmyra 422 1867 19

Waterproof 377 1884 12

Homochitto 322 1776 13

Total 78

Bank erosion, meander cutoffs, and bar and island changes may, in many 

instances, simply be part of the natural processes of a river that is in a state 

of dynamic equilibrium. However, the dramatic changes observed during 

this time period are indications that these natural processes had been 

disrupted and the channel was in a period of morphologic adjustment as it 

attempted to regain dynamic equilibrium. The magnitude of these changes 

is illustrated in Figure 2-1, which shows changes in the average top bank 

width for the reach of river between Vicksburg (RM 435) and the Red River 

(RM 312). Although there is uncertainty in the surveys during these older 

time periods, they do provide a good approximation of the order of 

magnitude of the width changes in the river. The survey of 1821 was the first 

available survey after the 1811 – 1812 earthquakes. Comparisons between 

this 1821 survey with the survey of 1880 showed that the average top bank 

width in this reach increased from approximately 2,500 feet (ft) to 

approximately 4,700 ft, or approximately 91%. Width increases of this 

magnitude would not be compatible with the natural meandering processes 

of a river in dynamic equilibrium but rather would be indicative of a river 

experiencing severe system instabilities. Identifying all the causes for this 

systematic instability is difficult, but the New Madrid earthquakes, coupled 

with the clearing of the streambanks and adjacent riparian areas, appear to 

be the dominant factors during this period. 
MRG&P Report No. 32 7 

Figure 2-1. Change in Mississippi River top bank width between 1820 and 1973 (adapted 

from Winkley [1994]). 

Prior to building levees, the entire Lower Mississippi River (LMR) valley 

below Cairo, IL, was a delta. Distributary channels carried high as well as 

some lower flows into various lowland basins. Figure 2-2 illustrates the 

spatial distribution of flood flows prior to levees. Flood protection began 

in the LMR valley in the early 1700s, but it was localized and 

discontinuous. Major floods in the mid- to late-1800s caused severe 

damage to some of these early levees. After the disastrous flood of 1874, a 

levee commission was created with the intent to evaluate and make 

recommendations for the levee system (Elliot 1932). However, it was not 

until the creation of the MRC in 1879 (see next section) that a more 

comprehensive approach was adopted. 

In summary, the LMR was undergoing significant morphological changes 

during this time period. The instabilities were driven by various factors, 

most notably the New Madrid earthquakes and clearing of the 

streambanks for wood-burning steamboats and agriculture. It is 

unfortunate that the river was undergoing such drastic morphologic 

changes just as the nation was beginning to use the river and settle into the 

Mississippi River valley. Many of the early navigation problems on the 

river were aggravated by the caving streambanks, bar building, and 

channel widening, which created a negative impression of the river system 

just as it was becoming the main navigation artery for the country. 
MRG&P Report No. 32 8 

Figure 2-2. LMR valley flows before levees (Winkley 1977). 

2.2.2 Late-1880s to 1929 

Schumm et al. (1994) subdivided the LMR in 24 reaches based on 

morphological characteristics and behavior in the Pre-cutoff time period. 

Reaches 21 through 24 cover the study reach (Lake Providence to Old 

River). Table 2-2 shows a summary of the characteristics of the 

geomorphic reaches 21 through 24. The reach boundaries are identified by 

1962 river miles (RM), but the reach lengths reflect 1880 river mileage. 

Therefore, the lengths are not directly comparable to the 1962 reach 

lengths. Reach patterns varied from sinuous (RM 484 to 405) to moderate 

sinuosity (RM 405 to 304). 
MRG&P Report No. 32 9 

Table 2-2. Geomorphic reach characteristics (adapted from Schumm et al. [1994]). 

Schumm 

Reach No. 

Reach 

Boundary 

Length in 

1880 RM Reach Pattern 

Projected 

Channel 

Slope × 

104 

Possible 

Control 

21 484 - 437 52 sinuous 0.77

lithology, 

Monroe Uplift

22 437 - 405 33.5 sinuous 1.30 lithology

23 405 - 370 50.5

moderate 

sinuosity 0.62 lithology

24 370 - 304 87

moderate 

sinuosity 0.65

lithology,

tributary (Red 

River)

The MRC, established in 1879, was created to plan and execute projects to 

improve navigation along the LMR. The MRC received federal funds from 

Congress for the construction of levees under a policy that considered 

levees part of the navigation improvement program. The MRC considered 

various options to provide dependable navigation within the LMR. The 

approaches considered included levees, reservoirs, outlets, and cutoffs. 

After considerable debate, the MRC settled on a levees-only policy. This 

approach was based on the assumption that the construction of levees 

would deepen the channel, thereby providing adequate navigation depths. 

The MRC recommended the design of levee grades that could contain the 

most frequent floods. The levee construction started in 1882 to complete 

the gaps along the existing levee system. 

As the average levee height increased and crevasses became less 

pronounced, peak flood stage height began to increase as the flow between 

the levees became more confined. This is illustrated in Figure 2-3, which 

shows the peak annual stages at Natchez, MS, from the early-1800s to 

1980 (Winkley 1977). As shown in Figure 2-3, the peak stages began to 

increase in the early-1900s up to the 1930s when the cutoffs temporarily 

lowered stages. 

The MRC also adopted a no-cutoff program in 1884 with the goal of 

preventing natural meander cutoffs (aka neck cutoffs) from occurring. 

This was accomplished by implementing bank stabilization in areas 

where a natural cutoff was considered likely. As a result of this policy, the 

Waterproof cutoff (RM 377), which occurred naturally in 1884, was the 

last meander cutoff allowed until 1929 when the MRC decided to allow 
MRG&P Report No. 32 10

the Yucatan cutoff just south of Vicksburg to develop. As discussed in 

Section 2.2.1, six natural cutoffs occurred in the 108-year period prior to 

1884. Therefore, it is only reasonable to assume that in the 45-year 

period between 1884 and 1929, several natural cutoffs would have 

naturally occurred without the intervention of the MRC policy. With the 

prevention of neck cutoff development, it is natural to assume that the 

length of the river would have increased dramatically during this period 

due to meander migration. However, this meander growth was somewhat 

offset by the numerous chute cutoffs that were allowed to develop during 

this period. These chute cutoffs shortened the river by approximately 

45 miles in the reach from Cairo, IL, to Vicksburg, MS, and as a 

consequence, the river only increased in length in this reach by 

approximately 14 miles between 1884 and 1929 (Winkley 1977). Winkley 

also noted that the rate of chute cutoffs increased dramatically from only 

0.09 chute cutoffs/year prior to 1884 to 0.29 chute cutoffs/year from 

1884 to 1929. This suggests that the river responded to the prevention of 

neck cutoffs by accelerating the development of chute cutoffs. 

As discussed in Section 2.2.1, the LMR was undergoing significant 

morphologic changes prior to the 1880s. This is supported by the 91% 

increases in channel width during this period (Figure 2-1). However, as 

shown in Figure 2-1, the channel width only increased by approximately 

2% between 1880 and 1911 and approximately 9% between 1911 and 1948. 

The slight increase (9%) between 1911 and 1948 probably reflects the 

effects of the man-made cutoffs between 1929 and 1942 (see section 2.3). 

This seems to indicate that the dramatic channel changes that 

characterized the pre-1880s period had slowed in the post-1880s. 

Winkley (1977) suggested that the LMR prior to 1927 was losing channel 

capacity (aggradation) at all gages. Specific gage records, developed at 

Lake Providence, Vicksburg, St. Joseph, and Natchez, were examined to 

determine if aggradational trends were evident during this period. 

Unfortunately, historical data prior to the 1930s were only available at 

Lake Providence and Vicksburg. As shown in Figure 2-4, the channel does 

appear to be slightly aggradational at high flows (1,500,000 cubic feet per 

second [cfs]) prior between 1900 and 1930.

For a while, it appeared that the levees-only approach was going to be 

successful. Numerous floods occurred during this period, and although 

there were some issues, the overall system seemed to perform satisfactorily. 
MRG&P Report No. 32 11

This all changed with the devastating flood of 1927. The 1927 flood was one 

of the worst natural disasters in U.S. history, and as a result of this flood, the 

MRC recognized that a more comprehensive approach was going to be 

needed to provide adequate flood control and navigation on the LMR.

Figure 2-3. Average levee heights and peaks stages at Natchez, MS (Winkley 1977). 
MRG&P Report No. 32 12

Figure 2-4. Specific gage records at Lake Providence and Vicksburg in the 

Pre-cutoff Period for 1,500,000 cfs. 

2.3 Cutoff Period (1929 – 1942) 

This section discusses the geomorphic changes in the study reach that 

have occurred in the Cutoff Period (1929 – 1942). 

The advantages and disadvantages of artificial cutoffs on the Mississippi 

River had been debated without consensus by river engineers since the mid1880s. As discussed in Section 2.2, the MRC adopted a cutoff prevention 

program between 1884 and 1929. However, following the 1927 flood, the 

MRC again revisited the idea of incorporating artificial cutoffs on the river 

as one component of the MR&T Project. In 1929, the first natural meander 

cutoff since 1884 was allowed to occur at the Yucatan Bend downstream of 

Vicksburg as part of a study to evaluate the response of the river to a cutoff. 

After monitoring the Yucatan cutoff for 2 years, the MRC initiated the cutoff 

program in 1931. Through this program, the USACE constructed 14 artificial 

cutoffs and allowed 2 natural cutoffs (Yucatan and Leland) to develop 

between 1929 and 1942 on the LMR. The locations of the cutoffs are shown 

in Table 2-3. These cutoffs shortened the river between Memphis, TN, and 

Old River, LA, by approximately 152 miles. Since 1942, no neck cutoffs have 

been constructed or allowed to develop. However, between 1932 and 1955, 

chute cutoffs were constructed at 40 locations between Cairo, IL, and 

Natchez MS, further shortening the river by another 55 miles. Following the 

cutoffs, meander migration continued as the river attempted to regain some 
MRG&P Report No. 32 13

of its length. This continued until the 1960s when further meander 

migration was essentially terminated by the revetment program. However, 

according to Winkley (1977), these length increases were offset by the chute 

cutoffs so that the river is still approximately 150 miles shorter today than 

prior to the cutoffs. 

The study reach included seven cutoffs: Willow, Marshall, Diamond, 

Yucatan, Rodney, Giles, and Glasscock. These cutoffs shortened the study 

reach by approximately 62 miles. (For a more detailed description of these 

cutoffs, the reader is referred to Winkley [1977].) However, during the 

cutoff period between 1929 and 1942, the dominant response was channel 

degradation. As shown in Figure 2-5, the stage reductions (degradation) at 

Vicksburg were in the range of 10 to 12 ft, while farther downstream at 

Natchez, the stage reductions were slightly less, in the 5 to 7 ft range. 

Table 2-3. Man-made meander cutoffs, 1929 – 1942 (adapted from Winkley [1977]). 

Cutoff Name River Mile* Year Opened 

Distance River 

Shortened (miles) 

Hardin 678 1942 16.9

Jackson 628 1941 8.7

Sunflower 625 1942 10.4

Caulk 575 1937 15.2

Ashbrook 549 1935 11.4

Tarpley 541 1935 8.6

Leland* 539 1933 9.8

Worthington 514 1933 4.3

Sarah 504 1936 5.3

Willow 463 1934 7.7

Marshall 448 1934 4.2

Diamond 424 1933 12

Yucatan* 408 1929 9.6

Rodney 388 1936 5.9

Giles 366 1933 11.1

Glasscock 343 1933 10.8

Total 151.9

* Natural cutoffs.
MRG&P Report No. 32 14

Figure 2-5. Specific gage records along the LMR (Winkley 1977). 

