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Article

Land Reclamation in the Mississippi River Delta

by
Glenn M. Suir
1,
Christina Saltus
2,* and
Jeffrey M. Corbino
3
1
U.S. Army Corps of Engineers, ERDC, Wetlands and Environmental Technologies Research Facility, Lafayette, LA 70504, USA
2
U.S. Army Corps of Engineers, ERDC, Geospatial Data Analysis Facility, Vicksburg, MS 39180, USA
3
U.S. Army Corps of Engineers, MVN, New Orleans, LA 70118, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2025, 17(5), 878; https://doi.org/10.3390/rs17050878
Submission received: 21 December 2024 / Revised: 24 February 2025 / Accepted: 25 February 2025 / Published: 1 March 2025
(This article belongs to the Special Issue Remote Sensing in Coastal Vegetation Monitoring)
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Abstract

:
Driven by the need to expand urban/industrial complexes, and/or mitigate anticipated environmental impacts (e.g., tropical storms), many coastal countries have long implemented large-scale land reclamation initiatives. Some areas, like coastal Louisiana, USA, have relied heavily on restoration activities (i.e., beneficial use of dredged material) to counter extensive long-term wetland loss. Despite these prolonged engagements, the quantifiable benefits of these activities have lacked comprehensive documentation. Therefore, this study leveraged remote sensing data and advanced machine learning techniques to enhance the classification and evaluation of restoration efficacy within the wetlands adjacent to the Mississippi River’s Southwest Pass (SWP). By utilizing air- and space-borne imagery, land and water data were extracted and used to compare land cover changes during two distinct restoration periods (1978 to 2008 and 2008 to 2020) to historical trends. The classification methods employed achieved an overall accuracy of 85% with a Cohen’s kappa value of 0.82, demonstrating substantial agreement beyond random chance. To further assess the success of the SWP reclamation efforts in a global context, broad-based land cover data were generated using biennial air- and space-borne imagery. Results show that restoration activities along SWP have resulted in a significant recovery of degraded wetlands, accounting for approximately a 30 km2 increase in land area, ranking among the most successful land reclamation projects in the world. The findings from this study highlight beneficial use of dredged material as a critical component in large-scale, recurring restoration activities aimed at mitigating degradation in coastal landscapes. The integration of remote sensing and machine learning methodologies provides a robust framework for monitoring and evaluating restoration projects, offering valuable insights into the optimization of ecosystem services. Overall, the research advocates for a holistic approach to coastal restoration, emphasizing the need for continuous innovation and adaptation in restoration practices to address the dynamic challenges faced by coastal ecosystems globally.

