MISSISSIPPI RIVER

Actions Are Needed to 

Help Resolve 

Environmental and 

Flooding Concerns 

about the Use of River 

Training Structures

Report to Congressional Requesters

December 2011

GAO-12-41

United States Government Accountability Office

GAO
United States Government Accountability Office

Highlights of GAO-12-41, a report to 

congressional requesters 

December 2011 

MISSISSIPPI RIVER

Actions Are Needed to Help Resolve Environmental 

and Flooding Concerns about the Use of River 

Training Structures 

Why GAO Did This Study

For more than 130 years the U.S. 

Army Corps of Engineers (Corps) has 

used dikes to “train” the Mississippi 

River channel and maintain adequate 

depth for navigation. The Corps relies 

heavily on these structures—including 

some with more recent designs—in the 

Middle Mississippi, between the 

confluences of the Missouri and Ohio 

Rivers. Over the past few decades, 

some researchers have raised 

concerns about the structures’ 

cumulative impacts on the environment 

and the height of floodwaters. For the 

Corps’ river training structures in the 

Middle Mississippi, GAO was asked to 

examine (1) key requirements and 

directives that govern their use, (2) 

how the Corps has addressed key

environmental requirements, (3) the 

extent to which their hydrologic and 

environmental impacts are monitored, 

and (4) concerns that researchers 

have raised about hydrologic and 

environmental impacts and how the 

Corps has responded. GAO reviewed 

relevant laws, regulations, agency 

documents, and key studies, and 

interviewed Corps officials and other 

researchers and experts.

What GAO Recommends

GAO recommends that the Department 

of Defense direct the Corps to prepare 

an environmental assessment for river 

training structures in the Middle 

Mississippi, obtain required water 

quality permits for new structures, and 

conduct physical and/or numerical 

modeling to assess the cumulative 

impact of structures on flood heights. 

The department generally agreed with 

these recommendations.

What GAO Found

The Corps’ authority to use river training structures in the Mississippi River 

comes from several Rivers and Harbors Acts, which collectively require the 

Corps to maintain a 9-foot navigation channel in the river, and several Water 

Resources Development Acts, which also authorize projects in the Corps’ civil 

works program. In using these structures, the Corps must comply with federal 

environmental laws such as the National Environmental Policy Act (NEPA), the 

Clean Water Act (CWA), and the Fish and Wildlife Coordination Act, as well as 

applicable state requirements. The Corps also has its own guidance that district 

offices are to use when planning, designing, and building river training structures.

In using river training structures in the Middle Mississippi, the Corps has 

addressed some environmental requirements but not all. For example, the Corps 

has undertaken consultation with other agencies in accordance with the Fish and 

Wildlife Coordination Act. However, the Corps has not complied with certain

requirements of NEPA or CWA. For example, in constructing new river training 

structures the Corps has continued to rely on an environmental impact statement 

prepared in 1976. Even though significant changes have occurred in the river 

and in the Corps’ design of its structures, it has not prepared the additional 

analyses required by NEPA to assess whether further environmental impact

analysis is warranted. Similarly, the Corps has not obtained the appropriate CWA

permits or state water quality certifications for river training structures as 

required.

The Corps routinely assesses some of the hydrologic impacts of its Middle 

Mississippi training structures but not the environmental impacts. For example, 

the Corps has performed physical and numerical modeling to assess the 

hydraulic impacts of proposed structures prior to construction, and it has routinely 

monitored the hydrologic impacts after construction through data collection and 

observation of the river’s surface elevation (known as river stage). The Corps has 

also analyzed the relationship between river stage and the volume and speed of 

river flow (known as discharge), looking for rising or falling trends that might

indicate whether the structures are having a cumulative effect during floods. The 

Corps, however, does not routinely monitor the environmental impacts of its 

structures after construction, although it has conducted studies to monitor 

impacts on certain endangered species, such as the pallid sturgeon, and on fish 

and wildlife habitats. 

Researchers have highlighted two key areas of concern with river training 

structures—degradation of river habitat and increased flooding. Although the 

Corps has attempted to address the habitat concerns, the agency and some

researchers disagree over flooding concerns. In response to the habitat 

concerns, the Corps has modified some river training structures to increase flows 

between them, and has begun installing newer types of structures in select

locations to promote aquatic habitat. Regarding flooding, the Corps disagrees 

with the concern that its structures have led to an increase in river stage during 

high flow events, and has undertaken various studies that support its position. 

Nevertheless, significant professional disagreement remains over this issue, 

which many experts believe could be resolved through additional physical and/or

numerical modeling. 

View GAO-12-41. For more information, 

contact Anu K. Mittal at (202) 512-3841 or 

mittala@gao.gov. 
Page i GAO-12-41 Mississippi River 

Letter 1 

Background 4

River Training Structures Must Adhere to Key Federal and State 

Requirements and Corps Guidance 11

The Corps Has Addressed Some but Not All of the Environmental 

Requirements for River Training Structures 20

The Corps Has Routinely Monitored the Hydrologic Impacts of 

River Training Structures after Construction, but Has Not 

Routinely Monitored Their Environmental Impacts 27

The Corps Has Modified Structures over Environmental Concerns 

but Disagrees That They Exacerbate Floods 37

Conclusions 47

Recommendations for Executive Action 48

Agency Comments and Our Evaluation 49

Appendix I Objectives, Scope, and Methodology 52

Appendix II Comments from the Department of Defense 56

Appendix III GAO Contact and Staff Acknowledgments 59

Figures

Figure 1: Management Area of the Six Districts within the Corps’ 

Mississippi Valley Division 5

Figure 2: Wing Dikes in the Middle Mississippi 6

Figure 3: Simplified Illustration of a River Cross-Section before and 

after Installing a Wing Dike 7

Figure 4: Illustration of Submerged Bendway Weirs on the Outside 

of a River Bend 8

Figure 5: Chevrons in the St. Louis Harbor 9

Figure 6: Photograph of a Small-Scale Physical Model 29

Figure 7: 1993 Rating Curve for the St. Louis Gauge 33

Figure 8: Specific Gauge Analysis for the St. Louis Gauge 34

Figure 9: Aerial and Close-up Views of Notched Wing Dikes in the 

Mississippi River 39

Figure 10: Close-up View of a Chevron in the St. Louis Harbor 40

Contents
Page ii GAO-12-41 Mississippi River 

Abbreviations

Corps U.S. Army Corps of Engineers

EA environmental assessment

EIS environmental impact statement

FONSI finding of no significant impact

FWS U.S. Fish and Wildlife Service

NEPA National Environmental Policy Act

NESP Navigation and Ecosystem Sustainability Program

SEIS supplemental environmental impact statement

USGS U.S. Geological Survey

WRDA Water Resources Development Act 

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Page 1 GAO-12-41 Mississippi River 

United States Government Accountability Office 

Washington, DC 20548 

December 9, 2011

The Honorable Timothy Bishop

Ranking Member

Subcommittee on Water Resources 

 and the Environment

Committee on Transportation and Infrastructure

House of Representatives

The Honorable Jerry Costello

Ranking Member

Subcommittee on Aviation

Committee on Transportation and Infrastructure

House of Representatives

The Mississippi River has long been a prime contributor to the nation’s 

physical and economic growth. As it flows from northern Minnesota south 

to the Gulf of Mexico, the river carries a significant volume of commerce, 

supplies water to the cities and industries along its course, and sustains 

vital ecosystems in the water and on shore. However, throughout its 

history—and most recently in 2011—the river has also been a source of 

major floods that have caused widespread damage to communities in its 

floodplain.1

 

1

A floodplain is a lowland area adjacent to inland and coastal waters that is subject to a 1 

percent or greater chance of flooding in any given year. 

Through legislation, Congress has directed the U.S. Army 

Corps of Engineers (Corps) to support Mississippi River navigation, 

provide flood protection, and restore the river’s environment. To fulfill its 

navigation mission, the Corps employs a variety of structures designed 

primarily to “train” the Mississippi River—diverting its flow of water and 

sediment to scour the river bottom in order to maintain an adequate 

navigation channel. The Corps relies heavily on these river training 

structures in the Middle Mississippi, which is a 195-mile stretch that 

extends from where the Missouri River joins the Mississippi River above 

St. Louis, Missouri, to where the Ohio River enters the Mississippi River 

at Cairo, Illinois. The Middle Mississippi is an integral part of a river 

system that handles nearly 500-million tons of waterborne commerce 

annually.

 
 

Page 2 GAO-12-41 Mississippi River 

The primary purpose of the Corps’ river training structures is to maintain 

the channel’s depth when water flow is low, but some researchers 

contend that the structures have unintended consequences during higherflow events, in particular those resulting in floods. Studies published in the 

1970s discussed the idea that the accumulation of hundreds of river 

training structures in the Middle Mississippi might unintentionally cause 

large volumes of water to “back up” in the river, thus increasing the height 

of flood waters. A recent series of floods in the St. Louis region in 2008 

rekindled this issue. In support of their claims, some researchers have 

analyzed trends over time between the height of the water’s surface (the 

river’s “stage,” commonly measured in feet) and the volume and speed of 

its flow (the river’s “discharge,” commonly measured in cubic feet per 

second). In addition to these concerns about the structures’ hydrologic 

effects,2

In this context, you asked us to report on the Corps’ use of river training 

structures in the Middle Mississippi. Our objectives were to examine (1) 

key requirements and directives that govern the Corps’ use of river 

training structures, (2) how the Corps has addressed key federal and 

state environmental requirements in the use of river training structures,

(3) the extent to which the Corps has monitored the hydrologic and 

environmental impacts of river training structures, and (4) concerns that 

researchers have raised about the hydrologic and environmental impacts 

of the Corps’ river training structures and how the Corps has responded 

to these concerns.

critics of the structures claim that the Corps’ assertions of 

environmental benefits produced by certain structures are unproven and 

not worth the risk of higher flood stages. In contrast, the Corps and other 

researchers contend that the structures produce the desired navigational 

and environmental benefits without increasing flood risk or severity.

To address the first objective, we reviewed relevant provisions in key 

federal and state laws, regulations, and guidance that govern the Corps’ 

use of river training structures. We determined these laws, regulations, 

and guidance to be key because they authorize construction of river 

training structures and relate to flooding and environmental impacts. We 

conducted interviews with Corps officials—specifically, agency engineers 

and attorneys, as well as biologists and other scientists. Our work 

 

2

For the purposes of this report, hydrologic effects include impacts associated with the 

movement and distribution of water, including flooding.
 

Page 3 GAO-12-41 Mississippi River 

focused on the Corps’ St. Louis District and its management of the Middle 

Mississippi. We also interviewed officials from the Corps’ national 

headquarters, its Mississippi Valley Division, and the division’s other five 

districts. To address the second and third objectives, we reviewed the 

Corps’ various assessments of its river training structures and compared 

them to the requirements we identified. We examined project 

documentation to determine how the Corps addressed these 

requirements. We also obtained in writing the Corps’ legal views on how it 

has complied with National Environmental Policy Act (NEPA)3

We conducted this performance audit from September 2010 through 

December 2011 in accordance with generally accepted government 

auditing standards. Those standards require that we plan and perform the 

requirements with respect to its river training structures constructed under 

the project to operate and maintain the navigation channel. In addition, 

we interviewed officials with the U.S. Fish and Wildlife Service (FWS), 

state resource agencies, and several nongovernmental organizations to 

obtain their views. To address the fourth objective, we conducted a 

detailed literature review of scientific periodicals and governmentsponsored research on the effects of river training structures. We used 

this review—along with interviews with officials from the Corps, FWS, the 

U.S. Geological Survey (USGS), and state resource agencies, as well as 

other researchers not affiliated with these parties—to compile the key 

concerns that have been raised about the structures’ hydrologic and 

environmental impacts. We then solicited the Corps’ response to the 

concerns identified by non-Corps parties. We also conducted structured 

interviews with a group of 16 experts in the fields of river engineering and 

water resources to obtain their comments on these concerns and to 

identify ways in which they might be resolved. We identified these experts 

through recommendations made during our interview process and by 

soliciting recommendations from relevant organizations, such as the 

National Research Council’s Water Sciences and Technology Board and 

the American Society of Civil Engineers. A more detailed description of 

our scope and methodology is presented in appendix I.

 

3

Pub. L. No. 91-190, 83 Stat. 852 (1970), codified as amended at 42 U.S.C. §§ 4321-4347 

(2011). Under NEPA, federal agencies must assess the effects of major federal actions—

those they propose to carry out or to permit—that significantly affect the environment. 

NEPA has two principal purposes: (1) to ensure that an agency carefully considers 

detailed information concerning significant environmental impacts and (2) to ensure that 

this information will be made available to the public.
 

Page 4 GAO-12-41 Mississippi River 

audit to obtain sufficient, appropriate evidence to provide a reasonable 

basis for our findings and conclusions based on our audit objectives. We 

believe that the evidence obtained provides a reasonable basis for our 

findings and conclusions based on our audit objectives.

The Corps first became responsible for supporting Mississippi River 

navigation under an act passed by Congress in 1824. Within the Corps, 

responsibility for managing the river rests with its Mississippi Valley 

Division, headquartered in Vicksburg, Mississippi. The division’s St. Louis 

District manages about 300 miles of the river, including the Middle 

Mississippi. For planning purposes, the river as a whole is divided into 

two parts: (1) the Upper Mississippi, which extends from northern 

Minnesota to the Ohio River confluence and includes the Middle 

Mississippi; and (2) the Lower Mississippi, which begins at the Ohio River 

confluence and empties into the Gulf of Mexico. Figure 1 shows the 

boundaries of the six Corps districts in the Mississippi Valley Division, as 

well as the Upper, Middle, and Lower Mississippi. 