During the Cutoff Period, 40 man-made chute cutoffs were developed by 

dredging material to improve the river alignment and navigation. From 

1932 to 1955, over 500,000 cubic yards (cy) of material were dredged 

between RM 942 and RM 357 to develop these chute cutoffs (Winkley 

1977). Within the study reach (RM 487.2 to RM 317), eight chute cutoffs 

were developed that shortened the reach approximately 6 miles.

2.4 Post-cutoff Period (1943 – present) 

This section discusses the geomorphic changes in the study reach that 

have occurred in the post-cutoff period (1943 – present). 
MRG&P Report No. 32 15

2.4.1 Channel improvements (revetments, dikes, and dredging) 

The period from the mid-1940s through the mid-1960s was one of 

significant adjustments on the LMR as the river responded to the cutoffs. 

The cutoffs significantly increased the channel slope and stream power in 

the system. As a consequence of these changes, bank erosion increased as 

the channel attempted to regain channel length. It was during this initial 

period following the cutoffs that an aggressive revetment program was 

initiated in an attempt to stabilize channel alignments. The revetment 

construction history in the study reach is shown in Figures 2-6 and 2-7. As 

shown in Figure 3-6, there was an increase in revetment construction 

beginning in the 1940s, reaching a peak in the 1950s and 1960s. By the mid1960s, most of the major meander bends had been stabilized, thereby fixing 

the alignments in place. Subsequent construction was mostly associated 

with upstream and downstream extensions of existing revetments. 

Figure 2-6. Revetment and dike construction timeline in the study reach. 
MRG&P Report No. 32 16

Figure 2-7. Total linear feet of revetments and dikes in study reach (by 10-mile increments). 

The revetment program has stabilized alignments in the river and 

significantly reduced bank caving in the river. Figure 2-8 shows the 

accumulated annual average bank caving volumes for the reach of river 

extending from just upstream of the Arkansas River to the ORCC during 

three time periods (Winkley 1973): 1877 – 1892, 1931 – 1942, and 1965 – 

1972. These curves were developed by calculating the area associated with 

the bankline movement between surveys. An average bank height of 40 ft 

was assumed for the volumetric computations. Using these curves, an 

estimate of the average annual bank caving volumes in the reach from 

Lake Providence to the ORCC was developed and is shown in Table 2-4. In 

Table 2-4, the data are presented for two time periods: (1) Pre-revetment 

Period, which represents the average of the two time periods 1877 – 1892 

and 1931 – 1942, and (2) Post-revetment Period. As shown in Table 2-4, 

the average annual bank caving volumes were reduced from approximately 

350,000,000 cy/year in the pre-revetment period to approximately 

30,000,000 cy/year in the post-revetment period. This is a reduction in 

sediment delivery from the channel banks to the system of approximately 

90%. However, because the size distribution of these sediments was not 

reported, the significance of these sediment reductions on the 

morphological changes in the river system is not clear. Note that with the 

continuation of the revetment program since the 1970s, the volume of 

sediment delivered from bank caving has essentially been eliminated. 
MRG&P Report No. 32 17

Figure 2-8. Accumulated annual average bank caving volumes from the Arkansas River to the 

ORCC (Winkley 1973). 

Table 2-4. Average annual bank caving volumes in the Lake Providence to Old River reach for 

the Pre- and Post-revetment Periods. 

Time Period 

Average Annual Bank Caving Volume 

(cy/year) 

Pre-revetment Period (average of 

1877–1892 and 1931–1942) 350,000,000

Post-revetment Period (1965–1972) 30,000,000

The cutoffs also imposed a new alignment on the channel system that 

altered the historic crossing patterns in the river. These alignment changes 

combined with the increased sediment delivery from bed material 

upstream resulted in increased maintenance dredging throughout the 

system. Figure 2-9 shows the dramatic increases in maintenance dredging 

in the Memphis, Vicksburg, and New Orleans Districts from the late-1940s 

through the late-1960s. After 1970, the amount of maintenance dredging 

began a long-term decreasing trend. The reduced maintenance dredging 

was a result of two interrelated factors. The first was the revetment 

program, which imposed much better planform alignments with more 

orderly pool-crossing patterns. The next, and arguably the most important 

factor, was the construction of training structures (dikes). The purpose of 
MRG&P Report No. 32 18

these dike structures is to provide adequate navigation depths by 

constricting the channel width, closing off secondary channels and chutes 

to reduce divided flow, and adjusting channel alignment. The effectiveness 

of the dike systems in reducing the need for maintenance dredging is 

supported by the inverse relation between the amount of dredging and the 

cumulative length of constructed dikes (Figure 2-9).

Figure 2-9. Relationship between total linear feet of dikes and maintenance dredging in the 

Vicksburg, and Memphis Districts. 

2.4.2 Flow regime in the Post-cutoff Period 

The Post-cutoff Period covers a span of over 70 years, and as would be 

expected with such a long time period, there is considerable variability in 

the annual flow regimes as well as periodic cycles of low and high flows. 

Figure 2-10 shows how the average annual flow, based on computed daily 

discharge data, varied from 1901 through 2014. The daily discharge values 

from 1943 to 2014 were obtained from the Vicksburg District. However, 

daily discharge data were not available for the pre-1943 period. Therefore, 

the measured discharge data were used to develop discharge-stage 

relationships that were then coupled with the daily stage data to produce 

the daily discharge values prior to 1943. Note that there were time spans in 

the pre-1943 period where measurements were sparse or nonexistent, and, 

therefore there is more uncertainty in these data than in the post-1943 
MRG&P Report No. 32 19

data. However, the data were sufficient to produce a reasonable 

approximation of the average annual discharges during this period. 

Of particular note in Figure 2-10 is the extreme low-water period between 

1952 and 1972. This 20-year low-flow period ended abruptly with the 1973 

flood. The average annual flow for this period (1952 – 1972) was only 

approximately 526,000 cfs, which is considerably less than the pre-1952 or 

post-1972 periods, which had average annual flows of approximately 

686,000 cfs and 662,000 cfs, respectively. Alluvial streams adjust to the 

flow regime imposed upon them. Therefore, the extreme flows of the 1973 

flood were forced upon a system that had adjusted to a 20-year low flow 

period. This may be a partial explanation for why the stage-discharge 

relationships shifted upward so abruptly during the 1973 flood.

Figure 2-10. Average annual discharges at Vicksburg. 

2.4.3 Specific gage records 

Specific gage analysis is an effective tool used by river engineers and 

scientists to assess the historical behavior of rivers. Watson et al. (2013) 

provides a detailed description of the specific gage analysis. 

Fundamentally, a specific gage record is simply a plot of river stage 

versus time for a specific discharge. A specific gage record can be 

developed by one or two methods. The first is referred to as the rating 

curve method and the second as the direct step method. For this study, 

the rating curve method was selected.
MRG&P Report No. 32 20

Specific gage records were developed at four stations in the study reach. 

Table 2-5 lists the location, station type, and period of record. The following 

is a brief discussion of the observed trends at each of the stations.

Table 2-5. Specific gage locations within the study reach. 

Station Name 

Location 

(RM) Station Type* 

Discharge 

Station 

Period of 

Record 

Lake Providence 487.2 Secondary Vicksburg 1906–2014

Vicksburg 435.7 Primary Vicksburg 1903–2016

St. Joseph 396.4 Secondary Natchez 1935–1996

Natchez 363.3 Primary Natchez 1935–2016

* Primary stations collect flow and stage data, and secondary stations collect stage data only.

Lake Providence 

The Lake Providence gage is a secondary station located at RM 487.2 AHP. 

Observed stages at Lake Providence were combined with discharges 

measured at Vicksburg (using a 1-day lag time) to generate the specific 

gage record. The period of record for the specific gage analysis extends 

from 1903 to 2014 (Figure 2-11). Bankfull stage is 37 ft on the Lake 

Providence gage. The channel degradation, which began in the early-1930s 

as a result of the cutoff, continued through the late-1940s to early-1950s. 

Since the 1950s, there have been some fluctuations in stage, but overall 

stages have remained relatively stable.

Vicksburg

Vicksburg is a primary station located at RM 435.7 AHP. The period of 

record for the specific gage analysis extends from 1903 to 2016 

(Figure 2-12). Bankfull stage is 43 ft on the Vicksburg gage. An abrupt 

decrease in stages for all flows occurred during the early-1930s, and this 

decreasing trend continued throughout the 1940s and early-1950s. Since 

then, stages for all flows greater than 200,000 cfs have fluctuated around 

what appears to be a generally increasing trend. In contrast, stages for a 

discharge of 200,000 cfs have been relatively stable since the 1950s. 
MRG&P Report No. 32 21

Figure 2-11. Specific gage record at Lake Providence, LA. 

Figure 2-12. Specific gage record at Vicksburg, MS. 
MRG&P Report No. 32 22

St. Joseph

St. Joseph is a secondary station located at RM 396.4 AHP. The specific 

gage record was developed by coupling daily stages observed at St. 

Joseph with discharges measured at Natchez using a 1-day time lag. The 

period of record for the specific gage analysis extends from 1935 to 1996 

(Figure 2-13). Bankfull stage is 40 ft on the St. Joseph gage. As shown in 

Figure 2-13, a decreasing trend in stages began in the mid-1930s and 

persisted into the early-1940s. Between the mid-1940s and the end of the 

period of record in the mid-1990s, stages for all but the lowest discharge 

exhibited an increasing trend. Stages for 200,000 cfs remained relatively 

stable.

Figure 2-13. Specific gage record at St. Joseph, LA. 

Natchez

Natchez is a primary station located at RM 363.3 AHP. The period of 

record for the specific gage analysis extends from 1935 to 2016 

(Figure 2-14). Bankfull stage is 48 ft on the Natchez gage. As shown in 

Figure 2-14, stages for all flows decreased abruptly in the late-1930s and 

continued to display a downward trend during the early-1940s. Since the 
MRG&P Report No. 32 23

mid-1940s, a general, increasing trend is evident in the stages associated 

with all selected flows.

Figure 2-14. Specific gage record at Natchez, MS. 

Specific gage summary

The study reach is responding in an expected manner following a series of 

meander cutoffs. At the upstream end of the reach, represented by the 

Lake Providence gage, the stages have been relatively stable since the 

early-1950s. Moving farther downstream, the gages (Vicksburg, St. Joseph, 

and Natchez) become progressively more aggradational. This suggests that 

the reach from Lake Providence to Vicksburg may be a transition reach 

between dynamic equilibrium and the aggradational trends that exist 

farther downstream. 

2.4.4 Water surface slope trends 

Water surface slope is an important parameter that provides a 

representation of the energy in a channel system. Slope is closely 

associated with the sediment transport capacity, and therefore any 

changes in channel slope can be used to infer morphologic changes in a 

channel system. Slope trends on the LMR are extremely important 
MRG&P Report No. 32 24

because of the dramatic increases that occurred immediately after the 

meander cutoffs. Tracking these slope changes in the Pre- and Post-cutoff 

Periods provides valuable insight into the morphology of the study reach.

Water surface slopes were calculated between the following sub-reaches: 

(1) Lake Providence to Vicksburg; (2) Vicksburg to St. Joseph; 

(3) St. Joseph to Natchez; and (4) Vicksburg to Natchez. Daily water 

surface slopes were calculated using daily stage data and the distance (in 

miles) between the gaging stations. Average annual slope values were then 

calculated for each year. 

Lake Providence to Vicksburg

Figure 2-15 shows the trends in average annual water surface slopes for 

the Lake Providence to Vicksburg reach. Table 2-6 presents the time 

periods, distances between the gages, and description of events that 

caused the distance change (cutoffs, meander activity, gage location 

change, etc.) in the Lake Providence to Vicksburg Reach. Table 2-7 shows 

the average slope values at various time periods in the reach. 

Figure 2-15. Average annual water surface slopes for the Lake Providence to Vicksburg reach. 
MRG&P Report No. 32 25

Table 2-6. Period of record and reach length data for the Lake Providence to Vicksburg reach. 