1. Introduction

Globally, coastal regions face substantial pressures to create or reclaim land, driven by the need to expand urban and industrial complexes, mitigate anticipated environmental impacts (e.g., tropical storms), and the urgent need to restore land in severely degraded landscapes. Land reclamation is the process of creating or restoring land by depositing sediment, soil, or other materials into shallow water areas, such as seas, rivers, or lakes. The demand for land reclamation is particularly acute in many coastal cities, where 106 out of 135 major coastal urban centers worldwide need to expand ports for bolstering global trade in order to enhance residential and commercial infrastructure to accommodate real estate growth and to elevate regional and global prominence [1,2]. Consequently, there has been a significant surge in land reclamation activities, with approximately 2530 km2 of land reclaimed in coastal areas between 2000 and 2020 [2]. China has emerged as a global leader in land reclamation endeavors, utilizing reclaimed land to alleviate population density pressures and foster industrial development [3,4].
Coastal nations worldwide have also adopted land reclamation strategies to shield vulnerable coastlines and dynamic ecosystems from escalating threats. Many of these coastal ecosystems have undergone degradation, rendering them increasingly susceptible to a myriad of natural and anthropogenic pressures [5,6]. Over 50 percent of all coastal wetlands have been lost in the past century, primarily due to coastal processes and episodic events including the rising frequency and intensity of storms and floods [7,8]. These impacts pose major concerns for densely populated low-lying coastal regions and are projected to inundate over 70 percent of all previously reclaimed lands by the year 2100 [1,2,9]. The synthesis of these multifaceted pressures underscores the critical imperative for comprehensive and proactive approaches to coastal land management, emphasizing sustainable practices that balance developmental needs with ecosystem resilience.
For many areas, like the coastal zone of Louisiana, wetland ecosystems constitute a substantial natural resource, contributing “significant goods and services, including flood control, water filtering and storage, food supply, shoreline and storm protection, cultural value, critical habitat, and regulation of major chemical, physical, and biological processes” [10,11]. For several millennia, the Louisiana deltaic plain experienced progradation through river sediment delivery to adjacent landscapes and shallow water areas during seasonal floods and other episodic events [12]. However, the deltaic plain has transitioned into an erosional phase controlled by compounding and interacting abiotic and biotic stressors. These include extreme climate events (i.e., hurricanes and floods), flood control interventions, subsidence, hydrologic alterations, oil and gas exploration (i.e., access canals), and subsurface hydrocarbon extraction [13,14,15,16,17,18]. Flood control measures have significantly contributed to wetland degradation along the Mississippi River in coastal Louisiana. These measures, which include dams/weirs along upper reaches and levees along lower reaches, have resulted in a 73 percent reduction in suspended sediment load from 1960 to 2009 (Tarbert Landing) [19]. The resultant sediment deficits have had adverse consequences on wetland vegetation productivity and marsh elevation, causing substantial wetland degradation and conversion into open water bodies [20,21,22]. Although Louisiana coastal wetlands account for 40 percent of the nation’s coastal wetlands, they have disproportionately accounted for 80 percent of total coastal wetland losses over the past century, predominantly attributable to prolonged sediment deficiencies [23,24]. Notably, the Mississippi River Delta (MRD) Basin, situated in the southeastern region of the Louisiana deltaic plain, has experienced some of the highest rates of wetland loss globally. From 1934 to 2016, this area has witnessed an astounding 55 percent loss in wetland coverage [18,25].
In Louisiana, as in other coastal regions of the United States, land reclamation serves as a vital strategy to counteract decades of severe wetland loss. Dredged sediments have emerged as pivotal resource materials utilized within authorized restoration activities and through synergistic applications known as beneficial use of dredged material (BUDM) [26]. The state of Louisiana has established long-term and comprehensive programs such as the Louisiana Coastal Area (LCA) and the Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA) to spearhead environmental restoration efforts focused on the creation, restoration, protection, and enhancement of coastal wetlands [27]. An example of such endeavors is the LCA Beneficial Use of Dredged Material (BUDMAT) Program, sanctioned under Title VII, Section 7006(d) of the Water Resources Development Act of 2007 (Public Law 110–114). This initiative utilizes dredged material from navigation projects to introduce river sediments into the coastal environment, restoring marshes, and constructing other environmental features [28]. Likewise, the CWPPRA program has made significant strides through dedicated dredging efforts and strategic placement of material, notably contributing to the nourishment and restoration of approximately 400 km2 of Louisiana coastal wetlands between 1990 and 2021 [27]. The reclamation process entails dredging material from nearby water bodies, such as rivers or estuaries, and placing them in designated areas. These activities aim to increase land elevation, promote vegetation establishment, and thus rebuild and restore critical wetland landscapes.
Dredging sediments represents a fundamental aspect of U.S. Army Corps of Engineers (USACE) navigation operations and maintenance (O&M) endeavors. O&M dredging typically entails the periodic extraction, conveyance, and disposal of vast quantities of naturally accumulated bottom sediments within navigation channels [26,29]. Historically, open water disposal and confined disposal facilities have served as the primary means of sediment placement for O&M dredging activities [30]. However, there has been a discernible increase in the utilization of BUDM in recent decades [31]. BUDM encompasses a spectrum of effective and positive uses of dredged material, spanning diverse categories such as the development of fish and wildlife habitats, recreational facilities, and industrial and commercial uses [32]. Between 1998 and 2023, approximately 12,000 dredged material placement events were recorded in the United States, with about 4000 incorporating BUDM applications at no additional cost to navigation O&M, resulting in the reclamation of approximately 175 km2 of land [33]. From its inception, BUDM applications for ecosystem restoration have been vigorously endorsed. While previous USACE goals have resulted in the beneficial use of approximately 40 percent of sediments dredged through the navigation mission, USACE has established a new target of 70 percent beneficial use by 2030 [31]. Although discontinuous reaches of the Mississippi River’s Southwest Pass (SWP) navigation channel have been dredged annually since 1945 (earliest record), those dredged materials were placed solely in open water disposal and confined disposal facilities until 1975, when the first SWP-related BUDM application was used to restore MRD wetlands [34].
In addition to dredged sediment placement, river and sediment diversions have also been used as primary wetland restoration strategies. Sediment diversions, which typically redirect sediment-laden water from rivers or estuaries into areas with sediment deficiencies, can be effective for long-term rebuilding and sustaining of marshes, barrier islands, and other coastal landforms [21]. Within the MRD, the West Bay Sediment diversion project was initiated to counter a 70 percent loss of coastal land (approximately 32.4 km2) and associated threats to the structural integrity of the adjacent SWP federal navigation channel and bank line (Figure 1) [35]. The primary objective of the West Bay Sediment diversion project is to reintroduce sediment from a diversionary channel of the Mississippi River to foster, nourish, and maintain approximately 40 km2 of fresh to intermediate marsh in West Bay. Monitoring conducted over the initial decade of operations revealed minimal land emergence, prompting adaptive management measures, including the construction of sediment trapping berms within the West Bay Sediment diversion outfall area [36]. This integrated approach also leveraged the placement cells (berms) to direct diverted river water and sediment to the westernmost segments of the West Bay outfall area, surpassing the placement limits of traditional dredging applications [35].
Federal, state, and local stakeholders have been actively promoting and participating in dredged material placement along the SWP channel for approximately 50 years. However, despite this prolonged engagement, the quantifiable benefits of these activities have lacked comprehensive documentation. These data and knowledge gaps can be significant since understanding these complex interplays is paramount for effective wetland management and restoration strategies aimed at bolstering ecological resilience amidst escalating stressors. Thus, this study aimed to leverage remote sensing data and advanced techniques to streamline the classification and evaluation of wetland restoration efficacy within critical ecosystems. The specific objectives were to (1) utilize high spatial resolution and multi-temporal imagery in conjunction with machine learning methodologies to classify wetland habitat features; (2) quantify and assess historical loss, recent wetland gains (as part of restoration measures), and landscape feature changes within the SWP study area (Figure 1); and (3) compare the extent of reclaimed wetlands to other large-scale reclamation projects around the world. Utilizing quantitative methodologies and geospatial analyses, this study focused on describing the temporal trajectories of wetland morphology, thereby delineating patterns of change across distinct temporal epochs. The integration of historical data spanning several decades with contemporary observations facilitates the discernment of long-term trends and the identification of critical inflection points coinciding with major restoration initiatives.