Background
 

Page 5 GAO-12-41 Mississippi River 

Figure 1: Management Area of the Six Districts within the Corps’ Mississippi Valley 

Division

River training structures have been used in the Middle Mississippi for 

more than 170 years; for example, they began to appear in the St. Louis 

area in the 1830s. However, significant construction in the Middle 

Mississippi commenced with the increased involvement of the federal 

government in the latter part of the 19th century. From 1879 to 1930, 

Congress passed a series of acts authorizing the Corps to create and 

maintain a navigation channel through the Mississippi River of sufficient 

depth to support year-round navigation. In the Middle Mississippi, the 

Corps’ “Regulating Works Project” provides for agency activities that 

support the operation and maintenance of the authorized channel, such 
 

Page 6 GAO-12-41 Mississippi River 

as dredging sediment from the bottom of the channel and constructing 

river training structures to better shape it for navigation.

The Corps typically builds river training structures by piling large stones 

on the river bottom in various configurations. The most common type of 

structure is a wing dike (also known as a wing dam or spur dike), which 

extends from one riverbank at an angle roughly perpendicular to river 

flow. See figure 2 for a photograph of wing dikes in the Middle 

Mississippi.

Figure 2: Wing Dikes in the Middle Mississippi

Note: Arrows indicate locations of wing dikes in the photograph. 

According to the Corps, wing dikes have been used on the Middle 

Mississippi in various forms since at least 1838. They are designed to 

maintain a navigable channel by concentrating river flow in the channel. 

This focuses the water’s energy and suspended sediment, scouring the 

river bottom and thereby deepening the channel. These structures are 

able to maintain the navigation channel because the Mississippi River is 

an alluvial valley, which means that the river bottom is made of soil and 

sand rather than rock and stone. Consequently, the riverbed is constantly 

shifting in response to the force of water and suspended sediment. River 
 

Page 7 GAO-12-41 Mississippi River 

training structures harness these forces and redirect them into the 

navigation channel. This allows barges to travel the river throughout the 

year, even when the river is low, while reducing the amount of dredging 

that is required to maintain the channel’s authorized depth. Figure 3 

illustrates the scouring effect a wing dike has on the river bed, resulting in 

a deeper navigation channel.

Figure 3: Simplified Illustration of a River Cross-Section before and after Installing a Wing Dike

In the last 20 years the Corps has begun to use new types of structures, 

known as bendway weirs and chevrons, to further train the Middle 

Mississippi. Since 1990, the Corps has used bendway weirs, which are 

specialized dikes placed on the outside of a river bend. These structures 

are angled upstream and are positioned entirely under water so that 

navigation traffic may pass over them. They are designed to redirect flows 

to the inside of the bend, thus widening the navigation channel and 

preventing it from migrating toward the outside of the bend. See figure 4 

for an illustration of bendway weirs.
 

Page 8 GAO-12-41 Mississippi River 

Figure 4: Illustration of Submerged Bendway Weirs on the Outside of a River Bend

Note: Arrows indicate locations of bendway weirs in the illustration. 

After 2000, the Corps introduced chevrons—arch-shaped dikes placed 

with their curved arches pointed upstream. They are designed to split the 

river’s downstream flow, thereby scouring the main navigation channel 

while creating a secondary channel near the bank. According to Corps 

documents and other studies, chevrons have the added benefit of 

promoting different kinds of aquatic habitat around the structures and in 

the secondary channels. See figure 5 for a photograph of three chevrons 

in the St. Louis harbor.
 

Page 9 GAO-12-41 Mississippi River 

Figure 5: Chevrons in the St. Louis Harbor

Note: Arrows indicate locations of chevrons in the photograph. 

Like chevrons, wing dikes can be built as a series of similar structures, 

known as a dike field, and are typically erected no higher than half 

bankfull—the stage when water is halfway up the river’s banks. This is 

approximately 15 feet on the St. Louis gauge, with flood stage at St. Louis 

beginning at 30 feet. Bendway weirs are placed lower in the channel, and 

according to the Corps, are always submerged.

According to Corps documents, there are currently more than 1,375 wing 

dikes, bendway weirs, chevrons, and similar structures4

 

4

This total includes other types of river training structures. For example, the St. Louis 

District uses regularly interspersed mounds of stone—known as multiple roundpoint 

structures—to create permeable dikes for navigation and environmental purposes.

in the Middle 
 

Page 10 GAO-12-41 Mississippi River 

Mississippi’s 195 river miles. Of this total, about 175 are bendway weirs. 

The type and pace of construction of river training structures has varied 

over time. For example, the St. Louis District built almost 450 such 

structures in the late 19th century, and another 250 in the 1930s; it 

constructed 150 bendway weirs from 1990 to 2000. The current pace of 

construction of these structures has slowed relative to the past, but the 

St. Louis District continues to repair and modify existing structures and 

has built some new ones. For example, from 2003 to 2010 the district 

constructed 23 chevrons in the Middle Mississippi, including 3 in the St. 

Louis harbor.

While not the subject of this review, it is important to note that the Corps 

uses other structures to fulfill its navigation and flood protection missions 

along the length of the Mississippi River. These additional structures 

include:

• Levees and floodwalls. Levees are earthen barriers built parallel to the 

river for flood protection, and floodwalls are artificial barriers that give 

additional protection to populated areas. Both types of structures 

narrow the river’s floodplain.

• Dams and locks. Dams are structures built across the entire width of 

the river to create pools that increase the depth of the river for 

navigation. They are used above the Middle Mississippi, where 

discharges are typically smaller relative to the rest of the river. Locks 

are gated chambers that allow navigation traffic to pass through the 

wall of a dam.

• Revetments. Revetments are concrete matting or graded stone 

placed on riverbanks to stabilize them and prevent erosion. 

Revetments keep the river in a fixed position—without them, the 

river’s natural tendency to meander could endanger lands and 

structures, including levees, in the floodplain.

Assessments of the impacts of river training structures rely upon both 

hydrologic and hydraulic research. Hydrology is the study of the 

movement, distribution, and quality of water, and includes the study of 

flooding. Hydrologic factors explain how (and how much) water enters a 

river system. Such factors include upstream rainstorms, snow melt, and 

runoff. In contrast, hydraulic factors are the physical forces that govern 

how water and sediment are conveyed once they enter a river system. 

Thus, the primary effect of river training structures is hydraulic, because 

they deflect water (and sediment) into the navigation channel. However, 
 

Page 11 GAO-12-41 Mississippi River 

the structures’ hydraulic and hydrologic effects can be linked. Specifically, 

if structures’ hydraulic effects increase river stage, the structures could 

contribute to an overall hydrologic effect.

The Corps and USGS have collected various types of historical 

hydrologic data on the Mississippi River through different approaches. For 

example, river stages have been measured daily at St. Louis since 1861. 

Because these measurements consist of river stage measured on a 

stream gauge, they are more straightforward than discharge 

measurements, which require accurate readings of flow velocity, river 

width, and river depth—the latter two measurements, when multiplied, 

form the river’s cross-sectional area, which determines the volume of flow 

it can convey. The Corps took most discharge measurements at St. Louis 

until 1933, using a variety of devices to record the speed of the river’s 

flow. These devices included surface floats, double floats, rod floats, and 

ultimately current meters.5 USGS assumed discharge measurement 

duties at St. Louis in 1933, and began operating the St. Louis stream 

gauge station to record continuous stage and discharge measurements. 

From 1933 to the early 2000s, USGS used Price current meters 

suspended from bridges—an improvement over earlier devices and 

methods—to measure discharge, before adopting even more precise 

instrumentation and methodology that is used today.

Key federal laws provide the Corps with the authority to construct and use 

river training structures in the Middle Mississippi for navigation and 

environmental purposes. In addition, in constructing these structures the 

Corps must comply with the environmental requirements of other key 

federal laws such as NEPA and the Clean Water Act, as well as 

applicable state requirements. Further, over a long history of using these 

training structures, the Corps has gained significant institutional 

knowledge that it has incorporated into guidance that its districts consult 

when planning, constructing, and maintaining these structures.

 

5

Surface floats are objects that are placed in the water and then timed to determine how 

long it takes them to float a known distance. When properly corrected for wind speed, they 

give an indication of flow velocity. Double floats are surface floats attached by twine to a 

subsurface float for improved accuracy. Rod floats are wooden poles with a length 

sufficient to span the depth of a stream. Current meters come in various configurations; 

the most common type uses a set of rotating cups, which the river’s current turns to 

indicate the flow’s velocity.

River Training 

Structures Must 

Adhere to Key Federal 

and State 

Requirements and 

Corps Guidance
 

Page 12 GAO-12-41 Mississippi River 

The following key federal laws provide the Corps the authority to use river 

training structures in the Middle Mississippi.

6

Rivers and Harbors Acts.7

Water Resources Development Acts.

The Rivers and Harbors Acts are a series of 

laws dating back to the 1800s that authorize the Corps to build and 

maintain public works projects and undertake other projects in the nation’s 

rivers and harbors. Among other things, these acts have required the 

Corps to maintain a navigation channel in the Mississippi River since 1878. 

The Rivers and Harbors Acts of 1927 and 1930 are of particular importance 

because they require the Corps to establish the current 9-foot navigation 

channel. Specifically, the 1927 act required the Corps to establish this 

depth for the navigation channel from the northern boundary of St. Louis to 

the mouth of the Ohio River near Cairo, Illinois, and to establish another 9-

foot navigation channel from Cairo to the Head of Passes in Louisiana. The 

1930 act establishes a similar channel from Minneapolis, Minnesota, to the 

mouth of the Illinois River. The Corps meets these requirements through 

the use of river training structures, in conjunction with locks, dams, 

revetments, and periodic dredging of the river bed.

8

 

6

In addition to the laws described in this section, other laws govern certain aspects of the 

Corps’ use of river training structures in the Middle Mississippi, such as the National 

Historic Preservation Act. We selected the laws presented in this report because, based 

on interviews and analysis of documents, they were the requirements most relevant to 

potential hydrologic and environmental impacts of river training structures.

The Water Resources 

Development Acts (WRDA) govern various aspects of conservation and 

development of water resources and, as the Rivers and Harbors Acts did 

previously, authorize the construction of water resources projects, 

including improvements to rivers and harbors of the United States. 

Several WRDA provisions are particularly relevant to the use of river 

training structures in the Middle Mississippi. For example, beginning in 

1986, WRDA authorizes the Corps’ Environmental Management 

Program, a joint federal-state partnership to restore and enhance the 

ecology of the Upper Mississippi. The 1990 WRDA requires the Corps to 

consider environmental protection as one of the primary goals for

7

Pub. L. No. 69-560, 44 Stat. 1010; Pub. L. No. 71-520, 46 Stat. 918.

8

WRDAs have been enacted periodically since 1986 to authorize and modify Corps civil 

works studies, projects, and programs. See, for example, Pub. L. No. 99-662, 100 Stat. 

4082 (1986); Pub. L. No. 101–640, 104 Stat. 4604 (1990); Pub. L. No. 110-114, 121 Stat. 

1041 (2007).

Key Federal Laws Provide 

the Corps with Authority 

to Use River Training 

Structures
 

Page 13 GAO-12-41 Mississippi River 

planning, design, construction, operations, and maintenance of its water 

resources projects. WRDA 2007 authorizes the Corps to develop 

ecosystem restoration projects within the Upper Mississippi-Illinois River 

waterway. These projects are administered under the Corps’ Navigation 

and Ecosystem Sustainability Program (NESP), a program designed to 

promote navigation efficiency and ecological restoration.

In using river training structures in the Middle Mississippi, the Corps must 

comply with the applicable environmental requirements of key federal 

laws, as well as state and other requirements. These key laws and 

requirements include the following:

National Environmental Policy Act.9 NEPA requires an agency to 

prepare a detailed statement on the environmental impacts of any “major 

federal action” significantly affecting the environment. Regulations 

promulgated by the Council on Environmental Quality implementing 

NEPA generally require an agency to prepare either an environmental 

assessment (EA)10 or an environmental impact statement (EIS).11

 

9

Pub. L. No. 91-190, 83 Stat. 852 (1970), codified as amended at 42 U.S.C. §§ 4321-4347 

(2011).

Agencies may prepare an EA to determine whether there is a significant 

potential impact on the environment, which would necessitate the 

preparation of an EIS. However, if the agency, in its EA, determines there 

are no significant impacts from the proposed action, then an agency 

should prepare a finding of no significant impact (FONSI). NEPA 

regulations state that federal agencies shall, to the maximum extent 

10An EA is a concise public document that provides sufficient evidence and analysis for 

determining whether to prepare an environmental impact statement or a finding of no 

significant impact, and is to include brief discussions of the need for the proposal, 

alternatives, the environmental impacts of the proposed action and alternatives, and a 

listing of agencies and persons consulted. 40 C.F.R. § 1508.9 (2011).

11An EIS is a more detailed statement than an EA, and NEPA implementing regulations 

specify requirements and procedures—such as providing the public with an opportunity to 

comment on the draft document—applicable to the EIS process that are not mandated for 

EAs. An EIS must, among other things, (1) describe the environment that will be affected, 

(2) identify alternatives to the proposed action and identify the agency’s preferred 

alternative, (3) present the environmental impacts of the proposed action and alternatives, 

and (4) identify any adverse environmental impacts that cannot be avoided should the 

proposed action be implemented. 42 U.S.C. § 4332(c) (2011), 40 C.F.R. §§ 1501.4, 

1508.11 (2011). 

River Training Structures 

Must Comply with 

Applicable Federal and 

State Environmental 

Requirements
 

Page 14 GAO-12-41 Mississippi River 

possible, encourage and facilitate public involvement in decisions that

affect the quality of the human environment. Under these regulations, 

agencies must provide a public comment period for a draft EIS; while 

there is no corresponding requirement for an EA, agencies may provide a 

public comment period. We reported in March 2010 that the Corps does 

not have clear guidance concerning whether it will provide a public 

comment period for draft EAs, and recommended the agency develop 

such guidance.12

Once an agency has prepared an EIS for a project, supplemental NEPA 

documentation is sometimes required. The Council on Environmental 

Quality’s regulations require supplemental documentation when an agency 

“makes substantial changes in the proposed action” or “[t]here are 

significant new circumstances or information” relevant to environmental 

concerns and bearing on the proposed action or its impacts.