Period 

Reach Length 

(miles) Description 

Pre-1935 63.2 This period reflects the Pre-cutoff conditions.

1935–1964 49.5 This period reflects the Marshall and Willow cutoffs in 1935.

1965–1976 48.4

This period reflects the gage change at Lake Providence, which 

shifted the gage downstream approximately 3.8 miles. It also 

reflects the growth along the outside of Cottonwood Bar. 

Therefore, the reduction in length is only slightly less than 1 mile.

1977–1984 49.7

This period reflects the gage location change at Vicksburg 

downstream approximately 1.3 miles.

1985–2014 48.2 This period reflects the realignment at Cottonwood Bar in 1985.

Table 2-7. Average annual water surface slopes for three time periods in the Lake Providence 

to Vicksburg reach. 

Average Annual Water Surface Slope 

Time Period No. 

1

Pre-cutoff 

Period (prior to 

mid-1930s)

Time Period 

No.2

(mid-1930s to 

mid-1940s)

Time Period No. 3

Post-cutoff Period 

(mid 1980s to 

present)

Percent

Increase 

between

Periods No.

1 and No. 2

Percent 

Increase 

between 

Periods No. 1 

and No. 3

0.000054 0.000078 0.000063 44% 16%

Beginning in the mid-1930s and continuing through the mid-1940s, there 

was a dramatic increase in slope in the Lake Providence to Vicksburg reach 

as a result of the cutoffs (Figure 2-15). During this period, slopes increased 

from approximately 0.000054 to 0.000078, an increase of approximately 

44% (Table 2-7). From the mid-1940s through the mid-1970s to early1980s, the slopes fluctuated but generally exhibited a decreasing trend. 

Since the early-1980s, the slopes have been relative stable, with an average 

slope of approximately 0.000063. As shown in Table 2-7, the present-day 

slopes (early-1980s to present) are approximately 16% higher than the 

Pre-cutoff slopes.

Vicksburg to St. Joseph

The changes in the average annual water surface slopes for the Vicksburg 

to St. Joseph reach are shown in Figure 2-16. Reach characteristics are 

shown in Table 2-8 and average Pre- and Post-cutoff slopes are shown in 

Table 2-9. Note that there are no data after 1996 due to the discontinuance 

of the St. Joseph gage. 
MRG&P Report No. 32 26

Figure 2-16. Water surface slope trends in the Vicksburg to St. Joseph reach. 

Table 2-8. Period of record and reach length data for the Vicksburg to St. Joseph reach. 

Period Length (miles) Description 

Pre-1932 68.4 This period reflects the Pre-cutoff reach length.

1932-1934 57

This period reflects the Yucatan cutoff in 1929,

which became effective around 1932.

1935-1944 43.5

This period reflects the Diamond cutoff, which 

became effective in 1935.

1945-1974 39.5 to 43.3

The initial length in 1945 was 39.5 miles, which 

reflected the movement of the St. Joseph gage 3 

miles upstream. By 1974, the reach had increased in 

length to 43.3 miles due to meander migration. A 

linear interpolation was used for the intervening 

years between 1945 and 1974. 

1975-1976 40.8

The Togo chute developed approximately 1975,

which shortened the reach about 2.5 miles.

1977-1996 39.5

This period reflects a reduction in length of 1.3 miles 

due to the movement of the Vicksburg gage.
MRG&P Report No. 32 27

Table 2-9. Average annual water surface slopes for three time periods in the Vicksburg to 

St. Joseph reach. 

Average Annual Water Surface Slope 

Time Period No. 1

Pre-cutoff Period 

(prior to mid1930s)

Time Period 

No.2

(mid-1930s 

to mid1940s)

Time Period No. 3

Post-cutoff Period 

(mid-1980s to 

1995)

Percent 

Increase 

between

Periods No.1 

and No.2

Percent 

Increase 

between 

Periods No.1 

and No.3

0.000054 0.000066 0.000063 24% 17%

Water surface slopes increased dramatically between the mid-1930s and the 

mid-1940s immediately after the artificial cutoffs. As shown in Table 2-9, 

channel slopes were approximately 24% higher immediately after the 

cutoffs (mid-1930s to mid-1940s) compared to the Pre-cutoff slopes. After 

the mid-1940s, the slopes began a decreasing trend, which generally 

continued until the early 1960s. From the early-1960s to 1995, channel 

slope exhibited alternating periods of increasing and decreasing trends but 

remained within an approximate range between 0.00006 and 0.000067 

with an average slope of approximately 0.000063. Comparison of the Precutoff and Post-cutoff (mid-1980s to 1995) data shows that the Post-cutoff 

slopes are still approximately 17% higher than the Pre-cutoff slopes 

(Table 2.9).

St. Joseph to Natchez

The trends in water surface slope for the St. Joseph to Natchez reach are 

shown in Figure 2-17. The period of record and reach length data for this 

reach are shown in Table 2-10. Table 2-11 provides the slope changes in 

the Pre- and Post-cutoff Periods. Again, the period of record only extends 

to 1996 due to the discontinuance of the St. Joseph gage. 

Following the cutoffs in the mid-1930s, the slopes in the study reach 

increased abruptly reaching a peak in approximately 1936. After this, the 

slopes decreased until approximately 1940 when the slope began to 

increase again. The slopes remained elevated until the mid-1950s when 

they decreased again. These initial slope increases, which persisted 

through the mid-1950s, were approximately 45% higher than the Precutoff slopes (Table 2-10). Since the mid-1960s up to 1996, the slopes have 

remained relatively stable with an average slope of approximately 

0.000053, which is approximately 29% higher than the Pre-cutoff slopes. 
MRG&P Report No. 32 28

Figure 2-17. Water surface slope trends in the St. Joseph reach to Natchez. 

Table 2-10. Period of record and reach length data for the St. Joseph to Natchez reach. 

Period Length (miles) Description 

1927–1935 47.8 This period reflects the Pre-cutoff reach length.

1936–1940 28.4

This period reflects the Giles and Rodney cutoffs,

which became effective in 1935 and 1936, 

respectively. The year 1936 was used to represent 

both for these calculations.

1941–1944 28.7

The Natchez gage was moved approximately 0.3 mile 

downstream in 1941

1945–1996 33

In 1945, the gage at St. Joseph was moved upstream 

approximately 4.3 miles.

Table 2-11. Average annual water surface slopes for three time periods in the St. Joseph to 

Natchez reach. 

Average Annual Water Surface Slope 

Time Period 

No. 1

Pre-cutoff 

Period (prior to 

mid-1930s)

Time Period 

No.2

(mid-1930s to 

mid-1940s)

Time Period 

No. 3

Post-cutoff 

Period 

(mid-1960s to 

1995)

Percent 

Increase 

between

Periods No.1 

and No.2

Percent 

Increase 

between 

Periods No.1 

and No.3

0.000041 0.000060 0.000053 45% 29%
MRG&P Report No. 32 29

Vicksburg to Natchez

The previous two sections discussed the slope trends for the Vicksburg to 

St. Joseph and St. Joseph to Natchez reaches. However, as discussed, the 

period of record in these two reaches only extended through 1996 due to 

the discontinuance of the St. Joseph gage. The advantage of considering 

the Vicksburg to Natchez reach is that is has a much longer period of 

record. However, it must be recognized that the slope calculations cover a 

much longer reach and therefore represent a somewhat more broad-scale 

view of the system. 

Figure 2-18 shows the slope trends for the Vicksburg to Natchez reach. 

Table 2-12 describes the time periods, distances between the gages, and 

description of events that caused the distance change (cutoffs, meander 

activity, gage location change, etc.) in the Vicksburg to Natchez Reach. 

Table 2-13 shows the average slope values at various time periods in the 

reach. 

Figure 2-18. Water surface slope trends in the Vicksburg to Natchez Reach. 
MRG&P Report No. 32 30

Table 2-12. Period of record and reach length data for the Vicksburg to Natchez reach. 

Period 

Length 

(miles) Description 

Pre-1932 116.2 This period reflects the Pre-cutoff conditions.

1932–1934 104

This period reflects the Yucatan cutoff in 1929, which 

became effective approximately 1932.

1935 91.3 This period reflects the Diamond cutoff.

1936–1940 71.9

This period reflects the Giles and Rodney cutoffs which 

became effective in 1935 and 1936, respectively. The year 

1936 was used to represent both for these calculations.

1941–1944 72.2

The Natchez gage was moved approximately 0.3 mile 

downstream in 1941.

1945–1976 73.8

In 1945, the gage at St. Joseph was moved upstream 

approximately 4.3 miles. Also, between 1945 and 1976, the 

channel length increased from 39.5 miles to 43.5 miles 

through meandering between Vicksburg and St. Joseph.

1977–2014 72.5

The Vicksburg gage was moved downstream approximately 

1.3 miles in 1977.

Table 2-13. Average annual water surface slopes for three time periods in the Vicksburg to 

Natchez reach. 

Average Annual Water Surface Slope 

Time Period No. 1

Pre-cutoff Period 

(prior to mid1930s)

Time Period No.2

(mid-1930s to 

late-1940s)

Time Period No. 3

Post-cutoff Period 

(Late 1980s –

present)

Percent 

Increase 

between

Periods No.1 

and No.2

Percent 

Increase 

between 

Periods No.1 

and No.3

0.000049 0.000064 0.000056 31% 16%

The Pre-cutoff slopes in this reach averaged approximately 0.000049. In 

the mid-1930s, the slopes increased and remained elevated through the 

late-1940s with an average slope of approximately 0.000064 (Figure 2-18). 

This was an increase of approximately 31% relative to the Pre-cutoff slopes 

(Table 2-13). Between the late-1940s and late-1960s, there was a decreasing 

trend in the slopes. From the late-1950s through the late-1980s, the slopes 

exhibited some fluctuations but were overall relatively stable. Since the late1980s, the slopes appear to have been on a slightly decreasing trend with an 

average slope of approximately 0.000056. This decreasing slope trend likely 

reflects the higher aggradation rates at Natchez as compared to Vicksburg. 

As shown in Table 2-13, the present-day slopes (late-1980s to present) are 

approximately 16% higher than the slopes in the Pre-cutoff Period.
MRG&P Report No. 32 31

Slope summary

The artificial cutoffs in the 1930s and early-1940s triggered substantial 

geomorphic change in the study reach. Initial increases in water surface 

slopes ranged from approximately 24% to 45%. These increases in slope 

increased sediment transport capacity significantly, resulting in channel 

degradation throughout the reach. Although the slopes have decreased 

from their initial peak conditions immediately after the cutoffs, the 

present-day slopes in the study reach are still higher (generally 

approximately 17%) than in the Pre-cutoff Period. 

2.4.5 Stage duration changes 

Stage duration curves were developed at the four major gaging stations in 

the study reach: Lake Providence, Vicksburg, St. Joseph, and Natchez. 

Although this section is primarily focused on the Post-cutoff Period, it is 

necessary to include some Pre-cutoff data as well, to place the present-day 

stage duration regime in a historical context. Stage duration data were 

developed for the five time periods shown in Table 2-14. Table 2-14 also 

lists the number of years of record in each time period and the average 

daily discharge for that period. The average daily discharge data were 

developed from the daily discharge data at the Vicksburg gage. 

Table 2-14. Time periods used in the development of the stage duration curves. 

Period Number of years Average Daily flow (cfs) 

1901 – 1921 20 575,800 cfs

1922 – 1944 22 565,200 cfs

1945 – 1972 27 573,000 cfs

1973 – 1993 20 676,000 cfs

1994 – 2014 20 648,000 cfs

Note that the two post-1973 time periods in Table 2-14 have similar 

average daily discharges. However, the flows in the pre-1973 periods are 

much smaller. This introduces some uncertainty when making 

comparisons between time periods. For this reason, the stage duration 

data were developed using two different approaches. The first was a 

straight calculation using all the data within the time period. This method 

uses all the data in the time period and therefore is a good representation 

of the actual flow regime that was experienced during that period. 