2. Methods

2.1. Study Area

The study area encompasses the wetlands and the shallow water features adjacent to the Southwest Pass (SWP) navigation channel within the MRD, positioned at the confluence of the Mississippi River and the Gulf of Mexico, approximately 130 km southeast of New Orleans, Louisiana (Figure 1; 89.3°W, 29.05°N; basemap from 13 November 2020). SWP, serving as the westernmost outlet of the Mississippi River, has functioned as the primary conduit for deep-draft navigation access to critical terminals and industries since its establishment in 1853 [37]. Extending approximately 31 km from the Head of Passes to the Gulf of Mexico, SWP exhibits a variable width ranging from 360 to 1500 m, at its narrowest and widest points, respectively. The SWP study area is a unique and dynamic environment consisting primarily of wetlands that are dominated by Phragmites australis and largely regulated by natural processes (i.e., water level, sediment deposition, and subsidence) and human activities (i.e., levee construction and wetland reclamation) [38].

2.2. Dredging Activities

To fully comprehend the magnitude of land reclamation in the study area, it is essential to first assess the history, quantities, and locations of the beneficial use of dredged material along the SWP. Historical records and archival data were reviewed to document the timeline and scale of dredging activities in the area [39,40,41,42,43]. Data on the volume of dredged material deposited annually was compiled, and specific deposition sites along SWP were identified. Existing GIS-based vector data were also obtained from the USACE New Orleans District and used to spatially delineate placement sites by year and quantity. This comprehensive assessment provided a baseline understanding of the contributions of dredged material to land reclamation efforts in the region, thereby allowing for a more informed analysis of the overall impact and significance of these activities within the broader context of wetland restoration.

2.3. Wetland Change Analysis

A comprehensive assessment of short- and long-term landscape changes offers critical insights into structural changes, serving as important precursors to understanding functional implications of wetland restoration efforts [44]. To evaluate wetland changes over time, this study utilized land and water data derived from multiple data sets (i.e., modified from existing habitat data and derived from air- and space-borne imagery). The land change assessments were performed using three distinct periods of analysis, the historical period (1934 to 1978), the initial BUDM period (1978 to 2008), and the reclamation period (2008 to 2020). One primary objective of this study was to compare recent land change trends to historical trends. Although dredged materials have been placed in shallow water areas along the Southwest Pass since the 1970s, more frequent and focused land reclamation applications did not begin until after 2000, including the West Bay sediment diversion and BUDM applications. Therefore, the restoration period was divided to better compare the benefits of previous techniques of dredged material placement (1978 to 2008) to those with specific land building purpose (2008 to 2020). The implementation of a comprehensive analytical framework, encompassing both historical precedents and recent interventions, facilitates a holistic understanding of restoration activities within this dynamic wetland system. In addition to fundamental land and water analyses, the mapping and assessment of broad-based land cover changes are crucial for determining the overall success of wetland restoration projects, as well as for monitoring and evaluating the ecological characteristics, functions, and integrity of wetlands systems. In this study, the land and water analyses were performed across the entire period of record (1934 to 2020), while the broad-based land cover classification and landscape change and pattern analyses were performed across the reclamation period (2008 to 2020).

2.4. Land Change Assessments

2.4.1. Historical Period

Quantifying and assessing historical wetland loss provides vital baseline data for comparisons to reclamation activities. This historical period, which spans 1934 to 1978, consists of the period of geospatial record that pre-dates the initial BUDM (1978 to 2008) and recent programmatic reclamation projects (2008 to 2020). Table 1 details the data and air- and space-borne imagery used to perform land and water assessments across the three analyses periods. Historical land change rates were calculated using existing land and water classification data derived from (1) U.S. Coastal and Geodetic Survey (USCGS) topographic sheets (1934), and (2) U.S. Geological Survey (USGS) National Wetland Inventory (NWI) data (1956 and 1978) (Table 1). The USCGS program generated shoreline and land and water products by manual photointerpretation and digitization of panchromatic imagery [45]. The USGS NWI data were produced as part of the U.S. Fish and Wildlife Service NWI Program using a manual photointerpretation and digitization of panchromatic and color infrared aerial photography along with a modified Wetlands and Deepwater Habitats of the United States classification scheme [46]. Code modifiers were used to conform the NWI habitat scheme to Louisiana specific wetland habitats [47]. For the land and water area change assessments, the adjusted habitat data were grouped into land and water categories using the Reclassify tool in ArcGIS 10.8, where land features consisted of uplands, emergent vegetation, wetland forest, or scrub–shrub; and water features consisted of any open water, floating or submerged aquatics, and non-vegetated mud flat. Although remote sensing provides a useful process for evaluating wetland change over time, there are limitations and uncertainties that must be considered. These uncertainties can be significant, especially when comparing data with vastly different spatial resolution or with substantially different analytical techniques. However, the resolution of the source imagery used to create the historical land and water data sets correspond closely with the high-resolution aerial and satellite imagery. Additionally, the broad spatial context of this project allows for the generalization of results, mitigating the influence of pixel size on overall land change assessments, particularly since the landscape consists of distinct features that are easily identifiable within the imagery. Nevertheless, to ensure maximum consistency between data sets, the historical data were rasterized, resampled (using cubic convolution), and co-registered to the 1 m resolution imagery.