According to Corps officials, the agency is presently 

developing such clarifying guidance. St. Louis District officials said that 

their practice is to provide a public comment period on any EA prior to 

finalizing a finding of no significant impact. 

13 A council 

document issued in 1981 suggests that if the EIS concerns an ongoing 

program and is more than 5 years old, it should be carefully reexamined to 

determine if a supplement should be prepared.14

 

12GAO, Delaware River Deepening Project: Comprehensive Reanalysis Corrected Errors, 

but Several Issues Still Need to Be Addressed,

An agency must take a 

“hard look” at the new information and project changes to determine if a 

supplemental EIS (SEIS) is needed; an EA may be used to do so. 

Similarly, the Corps’ own NEPA implementing regulations require the 

district commander to “review existing NEPA document(s) to determine if 

there are new circumstances or significant impacts which warrant the 

GAO-10-420 (Washington, D.C.: Mar. 31, 

2010).

1340 C.F.R. § 1502.9(c) (2011). Courts have explained that substantial changes to a 

project warrant supplemental NEPA documentation. A change is substantial if it presents 

a “seriously different picture of the environmental impact.” See, for example, Ark. Wildlife 

Fed’n v. U.S. Army Corps of Eng’rs, 431 F. 3d 1096 (8th Cir. 2005); Envtl. Def. Fund v. 

Marsh, 651 F. 2d 983 (5th Cir. 1981). Similarly, courts have stated that when new 

information presents a “seriously different picture of the environmental landscape” another 

in-depth look at the environment is necessary. In re Katrina Canal Breaches Consol. Litig., 

647 F. Supp. 2d 644, 723 (E.D. La. 2009). See also Blue Mountains Biodiversity Project v. 

U.S. Forest Serv., 229 F. Supp. 2d 1140 (D. Or. 2002).

14Council on Environmental Quality, Forty Most Asked Questions Concerning CEQ's 

National Environmental Policy Act Regulations, 46 Fed. Reg. 18,026 (Mar. 23, 1981).
 

Page 15 GAO-12-41 Mississippi River 

preparation of a...supplement to the EIS.”15 Then, after review of the new 

information and project changes, the Corps will determine whether to 

prepare an additional EA or SEIS.16 An EA is recommended if there are, 

among other things, “changes in environmental impacts [that] were not 

considered” in the original NEPA documentation.17 An EA or SEIS may 

also be used to ensure site-specific impacts and alternatives are evaluated 

when an initial EIS is broad or programmatic in nature. Additional, sitespecific analysis is required when the original EIS did not provide the 

required analysis and left gaps that could include significant impacts.18

Clean Water Act.

Thus, when unaddressed impacts are brought to light by new information 

or major changes in the operation or maintenance of Corps projects, the 

Corps is required to prepare supplemental NEPA documentation.

19 The Corps is also subject to many requirements of the 

Clean Water Act, which includes the goal of eliminating the addition of 

pollutants to waters of the United States. The Clean Water Act requires, 

among other things, that projects involving placement of dredged or fill 

material in federally regulated waters must obtain a permit, known as a 

Department of the Army Section 404 permit or simply a “dredge or fill” 

permit. With respect to the Corps’ own activities triggering a dredge or fill 

permit, the agency’s practice is generally to document that the activities are 

covered by a nationwide permit,20

 

1533 C.F.R. § 230, App. A (3a) (2011) (emphasis added). Additionally, the Corps’ 

regulations provide that supplemental documentation will be prepared according to CEQ 

regulations. 33 C.F.R. § 230.13(b) (2011).

or if not, to issue a permit-equivalent. In 

doing so, the Corps project team prepares a document evaluating the 

16According to the Corps’ regulations, a SEIS is prepared for “major changes in the 

operation and/or maintenance of completed projects,” among other things. 33 C.F.R. § 

230.6 (2011).

1733 C.F.R. § 230.7(d) (2011).

18See, for example, Recent Past Pres. Network v. Latschar, 701 F. Supp. 2d 49 (D.D.C. 

2010), State of Mississippi v. Marsh, 710 F. Supp. 1488, 1505-06 (S.D. Miss. 1989); 

Natural Res. Def. Council, Inc. v. U.S. Nuclear Regulatory Comm’n, 606 F.2d 1261, 1271 

(D.C. Cir. 1979).

19Federal Water Pollution Control Act, Pub. L. No. 92–500, 86 Stat. 884 (1972), codified 

as amended at 33 U.S.C. §§ 1251-1387, and generally referred to as the Clean Water Act.

20The Corps’ regulatory branch generally administers the permitting process, and has 

issued nationwide permits to provide a streamlined process for certain types of activities 

that it has found have only minimal impacts on the aquatic environment. 
 

Page 16 GAO-12-41 Mississippi River 

project’s compliance with EPA-promulgated guidelines21

Fish and Wildlife Coordination Act.

for the placement 

of fill material in federally regulated waters, including a determination of 

cumulative effects on the aquatic ecosystem, as well as to provide 

information demonstrating compliance with state water quality standards. 

The Corps regulatory section generally makes this document, known as a 

Section 404(b)(1) evaluation or statement of findings, available for public 

review as part of the public notice of the permit application.

22 The Fish and Wildlife Coordination 

Act authorizes the Secretary of the Interior to, among other things, provide 

assistance to, and cooperate with, federal, state, and public or private 

agencies and organizations in the development, protection, rearing, and 

stocking of all species of wildlife and their habitat; in minimizing damages 

from overabundant species; and in providing public shooting and fishing 

areas. Amendments to this law enacted in 1946 require consultation with 

FWS and the fish and wildlife agencies of states where the “waters of any 

stream or other body of water are proposed or authorized, permitted or 

licensed to be impounded, diverted, the channel deepened. . . or otherwise 

controlled or modified” by any federal agency.23

Endangered Species Act.

Consultation is to be 

undertaken for the purpose of preventing loss of and damage to wildlife 

resources, among other reasons.

24

 

21The guidelines were developed by EPA in consultation with the Corps. 45 Fed. Reg. 

85,344 (Dec. 24, 1980).

The Endangered Species Act requires that 

federal agencies ensure that any action they authorize, fund, or carry out 

is not likely to jeopardize the continued existence of a species protected 

under the act. To fulfill this responsibility, the agencies must, under some 

circumstances, formally consult with FWS when their actions may affect 

listed species or habitat identified as critical to the species’ survival. 

Formal consultations generally result in the issuance of biological 

22Acts of March 10, 1934, ch. 55, 48 Stat. 401, codified as amended at 16 U.S.C. §§ 661-

666c (2011).

23The consultation requirement applies to projects or units of projects whensoever 

authorized, except that it does not apply to any project or unit authorized before March 10, 

1934, if the construction of the particular project or unit has been substantially completed, 

defined as when 60 percent or more of the estimated construction cost has been obligated 

for expenditure.

24Pub. L. 93–205, 87 Stat. 884 (1973), codified at 16 U.S.C. §§ 1531-1544 (2011). 
 

Page 17 GAO-12-41 Mississippi River 

opinions by FWS. The biological opinion contains a detailed discussion of 

the effects of the action on listed species or critical habitat and FWS’s

opinion on whether the agency action is likely to jeopardize the continued 

existence of the species. In cases where a project as proposed is likely to 

either jeopardize the species or cause the destruction or adverse 

modification of its critical habitat, the opinion will provide “reasonable and 

prudent” alternatives to avoid jeopardy or adverse modification that FWS 

believes the agency could take in implementing the action. Additionally, 

biological opinions often contain provisions directing an agency to monitor 

and report on the effects of its action on listed species.25

Executive Order 11988.26

 

25These monitoring reports may contain information relevant to reinitiation of formal 

consultation, among other things. Reinitiation of formal consultation is required in four 

instances where discretionary federal involvement or control over the action has been 

retained or is authorized by law: (1) if the amount or extent of taking specified in the 

biological opinion is exceeded, (2) if new information reveals effects of the action that may 

affect listed species or critical habitat in a manner or to an extent not previously 

considered, (3) if the identified action is subsequently modified in a manner that causes an 

effect to the listed species or critical habitat that was not considered in the biological 

opinion, or (4) if a new species is listed or critical habitat designated that may be affected 

by the identified action. 50 C.F.R. § 402.16 (2011).

Executive Order 11988, Floodplain 

Management, was signed by the President in 1977. The executive order 

requires, among other things, that agencies determine whether a proposed 

action will occur in a floodplain, and if so, consider alternatives to avoid 

adverse effects and incompatible development in the floodplains and take 

actions to minimize potential harm to the floodplain. Under the executive

order, the floodplain is, in relevant part, defined as including the lowland 

and relatively flat areas adjoining inland waters, but does not include the 

river channel. The executive order also requires each agency to issue or 

amend existing regulations and procedures within 1 year to comply with the 

order; the regulations and procedures are to require the construction of 

federal structures and facilities to be in accordance with the standards and 

criteria and to be consistent with the intent of those promulgated under the 

National Flood Insurance Program, the primary federal government 

initiative supporting flood insurance for communities meeting minimum 

conditions. The National Flood Insurance Program requires that 

participating communities ensure that construction, fill, and certain other 

2642 Fed. Reg. 26,951 (May 24, 1977).
 

Page 18 GAO-12-41 Mississippi River 

activities in the floodway do not cause an increase in flood levels,27 but the 

executive order, however, was focused on the land portion of floodplains 

rather than the river channel and does not import the prohibition on 

floodway encroachment to federal agencies. The Corps regulation 

implementing the executive order specifies Corps policy and procedures for 

projects, including operation and maintenance activities, in the floodplain.28

The Corps regulation defines regulatory floodway as “the area regulated by 

Federal, State or local requirements; the channel of a river or other 

watercourse and the adjacent land areas that must be reserved in an open 

manner, i.e., unconfined or unobstructed either horizontally or vertically to 

provide for the discharge of the base flood29

State requirements. In addition to complying with federal requirements, 

the Corps’ use of river training structures must also comply with 

applicable state requirements. Specifically, federal agencies conducting 

projects requiring federal permits or licenses generally must obtain 

certification from the relevant state that the project will not cause or 

contribute to violations of the state’s water quality standards. In the 

Middle Mississippi, if a federal project in Missouri or Illinois complies with 

the conditions of certain nationwide permits, as well as conditions of the 

relevant state’s blanket water quality certification, then additional 

certification is generally not needed. Moreover, although states may set 

so the cumulative increase in 

water surface elevation from encroachment does not exceed one foot as 

set by the National Flood Insurance Program.”

 

2744 C.F.R. § 60.3(d)(3) (2011) (“[In the regulatory floodway, communities must] prohibit 

encroachments, including fill, new construction, substantial improvements, and other 

development within the adopted regulatory floodway unless it has been demonstrated 

through hydrologic and hydraulic analyses performed in accordance with standard 

engineering practice that the proposed encroachment would not result in any increase in 

flood levels within the community during the occurrence of the base flood discharge.”) 

28U.S. Army Corps of Engineers, Implementation of Executive Order 11988 on Flood Plain 

Management, ER 1165-2-26 (1984).

29The base flood is the flood that has a 1 percent chance of occurrence in any given year 

(also known as the 100-year flood).
 

Page 19 GAO-12-41 Mississippi River 

floodway standards, this generally does not impose a requirement on the 

Corps’ use of river training structures.

30

The Corps has internal guidance, informed by institutional knowledge, 

that further governs its use of river training structures in the Middle 

Mississippi. The primary guidance for the design of river training 

structures is the Corps’ engineering manual.31

Corps guidance also includes its policy for internal reviews of all Civil 

Works projects.

The manual’s section on 

training structures covers topics such as determining their length and 

height and the size of the stones used in constructing them. It also 

addresses flood control, cautioning structure designers to ensure that the 

amount of channel contraction does not unduly increase flood heights; 

discusses the performance and evaluation of training structures; and lists 

studies and factors that should be considered in the planning and design 

of training structures, including the modeling of such structures to help 

predict their impacts. In several places, the manual cites institutional 

knowledge as a factor that should be considered in designing and 

constructing training structures. For example, the manual states that, 

through experience and judgment, an engineer can evaluate various 

sections of the river that maintain adequate depths naturally and use that 

information to determine how to apply it to other sections.

32

 

30Generally, the federal government is not itself subject to regulation by state and local 

government. However, Congress may enact laws waiving supremacy and subjecting 

federal agencies to state and local regulation such as permit requirements. See, for 

example, Clean Water Act (33 U.S.C. § 1323(a)), Resource Conservation and Recovery

Act (42 U.S.C. § 6961(a)).

The policy establishes various levels of review, 

including district-level quality control review, agency technical review, and 

independent external peer review. The policy applies to all Civil Works 

projects “from initial planning though design, construction, and operation, 

maintenance, repair, replacement, and rehabilitation.” In addition, 

Mississippi Valley Division regulations establish, among other things, 

required approvals and reviews for river training structures and other 

31U.S. Army Corps of Engineers, Layout and Design of Shallow-Draft Waterways, EM 

1110-2-1611 (Washington, D.C.: Dec. 31, 1980). 

32U.S. Army Corps of Engineers, Civil Works Review Policy, Circular 1165-2-209 

(Washington, D.C.: Jan. 31, 2010).

The Corps Has Internal 

Guidance That Applies to 

the Use of River Training 

Structures
 

Page 20 GAO-12-41 Mississippi River 

channel improvements in the Mississippi River and key tributaries.33

In addition, the St. Louis District provided us with a written description of 

the process they use to assess the need for new training structures and 

then build and monitor them. This process is not currently documented in 

the Corps’ official guidance. According to the description provided by the 

district, the process includes several steps, such as (1) assessing river 

conditions and identifying sections of the river that have resulted in 

navigation problems, (2) designing structures using physical models of 

the river, (3) coordinating with key stakeholders, and (4) monitoring 

structures before and after construction. The description states that this 

process is consistent with the process that has been used throughout the 

Mississippi Valley Division for the past 50 years.