However, as noted there may be problems when trying to make relative 
MRG&P Report No. 32 32

comparisons to other time periods due to the variability in flows. The 

second approach is a flow-adjusted stage duration curve that selects 

specific years within each time period that produce approximately equal 

average daily flows for all time periods. Table 2-15 lists the selected years 

in each time period. As shown in Table 2-15, the average daily flows for the 

time periods are all within a few percent of each other. Using this 

approach reduces the number of years in each time period. However, it 

removes the uncertainty associated with varying flow regimes between the 

time periods and therefore allows for an unbiased comparison of stage 

duration changes through time. 

Table 2-15. Selected years with similar average daily discharges. 

Average Daily Discharge (cfs) 

1901 – 1921 1922 – 1944 1945 – 1972 1973 – 1993 1994 – 2014

1911 456,705 1936 455,442 1953 439,710 1988 439,128 2000 432,139

1902 480,372 1930 482,734 1959 484,323 1976 479,923 2012 474,121

1906 596,341 1926 568,322 1968 570,279 1992 569,330 2005 569,863

1909 615,778 1924 620,727 1946 620,178 1978 620,901 2003 616,513

1919 659,742 1923 650,196 1957 661,795 1989 668,202 1997 672,815

1920 710,853 1928 736,228 1949 690,756 1982 694,636 1998 707,875

1907 716,989 1935 773,945 1945 817,137 1974 814,748 2008 801,290

1916 725,102 1929 802,415 1950 872,071 1979 853,455 2011 857,621

Average 620,235 Average 636,251 Average 644,531 Average 642,540 Average 641,530

Lake Providence

The stage duration curve at Lake Providence is shown in Figure 2-19. 

Examination of these curves indicates that stages prior to 1944 were 

generally higher than in the post-1945 period, particularly at the higher 

stages (above approximately 95 ft). The stage duration curve for the 1945 – 

1972 period is much lower than in the post-1973 periods. This is likely a 

result of the lower discharges during this period. The flow-adjusted stage 

duration curve for Lake Providence is shown in Figure 2-20. Removing the 

influence of flow variability produces a slightly different view of the stage 

duration trends. As shown in Figure 2-20, both pre-1944 curves are 

consistently higher than the post-1945 curves. For example, a stage of 107, 

which is approximately the flood stage at the gage, was equaled or 

exceeded approximately 13% of the time prior to 1944 compared to 
MRG&P Report No. 32 33

approximately 3% for the 1944 – 1972 and the 1973 – 1993 periods and 

approximately 6% in the 1994 – 2014 period. Also, the 1944 – 1972 curve 

is now almost coincident with the 1973 – 1993 curve. Note that above a 

stage of approximately 90 ft, the 1994 – 2014 curve begins to deviate 

slightly from the other post-1944 curves, suggesting continued stage 

increases (aggradation) at the higher flows during this period. 

Figure 2-19. Lake Providence stage duration curve using time periods in Table 2-14. 
MRG&P Report No. 32 34

Figure 2-20. Flow-adjusted stage duration curves at Lake Providence. 

Vicksburg

The stage duration curves for Vicksburg (Figure 2-21) show that at the 

higher stages, the pre-1944 curves were generally higher than the post1945 curves. The 1945 – 1972 stage duration curve was generally lower 

than the post-1973 curves, which again probably reflects the lower 

discharges during this period. The flow-adjusted duration curves 

(Figure 2-22) show that the pre-1944 curves were consistently higher than 

the post-1944 curves at the higher stages (above a stage of approximately 

65 ft). As shown in Figure 2-22, an elevation of 89 ft (approximate flood 

stage elevation) in the pre-1944 period was equaled or exceeded 

approximately 12% of the time while in the post-1944 periods it was only 

equaled or exceeded between approximately 4% and 6% of the time. Below 

a stage of approximately 65 ft, the pre-1944 curves are still slightly higher 

than the post-1944 curves, but they are beginning to coalesce into 

approximately the same range. 
MRG&P Report No. 32 35

Figure 2-21. Vicksburg stage duration curve using time periods in Table 2-14. 

Figure 2-22. Flow-adjusted duration curves at Vicksburg. 
MRG&P Report No. 32 36

St. Joseph

The St. Joseph stage duration curves are shown in Figure 2-23. As shown 

in Figure 2-23, the most recent time period is the 1973 – 1993 period due 

to the discontinuance of the St. Joseph gage. As shown in Figure 2-23, 

there is considerable variability among the curves, making it difficult to 

identify any consistent temporal trends. However, when the flow-adjusted 

duration curves in Figure 2-24 are examined, a clearer picture emerges. As 

shown in Figure 2-24, the pre-1944 curves are somewhat higher than the 

post-1944 curves above a stage of approximately 55 ft. However, the stage 

variation range between the curves is much smaller than in the two 

upstream stations. In the pre-1944 period, the approximate flood stage 

elevation of 73 ft was equaled or exceeded approximately 10% of time 

while in the post-1944 periods, this stage was only equaled or exceeded 

approximately 5% of the time. At the lower stages, below approximately 

55 ft, there is considerable variability in the curves making it difficult to 

identify any significant trends.

Figure 2-23. St. Joseph Stage duration curve using time periods in Table 2-14. 
MRG&P Report No. 32 37

Figure 2-24. Flow-adjusted duration curve at St. Joseph. 

Natchez

The stage duration curves for Natchez (Figure 2-25) indicate that the post1973 stages are higher than all previous time periods throughout the entire 

stage range. However, examination of the flow-adjusted duration curves in 

Figure 2-26 provides a more insightful understanding of the trends. As 

shown in Figure 2-26, the curves have coalesced considerably particularly 

at the higher stages. Above a stage of approximately 55 ft, the curves for all 

time periods except 1993 – 2014 are tightly packed. Prior to 1993, a flood 

stage elevation of approximately 65 ft was equaled or exceeded 

approximately 5% of the time. However, this same stage in the 1993 – 

2014 time period was equaled or exceeded approximately 9% of the time.
MRG&P Report No. 32 38

Figure 2-25. Natchez stage duration curve using time periods in Table 2-14. 

Figure 2-26. Flow-adjusted duration curves at Natchez. 
MRG&P Report No. 32 39

Stage duration summary

The study reach has been subjected to significant geomorphic changes 

since the early-1900s, with the meander cutoffs in the 1930s being the 

primary driver of change. The specific gage discussion (Section 2.4.3) 

highlighted the degradational and aggradational changes of the river. The 

stage duration curves provide supplementary information that is critically 

important to ecological and geomorphic assessments (particularly 

sediment transport capacity) but also assists in developing a better 

understanding of flooding potential. 

Table 2-16 shows the stage duration changes for low water stages 

(approximately +5 on the gage), mid-bank stages (approximately +20 on 

the gage), and flood stages for the Pre-cutoff and 1993 – 2014 time 

periods. Also shown in Table 2-16 are the percent changes in duration 

between the time periods for each stage. Negative values indicate that the 

particular stage is equaled or exceeded less frequently in the present-day 

river compared to the pre-cutoff period. Positive values (shown in red) 

indicate that the stages are equaled or exceeded more frequently. As 

shown in Table 2-16, there is a general trend in duration changes from 

upstream to downstream. 

Lake Providence, located at the upstream end of the study reach, shows 

the largest stage duration changes, with reductions of approximately 24% 

at the low- to mid-range stages and 9% at the flood stages. Moving 

downstream, the percent changes become less and less, eventually 

showing increases in stage duration at Natchez. Of particular interest in 

Table 2-16 are the stage duration changes at the flood stage elevation. The 

flood stage elevation is the elevation where flooding begins to impact 

floodplain areas. This is also often associated with the bankfull stage, 

which is important for geomorphic studies. As shown in Table 2-16, the 

percentage of time that the flood stage is equaled or exceeded at Lake 

Providence and Vicksburg is approximately 6% to 9% less frequent than it 

was in the Pre-cutoff Period. The percent change at St. Joseph is also 

approximately 6%, but it must be remembered that this value reflects the 

changes only through 1993. It is likely that if data existed through 2014, 

this value would be much smaller and possibly even positive. At Natchez, 

the flood stage elevation is presently equaled or exceeded approximately 

9% of the time as compared to approximately only 5% of the time in the 

Pre-cutoff Period. Thus, these areas are being inundated for longer 

durations than previously.
MRG&P Report No. 32 40

Table 2-16. Stage duration changes for a range of flow conditions. 

Gage 

Location* 

Percentage of Time Stage Is Equaled or Exceeded 

Low Stage Mid-Bank Stage Flood Stage 

Precutoff 1993-

2014 

% 

Change 

Precutoff 1993-

2014 

% 

Change 

Precutoff 1993-

2014 

% 

Change 

Lake 

Providence

(69.71 ft) 95% 71% -24% 57% 33% -24% 15% 6% -9%

Vicksburg

(46.23 ft) 98% 90% -8% 64% 51% -13% 12% 6% -6%

St. Joseph**

(33.12 ft) 85% 90% 5% 55% 51% -4% 11% 5% -6%

Natchez

(17.23 ft) 98% 100% 2% 65% 70% 5% 5% 9% 4%

* Gage zero is shown parentheses.

** The present-day time period for St. Joseph is 1973-1993.

2.4.6 Bed material characteristics 

This section describes the bed material characteristic in the study reach. 

The data in this section come from three sources: (1) bed material samples 

collected at the permanent gaging stations at Vicksburg and Natchez; (2) 

the bed material trends based on the 1932, 1989, and 2013 sampling 

(Gaines and Priestas 2016); and (3) the Robbins (1977) bed material data 

collected as part of the Potamology Program in the 1960s and 1970s. 

Bed material trends at permanent gaging stations (Vicksburg to Natchez)

Bed material samples are available for the sediment stations at Vicksburg 

and Natchez for the period from 1985 to 2004 (Thorne et al. 2008).

These samples are collected in association with the measured suspended 

sediment data. Figure 2-27 shows the bed material trends at the 

Vicksburg station. Although there is considerable scatter in the data, 

there are no sustained long-term trends that are evident. It is interesting 

that the gravel component of the D84 plot disappears completely after 

1992. The reason for this loss of gravel is not clear. It may be a real 

physical phenomenon or some artifact of the sampling procedures. 

Further investigation of this is warranted. 

Box and whisker plots were developed to display the variability in the bed 

material data. The bottom of the box (referred to as the lower hinge) 
MRG&P Report No. 32 41

represents the 25th percentile of the data, and the top (upper hinge) 

represents the 75th percentile, with the band near the middle of the box 

representing the median particle size (D50). Note that this is not the same 

as the mean particle size unless the scatter is normally distributed, which 

is not the usual case for these samples. Fifty percent of the data is within 

the box (i.e., between 25th and 75th percentiles). The whiskers are related 

to the height of the box, which is referred to as the interquartile range 

(IQR). For this investigation, the extent of the whiskers was defined as the 

lowest data point within 1.5 × IQR of the lower quartile and the highest 

data point within 1.5 × IQR of the upper quartile. Data outside the whisker 

limits that are depicted as crosses are referred to as outliers. 

The box and whisker plots for the Vicksburg data are shown Figure 2-28. 

As shown in Figure 2-28, the median value (50th percentile) for D50 is 

approximately 0.41 millimeter (mm) while the 25th and 75th percentile 

values range from 0.37 mm to 0.47 mm, respectively. Also highlighted in 

Figure 2-28 are the multiple D84 outliers that reflect the occurrence of 

gravel in the samples.