2.4.2. BUDM and Reclamation Periods

The overall beneficial use period of record (1978 to 2020) was subdivided into an initial BUDM period (1978 to 2008) and a recent land reclamation period (2008 to 2020) (See Section 3.1. Dredging and Placement Activities for detailed description of beneficial use activities and periods). Land change rates during the initial BUDM period were calculated using existing data consisting of the following: (1) USGS NWI data (1978 and 1988) and (2) land and water thematic data classified using 1998 Louisiana Oil Spill Coordinator’s Office (LOSCO) and 2004 USGS Digital Orthophoto Quarter Quadrangle (DOQQ) (Table 1).
Similarly, land change assessments for the reclamation period (2008 to 2020) were performed biennially using high-resolution imagery from the Beneficial Use Monitoring Program (BUMP) (Table 1). Due to insufficient quality in the 2014 BUMP imagery, space-borne imagery was used as an alternative. This consisted of high-resolution (1.24 m) MAXAR WorldView-3 multispectral (8-band) data collected on 14 November 2014. The WorldView-3 imagery was acquired at no cost based on a contractual agreement between the Army Geospatial Center Imagery Office and the National Geospatial-Intelligence Agency. This agreement facilitates the acquisition of archived, unclassified, commercial imagery (i.e., MAXAR) at no cost to the Army services and intelligence communities [48]. Biennial and cumulative changes in land area during the reclamation period were calculated and compared to changes during the historical and BUDM periods.
To evaluate the amount of land reclaimed in the SWP study area, we can compare the land change within the historical period to the changes that occurred during the initial BUDM and reclamation periods. We also used these data to compare the amount of reclaimed land in the SWP study area with other large-scale restoration and reclamation projects globally. These projects, which were identified through a search and review of scientific literature and databases, were selected based on similar scale, objectives, and methods. Comparative analysis was conducted to assess the relative success of the SWP area reclamation efforts in the context of global reclamation initiatives.

2.5. Land Cover Classification

To assess the benefits associated with restoration activities in the SWP study area, broad-based land cover data were created using biennial BUMP photography and WorldView-3 images (Table 1). Since previous efforts to use manual photointerpretation to quantify BUDM benefits were labor-intensive [49], this study incorporated advanced remote sensing techniques to streamline the classification and evaluation process. The broad-based land cover classification process consisted of five primary sub-processes: (1) establishment of the classification schemas, (2) utilization of training data to generate decision trees, (3) performing supervised classifications, (4) refining classification data, and (5) performing accuracy assessments. In wetland mapping, a proper classification schema can be imperative for effective delineation of features and quantification of distribution, extent, and structural characteristics [50]. The classification schema used in this study was a six-class system based on general land cover features established by Suedel et al. [35]. The classes include dense vegetation, sparse vegetation, bare ground, developed, open water (including mud flats under low water conditions), and aquatic vegetation. This study used existing land cover data [35] and other ancillary imagery as training data for the initial supervised classification algorithm. All subsequent classifications used the final classification data from preceding dates as training data. The Multi-Resolution Land Characteristics Consortium, National Land Cover Dataset (NLCD) Mapping Tool (extension in ERDAS Imagine 2018; Hexagon Geospatial, Norcross, Georgia, USA) was the classification system used for this study. This classification system was deemed adequate for use in this study because the study area consists of a low complexity landscape (predominantly emergent wetlands and water), and its implementation in previous studies has generated sufficiently accurate classifications while maintaining interpretability and computational efficiency. The NLCD Sampling Tool, a component of the NLCD Mapping Tool, was initially employed in tandem with the response variable (i.e., spectral imagery) to query the training data and formulate classification rule sets. The C5.0 software [51] was then used (10 iteration boosting, 70/30 percent training and validation ratio, and stratified sampling), in conjunction with the rule set data, to generate Classification And Regression Tree (CART) predictive models. The NLCD Mapping Tool was then used to apply the CART decision tree model rules to the response variables (spectral imagery) to produce the classified image [52]. An inspection and refinement of the classified imagery was performed to remove noise (clusters below the minimum mapping unit) and recode any misclassified features. A final classification accuracy assessment was performed using image-based verification data (from ancillary high-resolution air- and space-borne imagery) and the traditional error matrix method [53]. In addition, the final general land cover classes were aggregated into distinct classes of land and water features and used as the reclamation period data in the land change analysis. The general land class consisted of dense wetland vegetation, sparse wetland vegetation, bare land, and developed features; and the water class consisted of open water and aquatic vegetation.

2.6. Landscape Metrics

The structure, function, and evolution of patches within a landscape can play a vital role in influencing key ecosystem processes and shaping overall ecological conditions. To better understand the impacts that restoration measures have on wetland integrity, it is essential to measure landscape structure and change [44]. At the local level, the structure of wetland patches is linked to topography and spatial attributes like wetland pattern and vegetation diversity. On a larger landscape scale, the spatial configuration of wetland patches, including size, shape, connectivity, and the composition of surrounding open water areas, forms essential components of the overall landscape structure. Landscape metrics were used to evaluate changes in total wetland extent (using aggregated land and water classes, 1934 to 2020), and the extent and configuration of land cover features (2008 to 2020). The FRAGSTATS landscape pattern analysis software (version 4.2.681) [54] was used to calculate class-level metrics using the land cover classification data generated from high-resolution imagery (Table 1). In addition to Total Area, this study assessed changes in Edge Density and Aggregation Index across the reclamation period (2008 to 2020). McGarigal et al. [54] defines Edge Density as “the sum of the lengths (m) of all edge segments involving the corresponding patch type, divided by the total landscape area (m2)”. The Aggregation Index is “calculated from an adjacency matrix, which shows the frequency with which different pairs of patch types (including like adjacencies between the same patch type) appear side-by-side on the map” [54]. Overall, landscape feature and pattern assessments can be useful for estimating short-term variations associated with restoration activities and/or predominant environmental conditions [55].