For 

example, the regulations require each district’s “general plan” to provide a 

general outline of proposed channel improvements, such as proposed 

location and type of training structures. These plans are to be approved 

by a Division team, which serves as the agency’s technical review under 

the Corps’ review policy.

The Corps has conferred with stakeholders on environmental impacts and 

has assessed these impacts to some extent, but has not prepared 

additional analyses—such as an EA—to assess site-specific impacts and 

alternatives, new information, and project changes to determine if a SEIS 

is required. The Corps also has not obtained Clean Water Act permits or 

state water quality certifications for river training structures as required.

In accordance with the Fish and Wildlife Coordination Act and the 

Endangered Species Act, the Corps has engaged in consultation with 

FWS about the environmental impacts of river training structures. 

Specifically, the Corps’ St. Louis, Rock Island, and St. Paul Districts 

consulted with FWS in the 1990s on the operations and maintenance of 

 

33U.S. Army Corps of Engineers, Mississippi Valley Division, Channel Improvement 

Engineering and Design Activities, Regulation No. 1110-2-8 (Vicksburg, Miss.: Oct. 27, 

2005).

The Corps Has 

Addressed Some but 

Not All of the 

Environmental 

Requirements for 

River Training 

Structures

The Corps Has Conferred 

with Stakeholders Prior to 

Constructing River 

Training Structures
 

Page 21 GAO-12-41 Mississippi River 

the 9-foot navigation channel. In its 2000 biological opinion, FWS 

determined that the operations and maintenance project jeopardizes the 

pallid sturgeon—a large native fish that FWS placed on the endangered 

species list in 1990—and results in harm to the interior least tern—a small 

bird that was placed on the endangered species list in 1985—in the 

Middle Mississippi.34

In addition to requirements for consultation and other actions to prevent 

harm to endangered species, the St. Louis District is required to submit 

annual reports to FWS on its implementation of the biological opinion’s 

reasonable and prudent alternatives. According to FWS, the St. Louis 

District is several years behind in providing these annual reports. In 

addition, the consultation culminating in the 2000 biological opinion did 

not include individual, site-specific effects or new construction impacts. 

According to the opinion and a Corps document, site-specific effects and 

new construction impacts for river training structures are to be handled 

under separate consultations, referred to as tier II biological assessments. 

The Corps provided us with examples of such assessments issued in 

2010 and 2011.

To prevent jeopardy for the pallid sturgeon, FWS’s 

biological opinion instructs the Corps to (1) conduct a habitat study in the 

Middle Mississippi, (2) facilitate development of a conservation and 

restoration plan, (3) implement a long-term program of aquatic habitat 

restoration, and (4) begin short-term implementation of aquatic habitat 

restoration measures. To minimize harm to the least tern, the opinion 

instructs the Corps to (1) modify training structure maintenance projects 

to maintain flow between sandbars and the shore and to reduce 

conversion of sandbar habitat to trees; (2) evaluate, and implement where 

appropriate, techniques that use dredge material to restore or enhance 

sandbar habitat and aquatic habitat; and (3) reduce the accretion of new 

and existing sandbars to the bank and reduce tree colonization on those 

sandbars.

According to officials at FWS and the state resource agencies in Illinois 

and Missouri, the St. Louis District confers with them prior to constructing 

river training structures. According to officials at the FWS field office that 

works with the St. Louis District, the district coordinates with them through 

activities conducted under the Fish and Wildlife Coordination Act, as well 

 

34U.S. Fish and Wildlife Service, Biological Opinion for the Operation and Maintenance of 

the 9-Foot Navigation Channel on the Upper Mississippi River System (May 2000).
 

Page 22 GAO-12-41 Mississippi River 

as through the implementation process for the 2000 biological opinion. 

This interaction occurs through the district’s River Resources Action 

Team, which coordinates and prioritizes projects in the Middle 

Mississippi, including those related to the biological opinion, and conducts 

an annual inspection tour of the river. Additionally, the Corps has 

consulted with the states prior to constructing river training structures. 

According to officials at the Illinois and Missouri Departments of Natural 

Resources and the Missouri Department of Conservation, the St. Louis 

District solicits their comments on proposed projects and involves them in 

river planning studies. As part of the St. Louis District’s planning process, 

it invites these stakeholders to its Applied River Engineering Center35 for 

physical modeling demonstrations, where district engineers describe 

proposed structures and solicit comments from stakeholders. Officials 

from both states told us they believe that the level of coordination is 

sufficient.

The St. Louis District has not performed the additional analyses of 

environmental impacts for river training structures that it has constructed 

in the last three decades as NEPA requires, but instead has continued to 

rely primarily on an EIS prepared more than 35 years ago. Specifically, in 

1976, the St. Louis District issued the Final Environmental Statement: 

Mississippi River between the Ohio and Missouri Rivers (Regulating 

Works).

36

 

35The Applied River Engineering Center was established by the St. Louis District in 1995 

to conduct applied river engineering in an office laboratory environment. With a staff of 

about 10, the center conducts work on behalf of customers such as landowners, private 

facility owners, and local municipalities, as well as agency partners such as FWS, the 

Missouri Department of Conservation, and the Illinois Department of Natural Resources. It 

has also partnered with other districts within the Corps including the Memphis, Rock 

Island, Vicksburg, New Orleans, Galveston, and Kansas City Districts.

The 1976 EIS focuses on the operation and maintenance of the 

Middle Mississippi navigation channel, including dikes, revetments, and 

any necessary dredging. It broadly discusses each component of its 

recommended plan, and discusses at a high level the implementation of 

dikes in general. It does not describe the environmental effects of river 

training structures or specify any design criteria or location for any 

structures. The EIS states that dikes could lead to degradation of the 

riverbed and aquatic organisms and acknowledges that some impacts of 

36U.S. Army Corps of Engineers, St. Louis District, Final Environmental Statement: 

Mississippi River between the Ohio and Missouri Rivers (Regulating Works) (St. Louis, 

Mo.: April 1976).

The Corps Has Not 

Prepared the Additional 

Environmental Analyses 

Required by NEPA
 

Page 23 GAO-12-41 Mississippi River 

the 9-foot channel project were “not... adequately assessed” or “not yet 

fully understood.”37 It also recognizes that the river is an ever-changing 

environment and states that a reassessment of project impacts would 

likely be necessary within 5 years.38

In the 35 years since the Corps issued its EIS, the St. Louis District has 

constructed new river training structures in the Middle Mississippi and 

intends to continue building such structures in the future as needed. For 

these new river training structures, the St. Louis District has continued to 

rely primarily upon the 1976 EIS as adequate for NEPA compliance. 

However, since 1976, the picture of potential impacts of these structures 

on the river environment has changed in some important respects. First, 

several river species have been listed as endangered (e.g., the least tern 

and the pallid sturgeon) and significantly more data has been developed 

on their populations as well as impacts of training structures on habitat for 

these and other species. For example, according to FWS’s 2000 

biological opinion, river training structures affect natural river processes, 

harming the least tern and pallid sturgeon. The 1976 EIS does not reflect 

today’s scientific understanding of the effect of river training structures on 

these species. The 1976 EIS also does not reflect the relative significance 

of various types of river habitat for other native species, given the losses 

in habitat diversity documented in FWS’s 2000 biological opinion and a 

The EIS briefly considers broad 

alternatives to the Regulating Works Project, namely no action; use of 

locks and dams; a change in project authorization to incorporate fish and 

wildlife enhancement; and the existing operation and maintenance 

activities, which formed the adopted plan. The EIS concludes that the 

actions proposed by the Regulating Works project do not significantly 

impact the river’s endangered species, among other things.

 

37“The effects of riverbed degradation on aquatic organisms in the Middle Mississippi 

River are not yet fully understood.” 1976 EIS at 215a. “The cumulative effect of 

channelization efforts in the Middle Mississippi River to date has not been adequately 

assessed. Perhaps the most serious adverse impact resulting from the 9-foot channel 

project on the Middle Mississippi River is reduction in size and diversity of the aquatic 

habitat.” Id. at 216.

38Corps officials stated that such provisions commonly appeared in EISs in the 1970s, but 

that they did not establish any requirements for further review.
 

Page 24 GAO-12-41 Mississippi River 

2004 Corps document.39

The lack of additional NEPA analysis by the St. Louis District is also 

inconsistent with Corps regulations and the practices of other districts. 

Corps regulations require the St. Louis District commander to “review 

existing NEPA document(s) to determine if there are new circumstances 

or significant impacts which warrant the preparation of a...supplement to 

the EIS.” However, we found that for river training structures this has 

generally not happened. The Corps’ position is that the agency has taken 

the requisite “hard look” at whether there are new or significant changes 

that would require additional NEPA documentation, and so far as the 

Corps has been able to determine to date, changes have not risen to a 

level of significance that would justify or require the preparation of a SEIS. 

The Corps produced one documented internal review, from 1994, of 

whether additional NEPA documents were needed for the Regulating 

Works Project.

Second, the St. Louis District has expanded the 

types of river training structures it uses in the Middle Mississippi. For 

example, the district began using bendway weirs in 1990 and chevrons 

after 2000, whereas the 1976 EIS focuses primarily on the use of wing 

dikes. Corps documents suggest that each of these types of river training 

structures may have different environmental impacts, but St. Louis District 

officials told us that while configurations of river training structures have 

evolved over time, the purpose and function of these structures 

themselves has changed very little. Finally, the 1976 EIS does not 

provide any information on site-specific structures or locations and 

discusses the environmental effects only at a high level. Without site- or 

location-specific information, the Corps has not documented to the public 

its consideration of such impacts and potential mitigation. Because the St. 

Louis District has not prepared any additional NEPA documents since 

1976, such as an EA or SEIS, we believe that the Corps has not fully 

implemented the requirements of NEPA for river training structures in the 

Middle Mississippi. The absence of additional NEPA analyses, we 

believe, limits opportunities for the Corps to evaluate new environmental 

circumstances and information that have arisen since 1976.

40

 

39U.S. Fish and Wildlife Service, Biological Opinion for the Operation and Maintenance of 

the 9-Foot Navigation Channel on the Upper Mississippi River System (May 2000); U.S. 

Army Corps of Engineers, Final Integrated Feasibility Report and Programmatic 

Environmental Impact Statement for the UMR-IWW System Navigation Feasibility Study

(Sept. 24, 2004).

The review, however, did not describe what changes the 

40The review did not determine whether a supplement to the EIS was “warranted,” as 

called for by Corps regulations, but rather whether one was legally required.
 

Page 25 GAO-12-41 Mississippi River 

Corps believed had taken place, or why it considered those changes to 

be environmentally insignificant.41 According to Corps officials, the St. 

Louis District has had discussions and briefings on this issue, and NEPA 

considerations have been discussed with the district commander at the 

budget, design, and construction phases for specific river training 

structures. However, the district did not provide documentation to us that 

demonstrated these discussions. Similarly, we found that the St. Louis 

District’s approach for preparing additional analyses is inconsistent with 

other Corps districts. For example, the Rock Island District, which is the 

district immediately to the north of the St. Louis District, has prepared 

eight EAs since 1992 for river training structure construction or 

modifications under its channel operation and maintenance authority. One 

of these EAs noted that the Rock Island District’s EIS42

In a written response to our inquiries about this issue, the Corps’ Chief 

Counsel stated that the agency strongly believes, “based on all 

information available to [the Corps] at this time,” that it is in full 

compliance with NEPA with regard to river training structures. The written 

response further stated, however, that “in the spirit of” NEPA regulations 

the Corps will voluntarily perform an additional EA for river training 

structures that “will determine whether there are undisclosed and 

currently unknown significant effects on the human environment that 

might require additional analysis and documentation.” Further, the written 

response stated that the Corps will make an objective and formal 

determination of whether to prepare a SEIS after the EA is completed but 

did not state whether it would make a draft of the EA available for public 

comment. The written response also noted that the Corps cannot commit 

for operation and 

maintenance of the 9-foot channel, prepared in 1974, does not address 

site-specific new construction of river training structures. As a result, the 

Rock Island District prepared additional NEPA documentation to address 

potential impacts of its construction. In addition, the Rock Island District 

provided the public an opportunity to comment on this EA before deciding 

whether or not to prepare an EIS.

 

41We note that the subject review was an internal document, whereas more typically, 

agencies use EAs, revised records of decision, or formal re-evaluation documents to 

announce such decisions.

42U.S. Army Corps of Engineers, Rock Island District, Operations and Maintenance, Upper 

Mississippi River, 9-Foot Navigation Channel, Final Environmental Impact Statement: 

Pools 11-22 (1974).
 

Page 26 GAO-12-41 Mississippi River 

to a specific time frame for completion of the EA, since no funds have 

been budgeted for it in fiscal year 2012.

As previously discussed, the Corps is obligated to obtain Clean Water Act 

permit-equivalents for placement of fill in federally regulated waters and 

obtain associated water quality certifications from relevant states, unless 

a nationwide permit applies. However, the St. Louis District has not 

obtained these permits for river training structures constructed under the 

Corps’ operation and maintenance authority. Instead, according to district 

officials, the agency builds new river training structures under its authority 

to maintain the river channel, and therefore they are considered to fall 

under a nationwide permit for maintenance issued by the Corps’ 

regulatory branch. In addition, St. Louis District officials told us they do 

not need the permit-equivalent because they are operating under the 

nationwide permit.

