Mississippi Valley Division Engineer Research and Development Center

Change in Lower Mississippi River Secondary Channels: 

An Atlas of Bathymetric and Photographic Data

Mississippi River Geomorphology and Potamology Report No. 8

Information is presented on the existing and long-term (1960s–2000s) trends in Lower 

Mississippi River (LMR) secondary channels to assist USACE and other agencies in the 

conservation and restoration of channel function and value. The methodology can be used 

to monitor the number of secondary channels within the LMR to demonstrate compliance 

with the USFWS 2013 Biological Opinion on the MR&T Channel Improvement Program. 

Data sets can be used to identify high-value secondary channels for conservation purposes 

and to prioritize secondary channels for restoration.

Background

Secondary channels provide a variety of habitat types and are highly productive while being 

protected from commercial navigation traffic. Depending on river stage and connectivity, 

secondary channels function as wetlands, isolated backwaters, connected backwaters, 

isolated secondary channels, and flowing secondary channels. Connectivity also affects 

substrates, water quality conditions, benthic invertebrate communities, and fish faunas. 

However, many secondary channels have closing dikes and sandbars that prevent 

connectivity at mid to low river flows. Altering these blockages to create a diversity of flow 

and connectivity improves habitat diversity and provides aquatic species access to highquality habitat. Diversifying secondary channels by notching closing dikes and monitoring 

the evolving geomorphology of island complexes is a primary conservation measure within 

the 2014 Conservation Plan for the Interior Least Tern, Pallid Sturgeon, and Fat 

Pocketbook Mussel. This atlas can be used as an important resource for these purposes.

Techniques

One set of bathymetric and photographic data for each decade from the 1960s to 2000s was 

gathered from the New Orleans (MVN), Vicksburg (MVK), and Memphis (MVM) 

Districts. A secondary channel was defined as a contiguous lower elevation area divided 

from the main channel by a vegetated or nonvegetated bar. Bars were identified by locating 

at least three adjacent bathymetric transects (approximately 1,000 ft intervals) with adjacent 

points whose elevations were > +5 ft Low Water Reference Plane (LWRP). An outline of 

the secondary channel was digitized for the following: inlet and outlet – drawing a line 

halfway between and parallel to the last bathymetric transect for the bar and the subsequent 

transect with no bar; riverward bank – connecting the bar’s highest elevation points; and 

landward bank – a line drawn through the first bathymetric point > +10 ft LWRP or just 

beyond if < + 10 ft LWRP. A secondary channel was no longer present when bathymetric 

data covered the area where the channel existed in prior or subsequent decades and (1) all 

data were less than +5 ft LWRP (bar eroded) or (2) a bar existed but at least two transects in 

the channel had no point lower than +10 ft LWRP. Fifteen riverbed models were generated 

from the bathymetric data, one model for each decade and district. Secondary channel 

outlines and riverbed models were used to calculate secondary channel area and volume at 

water surface elevations of -5, 0, +5, +10 ft LWRP. Because presence/absence and area and 

volume are determined primarily by the availability of bathymetric survey data, this study 

includes a subset of LMR secondary channels. Long, shallow secondary channels and those 

situated within the batture (e.g., old chutes, cutoffs) are likely to be excluded from this 

study because survey boats could not gain access. This report presents data and a visual 

atlas (example follows) for each of the 198 secondary channels identified in the LMR. 
Decadal data indicate that natural secondary channel formation 

still occurs within the LMR, albeit due to in-channel 

development rather than overbank flows. Over 5 decades, 100 

secondary channels were identified in MVM, 76 in MVK, and 

22 in MVN. Of these 198 channels, 102 had data for 4 of the 5 

decades (the 1980s included few channels due to low water). 

These data can be used to provide insight into secondary 

channel condition, abundance, and distribution. Restoration 

efforts can focus on channels with the largest declining area and 

volume. Alternatively, reaches of river with few channels can 

be targeted, and existing channels given priority or channel 

creation sites identified. By studying the large-scale distribution 

of secondary channels, planners can understand characteristics 

that lead to channel persistence and focus on sites with these 

characteristics. Finally, secondary channel habitat types could 

be classified to focus restoration on channels containing rare 

habitats. This report provides information that the numerous 

interested parties can utilize to prioritize objectives and identify 

restoration sites. 

For More Information 

To access the full version of Change in Lower Mississippi 

River Secondary Channels: An Atlas of Bathymetric and 

Photographic Data, click the following link: 

Additional MRG&P reports, historic reports, and MRG&P 

information can be accessed from the technology transfer 

section link at the MVD Historic Studies website: 

http://www.mvd.usace.army.mil/mrgp_pubs.

Results and Findings

 

Summary of Significant Findings

• Secondary channels continue to form 

naturally within the main channel. No 

overbank formation was observed.

• This study provides a 5 decade snapshot 

of the number and physical 

characteristics of 198 LMR secondary 

channels.

• Re-establishing a diversity of secondary 

channel connectivity is a priority for 

USACE partners and a conservation 

measure in the 2014 Conservation Plan.

• Data can be used to justify and target 

restoration actions by identifying trends 

for individual channels or for particular 

areas of interest.

Points of Contact 

Amanda Oliver, Author, Jaya Corporation, 

Amanda@jayacorp.com

Erin Guntren, Author, USACE MVS, 

Erin.F.Guntren@usace.army.mil

Barb Kleiss, Ph.D. MRG&P Technical Director 

USACE MVD, Barbara.A.Kleiss@usace.army.mil