3. Results

3.1. Dredging and Placement Activities

Established in 1879 by the U.S. Congress, the Mississippi River Commission (MRC) has worked (along with USACE) to maintain navigational control of the Mississippi River via deepening measures and flood mitigation strategies [56]. Historically, channelization and O&M deepening of the river and distributaries have utilized open water areas and confined facilities for the placement of large volumes of dredged material [30]. By the mid-1970s, the value of dredged material for wetland reclamation and marsh/shoreline nourishment was realized, and the MRC and USACE began implementing environmentally and economically beneficial alternatives to traditional open water or landfill disposal [49]. Efforts to beneficially use the millions of cubic meters of material dredged each year from SWP (as part of O&M) began in 1975 and continued annually until 2002 (Figure 2) [57]. The initial (1975 to 1979) O&M BUDM efforts along the SWP placed sediment on existing wetland features and in shallow open water areas but failed to create substantive new wetland areas due to insufficient intertidal elevations [49]. By the early 2000s, dredged sediments were placed at higher elevations (between +1 to +2 m Mean Low Gulf, MLG) within unconfined areas, leading to the creation of viable wetland landforms. However, due to operational and safety concerns related to a vessel grounding and an unrelated bank line failure, O&M-based BUDM activities were discontinued along the SWP channel between 2003 and 2008 [USACE, Personal Communications]. Since 2009, USACE has employed a more focused approach to beneficially using material dredged as part of SWP O&M activities. Figure 2 lists the placement area (in square kilometers) by year and the location of each O&M BUDM placement site (light greens represent earlier years and dark greens represent later years) within the SWP study area. The dredging quantities ranged from 2.2 to 11.2 million cubic meters for the years 2009 and 2019, respectively. The area of the placement sites by year ranged from 0.3 to 5.6 km2 for the years 2010 and 2017, respectively.
While the O&M program accounts for a majority of BUDM activities in the MRD, there are other programs that have contributed to wetland reclamation through the placement of dredged material. Some authorities and programs, like CWPPRA, Louisiana Coastal Area Beneficial Use of Dredged Material (LCA BUDMAT), and Continuing Authorities Programs have offset costs beyond those authorized for USACE O&M activities, thereby expanding the potential for BUDM applications. Since 2003, the CWPPRA program has placed more than 43,000,000 m3 of dredged material within the West Bay receiving basin (blue areas in Figure 1 and Figure 2) [58]. Some programs have also employed the reuse of previously dredged material for land reclamation. For instance, since the early 1900s, dredged material from the SWP channel has been deposited into a Hopper Dredge Disposal Area (HDDA) [59]. The HDDA is a naturally occurring scour hole whose depth was previously sustained by the Mississippi River’s erosional energy [59]. However, by the 1990s, the natural scouring process became insufficient for hopper dredges to safely access the HDDA for dredged material placement. In 1998, the USACE New Orleans District implemented a management plan to dredge the HDDA to a maximum depth of −12 m (MLG) to enhance its capacity. Some material dredged from the HDDA have thus been reused beneficially within the SWP study area. In 2015, the LCA BUDMAT program placed approximately 1.75 million m3 of HDDA material in the West Bay receiving basin to create wetlands and sediment trapping berms (constructed to slow the flow of diverted water, enhance sediment deposition, and increase the land building rate) (blue linear features in Figure 2). In 2015 and 2017, The USACE New Orleans District O&M activities placed approximately 5.7 and 5.4 million m3, respectively, of HDDA material for wetland restoration in the SWP study area (dark purple areas in Figure 2). To date, more than 60 km2 of low-elevation wetland features or shallow open water areas within the SWP study area have been utilized for the beneficial use of dredged material.

3.2. Land Cover Assessment

Assessments of change in land cover area during the recent reclamation period (2008 to 2020) were performed using wetland habitat data derived from air- and space-borne imagery. The land cover classification schema consisted of dense wetland vegetation, sparse wetland vegetation, bare land, developed features, open water, and aquatic vegetation. The general wetland classifications achieved an overall accuracy of 85%, with a Cohen’s kappa value of 0.82, indicating substantial agreement beyond chance. Misclassifications generally occurred between dense and sparse vegetation classes, and between water and aquatic vegetation classes (Table 2). Classification maps, which have been color-coded in accordance with the classification schema. These classification maps show a consistent pattern of land cover types with differences between years occurring primarily in areas where dredged materials were placed as part of restoration activities (Figure 2). While the classification maps provide the spatial distribution of land cover features within the reclamation period, Table 3 provides the class area (in km2) by year. The 2008 study area consisted predominantly of water, accounting for 70.3 percent of the study area, followed by dense vegetation, aquatic vegetation, sparse vegetation, bare ground, and developed features; accounting for 22.2, 4.4, 2.0, 0.7, and 0.4 percent of the study area, respectively (Table 3). However, by 2020, the land area increased by 24.4% (13.6 km2). These land gains were due primarily to increases in the areal extent of sparse vegetation and bare ground features and a decrease in open water areas and aquatic vegetation, which were associated with land reclamation as part of BUDM activities. Land changes in the northern reaches of the study area were also influenced by the West Bay sediment diversion, which resulted in subaerial growth within the bay [35]. Vegetation establishment on newly formed subaerial features in coastal wetland systems can take several growing seasons after restoration, depending primarily on elevation and hydrologic processes. Once established, however, vegetation will provide sediment and feature stabilization [38,55].