However, the Corps has not demonstrated that the construction of new 

river training structures, which typically involves the placement of 

thousands of tons of rock into the river, meets the requisite conditions for 

the nationwide permit for maintenance. This nationwide permit authorizes 

“the repair, rehabilitation or replacement of any previously authorized, 

currently serviceable, structure, or fill,” and “minor deviations in the 

structure’s configuration or filled area, including those due to changes in 

materials, construction techniques, or current construction codes or safety 

standards that are necessary to make the repair, rehabilitation or 

replacement.” The permit further notes that “the placement of riprap must 

be the minimum necessary to protect the structure or to ensure the safety 

of the structure.”43

 

43Riprap is defined as loose stone used as a cover for the purpose of stabilization.

St. Louis District officials did not provide us any 

evidence that would explain how new river training structures are 

consistent with the nationwide permit’s scope. Moreover, the Corps’ 

regulations applicable to all nationwide permits provide that no activity is 

authorized under any nationwide permit that is likely to jeopardize the 

continued existence of a threatened or endangered species or that will 

destroy or adversely modify the critical habitat of such species. As 

previously discussed, FWS determined in its 2000 biological opinion that 

the Corps’ channel maintenance activities jeopardize the pallid sturgeon, 

among other species. The St. Louis District could not explain to us how a 

The Corps Has Not 

Obtained Clean Water Act 

Permits
 

Page 27 GAO-12-41 Mississippi River 

nationwide permit would be applicable to project operations under these 

circumstances.44 Furthermore, officials at another Mississippi River Corps 

district that we contacted told us that the nationwide permit for 

maintenance is not applicable for new construction of river training 

structures and as a result they do not use such a permit in their district. In

light of these discrepancies, we believe that the St. Louis District has not 

obtained the permits required by the Clean Water Act, including obtaining 

the required state water quality certification for its river training structures.

For river training structures in the Middle Mississippi, the Corps has 

conducted preconstruction physical and numerical modeling to assess the 

potential hydraulic impacts of the structures and has routinely monitored 

the hydrologic impacts after construction through data collection and 

observation, among other activities. In contrast, the Corps has not 

routinely monitored postconstruction environmental impacts of its river 

training structures. The Corps has, however, conducted or contracted for 

a number of studies on specific environmental effects of its river training 

structures.

Prior to construction, the Corps has conducted physical and numerical 

modeling to assess the potential hydraulic impacts of proposed new river 

training structures and proposed modifications to existing structures. For 

example, at its Applied River Engineering Center, the Corps has 

 

44St. Louis District officials also provided us with a Section 404(b)(1) evaluation prepared 

in 1981 for the construction of dikes in the Middle Mississippi, but did not provide any 

associated permit-equivalent or explain its relevance. According to Mississippi Valley 

Division regulations, for compliance with the Clean Water Act, each district is to review its 

proposed channel improvement projects annually to determine if the planned work meets 

the requirements of the EPA guidelines, or if updates to the original Section 404 

evaluation are required. The regulation indicates that development of supplemental 

information or reevaluation and public notice under the Section 404(b)(1) process may be 

necessary. See U.S. Army Corps of Engineers, Channel Improvement Engineering and 

Design Activities. 

The Corps Has 

Routinely Monitored 

the Hydrologic 

Impacts of River 

Training Structures 

after Construction, 

but Has Not Routinely 

Monitored Their 

Environmental 

Impacts

The Corps Has Conducted 

Preconstruction Modeling 

to Assess Hydraulic 

Impacts
 

Page 28 GAO-12-41 Mississippi River 

assessed hydraulic impacts of river training structures by building smallscale physical models to help determine the impact that these structures 

might have on a given river section, such as changes in flow and 

sedimentation patterns.45 Corps officials told us that the Corps builds 

models for specific reaches of the river, to evaluate the effectiveness of 

the various river training structures prior to constructing them. The Corps 

uses field data, such as discharge, velocity, and sediment volume, to 

calibrate its models. The models are then run through a series of tests to 

obtain results. Corps engineers evaluate the results and refine the 

models, with input and review from biologists, fisheries specialists, other 

water resource scientists, the river industry, land owners, and other 

stakeholders. The results are recorded in reports that are publicly 

available on a Corps website.46 As of September 2011, the Corps’ 

website included 25 physical model reports that have been issued since 

1994. The Corps has also used physical models to solve problems such 

as repetitive dredging and other navigation-related issues. For example, 

in a report issued in 2004, the Corps built a physical model to evaluate 

and propose design modifications to existing training structures, and 

possibly introduce new training structures, for the purpose of improving 

navigation conditions and reducing the need for dredging in the St. Louis 

harbor.47

 

45According to Corps documents, small-scale synthetic bed models, called micro-models 

or hydraulic sediment response models, have been used since 1994 and replace largescale coal bed models. With these small-scale models, engineers are able to replicate the 

mechanics of an actual river or stream on an area the size of a normal table top. 

Figure 6 is a photograph of a small-scale physical model similar 

to the one used in the St. Louis harbor report.

46For copies of modeling studies, see the Corps’ Applied River Engineering Center’s 

website at http://www.mvs.usace.army.mil/arec/reports_hsrmodels.html (accessed Sept. 

15, 2011). 

47U.S. Army Corps of Engineers, Sedimentation and Navigation Study of the Middle 

Mississippi River in the St. Louis Harbor River Miles 192.0 to 172.0: Hydraulic Micro 

Model Investigation, Technical Report M31 (St. Louis, Mo.: 2004). 
 

Page 29 GAO-12-41 Mississippi River 

Figure 6: Photograph of a Small-Scale Physical Model

Note: The model employed a horizontal scale of 1 inch equals 1,000 feet and a vertical scale of 1 

inch equals 100 feet. 

The Corps has also at times used numerical models to assess the 

potential hydraulic impacts of training structures prior to their construction. 

Numerical models are computer programs that simulate the behavior of a 

river section. Like physical models, numerical models use field data from 

the actual section, such as river stage, discharge, and cross-sectional 

width. The Corps runs these data through a complex set of equations to 

produce quantitative estimates of how the river will respond to changes,

such as the addition or modification of training structures. According to an 
 

Page 30 GAO-12-41 Mississippi River 

official with the Corps’ Engineer Research and Development Center,48

In contrast, the Corps has not assessed the potential hydrologic impacts 

of proposed new river training structures or proposed modifications to 

existing structures prior to their construction because it believes the 

structures have no impact on flooding, according to agency officials. 

According to Corps officials, both physical and numerical models are 

limited in their ability to assess hydrologic impacts of river training 

structures. For example, according to these officials, small-scale physical 

models cannot be used to predict changes in river stage. They said this is 

because of the large differences in scale between the model and the 

actual size of the river section being modeled. Because of these large 

differences, it is not possible to measure very small changes in river stage 

detected in the model and translate them into predicted changes in actual 

river stage. In addition, there are other factors that may impact river 

stage, such as bank vegetation, that are not feasible to reproduce in a 

small-scale model, according to a St. Louis District official responsible for 

modeling. As with physical models, a district official told us that while 

numerical models could theoretically be used to predict impacts of 

numerical models can run analyses in one, two, or three dimensions. The 

two- and three-dimensional models can perform more complex analyses, 

but on a shorter stretch of river than a one-dimensional model. According 

to this official, the Corps commonly uses one-dimensional models to 

analyze changes in the floodplain for a large river section. Twodimensional models can analyze lateral and longitudinal velocities for a 

smaller river section, and three-dimensional models can analyze vertical 

velocities for an even smaller river section. Models can be used in 

tandem—for example, results from three-dimensional modeling can be 

used to improve a two-dimensional model. Numerical models are able to 

show the effects that training structures have on the river as its flow goes 

around the structures, including flow separation and sediment capture, 

the official told us. In certain circumstances, the Corps has run numerical 

models in conjunction with physical models to help it to obtain a clearer 

picture of the expected results.

 

48The Engineer Research and Development Center is a diverse engineering and scientific 

research organization that conducts research and development in support of the Corps’ 

military and civil works missions, as well as for other federal agencies, state and municipal 

authorities, and U.S industry. Headquartered in Vicksburg, Mississippi, the Center 

operates seven laboratories in various locations in the United States, has a staff of about 

2,500 federal employees, and an annual research program exceeding $1 billion.
 

Page 31 GAO-12-41 Mississippi River 

training structures on river stage prior to construction, the Corps is not 

aware of a model study that has proven this capability.49

According to the St. Louis District, along with physical and numerical 

modeling, the Corps also monitors the section of the river where it plans 

to build or modify training structures by collecting data, including 

hydrographic surveys of the river bottom, velocities of the river current, 

stages, and discharges. In addition, the Corps conducts several reviews 

before constructing or modifying training structures. Specifically, 

according to the St. Louis District, engineers throughout the division 

review the proposals, as do federal and state partner agencies, such as 

FWS, the Illinois Department of Natural Resources, and the Missouri 

Department of Conservation, as well as the navigation industry. In 

addition, Corps officials told us that all training structure proposals 

undergo, at the general plan stage, a formal review by a committee 

consisting of representatives from all six districts in the Mississippi Valley 

Division. This is conducted per division regulations establishing reviews 

and approvals, including those under the Corps Civil Works Review 

Policy.

Further, the 

official said that because the Corps believes training structures have no 

impact on river stage, the St. Louis District does not believe it is 

necessary to perform numerical modeling for assessing river stage 

impacts.

According to the St. Louis District, once training structures are built, it 

routinely monitors their hydrologic impacts through several methods. 

First, it collects data to measure the structures’ effects and to compare 

with preconstruction data. For example, St. Louis District engineers 

conduct hydrographic surveys of the river bottom to confirm that the 

structures have improved the channel’s ability to convey water and 

sediment. Also, according to Corps officials and documents, the Corps 

collects and monitors discharge and other relevant data with instruments 

that, for example, measure the velocity of water at various depths or the 

height of water over a given structure. Engineers also monitor stream 

gauges—37 operating on the Middle Mississippi—both upstream and 

 

49According to the Corps, because of the interest in potential river stage impacts due to 

river training structures, the agency has contracted with a university to perform research 

using a numerical model to evaluate any changes in river stage due to three chevrons 

constructed in the St. Louis harbor. This study is also addressed later in this report. 

The Corps Routinely 

Monitors Postconstruction 

Hydrologic Impacts
 

Page 32 GAO-12-41 Mississippi River 

downstream of training structures to determine whether river stage 

changed after construction of particular training structures.

As part of its monitoring of stream gauges, the Corps conducts “specific 

gauge analysis,” which it defines as a graph of river stage for a specific 

discharge at a particular gauging location plotted against time. St. Louis 

District officials told us the Corps does this to track changes in river stage 

over time and, in particular, to determine if stage is trending upward or 

downward for a given discharge. This analysis can help determine any 

cumulative impact of river training structures on river stage. Conducting a 

specific gauge analysis requires two steps. The first step is to develop a 

“rating curve,” which is a graph of a series of points that plots river stage 

(measured in feet) against discharge (measured in cubic feet per second) 

over time (usually 1 year). Once the points are plotted, a line is fitted 

through them to create a rating curve for that year. Figure 7 is an example 

of a rating curve for the St. Louis gauge in 1993, a year that saw heavy 

flooding on the Middle Mississippi. The same technique is used to 

develop rating curves for each year of interest.
 

Page 33 GAO-12-41 Mississippi River 

Figure 7: 1993 Rating Curve for the St. Louis Gauge

Note: This graphic is presented solely as an example of the Corps’ hydrologic monitoring. We did not 

attempt to independently reproduce the information depicted. 

The second step is to use the rating curves developed in step one to plot 

the river stage for specific discharges for each year. This is done in a 

specific gauge analysis graph. Figure 8 shows such a graph for the St. 

Louis gauge for a period starting in the early 1930s and ending in the late 

2000s.
 

Page 34 GAO-12-41 Mississippi River 

Figure 8: Specific Gauge Analysis for the St. Louis Gauge

Note: This graphic is presented solely as an example of the Corps’ hydrologic monitoring. We did not 

attempt to independently reproduce the information depicted. 

In determining any trends in river stage for the specific gauge analysis in 

figure 8, one would need to pick a discharge amount, and then draw a 

line through the points representing observed stages associated with that 

discharge over a period of years to see if the line is rising, falling, or 

remaining essentially flat over time. For example, in observing the plotted 

river stages associated with the 300,000 cubic feet per second 

discharge—a level generally corresponding with a stage of about 20 feet, 

which is well within the river’s banks—it appears that the trend in river 

stage has been essentially flat. This indicates that this discharge amount 
 

Page 35 GAO-12-41 Mississippi River 

resulted in about the same river stage height in the 2000s as it did in the 

1930s.

The second way the Corps monitors the hydrologic impacts of river 

training structures is by physically observing them, according to officials 

we spoke with. For example, they observe them to determine whether 

there are any readily identifiable visual effects on flow. In addition, a St. 

Louis District official said that a team of Corps officials—which includes 

engineers, biologists, and other scientists—along with other key 

stakeholders, conduct an annual multiday inspection tour that enables 

participants to observe training structures up close and discuss the 

potential need for new structures. Participating stakeholders include 

FWS, the Illinois Department of Natural Resources, the Missouri 

Department of Conservation, nongovernmental organizations such as the 

Nature Conservancy and the Prairie River Audubon, and university 

faculty.

Third, for decades the Corps has conducted its own studies of the 

impacts of structures on the shape of the channel and flooding after 

construction. For example, the Corps issued a paper in 1964 that 

presented, among other things, the variations in rating curves with 

respect to time and stage and causes for some of the changes in the 

stage-discharge relationship.50 The Corps conducted similar studies in the 

1970s, 1980s, and 1990s. Another study the Corps completed in 2009 

examined the limits of using specific gauge analysis to analyze the effects 

of river training structures on flood heights. A more recent Corps study in 

2011 looked at the effects of bendway weir construction on the shape of 

the channel. Specifically, this study examined 22 bendway weir fields, all 

but 1 located in the Middle Mississippi, over 5 periods (1976, 1982, 1986, 

2005, and 2007) to compare certain parameters before and after 

installation.