At Natchez (Figure 2-29), there were no sustained bed material trends that 

could be observed. However, there was a period between 1998 and 2001 

when the bed material apparently became much finer. The D84 plot in 

Figure 2-29 shows a loss of gravel after 1988. This loss of gravel, as well as 

the fining of the bed between 1998 and 2001, warrants further 

investigation to determine whether these are real phenomena or some 

artifact of the sampling procedures. As shown in the box and whisker plot 

in Figure 2-30, the D50 for Natchez is approximately 0.36 mm, with an 

IQR between 0.33 mm and 0.39 mm.

In summary, there were no sustained temporal trends in the bed material 

data at either Vicksburg or Natchez. Spatially, there does appear to be a 

general fining of the bed in the downstream direction. For example, the 

D50 at Vicksburg is approximately 0.41 mm as compared to Natchez with a 

D50 of 0.36 mm. There are also two interesting phenomenon that need to 

be further investigated. The first is the apparent absence of grain size data 

larger than gravel in the late 1980s to early 1990s, and the second is the 

apparent fining of the bed at Natchez between 1998 and 2001. 
MRG&P Report No. 32 42

Figure 2-27. Bed Material trends at the Vicksburg gaging station. 

Figure 2-28. Box and whisker plot for the Vicksburg bed material data. 
MRG&P Report No. 32 43

Figure 2-29. Bed material trends at the Natchez gaging station. 

Figure 2-30. Box and whisker plot for the Natchez bed material data. 
MRG&P Report No. 32 44

Gaines and Priestas (2016) particle size distributions of bed sediments

Gaines and Priestas (2016) compared bed material gradations collected in 

2013 to bed material gradations for 1932 (WES 1935) and 1989 (Nordin 

and Queen 1992). The findings documented in the report are based on 754 

bed material samples collected in November 2013 at 496 locations spaced 

at intervals of 2 to 3 miles along the Mississippi River between Grafton, IL, 

and Head of Passes, LA. Data collection procedures in 2013 were matched 

as closely as possible to the procedures used for the collection of bed 

material samples in 1932 and 1989. (More detailed information about the 

sampling protocols and particle size analysis are included in the Gaines 

and Priestas (2016) report.)

In this section, the bed material data contained in the Gaines and Priestas 

(2016) report that pertain to the study reach are presented. Figure 2-31

shows the downstream trends in median (D50) grain sizes measured in 

November 2013 in the LMR between Cairo, IL, and Head of Passes, LA. 

River miles between Lake Providence and Old River are within the red 

box. According to the regression line in Figure 2-31, the D50 at Vicksburg 

and Natchez is approximately 0.36 and 0.3 mm, respectively. These values 

are slightly less than the D50 values reported in the previous section for the 

permanent gaging stations at Vicksburg and Natchez. A possible 

explanation for these differences may be that the Gaines and Priestas data 

were a single collection near the thalweg while at the permanent gaging 

stations, the data are averaged across the entire cross section. 

Figure 2-32 shows downstream trends in the bed material grain size 

distributions in the Lower Mississippi River in 1932 (a), 1989 (b), and 2013 

(c). River miles between Lake Providence and Old River are shown within 

the red box. The study reach had a higher amount of very coarse sand and 

gravel (2 mm or larger) in 1932 when the bed material grain size 

distributions are compared with the 1989 and 2013 gradations. It is also 

noticed that very fine sand (0.0625 mm – 0.125 mm), coarse silt (0.004 mm

– 0.062 mm), and clay (< 0.004 mm) have decreased over time. In fact, in 

1989 and 2013, there was essentially no bed material finer than very fine 

sands in the bed, with the exception of a very small amount near the 

downstream end of the reach in 1989. However, the amount of medium 

sand within the study reach has increased relative to the 1932 sampling.

In summary, the Gaines and Priestas (2016) data confirm that there is a 

downstream fining in the bed material size in the study reach, with the 
MRG&P Report No. 32 45

average D50 at Vicksburg and Natchez being approximately 0.36 mm 

and 0.3 mm, respectively. Comparison of the data also revealed a 

significant reduction in the amount of gravel in the bed relative to the 

1932 sampling. Their data also show that there were no appreciable 

amounts of bed material in the very fine sand, silts, and clay ranges in the 

1989 and 2013 data. 

Figure 2-31. Downstream trends in D50 in November 2013 – Study reach outlined in red 

(Gaines and Priestas 2016). 
MRG&P Report No. 32 46

Figure 2-32. Downstream trends in bed material grain size distributions in the LMR in (a) 

1932, (b) 1989, and (c) 2013 – Study reach outlined in red (Gaines and Priestas 2016). 

Robbins (1977) bed material trends

Robbins (1977) published a study of the suspended sediment and bed 

material trends within the USACE Vicksburg District reach to identify 

possible trends in the datasets that might have relevance for navigation 

and flood control. Using the Robbins (1977) data, Thorne et al. (2017) 
MRG&P Report No. 32 47

conducted detailed analysis of the spatial and temporal bed material 

trends. The data presented herein are summarized from these two reports. 

As part of the Vicksburg District’s Potamology Program, the Vicksburg 

District was divided into 25 potamology reaches. Between 1966 and 1974, 

the district conducted extensive data collection and analyses in these 

reaches. Typically data that were collected (sometimes several times per 

year) included hydrographic surveys, suspended sediment samples, bed 

material samples, slope measurements, and discharge measurements. 

Fourteen of the 25 reaches were included within the study reach between 

Lake Providence and Old River (Table 2-17). In each reach, bed sediment 

samples were collected at specific sediment study ranges. At each range, 

between 4 and 12 bed material samples were collected, depending on the 

width of the cross section. 

The extensive sampling conducted in the potamology reaches over the 

9-year period provides valuable insight into the variability of the bed 

material composition. Figure 2-33 shows the variability between years in 

the bed material gradations for four selected reaches. Examination of 

these plots clearly shows that there is considerable temporal variability in 

the bed material gradation. For example, for the Cottonwood Bar reach, 

the D50 is seen to vary from approximately 0.2 mm to 0.45 mm.

Box and whisker plots were developed to show the trends and variability in 

the D50, D16, and D84 values in the study reach (Figure 2-34). As shown 

in Figure 2-34, there are reach-scale fluctuations in the data, but there is 

no evidence of significant downstream, decreasing trends. However, there 

does appear to be a coarsening of the bed material in the Belle Island to 

Vicksburg reach (RM 456.6 – 443.4). The average D50 for the study reach 

is approximately 0.31 mm.

In summary, the potamology data indicate that there are considerable 

variability and reach-scale fluctuations in the bed material data between 

years. However, no downstream, decreasing trends in the data were 

observed. The Robbins (1977) data indicate that the dominant bed size is 

sand with an average D50 of approximately 0.31 mm. The D16 fluctuates 

within the fine sand range while the D84 is typically in the lower end of the 

coarse sand size classes. However, there are some reaches that do contain 

significant quantities of gravel size material.
MRG&P Report No. 32 48

Table 2-17. Fourteen potamology reaches used in the bed material analysis. 

Potamology Reach 

Extent 

(RM AHP) 

RM 

(Mid-Point) 

Reach 

Length 

(miles) Period of Record 

Ajax Bar 485.7 – 479.7 482.7 5.8 1966 –1974

Ajax-Cottonwood 472 – 479.8 475.9 7.8 1968 – 1974

Cottonwood Bar 467.8 – 472 469.9 4.2 1966 –1974

Cottonwood Belle Island 461.4 – 467.8 464.6 6.4 1967 –1974

Belle Is. – Milliken Bend 451.8 – 461.4 456.6 9.6 1966 – 1974

Milliken Bend – Vicksburg 435 – 451.8 443.4 16.8 1968 – 1974

Racetrack Towhead 422.8 – 435 428.9 12.2 1966, 1968 – 1974

Point Pleasant 407 – 422.8 415.1 15.4 1966, 1970 – 1974

Grand Gulf 407.3 – 395.1 401.3 12.2 1970 – 1974

Rodney 395.1 – 381.3 388.3 13.8 1966, 1968 – 1974

Waterproof 381.3 – 368.1 374.8 13.2 1966, 1970 – 1974

Natchez 368.1 – 355.1 361.7 13 1970 – 1974

St. Catherine 355.1 – 338.5 346.9 16.6 1971 – 1974

Bougere 338.5 – 320.4 329.5 18.2 1972 – 1974

Figure 2-33. Selected bed material gradation curve in the research study. 
MRG&P Report No. 32 49

Figure 2-34. Box and whisker plots of D50, D16, and D84 for the 14 potamology reaches. 

Gravel observations

In addition to his analysis of bed material samples, Robbins (1977) also 

commented at length on the potential causes of a significant increase in 

the extent of exposed gravel on middle bars and islands between the 

upstream limit of the Vicksburg District (at RM 606AHP) and Natchez 

Island (at RM 357 AHP), approximately 78 RM downstream from 

Vicksburg. These observations were based on field investigation between 

1973 and 1975. Robbins (1977) concluded that the floods of 1973, 1974, and 

1975 were responsible for transporting and depositing gravel material on 

top of islands and middle bars. These deposits were at relatively high 

elevations only attained during flood events. Robbins listed a series of 

important observations that add important supplementary information to 

the results from the bed material samples. For this reason, his 

observations are summarized herein.

1. In the Cottonwood Bar potamology reach, gravel formed an extensive, 

continuous sheet at the head of a middle bar in the left channel 

(RM 470) comprising particles with long axes typically to 80 to 120 

mm (3 to 5 inches [in.]) in size.
MRG&P Report No. 32 50

2. At Togo Island Dike No. 2 (RM 416), river-transported gravel had filled 

the gaps between the quarry-run stone forming the dike 350 ft out into 

the river. The river gravel ranged in size up to approximately 60 mm 

(expressed as 2 in. in the Robbins Report) when measured along the 

major axis. As the crest of the dike is 10 to 15 ft above the river bed, the 

presence of gravel in the top of the dike indicates that gravel must have 

been carried in suspension, possibly due to very intense turbulence 

around the dike during high water. While this suggests that the LMR is 

capable of transporting coarse sediment in suspension during flood 

flows, Robbins noted that coarse sediment is excluded from suspended 

sediment samples because the nozzle of the P- 61 suspended sediment 

load sampler is only 0.48 mm (3/16 in.) in diameter.

3. Gravel cover was often extensive at the head of Middle Ground Island 

(RM 409). However, excavation of a trench through the bar head 

showed the gravel to be an armor layer with a thickness approximately 

equal to the diameter of the larger particles, which was underlain by 

sand that had gravel interspersed within it,

4. Gravel cover was observed at the heads of bars and islands as far 

downstream as RM 388.4, which is between Vicksburg and Natchez. 

5. While gravel deposits were found through a substantial proportion of 

the Vicksburg reach, the proportion of the bed of the LMR that was 

covered by gravel is small compared to that covered by sand. 

Nevertheless, the effect of a gravel armor layer at the head of a bar or 

islands tends to anchor the features in place, at least at low and 

intermediate flows and perhaps at all but the highest flows. Hence, the 

morphological influence and significance of the gravel armor may be 

considerable despite the relatively small area that it covers.

6. The extent and size of coarse bed sediment found at multiple locations 

within the Vicksburg District indicates that during high flows, the river 

transports particles far coarser than those collected during routine 

sampling. This indicates that while suspended load sampling records 

provide reliable estimates of the capacity of the Lower Mississippi 

River to transport sediment, they do not provide a reliable guide to the 

competence of the river because the largest sizes of material 

transported are evidently much larger than the orifice size of the 

samplers routinely used to measure the suspended sediment load.