3.3. Landscape Metric Assessment

Class Area, Edge Density, and Aggregation Index values were calculated for each year and class using the wetland classification data. Table 4 provides the change rates within the reclamation period (2008 to 2020) for each landscape metric by class. Although there was a 0.58 km2/year reduction in dense vegetation, this was offset by 1.41 and 0.45 km2/year increases in sparse vegetation and bare ground, respectively (Table 4). The open water and aquatic vegetation areas experienced consistent losses across the reclamation period, decreasing by 1.1 and 0.18 km2/year, respectively. These increases in land features and reductions in water features were largely driven by dredged material placement in shallow open water areas and on existing vegetated features. Relatively large increasing rates of edge density were observed in dense vegetation (5.37 m/ha/yr), sparse vegetation (5.79 m/ha/yr), and bare ground (1.32 m/ha/yr) across the reclamation period. Conversely, the edge density of the open water class experienced a moderately decreasing change rate. Within a degrading wetland system, increasing edge densities could indicate increased vulnerability to external influences or habitat degradation; however, in a restored landscape (i.e., SWP study area within the reclamation period) higher densities may be indicative of increased habitat diversity, higher ecological function, and an overall healthier wetland system. When assessing aggregation, the sparse vegetation class experienced the largest rate of change (+0.81%/yr), followed by aquatic vegetation (−0.35%/yr), dense vegetation (−0.27%/yr), bare ground (+0.21%/yr), developed (+0.10%/yr), and open water (+0.01%/yr). The increasing aggregation in the sparse vegetation and bare ground is a direct result of dredged material placement in the landscape, which contributed to more disaggregated patches of dense vegetation. In a prograding or restored landscape, increasing land area can result in higher levels of aggregation, spatial integrity, and resiliency.

3.4. Long-Term Land Change

3.4.1. Land Change–Temporal Analysis

Examination of land and water data derived from historical aerial photography enables the identification and empirical documentation of landscape changes that have occurred within the SWP study area prior to reclamation activities. Figure 3 plots the subaerial land area and dredged material placement sites within the period of analysis timeframe (1934 to 2020). In 1934, the SWP project area (224.4 km2) comprised 120.7 km2 of water (53.8% of total) and 103.7 km2 of wetland (46.2% of total) features. The land area changed consistently across the historical period, decreasing to 80.6 km2 (35.9%) and 44.5 km2 (19.8%) by 1956 and 1978, respectively (Figure 3). The rate of loss was linear (r2 = 0.98) at 1.35 km2 per year across the 44-year historical period of record (1934 to 1978). The incurred losses stem predominantly from compaction-induced subsidence (~1.5 m per century), sediment depletion, erosional forces (i.e., tidal and wave energies), hurricanes, and anthropogenic activities (i.e., navigation O&M and access canal construction for mineral exploration and extraction) [60]. These historical data and trends provide a baseline with which changes during the reclamation period can be compared.
The BUDM period spanned from 1978 to 2008 and consisted initially of ad hoc placement of dredged material into unconfined open water areas. The 1978, 1988, 1998, 2004, and 2008 land features within the SWP study area totaled 44.5, 40.3, 50.6, 56.1, and 56.7 km2, respectively. From 1978 to 2008, the study area experienced an increasing rate of land change (0.51 km2 per year, r2 = 0.76), signifying a landscape that shifted from a degrading system (historical period) to one with moderate land gain (initial BUDM period) (Figure 3). The land gains after 1988 (which serves as the deflection point at which the land area minima occurred) were a direct result of the O&M-based beneficial use of material dredged from the SWP channel between 1975 and 2002. However, with little to no BUDM activity occurring between 2003 and 2008, the amount of land comprising the SWP study area went relatively unchanged between 2004 (56.1 km2) and 2012 (57.3 km2) (Figure 3). However, BUDM activities between 2012 and 2020 placed larger quantities of dredged material into larger placement areas, resulting in significant increases in land. Total subaerial land within the SWP study area increased to 61.0 km2 in 2012 and 70.4 km2 by 2020 (Figure 3). The land area change rate within the intensive reclamation period (2008 to 2020) was 1.24 km2 (R2 = 0.9), driven predominantly by BUDM activities and the West Bay sediment diversion.

3.4.2. Land Change–Spatial Analysis

Figure 4 shows the spatial distribution of land change within the SWP study area. Land gains are color ramped (dark blue to light green) according to pairwise subperiods (e.g., 1934 to 1956, 1956 to 1978), representing pre- and post-reclamation change, respectively (Figure 4). The areas of land loss are also color ramped (light orange to dark reds) by pairwise subperiods. Land loss primarily took place early in the historical period (1934 to 1978) and largely in the West Bay area (northern SWP study area) and along the southern reach of SWP (Figure 4). Smaller and more isolated areas of loss occurred later in the period of record, converting from wetland to interior wetland ponds near the terminal end of SWP. The areas that experienced land gains occurred across a wider temporal swath, which reflects the positive impact of initial BUDM activities and the recent reclamation efforts, including sediment retention features and marsh creation areas. However, land gains were observed within the historical period along SWP and below West Bay. These gains were likely a result of natural land building processes that are typical in riverine systems and potentially due to dredged sediment placement in confined disposal facilities.