 

50U.S. Army Corps of Engineers, Waterways Experiment Station, Study of Effect of 

Regulation Works on Stream Flow (Vicksburg, Miss.: February 1964).
 

Page 36 GAO-12-41 Mississippi River 

According to Corps officials, the St. Louis District does not routinely 

monitor the environmental impacts of the different kinds of river training 

structures after they have been constructed. The monitoring that it does 

conduct is focused more on bendway weirs and chevrons than on the 

more prevalent wing dikes. Corps officials told us this is because routine 

monitoring of environmental effects is costly—as much as $320,000 for 4 

years of pre- and post-construction monitoring of a single dike field, and 

potentially more if contractors are used. Moreover, they told us that 

routine monitoring is unnecessary for wing dikes because the St. Louis 

District has more than 100 years of experience with these kinds of river 

training structures.

In contrast, FWS and Missouri Department of Conservation officials told 

us that additional monitoring is needed for some of these river training 

structures—in particular chevrons and bendway weirs—because not 

enough is known about how species respond to these structures. 

According to officials at the FWS field office that works with the St. Louis 

District, in recent years they have opposed the construction of new 

bendway weirs in the Middle Mississippi due to a lack of information 

regarding the biological and physical impacts of the structures. These 

FWS officials, however, acknowledged that the Corps has shown a 

willingness to conduct more monitoring of the physical and biological 

impacts of river training structures in the future.

According to Corps officials, the Corps has undertaken some assessments 

to monitor impacts on species identified in the 2000 biological opinion. For 

example, the Corps has identified 17 projects designed to implement the 

reasonable and prudent alternatives in the biological opinion for the pallid 

sturgeon and least tern. These projects include efforts to quantify young 

pallid sturgeon groups in the Middle Mississippi and to monitor the least 

tern population. The Corps has also conducted follow-up biological 

assessments for several new river training structures to address the 

proposed structures’ site-specific impacts on these species. FWS noted in 

its concurrence letter on one of these follow-up assessments that it is 

unclear whether the benefits of proposed river training structure 

construction in one river reach (and the consequent reduction in 

maintenance dredging) “can fully compensate for the project impacts,” but 

concluded that the construction met the standards set by the reasonable 

and prudent alternatives. FWS officials told us that these kinds of efforts 

are challenging because of data limitations, but they believe that more work 

needs to be done, particularly related to the longer-term habitat restoration 

measures. The Corps is in the process of developing its pallid sturgeon 

conservation and restoration plan. As part of this effort, the Corps is 

The Corps Does Not 

Routinely Monitor 

Environmental Impacts 

after Construction but Has 

Conducted Various Studies
 

Page 37 GAO-12-41 Mississippi River 

participating in a soon to be published study with the Missouri Department 

of Conservation and a university in the region that analyzed habitat 

selection patterns of adult pallid sturgeon and determined that these fish 

tend to congregate near the tips of wing dikes.51

While the Corps has not performed routine environmental monitoring for 

its river training structures, it has conducted or contracted for a number of 

studies that examine the impacts of the structures on some types of fish 

and wildlife habitats. Officials at the St. Louis District estimate that, 

between the Corps, its contractors, and other academics, more than 50 

studies have been published on various environmental effects of training 

structures in the Mississippi and other rivers dating back to at least 1982. 

Several of these studies indicate that the structures may negatively affect 

the environment by converting river habitat into terrestrial habitat and by 

making the habitat that remains in the river more homogenous. However, 

studies also show that modifications can be made to the structures to 

reduce these negative impacts, as discussed in further detail later in this 

report.

Two primary concerns have been raised by various researchers with 

regard to the impacts of river training structures in the Middle Mississippi. 

One set of concerns relates to the degradation of river habitat, and the 

Corps has modified some structures in response to these concerns. The 

second set of concerns is that the structures are associated with 

increased flooding. The Corps disagrees with this correlation and has

taken a number of steps to demonstrate why it believes that this 

relationship does not exist. However, despite the Corps’ efforts, 

professional disagreement remains over the cumulative impact of river 

training structures during periods of high flow. Experts in the fields of river 

engineering and water resources told us that physical and numerical 

modeling could help resolve this issue.

 

51James Garvey, et al., Habitat Selection and Movement of Naturally Occurring Pallid 

Sturgeon in the Mississippi River (forthcoming). 

The Corps Has 

Modified Structures 

over Environmental 

Concerns but 

Disagrees That They 

Exacerbate Floods
 

Page 38 GAO-12-41 Mississippi River 

Some researchers have reported that river training structures can 

degrade river habitat for fish and bird species. According to these 

researchers, in a natural river there are areas of faster and slower 

current, as well as tree snags and other debris on the bed of the river. 

There may also be sand bars in the channel, or secondary channels that 

flow around islands and rejoin the main channel on the other side. 

According to these researchers, in a river managed by wing dikes, the 

navigation channel gets deeper as flows are directed into it. As a result, 

areas in between wing dikes can fill with sediment, in some cases 

replacing aquatic habitat with terrestrial habitat, while secondary channels 

can become disconnected from the deeper main channel during low 

flows. This transformed habitat can negatively impact the species that 

reside there. For example, fish species encounter water that grows 

shallower; in some cases, water in a secondary channel closed off from 

the main flow becomes low in oxygen content, further degrading river 

habitat for fish and other species. Similarly, as wing dikes change 

sedimentation patterns in the river, birds’ nests on sandbars that become 

connected to the riverbank may become accessible to land-based 

predators. Moreover, river training structures can reduce the complexity 

of the habitat on the bottom of the channel—for example, a greater 

concentration of downstream flow means there are fewer tree limbs and 

other natural debris on the channel bed that may house smaller species. 

According to FWS officials that work with the St. Louis District, channel 

degradation resulting from river training structures alters the natural 

process of erosion and deposition that sustains various types of aquatic 

habitats.

In response to these concerns, the Corps has taken steps to reduce the 

impacts of its structures on river habitat. One key improvement is the 

notching of existing wing dikes, which allows water to flow through an 

individual wing dike or dike field while maintaining each structure’s ability 

to focus flows into the navigation channel. Benefits of dike notches 

include the conversion of sediment-laden areas between dikes back to 

aquatic habitat, the ability for fish to pass through the dikes, and 

increased oxygen levels in the secondary channels. One environmental 

group that we spoke to confirmed the notches’ success at counteracting 

the loss of aquatic habitat and has partnered with the Corps to notch wing 

dikes, as has FWS. See figure 9 for aerial and close-up views of notched 

wing dikes in the Mississippi River.

Some Researchers Have 

Reported That Structures 

Degrade Habitat, and the 

Corps Has Made 

Modifications in Response
 

Page 39 GAO-12-41 Mississippi River 

Figure 9: Aerial and Close-up Views of Notched Wing Dikes in the Mississippi River

Note: Arrows indicate locations of notched wing dikes in the left photograph. 

In addition, Corps biologists and engineers told us that after many 

decades of using wing dikes on the Middle Mississippi, the agency 

designed its chevrons specifically to reduce environmental impacts. 

According to these officials, chevrons also create more diverse habitat 

than wing dikes. As the river plunges over and flows around the archshaped structures, it creates pools behind the arch and in the scour holes 

on either end, each of which provides deep water habitat for fish. When 

the river is below the chevron’s top crest, the plunge pools become areas 

of calm water sheltered from upstream flows where fish can congregate 

to feed. Corps officials told us that, over the past 10 years, they have 

increasingly used these structures for environmental enhancement in the 

Middle Mississippi with the encouragement of FWS. FWS officials 

confirmed that they generally prefer chevrons to the St. Louis District’s 

other river training structures because of their relative habitat benefits. 

Figure 10 shows a closer view of one of the three chevrons in the St. 

Louis harbor.
 

Page 40 GAO-12-41 Mississippi River 

Figure 10: Close-up View of a Chevron in the St. Louis Harbor

Corps officials also noted two additional environmental benefits that 

partially offset the disruption to the natural river caused by their river 

training structures. First, Corps officials in multiple districts told us that the 

introduction of stone into a river largely devoid of it provides habitat for 

the macroinvertebrates52 that serve as the basis for the river’s food chain. 

Second, Corps officials told us that the structures are less injurious to the 

environment than the dredging that would otherwise be necessary to 

maintain the required 9-foot channel. Specifically, dredging requires 

repeated disturbance of the channel bottom, and the species residing 

there, and further disturbance in the area of the river where the dredged 

material is deposited. Aggregate data from several Mississippi River 

districts show that the Corps has steadily decreased dredging over the 

past 50 years as its construction of river training structures has increased.

 

52Macroinvertebrates are animals without backbones that are large enough to be seen 

with the naked eye. In the Middle Mississippi, these species include aquatic earthworms, 

flies, beetles, crayfishes, and freshwater mussels, among others.
 

Page 41 GAO-12-41 Mississippi River 

Some researchers in the Middle Mississippi region have issued reports—

based on statistical analysis of historical river stage and discharge data—

that link the proliferation of river training structures in the region with 

higher river levels during periods of high river flow. These researchers 

who are critical of the structures’ effects report that by creating 

impediments in the river to concentrate low flows, the structures raise the 

river’s height during higher-flow events, especially floods. For example, 

one professor at Southern Illinois University Carbondale—who has 

partnered with numerous co-authors to publish a series of journal articles 

on the subject53

According to this researcher, the effect of the structures is reversed at 

higher flows because adding dikes to a river channel (1) constricts the 

river, reducing its ability to convey floodwaters and (2) makes the channel 

rougher and more resistant to flow. His research shows these effects are 

compounded when there are multiple dikes that are each hundreds of feet 

long, as is common on the Middle Mississippi. According to this 

researcher, these effects have been recognized in other countries as well. 

He cites the example of the Netherlands, which has begun lowering 

dozens of wing dikes along a branch of the Rhine River and plans to 

lower hundreds more as part of a nationwide effort to reduce flood risk in 

that river’s floodplain.

—told us that there is a general consensus that flood 

stage magnitudes have risen over time on the Middle Mississippi. 

Drawing on historical river stage and discharge records for St. Louis and 

elsewhere on the Middle Mississippi, he has reported that cumulative 

hydrologic impacts resulting from the proliferation of river training 

structures have caused this change. Through specific gauge analysis, this 

researcher found that when flows are below the top level of wing dikes 

and concentrated in the channel, river stage decreases because those 

flows erode the channel bottom. When flows are above the top level of 

the structures but still well within the river’s banks, he found no net effect 

on river stage; but when river flows approach the top of the banks and 

overflow into the floodplain, he found a clear increase in stage.

 

53For example, Nicholas Pinter, Russell Thomas, and Joseph H. Wlosinski, “Assessing 

Flood Hazard on Dynamic Rivers,” Eos, Transactions, American Geophysical Union, vol. 

82, no. 31 (Washington, D.C.: July 31, 2001); Jonathan W.F. Remo and Nicholas Pinter, 

“Retro-modeling the Middle Mississippi River,” Journal of Hydrology, vol. 337 (2007); 

Nicholas Pinter, Abebe A. Jemberie, Jonathan W. F. Remo, Reuben A. Heine, and Brian 

S. Ickes, “Cumulative Impacts of River Engineering, Mississippi and Lower Missouri 

Rivers,” River Research and Applications, vol. 26 (2010).

Some Researchers Have 

Reported That Structures 

Increase Flood Stages, but 

the Corps Disagrees
 

Page 42 GAO-12-41 Mississippi River 

A professor at Washington University in St. Louis, who has studied the 

region since the mid-1990s, has also reported that river training structures 

can worsen flooding. His research has focused on historical river stage 

data for the Middle Mississippi. In a 2001 paper, he compared this 

historical record for the prior 140 years to the Corps’ river management 

practices over that period.54

Other researchers have also published papers documenting increased 

river stages due in part to river training structures. Two widely discussed 

studies published in 1975 were among the first to advance this theory.

He found that flood stages for similar 

discharges have increased steadily in the Middle Mississippi since 

continuous stage-discharge records have been kept and concluded that 

wing dikes have contributed to this increase in river stage. According to 

his research, this has resulted in major floods recurring with greater 

frequency and severity than in earlier eras. Further, he told us that among 

several factors that could have increased river stage—ranging from river 

training structures to levees and climate change—the Corps’ wing dikes 

are responsible for the largest share of this increase.

55

We reported on these studies in August 1995 as part of a review of the 

performance of Mississippi River levees in the 1993 Midwest flood.56

 

54Robert E. Criss and Everett L. Shock, “Flood Enhancement through Flood Control,” 

Geology, vol. 29, no. 10 (October 2001).

 At 

that time, we reported that researchers had used trend analysis to assert 

a relationship between long-term increases in flood levels and the Corps’ 

use of levees and river training structures. However, we found that the 

value of these studies was limited by a lack of accurate information about 

historic discharge rates and by conflicting results. In the additional studies 

that have appeared in scientific journals over the ensuing years stating 

that large discharges on the Middle Mississippi are now associated with 

55C.B. Belt, Jr., “The 1973 Flood and Man’s Constriction of the Mississippi River,” Science, 

vol. 189, no. 4204 (Aug. 29, 1975); Michael A. Stevens, Daryl B. Simons, and Stanley A. 

Schumm, “Man-Induced Changes of Middle Mississippi River,” Journal of the Waterways, 

Harbors, and Coastal Engineering Division: Proceedings of the American Society of Civil 

Engineers, vol. 101, no. WW-2 (May 1975).

56Intense rainfall that deluged the upper Mississippi River basin in the spring and summer 

of 1993 caused the largest flood ever measured at St. Louis. This unprecedented event in 

nine Midwestern states generated the highest flood crests ever recorded at 95 measuring 

stations on the region’s rivers, required the evacuations of tens of thousands of people, 

and created large-scale disruptions in transportation, business, and public services. See 

GAO, Midwest Flood: Information on the Performance, Effects, and Control of Levees,

GAO/RCED-95-125 (Washington, D.C.: Aug. 7, 1995).
 

