Saving & Restoring Our Wetlands: A Guide to Thin-Layer Placement
Tidal wetlands play a critical role in protecting coastal communities, supporting wildlife, and maintaining water quality. Yet many of these systems are under increasing stress as rising water levels, land subsidence, and altered sediment dynamics outpace natural recovery processes, especially in highly developed coastal areas.
To address this challenge, the Elizabeth River Project, in partnership with Anchor QEA, released guidance for using thin-layer placement (TLP), Wetland Restoration Using Thin Layer Placement: Best Management Practices for the Commonwealth of Virginia. Developed with funding from the National Fish and Wildlife Foundation, and completed in collaboration with Hampton Roads Planning District Commission, the guide provides a framework for using TLP as a wetland restoration and marsh elevation enhancement tool.
What Is Thin-Layer Placement?
TLP is the purposeful application of a relatively thin layer of clean sediment, often beneficially reused dredged material, to degraded wetlands or shallow-water environments. When properly designed, TLP can help marshes regain elevation, improve vegetation health, and better withstand ongoing erosion and flooding pressures.
Unlike traditional dredged material placement, TLP is intended to work with natural processes. Projects are designed to support vegetation recovery, minimize ecological disruption, and deliver long-term habitat and resilience benefits.
Why TLP Matters in Virginia
Virginia’s coastal wetlands face unique constraints. In many urban and industrial areas, marshes are backed by roads, buildings, and other infrastructure that limit inland migration. In these settings, elevation loss can translate directly into habitat loss and reduced protection for adjacent communities.
The new guidance recognizes these realities and adapts national TLP best practices to Virginia’s ecological conditions, regulatory framework, and sediment management needs. It also complements parallel efforts underway to expand beneficial use options for dredged material across the Commonwealth.
From Concept to Implementation
The guidance walks practitioners through the full lifecycle of a TLP project:
- Identifying appropriate sites and sediment sources
- Establishing clear project goals and performance criteria
- Navigating permitting and time-of-year restrictions
- Designing placement methods and elevation targets
- Monitoring vegetation, elevation, and habitat recovery
- Applying adaptive management over time
Case studies from the Atlantic and Gulf Coasts illustrate how TLP has been implemented elsewhere and what lessons may apply in Virginia.
Broader Relevance Beyond Virginia
While the guidance is tailored to Virginia’s coastal systems, many of the principles it outlines extend well beyond the Commonwealth. The framework builds directly on national TLP guidance developed by the U.S. Army Corps of Engineers and reflects lessons learned from projects across the Atlantic and Gulf Coasts. As a result, the document’s emphasis on site assessment, sediment compatibility, elevation targeting, regulatory coordination, and long-term monitoring aligns with best practices already being applied or actively explored in other coastal regions.
Just as importantly, the conditions driving the need for TLP in Virginia are not unique. Across the United States, tidal wetlands in urbanized and industrial settings face similar constraints: limited opportunities for inland migration, disrupted sediment supply, and increasing exposure to flooding and storm impacts. In these contexts, the guide’s process-oriented approach offers a transferable model that practitioners in other states can adapt to local ecological conditions and regulatory frameworks.
A Tool for Practitioners and Decision-Makers
Written for a broad audience of engineers, scientists, regulators, and restoration partners, the document is intended to support informed decision-making rather than prescribe one-size-fits-all solutions. As emphasized by the Elizabeth River Project in its foreword, TLP is most effective when integrated into broader coastal resilience planning and applied with careful consideration of site-specific conditions.
By providing a clear, science-based roadmap, the guidance helps advance wetland restoration efforts that protect ecological function while supporting the long-term resilience of Virginia’s coastal communities.
Contributors to the Guide include Gabriella DiPetto, Barbara Gavin, and Phoebe Murrell of Elizabeth River Project, the Project Sponsor; KC Filippino of Hampton Roads, Planning District Commission, the Project Co-Sponsor; and from Anchor QEA: Ram Mohan, Project Director; Josef Rieger, Project Manager; Mindy Strevig, Former Project Manager; Travis Merritts, Senior Technical Reviewer; Katie Haviland, Lauren Folkert, and Jill Zwierz, Technical Researchers/Writers; Ken Mayo, Senior Document Editor; Zheng Fang, Senior Graphics Editor; and Zelini Hubbard, Project Coordinator.
Joe Rieger is a Senior Managing Scientist and Ram Mohan, PhD, PE, F.ASCE, is a Principal Engineer and Coastal Resilience Lead at Anchor QEA.
Get in touch with Joe Rieger.
Get in touch with Ram Mohan.