4. Discussions

The SWP study area provides a compelling example of how targeted dredging and sediment placement can reverse historical wetland loss and contribute to land reclamation. The combination of BUDM activities and sediment diversion has resulted in a net gain of wetland area, contrasting sharply with previous periods of decline. However, uncertainty can persist regarding the long-term stability of restored wetlands, especially considering the frequency and intensity of abiotic pressures, such as hurricanes and subsidence.
Globally, there has been a notable increase in the interest and implementation of land reclamation projects. Yet, several countries have engaged in land reclamation for over a century. Leading the world in reclaimed lands are China, the Netherlands, South Korea, the United States, and Japan, with reclaimed areas of 13,500 km2, 7000 km2, 1550 km2, 1000 km2, and 500 km2, respectively [61]. Figure 5 highlights some of the world’s largest and most notable reclamation projects, ranging from 5.6 km2 for the iconic Palm Jumeirah in Dubai to 20 km2 for the Maasvlakte 2 project in the Netherlands. While many large-scale reclamation projects are designed for industrial, residential, or mixed-use purposes, some are driven by ecosystem restoration needs. Notably, reclamation activities along SWP associated with both ship channel maintenance and dedicated environmental programs have led to a 30.1 km2 increase in land area, surpassing many prominent global initiatives. The SWP restoration efforts are particularly significant when compared to other major international projects. This initiative has focused on restoring and enhancing coastal ecosystems through BUDM and sediment diversion. These efforts aim to rebuild wetlands, improve habitat quality, and increase biodiversity. The SWP project highlights the critical role of reclamation in supporting ecosystem services, including flood protection, water quality improvement, and carbon sequestration. By prioritizing ecological restoration, the SWP initiative sets a benchmark for future reclamation projects worldwide, demonstrating that large-scale land reclamation can successfully balance human and environmental needs. This positions the SWP project as a notable global effort in reshaping and expanding coastal areas while enhancing their ecological integrity.

5. Conclusions

Coastal land reclamation poses significant challenges in balancing environmental concerns with the need to expand coastal infrastructure while preserving valuable ecosystem habitats. The diverse needs of stakeholders within coastal regions add complexity to coastal restoration and management efforts. To address these challenges, integrated management approaches should be implemented, considering the dynamic nature of wetland ecosystems and their critical roles in climate regulation, biodiversity preservation, and other ecosystem services. Therefore, successful implementation of large-scale wetland reclamation often requires measures tailored to site-specific needs, conditions, challenges, and resources.
Key components of these integrated approaches are BUDM and sediment diversions. These measures offer substantial long-term land-building benefits by repurposing sediment to restore and enhance wetland areas. This method not only supports the creation of sustainable landforms but also contributes significantly to the resilience of coastal landscapes against erosion and environmental impacts. The strategic application of dredged material can help rebuild wetlands, improve habitat quality, and increase biodiversity, thereby enhancing ecosystem services.
In summary, a holistic strategy is needed to effectively manage coastal land reclamation and wetland restoration. This strategy should recognize the ecological value of wetlands and their contribution to sustainable development goals, such as reversing land degradation and promoting habitat diversity. Emphasizing the beneficial use of dredged material provides foundational knowledge for large-scale, recurring restoration activities in degrading coastal landscapes. These efforts contribute to improved estimates and predictions of wetland reclamation measures, fostering more resilient and sustainable coastal environments.

Author Contributions

Conceptualization, G.M.S. and J.M.C.; methodology, G.M.S. and C.S.; software, G.M.S.; validation, G.M.S., C.S. and J.M.C.; formal analysis, G.M.S.; investigation, G.M.S.; data curation, G.M.S. and J.M.C.; writing—original draft preparation, G.M.S.; writing—review and editing, G.M.S., C.S. and J.M.C.; visualization, G.M.S.; supervision, G.M.S. and J.M.C.; project administration, J.M.C.; funding acquisition, J.M.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the U.S. Army Corps of Engineers, New Orleans District, New Orleans, LA, USA and the U.S. Army Engineering Research and Development Center’s Dredging Operations Technical Support (DOTS) Program, Vicksburg, MS, USA.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request. However, an exception applies to the WorldView satellite data which is not available due to contract restrictions.

Acknowledgments

The authors would like to thank Burton Suedel (Dredging Operations Technical Support Program), for his support in authorizing and funding this work unit. The use of trade, product, or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Government. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

List of Abbreviations

AbbreviationDefinition
BUMPBeneficial Use Monitoring Program
BUDMBeneficial Use of Dredged Material
BUDMATBeneficial Use of Dredged Material Program
CARTClassification And Regression Tree
CWPPRACoastal Wetlands Planning, Protection, and Restoration Act
DOQQDigital Orthophoto Quarter Quadrangle
FRAGSTATSFragmentation Analysis
HDDAHopper Dredge Disposal Area
LCALouisiana Coastal Area
LOSCOLouisiana Oil Spill Coordinator’s Office
MLGMean Low Gulf
MRCMississippi River Commission
MRDMississippi River Delta
NLCDNational Land Cover Dataset
NWINational Wetland Inventory
O&MOperations and Maintenance
SWPSouthwest Pass
USACEUnited States Army Corps of Engineers
USCGSUnited States Coastal and Geodetic Survey
USGSUnited States Geological Survey