Page 43 GAO-12-41 Mississippi River 

higher river stages than in prior eras, the authors generally conclude that 

multiple river training structures have a cumulative impact on flood 

heights that is greater than any one structure’s effect.

The Corps, however, disagrees with the conclusions of these 

researchers, and agency officials told us that the structures are so deeply 

submerged during flood events that they are essentially invisible to the 

river’s flow. They said that they base this understanding of the structures’ 

cumulative effects on their professional expertise, their more than 100 

years of experience managing the river, and on past studies conducted 

by Corps engineers and independent researchers. Based on this body of 

knowledge they agree that wing dikes reduce river stages at low flows as 

those flows are deflected into the channel; they also agree that levees are 

responsible for some increase in flood stages because they are designed 

to hold floodwaters back from portions of the floodplain, which can force 

these waters higher. However, they disagree that the structures have a 

cumulative impact on the river’s stage during high-flow events. According 

to Corps officials, as the Middle Mississippi approaches flood stage and 

eventually overflows its banks, any constriction of the river channel is 

dwarfed by the much wider and deeper dimensions of the flow. Corps 

officials told us that the greatest effect from river training structures 

occurs just as they are overtopped, not when they are submerged by 30 

feet or more (as is the case during some St. Louis floods). According to 

these officials, the specific gauge analysis results reported by researchers 

to support their conclusions are both counterintuitive and contrary to 

established models of hydraulic behavior. Corps officials also told us that 

although specific gauge analysis is a powerful tool to assess trends in the 

river stage-discharge relationship over time, it alone cannot isolate the 

effects of river training structures from other changes in the river and 

floodplain. A second limitation of specific gauge analysis is that it cannot 

account for natural variables like water temperature, sediment load, and 

bank vegetation—all of which can affect river stage. Additionally, they 

stated that there are not enough measured discharges for large floods to 

support a definitive trend analysis. They further stated that comparisons 

with rivers in other countries must take into account important differences, 

such as wing dikes that may be taller than those in the Middle Mississippi. 

We spoke with a researcher from the Netherlands who confirmed that 

wing dikes on a branch of the Rhine are being lowered to reduce flood 
 

Page 44 GAO-12-41 Mississippi River 

heights, as previously discussed, but also confirmed that these dikes sit 

relatively higher in the river than those in the Middle Mississippi.57

Moreover, according to Corps officials, inaccuracies in historical flood 

data have led to the false conclusion that river stages have grown over 

time for similar discharges—a position that we also reported in August 

1995.58 River discharge on the Middle Mississippi has been continuously 

measured by the USGS since 1933; before then, the Corps was 

responsible for such measurements, using devices and measurement 

techniques that were generally less accurate than those later used by 

USGS. For example, the Corps took its discharge measurements at St. 

Louis from boats, often with floating gauges, whereas USGS 

measurements were made from bridges with meters that were used 

consistently for the rest of the century. In 1935, 1949, and 1952, the 

Corps tested its earlier methodology against the USGS methodology and 

concluded that early Corps discharge measurements were systematically 

overstated, especially during floods. Consequently, the Corps now 

assesses pre-1933 data separately from post-1933 data in its own 

specific gauge analysis. In addition, the Corps reduced some of its 

historical discharge measurements to account for its earlier 

overstatements. Both of these approaches tend to flatten the rising trend 

that has been alleged by other researchers for river stage increases over 

time. Researchers who have used historical discharge data to link river 

training structures to increasing stages for similar discharges told us that 

the Corps’ revised approaches were inappropriate and served to mask a 

dangerous flooding trend. In response, the Corps cited a recent USGS 

study it commissioned that characterized the accuracy of pre-1933 

discharge measurements as “questionable” and recommended further 

examination of the historic record.59

In addition to its own research, the St. Louis District recently 

commissioned four external reviews of the relationship between river 

 

57According to this researcher, the navigation channel in this branch of the Rhine has 

steadily deepened over the years while the crests of its wing dikes have maintained their 

original heights.

58GAO/RCED-95-125, 43.

59U.S. Geological Survey, Examination of Direct Discharge Measurement Data and 

Historic Daily Data for Selected Gages on the Middle Mississippi River, 1861-2008, 

Scientific Investigations Report 2009-5232 (Reston, Va.: 2009).
 

Page 45 GAO-12-41 Mississippi River 

training structures and river stage, three of which have been completed 

and generally support the Corps’ position.60 The completed studies were 

prepared by a USGS hydrologist, a pair of engineers with several 

decades of experience on the Mississippi River, and a statistics professor

from Missouri University of Science and Technology. However, 

researchers who have raised concerns about the structures told us that, 

in their opinion, contractors reporting directly to the Corps—no matter 

how well-respected—are not sufficiently independent to resolve this 

issue. These researchers believe that a study conducted by an 

independent body like the National Research Council would have greater 

credibility.

The Corps has engaged critics of its river training structures in several 

ways in an attempt to resolve these disagreements. For example, it has 

invited them to attend the St. Louis District’s annual inspection tour. In 

addition, it has invited critics to visit district modeling facilities and meet in 

person to discuss their research and relevant data. Some meetings did 

take place between the Corps’ critics and officials from the St. Louis 

District, Mississippi Valley Division, and Corps headquarters. However, 

neither the Corps nor its critics reported that these meetings were 

successful in resolving their disagreements. Corps officials told us that 

their efforts to provide data to the critics of their river training structures 

were not reciprocated. The critics who attended these meetings told us 

that they believe the Corps listens only to its own staff in its thinking on 

this issue, rarely publishing its analyses in peer-reviewed journals where 

its assumptions and methodologies could be vetted by the scientific 

community. One river expert who is familiar with this dispute told us that 

while he is skeptical of work that has been done linking river training 

structures to increased flood stages, the Corps has not done a thorough 

job of publishing the research it has completed on the subject at both the 

district and national levels. St. Louis District staff agreed that they could 

do a better job sharing their analyses with the public. They told us that 

many studies are available on the district’s website but that they generally 

have neither the time nor the resources to prepare articles for journal 

publication.

 

60The district expects the fourth study—numerical modeling of chevron effects by a 

university hydraulics laboratory—to be completed by March 2012.

The Corps Has Engaged 

Critics in Several Ways, but 

Significant Professional 

Disagreement Remains
 

Page 46 GAO-12-41 Mississippi River 

We contacted 16 experts in river engineering and water resources to see 

if there was a possible resolution to the disagreement that exists between 

the Corps and its critics.61

Thirteen of the 16 experts told us that the question of river training 

structures’ cumulative effects on flood stages could be appropriately 

addressed by physical or numerical modeling or a combination of the two. 

As one expert told us, experimental modeling is much more likely to be 

successful than studies trying to unravel stage-discharge relationships 

over many decades, since so many physical changes have occurred in 

the river during that time. This expert recommended a numerical model of 

a large river section with input from a physical model. Similarly, another 

expert—who is familiar with the capabilities of hydraulics laboratories—

agreed that a combination of physical and numerical modeling should be 

capable of isolating river training structures’ effects on river stage. St. 

Louis District officials told us that they have a numerical modeling team, 

but, as noted previously, the district’s physical models are primarily smallscale models that are not capable of predicting structures’ effect on river 

stage. We also spoke with staff from the Corps’ Engineer Research and 

Development Center, which conducts numerical and large-scale physical 

modeling for Corps districts nationwide, to determine if they thought 

modeling was a feasible option. The staff, including two modelers with 

more than 35 years of experience each, told us that cumulative effects on 

river stage are an important issue that, with sufficient time and resources,

could be assessed using a large-scale model. One modeler emphasized 

These experts generally agreed with the Corps’ 

understanding of the impact of river training structures on flood stages, 

but they were less certain about the nature of the cumulative impact from 

many such structures aggregated over many river miles. Specifically, 

there was general agreement among the 16 experts that the influence of 

river training structures on river stage is diminished during periods of high 

flow. However, many of these experts told us that the magnitude of this 

effect would depend on specific characteristics of the structures and the 

river (similar to the Corps engineering manual’s guidance regarding the 

influence of channel contraction on flood heights noted earlier in this 

report). For example, one expert identified the height of a structure 

relative to the overall river depth as the most important factor, and a 

second stated that the overall number of structures and their spacing are 

key considerations.

 

61See appendix I for the names of these experts and how they were selected.

Experts Told Us That 

Modeling Could Help 

Determine Structures’ 

Effect on Flood Stages
 

Page 47 GAO-12-41 Mississippi River 

the importance of modeling the effects of an entire dike field, rather than 

using the results from a single structure to predict cumulative effects.

Corps officials acknowledged that their structures’ cumulative impact on 

river stage in the Middle Mississippi has not been modeled. While they 

told us that numerical and physical modeling could potentially be used to 

gain additional information on structures’ effect on river stage, they 

maintain that based on the results of studies conducted by the agency 

and others, they are confident of their understanding of river training 

structures and do not think that additional modeling would resolve the 

issue. Thus, in the absence of specific funding, they are reluctant to incur 

the costs of additional modeling. According to the Corps and other 

experts we spoke with, such costs could range from hundreds of 

thousands to several million dollars, in part because of the large cost of 

collecting river data to calibrate a model—especially if modelers tried to 

simulate hundreds of river miles. However, based on our discussions with 

experts, we believe a simplified model that focuses on some of the key 

attributes of the Middle Mississippi could be useful in resolving disputes 

over the river stage effects of a large dike field. The St. Louis District is 

currently funding two more limited studies, both at university 

laboratories—(1) a numerical model focused on the three chevrons in the 

St. Louis harbor and (2) a physical model with up to four structures built 

by a district engineer doing graduate research. According to the Corps, 

both models are assessing the effect of multiple river training structures 

on river stage. Studies such as these that test the Corps’ conclusions 

regarding the effects of its structures are worthwhile because, as 1 of the 

16 experts told us, “a good flood defense scheme is one that people 

believe in; otherwise, anxiety and fear can measurably diminish a 

community’s quality of life.” 

Congress requires the Corps to maintain a shipping channel in the 

Mississippi River that is navigable year-round from northern Minnesota to 

the Gulf of Mexico. By maintaining the channel, the Corps has enabled 

millions of tons worth of commerce to safely pass through the Mississippi. 

Over many decades of meeting this substantial challenge, the Corps has 

found that, in comparison to dredging, river training structures are often a 

more efficient, effective, and environmentally friendly way of maintaining 

the required depth. However, river training structures also have 

environmental impacts that the St. Louis District has not fully addressed. 

Specifically, in constructing new river training structures in the Middle 

Mississippi, the St. Louis District has not complied with certain federal 

and state environmental requirements, in particular with regard to NEPA 

Conclusions
 

Page 48 GAO-12-41 Mississippi River 

and CWA. The district continues to rely primarily on an EIS published 35 

years ago and has not prepared any post-EIS analyses as NEPA 

requires, even though significant changes have occurred in the river and 

in the design of its structures. Although the Corps has stated that it will 

prepare such an analysis in response to our findings, it is unclear when 

this will occur, what the scope of it will be, and whether it will be available 

for public comment. The St. Louis District also did not follow the Corps’ 

NEPA regulations calling for its review of new information that could 

warrant the preparation of a supplement to its existing EIS. In addition, 

the district has inappropriately relied upon a nationwide permit for 

maintenance to comply with the requirements of Section 404 of CWA for 

the construction of new river training structures. This new construction 

does not match the scope of the maintenance permit, and is inconsistent 

with Corps regulations and other districts’ practice.

In addition to its navigation and environmental missions, the Corps also 

has a mandate to provide flood protection to communities along the 

Mississippi River. For those who live near the river, it is important to have 

confidence that the Corps’ construction of river training structures for 

navigational and environmental benefits is not inadvertently increasing 

their flood risk. Based on its extensive experience with these structures 

and studies it has conducted as well as those conducted by others, the 

Corps remains confident in its conclusion that its river training structures 

do not exacerbate floods. However, there remains significant professional 

disagreement between the Corps and the critics of its structures. 

According to experts, one solution for resolving this disagreement is to 

conduct physical or numerical modeling to assess the cumulative effects 

of river training structures during periods of high flow.

We are recommending that the Secretary of Defense direct the Chief of 

Engineers and Commanding General of the U.S. Army Corps of 

Engineers to take the following five actions:

• To help ensure compliance with NEPA,

• prepare an EA to determine, in accordance with Council on 

Environmental Quality and Corps regulations, whether there are 

significant new circumstances or information relevant to the 

Middle Mississippi navigation project’s environmental concerns 

that have emerged since publication of the 1976 EIS, and if so, 

prepare a SEIS in accordance with NEPA, or if not, prepare a 

finding of no significant impact in accordance with NEPA;

Recommendations for 

Executive Action
 

Page 49 GAO-12-41 Mississippi River 

• develop and present in the EA an approach to ensure that sitespecific impacts are assessed, as appropriate, for new river 

training structures in the Middle Mississippi; and

• review and revise as needed St. Louis District procedures to 

ensure that determinations of whether existing NEPA documents 

need to be supplemented are performed in accordance with Corps 

regulations implementing NEPA and documented.

• To help ensure compliance with CWA, obtain CWA Section 404 

permit-equivalents and state water quality certifications as required for 

new river training structures in the Middle Mississippi. 

• To help resolve concerns over river training structures’ cumulative 

effect on river stages during periods of high flow, conduct physical or 

numerical modeling, or some combination thereof, to provide further 

insight into the relative magnitude of this effect for flood conditions on 

the Middle Mississippi. The Corps should determine and conduct the 

appropriate level of review for such modeling under its Civil Works 

Review Policy, including consideration of independent external peer 

review.