Although not always captured in the bed material samples, the 

observations by Robbin (1977) indicate that there are numerous gravel 

locations throughout the river. He also notes that while they may only 
MRG&P Report No. 32 51

comprise a small portion of the bed, they can be significant 

morphologically. Additionally, gravels are extremely important from a 

habitat perspective. For this reason, a gravel study was conducted in 2011 

using visual observations from the 2005 and 2007 geo-referenced Red 

Hen videos. Using these videos, locations where gravel was present were 

documented. The following classification system was in the study: GS – 

gravel predominant with some sand present; SG – sand predominant with 

considerable gravel observed; SPG – mostly sand with possible gravel 

observed but not definitive, or gravel only observed in a few isolated 

locations; S - predominantly sand with little to no gravel. The results of 

this analysis are shown in Table 2-18. The bed classifications for both 

2005 and 2007 as well as a composite of the two years are shown in Table 

2-18. Also indicated in the Comments column are observations from a 

1989 boat trip along the entire river. During this trip, Mr. Robert 

Rentschler, a geomorphologist with the Vicksburg District, made 

meticulous notes of all locations where he observed gravel outcrops. His 

observations are included in Table 2-18. Based on the composite 

observations, there was one location with a GS classification, 10 with SG, 

and 18 with SPG. Note locations where gravel may have been observed in 

one year but not the other. This suggests that the gravel may be exposed 

under certain flow conditions but buried under sand at others.

Table 2-18. Bed classification from 2005 and 2007 geo-referenced videos. 

River 

Mile Location

2005 

Observation

2007 

Observation

Composite 

2005–2007 

Observation Comments

486 LB SPG SPG SPG

Mostly sand with a few possible 

gravel deposits (Baleshed -

Ajax). Gravel seen here in 

1989.

477 RB SG SG SG

Gravel deposits on mostly sand 

bar (much more gravel in 

2007). Gravel seen here in 

1989.

471a RB S SG SG 2005 sand (sand with gravel on 

closure side of dike in 2007).

471 LB GS GS GS Local gravel deposit at US end 

of Arcada Dikes.

470 RB S S S

Sand on bar in old Cottonwood 

channel — no presence of 

gravel.
MRG&P Report No. 32 52

River 

Mile Location

2005 

Observation

2007 

Observation

Composite 

2005–2007 

Observation Comments

469 LB SPG SPG SPG

Mostly sand with a few possible 

gravel deposits — gravel not 

seen here in 1989.

464 LB SPG - SPG

Mostly sand with a few possible 

gravel deposits (limited visibility 

due to stage in 2007). Gravel 

not seen here in 1989.

461 RB SG SPG SG

Gravel on bar, mostly sand 

(more sand less gravel in 

2007). Gravel seen here in 

1989.

456 LB SG SG SG

Mostly sand with some gravel 

deposits — gravel seen here in 

1989.

450 LB S S S

Mostly sand in dike fields —

gravel not seen here in 1989

447 RB SG SG SG

Mostly sand with some deposits 

of gravel (also possible gravel 

wave).Gravel seen here in 

1989.

443 LB SPG S SPG

Mostly sand, possibly a little 

gravel, but not clear (not much 

seen in 2007). Gravel seen 

here in 1989.

439 RB SG SG SG

Mostly sand with local deposits 

of gravel (limited visibility due to 

stage in 2007). Gravel not seen 

here in 1989.

435 RB S S S Mostly sand on point bar

431 RB S S S

Mostly sand observed through 

dike field — gravel not seen 

here in 1989.

429 LB SPG SPG SPG

Mostly sand with possible 

gravel — gravel not seen here in 

1989.

426 RB S SPG SPG

Mostly sand on bar (possible 

signs of gravel in 2007). Gravel 

not seen here in 1989.

422 LB SPG SPG SPG

Mostly sand with possibly 

gravel — gravel not seen here in 

1989.

420 RB S SPG SPG

Mostly sand point bar (possible 

signs of gravel in 2007). Gravel 

not seen here in 1989.
MRG&P Report No. 32 53

River 

Mile Location

2005 

Observation

2007 

Observation

Composite 

2005–2007 

Observation Comments

414 LB SG SG SG

Mostly sand with some deposits 

of gravel — gravel not seen here 

in 1989.

409 RB SPG SG SG

Mostly sand with some possible 

gravel (saw considerable gravel 

in 2007). Gravel seen here in 

1989.

403 RB S S S

Mostly sand in dike field —

gravel not seen here in 1989.

398 LB SPG SPG SPG

Mostly sand with possible 

gravel (poor picture quality). 

Gravel not seen here in 1989.

393 RB SPG SPG SPG

Mostly sand with possible 

gravel — gravel not seen here in 

1989.

388 RB S S S

Mostly sand, no sign of gravel —

gravel seen here in 1989 at DS 

end of island, which is now 

tree-lined.

384 LB S SPG SPG

Mostly sand on large point bar 

(2007- mostly sand with

possible gravel). Gravel not 

seen here in 1989.

377 RB S SPG SPG

Mostly sand on island (possible 

signs of gravel in 2007). Gravel 

not seen here in 1989.

372 LB SPG SPG SPG Mostly sand with possible 

gravel in places.

369 LB SPG - SPG

Mostly sand in dike field but 

some possible gravel seen (not 

much visible bar in 2007).

367 RB S - S

Mostly sand in dike field (water 

too high in 2007 to see bars).

Gravel not seen here in 1989.

358 RB S S S

Mostly sand in dike field —

gravel not seen here in 1989.

356 LB SPG SPG SPG

Mostly sand but possible gravel 

locations — gravel seen here in 

1989.

350 LB S S S

Mostly sand — gravel not seen 

here in 1989.
MRG&P Report No. 32 54

River 

Mile Location

2005 

Observation

2007 

Observation

Composite 

2005–2007 

Observation Comments

346 RB SPG SPG SPG

Mostly sand but with possible 

gravel observed — gravel seen 

here in 1989.

341 LB S S S

Mostly sand — gravel not seen 

here in 1989.

337 RB SG SG SG

Mostly sand but considerable 

gravel also present — gravel not 

seen here in 1989.

330 LB SPG SPG SPG Mostly sand with possible 

gravel in places.

326 RB SG SG SG Sand with gravel at head of 

island.

324 RB S S S Sand around island.

321 RB SPG SPG SPG Mostly sand but with possible 

gravel observed.

Bed material summary

Bed material data routinely collected at the permanent gaging stations 

(Vicksburg and Natchez) reveal the short- to medium-term variability in 

bed material properties and downstream trends in sediment 

characteristics based on repeat data for specific points (gaging ranges) that 

are widely spaced along the length of the river. These data indicated that 

there were no sustained temporal trends in the bed material composition 

at either Vicksburg or Natchez. The average D50 at Vicksburg and Natchez 

was approximately 0.41 mm and 0.36 mm, respectively, suggesting that 

there may be a general downstream, decreasing trend in the bed material. 

The Gaines and Priestas (2016) data provide insight into the long-term 

(decadal) variability and trends in the bed material at the system-scale. 

Their analysis showed a significant reduction in the amount of gravel in 

the 1989 and 2013 surveys relative to the 1932 sampling. A downstream 

fining in the bed material size was also confirmed, with the average D50 at 

Vicksburg and Natchez being approximately 0.36 mm and 0.3 mm, 

respectively. These values are slightly less than the data at the permanent 

gaging stations but are still firmly in the medium sand range.

The Gaines and Priestas (2016) data also show that there were no 

appreciable amounts of bed material in the very fine sand, silts, and clay 
MRG&P Report No. 32 55

ranges in the 1989 and 2013 data. As Gaines and Priestas (2016) point out, 

it is difficult to assign definitive causal links between the observed bed 

material changes natural and anthropogenic factors. However, one factor 

that warrants further consideration is the increased slopes that have 

occurred in the study reach. As discussed in Section 2.4.4, the channel 

slopes were increased dramatically following the cutoffs in the mid-1930s.

Therefore, the bed material samples in 1932 reflect in a much lower energy 

system than the present-day river, in which the slopes are almost 20% 

higher than they were in 1932. With slope increases of this magnitude, it is 

very conceivable that the finer sediments (very fine sand and finer) are 

being transported through the reach and are therefore not being found in 

the bed in appreciable quantities. 

The Robbins (1977) data used repeated sampling in 14 potamology reaches 

between 1966 and 1974 to establish short-term (inter-annual) variabilities, 

and trends at the reach-scale. Analysis of these data did not reveal any 

sustained downstream decreasing trends in the bed material composition. 

The average D50 for the entire reach in the 1966–1974 time period was 

approximately 0.31 mm.

Taking all these observations together, the results indicate that the bed 

throughout the Vicksburg District is predominantly formed in sand, with 

the D50 being squarely in the medium sand range. However, the bed does 

include significant amounts of gravel at some locations, and this may, 

evidently, be exposed at the surface periodically. 

2.4.7 Channel geometry trends 

Little et al. (2017) conducted a detailed geometric data analysis for the 

Mississippi River from ORCC to St. Louis, MO, or approximately RM 325 

AHP to RM 180 Above Mouth of the Ohio River. This study documented 

the long-term trends in the dimension, pattern, and profile of the LMR 

and Middle Mississippi River. Hydrographic survey data from 1975 to 

2013 were used to determine spatial and temporal variations in channel 

geometry and volume. Trends of geometric change (area, depth, width, 

conveyance, and channel volume) were identified along defined 

geomorphic reaches of the river. The following is a brief summarization of 

the results for the Lake Providence to Old River reach. (For detailed 

information, the reader is referred to Little et al. [2017].)
MRG&P Report No. 32 56

Little et al. (2017) reported a decreasing trend for the period 1975 to 2013 

in channel area, hydraulic depth, conveyance, and channel volume for the 

portion of the study reach from approximate RM 325 to RM 435 in the 

vicinity of Vicksburg. In this study, they examined the pools and crossings 

individually and found the patterns of decreasing trends to be similar for 

both. They attributed these decreases to the general depositional trends in 

this portion of the river. The absence of significant cross-sectional and 

volumetric changes in the reach from approximately Vicksburg (RM 435) 

to Lake Providence (RM 487) led Little et al. (2017) to classify this reach as 

a transition zone from the depositional trends downstream to more stable 

conditions (dynamic equilibrium). 

The cumulative volume change plots developed by Little et al. (2017) help 

visualize the observed trends discussed above. These plots allow the 

spatial extent of the average volumetric change rates over time to be 

readily determined. The cumulative volume change plots referenced to the 

Low Water Reference Plane (LWRP) for the entire Vicksburg District 

reach are shown in Figure 2-35. The study reach is highlighted in the red 

box. A negative slope of the cumulative volume change curve indicates 

deposition (negative cumulative volume change) while a positive slope 

indicates erosion (increasing cumulative volume). If the cumulative 

volume change curve is neither increasing nor decreasing over some time 

period, then this is an indication of dynamic equilibrium. As shown in 

Figure 2-35, the reach from approximately RM 325 to approximately 

RM 425 near Vicksburg exhibited a consistent rate of channel volume 

decrease (negative slope) for the 1975 to 2013 time period, indicating that 

this was a depositional zone during this period. From Vicksburg (RM 435) 

up to Lake Providence (RM 487), the cumulative channel volume change 

fluctuated but remained fairly constant in magnitude, indicating that there 

was no significant net erosion or deposition during this time period.

In summary, the analysis of the channel geometry parameters indicate 

that the river channel in the lower portion of the study reach (RM 325 to 

near Vicksburg RM 435) was in a depositional or aggradational state for 

the 1975 to 2013 time period. The reach upstream of Vicksburg to Lake 

Providence appears to be a transition reach of little to no change in the 

channel geometry. This suggests that this reach may be approaching 

dynamic equilibrium. 
MRG&P Report No. 32 57

Figure 2-35. Cumulative volume change curves for the Vicksburg District. Study reach 

outlined in red. 

