Beneficial Use of Dredge Material in Mangrove Restoration Projects

Project Information

The overarching goal of this project is to provide the United States Army Corps of Engineers (USACE) with science-based evidence on how thin layer placement (TLP) influences mangrove ecosystems. At present, the effects of TLP on mangroves remain largely unknown, creating a critical knowledge gap that limits the ability of USACE to effectively plan and make informed decisions regarding the beneficial use of dredged material (BUDM) in these sensitive coastal environments. In keeping with the principles of Engineering With Nature (EWN), this project will use a systems approach that harnesses natural processes to restore ecological function while supporting social and economic benefits. By focusing on tidal reconnection and sediment reuse, the effort not only enhances ecosystem resilience but also contributes to sustainable strategies for long-term sediment management and coastal protection.

Dead mangrove trees in barren soil. — Ghost mangrove forest in Florida caused by excessive flooding due to impoundment conditions.

Man in a purple shirt,white vest, blue gloves and white hat squats while examining damaged mangrove root system. — Dr. Andre Rovai examining damage to mangrove tree prop root systems caused by both erosion and excessive sedimentation.

Problem

Although mangroves and coastal marshes often co-occur within the intertidal zone, they are structurally and physiologically distinct plant communities with unique life-history traits that influence how they respond to restoration methods such as the BUDM³. While TLP has been shown to successfully restore elevation and resilience in coastal marshes^1,2, its effects on mangrove ecosystems remain undocumented, leaving the USACE without the science-based evidence needed to guide restoration decisions. To address this gap, the project will test TLP within a degraded mangrove forest at Woodring Point in the J.N. “Ding” Darling National Wildlife Refuge (Sanibel, Florida), a site that has suffered decades of tidal disconnection, vegetation dieback, and elevation loss from soil organic matter decomposition. Here, TLP offers a promising nature-based solution to restore mangrove habitat, enhance resilience to relative sea level rise, and provide a sustainable pathway for long-term dredged sediment placement. By generating standardized metrics and guidelines, this work will equip USACE districts with the knowledge required to implement BUDM in mangrove ecosystems, with applicability across coastal states in the southeastern United States as well as in all U.S. territories outside the continental United States.

Solution

To restore the degraded mangrove site, this project will harness natural processes by integrating ecological engineering and ecosystem development approaches to establish standardized guidelines for assessing the outcomes of the BUDM in mangrove ecosystems. Restoration will involve coupling existing LiDAR-based Digital Elevation Models (DEM) with novel Terrestrial Laser Scanning (TLS) to design and excavate a tidal runnel, reinstating tidal flushing and natural hydrology. Sediments from the excavation will be repurposed to construct experimental raised elevation plots, TLP to restore lost elevation capital. TLS will then be employed to monitor surface elevation dynamics and vegetation responses over time.

The overarching objective of this project is to provide the USACE with standardized guidelines for evaluating the effectiveness of BUDM in mangrove ecosystems. The specific objectives are to:

Restore the hydrology of the degraded mangrove site by reconnecting tidal flushing through the creation of a tidal runnel.
Simulate TLP by using sediments from the excavated tidal runnel to raise surface elevation suitable for mangrove development.
Assess the response and successional trajectory of surviving mangrove vegetation and new seedling recruitment on the placed material.
Evaluate how mangrove vegetation succession or mortality influences sediment retention, compaction, and stability.
Determine the potential of BUDM to restore mangrove forests that are not keeping pace with sea level rise.

Impact

This project will have significant impact by providing USACE with the first standardized guidelines for assessing the outcomes of BUDM in mangrove ecosystems. These guidelines will enable practitioners to replicate implementation and monitoring protocols across both continental United States (CONUS) and outside the continental United States (OCONUS) coastlines where mangroves occur. By addressing a critical knowledge gap, this research reduces uncertainties surrounding TLP, empowering USACE to make faster, more confident decisions that couple BUDM with strategies enhancing mangrove resilience to sea level rise.

Aligned with the EWN mission, the project leverages natural processes—such as tidal reconnection—to restore hydrology, nutrient cycling, and sedimentation patterns that are essential for long-term mangrove regeneration and soil elevation maintenance. This nature-based approach not only increases ecological resilience but also enhances coastal protection from storm surge and wave energy, providing tangible benefits to surrounding infrastructure and communities. Furthermore, the collaborative design and execution of this pilot study—bringing together federal agencies, research institutions, and local stakeholders—ensures broad engagement, transparency, and co-development of strategies that strengthen both scientific rigor and social acceptability.

By producing transferable knowledge and science-based guidelines, the project positions USACE as a leader in advancing nature-based solutions that complement or replace traditional gray infrastructure, thereby saving time and resources while improving credibility and resilience outcomes. Datasets will be archived in permanent repositories, and project results will be shared through the global mangrove restoration tracker tool to promote transparency and stakeholder integration¹⁵.

Principal Investigators

Dr. Jacob Berkowitz, Research Soil Scientist, USACE-ERDC Environmental Laboratory

Dr. Andre Rovai, Research Biologist & Coastal Carbon Network Director, Smithsonian Environmental Research Center

Dr. Jeremy Conrad, United States Fish and Wildlife Service

Team Members

Dr. Safra Altman, Research Ecologist, USACE-ERDC Environmental Laboratory

Dr. Nathan Beane, Research Forester, USACE-ERDC Environmental Laboratory

Dr. Robert Chancia, Researcher/Engineer I, Rochester Institute of Technology

Bob Gerwig, J.N. “Ding” Darling National Wildlife Refuge Manager, United States Fish and Wildlife Service

Krystyna Powell, Research Biologist, USACE-ERDC Environmental Laboratory

Jaybus Price, Research Biologist, USACE-ERDC Environmental Laboratory

Avery Renshaw, Biological Science Technician, United States Fish and Wildlife Service

Dr. Jarrell Smith, Research Civil Engineer, USACE-ERDC Coastal & Hydraulics Laboratory

William Tomlinson, Biological Science Technician, USACE-ERDC Environmental Laboratory

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Collaborators

Point of Contact

Jacob Berkowitz, PhD, PWS, CPSS

Research Soil Scientist, USACE-ERDC Environmental Laboratory

Jeremy Conrad, PhD

Coastal Ecologist, United States Fish and Wildlife Service

Andre Rovai, PhD

Research Biologist & Coastal Carbon Network Director, Smithsonian Environmental Research Center

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Engineering With Nature® is the intentional alignment of natural and engineering processes to efficiently and effectively deliver economic, ecological, and social benefits through collaboration.