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Figure 1. Location map of the Southwest Pass study area.
Figure 1. Location map of the Southwest Pass study area.
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Figure 2. Area and location of dredged material placement sites within the Southwest Pass study area. Early dredged material placement activity locations were not always documented (those listed as historical SWP O&M).
Figure 2. Area and location of dredged material placement sites within the Southwest Pass study area. Early dredged material placement activity locations were not always documented (those listed as historical SWP O&M).
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Figure 3. Total subaerial land and placement site area within the Southwest Pass study area from 1934 to 2020 for three time periods: historical 1934–1978, initial BUDM 1978–2008, and current reclamation 2008–2020.
Figure 3. Total subaerial land and placement site area within the Southwest Pass study area from 1934 to 2020 for three time periods: historical 1934–1978, initial BUDM 1978–2008, and current reclamation 2008–2020.
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Figure 4. Land gain (greens and blues) and loss (oranges and reds) areas within the Southwest Pass study area from 1934 to 2020.
Figure 4. Land gain (greens and blues) and loss (oranges and reds) areas within the Southwest Pass study area from 1934 to 2020.
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Figure 5. List of the top coastal land reclamation projects using dredged sediment.
Figure 5. List of the top coastal land reclamation projects using dredged sediment.
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Table 1. List and description of remotely sensed data used to evaluate habitat and land change within the Southwest Pass study area.
Table 1. List and description of remotely sensed data used to evaluate habitat and land change within the Southwest Pass study area.
PhaseProgramTypeYearData SourceResolution
Historical PeriodTopographic SheetLand and Water Data1934U.S. Coast and Geodetic Survey1:20,000
National Wetland InventoryLand and Water Data1956U.S. Geological Survey1:24,000
National Wetland InventoryLand and Water Data1978U.S. Geological Survey1:24,000
Initial BUDM PeriodNational Wetland InventoryLand and Water Data1988U.S. Geological Survey1:24,000
LOSCODOQQ1998La. Oil Spill Coordinator’s Office1:10,000
National Aerial Photography ProgramDOQQ2004U.S. Geological Survey1:24,000
Beneficial Use Monitoring ProgramAerial Photo2008U.S. Department of Agriculture1 m
Recent Land Reclamation PeriodBeneficial Use Monitoring ProgramAerial Photo2010U.S. Army Corps of Engineers1 m
Beneficial Use Monitoring ProgramAerial Photo2012U.S. Army Corps of Engineers1 m
Global Enhanced GEOINT Delivery (G-EGD) ProgramWorldView-3 Satellite Imagery2014MAXAR Technologies1.24 m
Beneficial Use Monitoring ProgramAerial Photo2016U.S. Army Corps of Engineers1 m
Beneficial Use Monitoring ProgramAerial Photo2018U.S. Army Corps of Engineers1 m
Beneficial Use Monitoring ProgramAerial Photo2020U.S. Army Corps of Engineers1 m
Table 2. Confusion matrix of the supervised classification images.
Table 2. Confusion matrix of the supervised classification images.
Classified DataReference Data
Land Cover ClassesDVSVBGDOWAVRow
Total		User’s
Accuracy (%)
Dense Vegetation (DV)541600007077.14
Sparse Vegetation (SV)95600507080.00
Bare Ground (BG)08555207078.57
Developed (D)00065507092.86
Open Water (OW)05046107087.14
Aquatic Vegetation (AV)01101677095.71
Column total638656747467420Overall
accuracy
85.24%
Producer’s accuracy (%)85.7165.1298.2187.8482.43100.000.00
Table 3. Area in square kilometers for land cover types (dense vegetation, sparse vegetation, bare ground, developed, open water, and aquatic vegetation) from 2008 to 2020 within the Southwest Pass study area.
Table 3. Area in square kilometers for land cover types (dense vegetation, sparse vegetation, bare ground, developed, open water, and aquatic vegetation) from 2008 to 2020 within the Southwest Pass study area.
DateDense VegetationSparse VegetationBare GroundDevelopedOpen WaterAquatic Vegetation
km2
200849.94.41.50.8157.89.9
201042.011.82.61.0160.36.7
201240.014.61.81.0164.92.2
201434.920.05.21.0158.94.5
201644.515.82.90.9154.85.4
201840.820.76.80.7147.77.7
202038.424.36.71.0149.14.9
Table 4. Class-level mean area, edge density, and aggregation index values within the Southwest Pass study area from 2008 to 2020.
Table 4. Class-level mean area, edge density, and aggregation index values within the Southwest Pass study area from 2008 to 2020.
Change Rate (2008–2020)Dense VegetationSparse VegetationBare GroundDevelopedOpen WaterAquatic Vegetation
Class Mean Area
(km2/Yr)		−0.581.410.45−0.01−1.10−0.18
Edge Density
(meters/hectare/year)		5.375.791.32−0.07−0.960.64
Aggregation Index (percentage/year)−0.270.810.210.100.01−0.38
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Suir, G.M.; Saltus, C.; Corbino, J.M. Land Reclamation in the Mississippi River Delta. Remote Sens. 2025, 17, 878. https://doi.org/10.3390/rs17050878

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Suir GM, Saltus C, Corbino JM. Land Reclamation in the Mississippi River Delta. Remote Sensing. 2025; 17(5):878. https://doi.org/10.3390/rs17050878

Chicago/Turabian Style

Suir, Glenn M., Christina Saltus, and Jeffrey M. Corbino. 2025. "Land Reclamation in the Mississippi River Delta" Remote Sensing 17, no. 5: 878. https://doi.org/10.3390/rs17050878

APA Style

Suir, G. M., Saltus, C., & Corbino, J. M. (2025). Land Reclamation in the Mississippi River Delta. Remote Sensing, 17(5), 878. https://doi.org/10.3390/rs17050878

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