2.4.8 Suspended sediment trends 

The reductions in the sediment loads on the LMR have been documented 

by numerous researchers (Keown et al. 1981; Kesel 1988; Horowitz 2010; 

Meade and Moody 2010; Allison et al. 2012; Little and Biedenharn 2014; 

Robbins 1977; and Thorne et al. 2008). The reported decreases in the 

suspended sediment loads typically ranged from approximately 40% to 

85%. A word of caution is warranted here before further discussion of the 

sediment data. The reported reductions are based on measured suspended 

sediment loads at various locations along the river, but the benchmark 

station for most of these studies has been the station at Tarbert Landing, 

LA. Unfortunately, recent revelations by the U.S. Geological Survey 

(USGS) have shown that errors in the laboratory analysis have resulted in 

concentration being significantly higher than they should be. The USGS is 

currently working to correct this historical database. Within the study 

reach, there are two long-term sediment stations at Vicksburg and 

Natchez, which are maintained by the Vicksburg District. Keown et al. 

(1981) utilized these stations in their analysis. As part of the MRG&P 

efforts, these data were recently examined, and numerous problems were 

identified with the database. Some of these issues were corrected, but 

there are still numerous issues that need further examination. 

Unfortunately, these problems do cast a shadow over the reported 
MRG&P Report No. 32 58

sediment studies. However, even though the study results may have been 

compromised by the data issues, it is felt that the overall reduction trends 

that have been reported are reasonable given the magnitude of the changes 

in the basin resulting from the construction of dams in the upper basin, 

land conservation programs in the basin, and the comprehensive 

revetment program along the LMR. 

Before progressing further, another cautionary note is needed concerning 

the interpretation of sediment trends. The reported reductions in 

sediment loads are typically based on total measured suspended sediment 

measurements, which are chiefly comprised of fine material (silts and 

clays). Although a definitive classification of wash load is somewhat 

controversial, it is generally accepted that silts and clays should be 

considered to be wash load throughout most portions of the LMR, 

particularly above Baton Rouge, LA. Therefore, these total suspended 

sediment measurements are not representative of the bed material loads 

in the river. Consequently, the reported reductions in sediment load refer 

to reductions in fine sediment loads and not bed material loads. While 

most studies have focused on the total suspended sediment trends, 

Thorne, et al. (2008) and Little and Biedenharn (2014) did segregate the 

data into fines (silts and clays) and sand loads. Their studies indicated that 

the fine loads at Tarbert Landing had exhibited a decreasing trend since 

the 1950s, but there were no discernible trends in the sand loads. 

In summary, it is reasonable to assume that the fine sediment loads in the 

study reach have decreased significantly over the past 50 to 100 years as a 

result of upstream dam construction, land conservation efforts in the 

basin, and the revetment program. These sediments are critically 

important from an ecological perspective but are less important from a 

morphological perspective. Although the fine sediment loads have been 

reduced, there are no data that suggest a reduction in the coarse sediment 

(bed material loads). In fact, it is more likely that the bed material loads 

are actually higher today than 50 years ago due to the increased channel 

slopes through the study reach (see section 2.4.4). 
MRG&P Report No. 32 59

3 Summary

A summary of the geomorphic trends in the study reach is presented here 

in three sections: (1) Pre-cutoff Period; (2) Cutoff Period; and (3) Postcutoff Period.

3.1 Pre-cutoff Period (early-1800s to 1929) 

The LMR between the early-1800s to the late-1870s was undergoing 

significant morphological changes as a result of various factors including 

the New Madrid Earthquakes, clearing of the streambanks for woodburning steamboats and agriculture. These instabilities were evidenced by 

the extreme width increases (approximately 91% between 1821 and 1880) 

and bar and island building. Many of the early navigation problems on the 

river were aggravated by the caving streambanks, bar building, and 

channel widening, which created a negative impression of the river system 

just as it was becoming the main navigation artery for the country. 

Levee building in the 1800s was generally localized and discontinuous. 

Prior to levees, the LMR valley below Cairo, IL, was characterized by 

numerous distributary channels that carried high as well as some lower 

flows into various lowland basins. Major floods in the mid- to late-1800s 

caused severe damage to some of these early levees, which led to the 

development of the MRC in 1879. The MRC considered various options to 

provide dependable navigation within the LMR. The approaches 

considered included levees, reservoirs, outlets, and cutoffs. After 

considerable debate, the MRC settled on a levees-only policy. This 

approach was based on the assumption that the construction of levees 

would deepen the channel, thereby providing adequate navigation depths.

The MRC also adopted a no-cutoff program in 1884 with the goal of 

preventing natural cutoffs from occurring. This was accomplished by 

implementing bank stabilization in areas where a cutoff was considered 

likely. As a result of this policy, the Waterproof cutoff (RM 377), which 

occurred naturally in 1884, was the last meander cutoff allowed until 1929 

when the MRC decided to allow the Yucatan cutoff just south of Vicksburg 

to develop. 

The river in the post-1880s was still a dynamic river; although compared 

to the pre-1880s period, the rates of change had slowed considerably. 
MRG&P Report No. 32 60

Although data are sparse in this period, it does appear, based on specific 

gage records and historical references (Winkley 1977), that the river in the 

study reach was slightly aggradational during this period. 

The 1927 flood was a galvanizing event for the valley and indeed the entire 

nation. As a result of the 1927 flood, the MRC recognized that the 

levees-only approach, which lasted for 50 years, was going to have to be 

revisited. With the FCA of 1928, the MR&T was initiated. The MR&T 

produced a massive, comprehensive system for flood control and channel 

stabilization that includes levees, channel modifications, and floodways as 

well as tributary reservoirs and other basin improvements.

3.2 Cutoff Period (1929–1942) 

The advantages and disadvantages of artificial cutoffs on the Mississippi 

River had been debated without consensus by river engineers since the 

mid-1880s. In 1929, the first cutoff since 1884 was allowed to occur at the 

Yucatan Bend downstream of Vicksburg as part of a study to evaluate the 

response of the river to a cutoff. After monitoring the Yucatan cutoff for 

2 years, the MRC initiated the cutoff program in 1931. Through this 

program, the USACE constructed 14 artificial cutoffs and allowed 2 natural 

cutoffs (Yucatan and Leland) to develop between 1929 and 1942 on the 

LMR. Seven cutoffs were constructed in the study reach between Lake 

Providence and just south of Natchez. These cutoffs shortened the reach 

by approximately 62 miles. The cutoffs have had a substantial geomorphic 

impact on the river compared to any other natural or anthropogenic factor 

in the past several hundred years. 

During the cutoff period between 1929 and 1942, the dominant response 

in the study reach was channel degradation and slope increase. The stage 

reductions due to degradation resulting from the cutoffs were in the range 

of 10 to 12 ft at Lake Providence and Vicksburg. Farther downstream at St. 

Joseph and Natchez, the stage reductions were slightly less, in the 5 to 7 ft 

range. The meander cutoffs triggered tremendous slope increases in the 

study reach. Initial increases in water surface slopes ranged from 

approximately 25% to 45%. These increases in slope increased sediment 

transport capacity significantly, resulting in channel degradation 

throughout the reach. 
MRG&P Report No. 32 61

3.3 Post-cutoff Period (1943 to Present) 

3.3.1 Channel improvements features 

The period from the mid-1940s through the mid-1960s was one of 

significant adjustments on the LMR as the river responded to the cutoffs. 

The cutoffs significantly increased the channel slope and stream power in 

the system. As a consequence of these changes, bank erosion increased as 

the channel attempted to regain channel length. It was during this initial 

period following the cutoffs that an aggressive revetment program was 

initiated in an attempt to stabilize channel alignments. By the mid-1960s, 

most of the major meander bends had been stabilized, thereby fixing the 

alignments in place. The revetment program not only provided for an 

improved and stable channel alignment but also significantly reduced the 

sediment loading to the river from streambank erosion. The average annual 

bank caving volumes were reduced from approximately 350,000,000 cy per 

year in the pre-revetment period to only approximately 30,000,000 cy per 

year by the early-1970s based on Winkley 1974 estimation of accumulated 

annual bank caving volumes. Although this is a reduction in sediment 

delivery of approximately 90%, further studies are needed to determine 

what percentage of this material would be considered wash load or bed 

material load in the river system. Note that with the continuation of the 

revetment program since the 1970s, the volume of sediment delivered from 

bank caving has essentially been eliminated.

The cutoffs imposed a new alignment on the channel system that altered 

the historic crossing patterns in the river. These alignment changes 

combined with the increased sediment delivery from upstream resulted in 

increased maintenance dredging throughout the system, which peaked in 

the late-1970s. After 1970, the amount of maintenance dredging began a 

long-term decreasing trend as a result of two factors: (1) the revetment 

program imposed much better planform alignments with more orderly 

pool-crossing patterns and (2) the construction of training structures 

(dikes). The dikes are, arguably, the more significant of these two factors, 

as evidenced by the inverse relation between the amount of dredging and 

the cumulative length of constructed dikes. 

3.3.2 Channel stability 

The study reach is responding in an expected manner following a series of 

meander cutoffs. At the upstream end of the reach, represented by the 
MRG&P Report No. 32 62

Lake Providence gage, the specific gage trends have been relatively stable 

since the early 1950s. Moving farther downstream, the gages (Vicksburg, 

St. Joseph, and Natchez) become progressively more aggradational. This 

suggests that the reach from Lake Providence to Vicksburg may be a 

transition reach between dynamic equilibrium and the aggradation trends 

that exists farther downstream. The analysis of channel geometry 

parameters (area, depth, conveyance, and volume) between 1975 and 2013 

support these same trends.

Flow-adjusted stage duration curves were developed to provide 

supplementary information that is critically important to ecological and 

geomorphic assessments (particularly sediment transport capacity) but 

also assists in developing a better understanding of flooding potential. 

These flow-adjusted stage duration curves indicate that the percentage of 

time that the flood stage is equaled or exceeded at Lake Providence and 

Vicksburg is approximately 6% compared to approximately 12% to 15% in 

the Pre-cutoff Period. Thus, the amount of time that these overbank areas 

are flooded is less today than in the Pre-cutoff Period. At Natchez, the 

flood stage elevation is presently equaled or exceeded approximately 9% of 

the time as compared to approximately 5% of the time in the pre-cutoff 

Period. 

As previously noted, the meander cutoff significantly increased the 

channel slopes (25% to 45%). Although these slopes have decreased from 

their peak conditions in the 1940s, the present-day slopes in the study 

reach are still higher (generally, approximately 17%) than in the Pre-cutoff 

Period. 

3.3.3 Bed material trends 

Analysis of bed material data indicates that the bed throughout the study 

reach is predominantly formed of sand, with the D50 being squarely in the 

medium sand range. The D16 fluctuates within the fine sand range while 

the D84 is typically in the lower end of the coarse sand size classes. 

Long-term (decadal) scale analysis by Gaines and Priestas (2016) showed 

a significant reduction in the amount of gravel in the 1989 and 2013 

surveys relative to the 1932 sampling. Although the amount of gravel 

based on bed material samples has decreased, visual observations confirm 

that gravel is present throughout the study reach at various locations. 

While these gravels may comprise a small fraction of the total bed 
MRG&P Report No. 32 63

material, they are significant from a morphological and ecological 

perspective. It is also important to recognize that these gravel features may 

be exposed and covered by sands periodically.

The Gaines and Priestas (2016) analysis also showed that while the 1932 

bed did contain sediments in the very fine sand, silts, and clay ranges, 

these fine sediments were not found in any appreciable amounts in the 

1989 and 2013 data. It is difficult to assign definitive causal links between 

the observed bed material changes natural and anthropogenic factors. 

However, one factor that warrants further consideration is the increased 

slopes that have occurred in the study reach as a result of the cutoffs. 

Therefore, the bed material samples in 1932 reflect a much lower energy 

system than the present-day river in which the slopes are almost 20% 

higher than they were in 1932. With slope increases of this magnitude, it is 

very conceivable that the finer sediments (very fine sand and finer) are 

being transported through the reach acting as wash load and are therefore 

not being found in the bed in appreciable quantities. 