We provided a draft of this report to the Department of Defense for review 

and comment. The department generally concurred with the 

recommendations in our report. Specifically, the department agreed that 

the Corps should prepare an EA to determine whether there are 

significant new circumstances or information relevant to the Middle 

Mississippi navigation project’s environmental concerns that have 

emerged since publication of the St. Louis District’s 1976 EIS, and that 

the Corps should prepare a subsequent SEIS if the EA identifies 

undisclosed and currently unknown significant effects on the human 

environment that may require additional analysis and documentation. The 

department also agreed that the Corps should develop and present in the 

EA an approach to ensure that site-specific impacts are assessed, as 

appropriate, for new river training structures in the Middle Mississippi, and 

that the Corps should review and revise St. Louis District procedures to 

ensure that determinations of whether existing NEPA documents need to 

be supplemented are performed in accordance with Corps regulations 

implementing NEPA and documented. While we are encouraged by the 

department’s response, we note that under NEPA, the Corps must 

consider relevant external studies in addition to its own.

Agency Comments 

and Our Evaluation
 

Page 50 GAO-12-41 Mississippi River 

With respect to our recommendation that the Corps obtain required CWA 

Section 404 permit-equivalents and state water quality certifications for 

new river training structures in the Middle Mississippi, the department 

agreed that the Corps should perform all CWA assessments and obtain 

any certifications required by law and regulation. However, the 

department did not agree with our report finding that the Corps relied on a 

nationwide permit for maintenance as the mechanism for ensuring CWA 

compliance for river training structure construction in the Middle 

Mississippi. Instead, the department stated that the Corps has relied on 

its 1976 EIS and a CWA Section 404(b)(1) evaluation. The department’s 

statement is inconsistent with the information provided to us by Corps 

officials during the course of our review. According to some Corps 

officials, the agency relies on the nationwide permit to ensure compliance 

with CWA requirements for construction of river training structures in the 

Middle Mississippi. Although the Corps also provided us its 404(b)(1) 

evaluation from 1981, it did not provide any documentation of a permitequivalent, public notice, or state permits, all of which would need to 

accompany the 1981 evaluation in order to fully meet CWA requirements. 

Given the conflicting information provided to us by the department and 

the Corps, we believe that the Corps should consider including a 

description of how it is complying with CWA requirements when it 

prepares its forthcoming EA. 

Finally, the department partially concurred with our recommendation that 

the Corps conduct physical or numerical modeling, or some combination 

thereof, to provide further insight into the cumulative effect of river training 

structures during flood conditions on the Middle Mississippi, stating that 

the implementation of this modeling would be subject to funding and the 

results of the Corps’ ongoing monitoring and analysis. The department 

also stated that the Corps will consider independent external peer review 

of the results of its ongoing studies. While we agree that this may be 

helpful, it does not directly address our recommendation that the Corps 

consider independent external peer review of any new physical and/or 

numerical modeling that it undertakes.
 

Page 51 GAO-12-41 Mississippi River 

We are sending copies of this report to the Secretary of Defense, the 

Chief of Engineers and Commanding General of the U.S. Army Corps of 

Engineers, appropriate congressional committees, and other interested 

parties. In addition, the report is available at no charge on the GAO 

website at http://www.gao.gov. 

If you or your staff have any questions about this report, please contact 

me at (202) 512-3841 or mittala@gao.gov. Contact points for our Offices 

of Congressional Relations and Public Affairs may be found on the last 

page of this report. GAO staff who made key contributions to this report 

are listed in appendix III.

Anu K. Mittal

Director, Natural Resources and Environment
Appendix I: Objectives, Scope, and 

Methodology

Page 52 GAO-12-41 Mississippi River 

In the context of the Middle Mississippi, our objectives were to examine 

(1) key requirements and directives that govern the U.S. Army Corps of 

Engineers’ (Corps) use of river training structures, (2) how the Corps has 

addressed key federal and state environmental requirements in the use of 

river training structures, (3) the extent to which the Corps has monitored 

the hydrologic and environmental impacts of river training structures, and 

(4) concerns that researchers have raised about the hydrologic and 

environmental impacts of the Corps’ river training structures and how the 

Corps has responded to these concerns. Our work focused on the Corps’ 

St. Louis District and its management of the Middle Mississippi.

To address the first objective, we reviewed relevant provisions in key 

federal and state laws, regulations, and guidance that govern the Corps’ 

use of river training structures. We determined these laws, regulations, 

and guidance to be key because they authorize construction of river 

training structures and they relate to flooding and environmental impacts. 

We traveled to St. Louis to meet with officials from the Corps’ Mississippi 

Valley Division and St. Louis District, specifically agency engineers, 

attorneys, biologists, and other scientists. We conducted separate 

interviews with engineering and environmental staff from each of the five 

remaining districts in the Mississippi Valley Division—Memphis, New 

Orleans, Rock Island, St. Paul, and Vicksburg—to learn about their 

requirements for river training structures. We interviewed state officials 

involved in reviewing activities on the Mississippi River, including officials 

with the Illinois and Missouri Departments of Natural Resources and the 

Missouri Department of Conservation, to identify any requirements they 

have related to the Corps’ river training structures. We also reached out 

to local officials in the city of St. Louis and three St. Louis-area counties—

St. Clair County, Illinois; St. Charles County, Missouri; and St. Louis 

County, Missouri—but all four told us they were not aware of any actions 

by their jurisdictions to regulate Corps activities related to river training 

structures on the Mississippi River.

To address the second objective, we reviewed Corps documentation for 

compliance with the National Environmental Policy Act (NEPA), the Clean 

Water Act, the Fish and Wildlife Coordination Act, and the Endangered 

Species Act. With respect to NEPA, we reviewed relevant environmental 

assessments, environmental impact statements, and a biological opinion 

issued by the U.S. Fish and Wildlife Service (FWS) in 2000. We 

interviewed officials with the Corps’ Office of General Counsel and 

obtained in writing the Corps’ legal views on how it has complied with 

NEPA requirements with respect to its river training structures built under 

the navigation authority. We interviewed officials with the FWS Illinois 

Appendix I: Objectives, Scope, and 

Methodology 
Appendix I: Objectives, Scope, and 

Methodology

Page 53 GAO-12-41 Mississippi River 

Sub-Office to discuss Corps actions related to the Endangered Species 

Act. We also reviewed Corps documentation relative to state 

requirements and interviewed relevant Corps, state, and local officials 

discussed previously. We interviewed officials with several 

nongovernmental organizations to obtain their views, including American 

Rivers, the American Society of Civil Engineers, the Association of State 

Floodplain Managers, the Lower Mississippi River Conservation 

Committee, the National Wildlife Federation, and the St. Louis Confluence 

Riverkeeper. 

To address the third objective, we reviewed the Corps’ various 

assessments of its river training structures. We examined documentation 

from selected projects to become familiar with how the Corps assesses 

its structures’ impacts. We interviewed Corps officials on the extent to 

which the Corps conducts pre- and post-construction hydraulic, 

hydrologic, and environmental assessments of river training structures. 

We reviewed reports on Corps modeling efforts. During our trip to St. 

Louis, we visited the St. Louis District’s Applied River Engineering Center 

to discuss and observe modeling efforts and we participated in a districtled river tour of the Middle Mississippi near St. Louis that included 

observing river training structures. In our interviews with other districts 

within the division, we discussed the extent to which they conduct 

hydraulic, hydrologic, and environmental assessments of river training 

structures. We also interviewed the previously mentioned 

nongovernmental organizations for their views.

To address the fourth objective, we conducted a detailed literature review 

of scientific periodicals and government-sponsored research on the 

effects of river training structures. Specifically, we used an iterative 

process to identify relevant research. We identified search terms that we 

refined as we reviewed the literature for terminology related to this topic. 

In addition, we reviewed the bibliographies of literature we had found to 

identify further studies for review. The documentary sources cited in our 

report were reviewed for methodological strength and reliability and we 

ultimately determined them to be sufficiently reliable for our purposes. We 

believe we have included the key studies and have qualified our findings, 

where appropriate. However, we may not have identified all of the studies 

with findings relevant to our objectives. We used this review—along with 

interviews of officials from the Corps (as described previously), FWS, 

U.S. Geological Survey, and state resource agencies, as well as other

researchers not affiliated with these parties—to compile the key concerns 

that have been raised about the structures’ hydrologic and environmental 

impacts and how the Corps has addressed those concerns. We 
Appendix I: Objectives, Scope, and 

Methodology

Page 54 GAO-12-41 Mississippi River 

interviewed the authors of two of the four recent studies commissioned by 

the Corps to evaluate the research that links river training structures to 

increased stage. (We did not interview the authors of the remaining two 

studies because one was a summary review of other authors’ statistical 

analysis and the other was a modeling exercise still underway at the time 

this report was issued.) We spoke with officials with the Corps’ Engineer 

Research and Development Center to discuss physical and numerical 

modeling. We met with officials with the National Research Council’s 

Water Sciences and Technology Board to discuss the Board’s role with 

respect to resolving professional disagreements over complex scientific 

issues. We also interviewed the previously mentioned nongovernmental 

organizations for their views.

In addressing the fourth objective, we conducted structured interviews 

with 16 experts in the fields of river engineering and water resources on, 

among other things, river training structures’ potential effects on river 

stage; whether such effects can be isolated from other structures, such as 

levees, or other hydrologic factors, such as climate change; and, if so, 

how this might be done. We used the “snowball sampling” technique to 

identify these knowledgeable experts. Specifically, we identified these 

experts through recommendations made during our interview process and 

by soliciting recommendations from the following organizations: the 

National Research Council’s Water Sciences and Technology Board; the 

American Society of Civil Engineers, including its American Academy of 

Water Resource Engineers; the American Geophysical Union; the 

Colorado State University Water Institute; and the World Association of 

Waterborne Transport Infrastructure. We sought a balance of experts 

between those currently engaged in applied engineering and those 

currently in academic positions, and also sought those who were, to the 

extent possible, independent from both the Corps and the critics of its 

river training structures. Prior to interviewing the 16 experts, we pretested 

the structured interview with three subject matter experts and, based on 

those results, made adjustments to the structured interview as necessary. 

The names of the 16 experts we interviewed are listed alphabetically in 

table 1. 
Appendix I: Objectives, Scope, and 

Methodology

Page 55 GAO-12-41 Mississippi River 

Table 1: List of Interviewed Experts

List of experts

1 Nani G. Bhowmik, Ph.D., P.E., Life Member and Fellow, ASCE, F. IWRA, M. AGU, 

D. WRE, Principal Scientist Emeritus, Illinois State Water Survey, Prairie Research 

Institute, University of Illinois

2 Jeff Bradley, Ph.D., P.E., D.WRE, President, WEST Consultants

3 Mike Buechter, P.E., Principal Engineer, Metropolitan St. Louis Sewer District

4 John Cassidy, Ph.D., P.E., Dist.M.ASCE, NAE, Hon.D.WRE, Independent 

Consultant Specializing in Hydraulic and Hydrologic Engineering (also former Chief 

Hydraulic Engineer at Bechtel Corporation)

5 Tim Dean, P.E., LEED® AP, Civil Engineer, Intuition & Logic, Inc.

6 David Galat, Ph.D., Adjunct Associate Professor, Department of Fisheries and 

Wildlife Sciences, University of Missouri

7 Marcelo Garcia, Ph.D., Professor, Department of Civil and Environmental 

Engineering, and Director, Ven Te Chow Hydrosystems Laboratory, University of 

Illinois

8 Robert R. Holmes, Jr., Ph.D., P.E., D.WRE, Hydrologist, U.S. Geological Survey

9 Susan McCrary, P.E., Senior Civil Engineer

10 Gary Parker, Ph.D., Professor, Department of Civil and Environmental Engineering 

and Department of Geology, University of Illinois

11 Timothy J. Randle, M.S., P.E., D.WRE., Manager, Sedimentation and River 

Hydraulics Group, U.S. Bureau of Reclamation

12 Bruce Rhoads, Ph.D., Professor and Head of the Geography Department and 

Affiliate Professor in the Department of Geology and the Department of Civil and 

Environmental Engineering, University of Illinois

13 Doug Shields, Jr., Ph.D., P.E., Research Hydraulic Engineer, USDA-Agricultural 

Research Service

14 Colin Thorne, Ph.D., Chair, Physical Geography Department, Nottingham 

University (England)

15 Chris Thornton, Ph.D., P.E., Director, Engineering Research Center, Colorado 

State University

16 Chester Watson, Ph.D., P.E., Biedenharn Group, LLC (Emeritus Professor of Civil 

Engineering, Colorado State University)

Source: GAO.

We conducted this performance audit from September 2010 through 

December 2011 in accordance with generally accepted government 

auditing standards. Those standards require that we plan and perform the 

audit to obtain sufficient, appropriate evidence to provide a reasonable 

basis for our findings and conclusions based on our audit objectives. We 

believe that the evidence obtained provides a reasonable basis for our 

findings and conclusions based on our audit objectives.
Appendix II: Comments from the Department 

of Defense

Page 56 GAO-12-41 Mississippi River 

Appendix II: Comments from the Department 

of Defense
Appendix II: Comments from the Department 

of Defense

Page 57 GAO-12-41 Mississippi River 

Note: All recommendations 

can now be found on 

pages 48 and 49.
Appendix II: Comments from the Department 

of Defense

Page 58 GAO-12-41 Mississippi River 
Appendix III: GAO Contact and Staff 

Acknowledgments

Page 59 GAO-12-41 Mississippi River 

Anu K. Mittal, (202) 512-3841 or mittala@gao.gov

In addition to the individual listed above, Vondalee R. Hunt (Assistant 

Director), Elizabeth Beardsley, David Brown, George Depaoli, Mark 

Keenan, Perry Lusk, and Rebecca Shea made significant contributions to 

this report. Michael Armes, James Ashley, Cheron Green, Richard 

Johnson, Justin Mausel, Sarah M. McGrath, Nathan Morris, Madhav 

Panwar, Holly Sasso, Aaron Shiffrin, Ben Shouse, and Vasiliki 

Theodoropoulos also made key contributions.

Appendix III: GAO Contact and Staff 

Acknowledgments 

GAO Contact

Staff 

Acknowledgments

(361232)
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