3.3.4 Sediment load trends 

Fine sediment loads have been reduced significantly in the study reach over 

the past 50 to 100 years as a result of upstream dam construction, basinwide land conservation efforts, and the comprehensive revetment program 

on the LMR. Although the fine loads have been reduced, it appears that the 

bed material loads may, in fact, be greater than they were in the Pre-cutoff 

Period due to the increased slopes resulting from the cutoffs.
MRG&P Report No. 32 64

4 Recommendations

This investigation provided valuable insight into the morphologic 

character of the study reach. However, there are still many technology 

gaps that exist, not only for the study reach but for the entire LMR. The 

following is a list of MRG&P efforts that are recommended to further the 

understanding of this complex river system. 

1. Eco-Potamology Reaches. This type of assessment, where a study 

reach is selected for a detailed geomorphic study, needs to be expanded 

to other reaches of the LMR. In the 1960s and 1970s, the Vicksburg 

District divided its district into 25 potamology study reaches where 

detailed data collection and geomorphic and river engineering 

investigations were conducted on an annual basis. This was a very 

effective program that produced valuable findings for the LMR. Given 

the present-day funding levels as compared to the 1960s and 1970s, it 

is doubtful that the entire LMR could be divided into distinct 

potamology reaches. However, based on the current knowledge of the 

system, the river could be divided into representative reaches where 

detailed analyses could be conducted and then expanded to the 

remainder of the system. In contrast to the original potamology 

reaches, these new reaches would also include an ecological 

component. The first step in this effort would be to create a team that 

would identify the appropriate study reaches and the types of analysis 

that would be required.

2. Long-Term Geomorphic Tool. This report illustrated that the 

morphologic response of the LMR is complex and must be considered 

over long time scales (multiples of decades or longer). Geomorphic 

studies such as this capture the historical morphological response of 

the system and provide the framework for modeling future scenarios. 

There is a plethora of existing deterministic river engineering models 

that focus on short-term (50 years or fewer) investigations of 

hydraulics, flooding, habitats and channel morphological response, 

typically within reaches of interest and over project-design time-scales. 

The ability to consider a wide range of future-year scenarios in a 

morphological tool that can be run quickly and over annual, decadal, 

and centennial time-scales, and bounded by levels of confidence on 

estimates, will undoubtedly provide a major advancement in 

technology for river engineers and scientists involved in the sustainable 

management of large rivers such as the LMR. The U.S. Army Engineer 
MRG&P Report No. 32 65

Research and Development Center has recently initiated the 

development of a morphological tool capable of long-term forecasting 

of river channel evolution under a wide range of possible future 

scenarios. This type of tool could be extremely valuable as a long-term 

planning and engineering tool for LMR.

3. Sediment Budget. A sediment budget was recently completed for the 

LMR, which focused on the measured suspended sediment data. While 

this is a valuable contribution, it only tells part of the story of the 

Mississippi River sediment loads because it only addresses the fine 

loads (wash loads) in the system. The delivery of the bed material is a 

much more complicated process but is one that needs to be fully 

investigated. This is a critical piece of information because most of the 

researchers who have published studies in the journals have ignored or 

misrepresented the role of the bed material loads. This type of study 

would use much of the recently developed results on slope, stream 

power, specific gage, channel geometry, suspended sediment data, and 

bed material samples. It would also need to expand on the estimates of 

sediment supply from bank caving reported herein to identify how 

much of this bank material would be delivered as wash load or bed 

material load to the system. It would then be necessary to weave all this 

information together to establish the historical and present-day 

linkages between the sources, pathways, and sinks in the system. 

Specifically, this would address the following: (1) the major sediment 

sources in the system and how they have changed over time; (2) the 

manner in which these sediments have been delivered through the 

pathways (channel systems), either as bed material or wash load; and 

(3) the depositional (sink) areas and how they have changed over time. 

The result would be a conceptual sediment budget that would be 

extremely valuable in understanding the historical behavior in the 

system, identifying the impacts of construction features (revetments, 

dams, etc.) as well as serving to better understand the delivery of 

sediments through the present-day system. 

4. Innovative Daily Stage Recorders. One of the most useful data 

sets available on the river is the daily stages, which can be used to 

produce daily water surface slopes. Water surface slopes reflect the 

energy in the channel system and therefore provide valuable insight 

into the morphological character of the channel system. Unfortunately, 

the gaging stations on which these data are based are generally located 

approximately 50 miles apart. For this reason, a study needs to be 

conducted to identify more cost-effective methods to obtain daily stage 
MRG&P Report No. 32 66

data at a much closer spacing. For example, recent studies of dike 

notching at Coffee Point resulted in the development of a camera 

system that shows promise as a tool for capturing daily stage readings. 

5. Dike Impacts. River training structures (dikes) have been used on the 

LMR as a navigation aid since the 1960s. These structures have proven 

extremely effective in reducing the maintenance dredging along the 

river; however, concerns have been raised about potential increases in 

flood stages as a result of these structures. Recent studies (empirical and 

numerical) have been conducted on the 21 dike systems in the Cobb data 

base. These studies provided considerable insight into the impacts of 

dikes on channel morphology and flood elevations. However, much work 

is still needed to fully understand the hydraulic and morphological 

impacts of these structures. Specifically, a new data base (separate from 

the Cobb data base) needs to be developed and analyzed. Additional dike 

systems also need to be analyzed with Adaptive Hydraulics to 

complement the empirical studies. 

6. Characterization of Gravel in the LMR. Gravel deposits in the 

LMR play an important role with respect to geomorphology and 

provide spawning habitat for some fish species, including the 

endangered pallid sturgeon. Recent studies have begun the process to 

identify locations of gravel along the river. However, sampling over a 

period of years is needed to acquire a good estimate of the spatial 

extent of these gravel deposits. Additionally, field data collection is 

needed at selected locations to field-verify the analytical results, 

characterize the gravel (mineralogy and size gradations), and obtain an 

estimate of thickness of gravel deposits. 

7. Geologic Outcrops. A recent MRG&P report (Biedenharn et al. 

2018) documented the presence of numerous geologic outcrops 

throughout the LMR. These outcrops may play an important role in the 

future morphological character of the river. For this reason, additional 

studies are needed to (1) more definitively identify the locations and 

characteristics of these outcrops and (2) develop a better 

understanding about how these outcrops would actually affect the 

morphological trends in the river.

8. Floodplain Impacts. The stage duration data developed in this study 

revealed spatial and temporal variations in the degree of inundation of 

the floodplain in the study reach. Recent numerical model studies have 

also indicated the importance of these floodplain features with respect 

to flood elevations. Further studies are needed to gain a better 
MRG&P Report No. 32 67

understanding of the channel and floodplain interaction, particularly 

as it relates to flood elevations.

9. Dike Notching Studies. Dike notching is continuing throughout the 

LMR. A detailed study of the newly notched Coffee Point dikes just 

began. The morphological and ecological impacts of dike notching are 

not fully understood. For this reason, consideration should be given to 

conducting detailed morphologic and ecological studies at more dike 

notching sites throughout the LMR. These studies should include both 

empirical and numerical analyses. 

10. Slope and Stream Power Studies. Most all the sediment studies 

reported in the literature over the past 30 years have indicated 

significant reductions (50% to 85%) in sediment loads in the river. In 

fact, this is the generally held belief by most people in the valley. 

However, as with most issues related to the river, this is oversimplification of a complex process. This report of the Lake Providence 

to Old River Reach has shown that water slopes are still much greater 

today than prior to the cutoffs. This suggests that the bed material 

loads in the river may be much higher than they were 60 years ago. As 

noted in this report, these increased slopes may be a contributing 

factor to the reductions in the amount of fines found in the present-day 

river compared to the river in 1932. Further studies are needed to 

better understand these slope and stream power trends and the 

potential implications to the sediment delivery in the LMR. 

11. Bed Material Sampling. The Lake Providence to Old River study 

highlighted the bed material trends in the study reach and showed that 

there is considerable spatial and temporal variability in these data. Bed 

material is a critical component in numerical modeling and 

geomorphic studies. Because of this, consideration should be given to 

the development of a comprehensive bed material sampling plan along 

the LMR. Perhaps this could be incorporated into the Eco-Potamology 

Reach studies mentioned in number 1.
MRG&P Report No. 32 68

References

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Donaldsonville, LA, as Revealed by Specific Gage Records. Report No. 10. 

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Geology on the Morphologic Response of the Lower Mississippi River. Report 

No. 17. Vicksburg, MS: U.S. Army Engineer and Development Center. 

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and Navigation. Volume No. 1. Vicksburg, MS: U.S. Army Corps of Engineers. 

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MRG&P Report No. 32 69

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MRG&P Report No. 32 70

Unit Conversion Factors

Multiply By To Obtain 

acres 4,046.873 square meters

acre-feet 1,233.5 cubic meters

cubic feet 0.02831685 cubic meters

cubic inches 1.6387064 E-05 cubic meters

cubic yards 0.7645549 cubic meters

feet 0.3048 meters

gallons (U.S. liquid) 3.785412 E-03 cubic meters

inches 0.0254 meters

miles (U.S. statute) 1,609.347 meters

square feet 0.09290304 square meters

square miles 2.589998 E+06 square meters
MRG&P Report No. 32 71

Acronyms and Abbreviations

AHP Above Head of Passes

cfs cubic feet per second

cy cubic yards

FCA Flood Control Act

ft foot/feet

in. inch

IQR interquartile range

LMR Lower Mississippi River

mm millimeter

MRC Mississippi River Commission

MRG&P Mississippi River Geomorphology and Potamology Program

MRT Mississippi River and Tributaries

MVD Mississippi Valley Division

ORCC Old River Control Complex

RM river mile

USACE U.S. Army Corps of Engineers

USGS U.S. Geological Survey
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data 

sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect

of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations

and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of

law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE 

April 2020

2. REPORT TYPE

Final Report

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Lake Providence to Old River Geomorphology Assessment

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Waleska Echevarria-Doyle and David S. Biedenharn and Charlie D. Little Jr.

5d. PROJECT NUMBER

No. 470711

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND 

ADDRESS(ES)

Coastal and Hydraulics Laboratory

U.S. Army Engineer Research and 

Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

Mendrop Engineering Resources, LLC

3530 Manor Drive, Suite 2

Vicksburg, MS 39180

8. PERFORMING

ORGANIZATION REPORT

NUMBER

MRG&P Report No. 32

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

U.S. Army Corps of Engineers, Mississippi Valley Division

Mississippi River Geomorphology & Potamology Program

1400 Walnut Street

Vicksburg, MS 39180

10. SPONSOR/MONITOR'S ACRONYM(S)

USACE MVD

11. SPONSOR/MONITOR'S

REPORT NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release; distribution is unlimited.

13. SUPPLEMENTARY NOTES

14. ABSTRACT

This report integrates information from previous geomorphic studies coupled with new analysis to provide a comprehensive geomorphic 

characterization of the Lake Providence (River Mile [RM] 487.2 Above Head of Passes [AHP]) to Old River Control Complex, (RM 317 

AHP) reach from the early-1800s to present. Individual components of this study included the following: historical geomorphic studies, 

development of an events timeline, specific gage records, stage and flow duration trends, trends in water surface slopes, bed material 

studies, suspended sediment data, channel geometry data, and effects of channel improvement features (cutoffs, dike, revetment, and 

dredging). These individual assessments were consolidated to develop an overall assessment of how the study reach has evolved since the 

early-1800s.

15. SUBJECT TERMS 

Lake Providence (La.)—Geomorphology, Mississippi River—Alluvial plain, River channels

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

ABSTRACT

SAR

18. NUMBER 

OF 

PAGES

80

19a. NAME OF RESPONSIBLE PERSON

Waleska Echevarria-Doyle a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

601- 634-4373

Standard Form 298 (Rev. 8/98) 

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