Many coastal tidal marshes have been significantly degraded by roadways and other projects that restrict tidal flows, limiting their ability to provide vital ecosystem services including support of fish and wildlife populations, flood protection, water quality maintenance, and open space. Tidal Marsh Restoration provides the scientific foundation and practical guidance necessary for coastal zone stewards to initiate salt marsh tidal restoration programs. The book compiles, synthesizes, and interprets the current state of knowledge on the science and practice of salt marsh restoration, bringing together leaders across a range of disciplines in the sciences (hydrology, soils, vegetation, zoology), engineering (hydraulics, modeling), and public policy, with coastal managers who offer an abundance of practical insight and guidance on the development of programs. The work presents in-depth information from New England and Atlantic Canada, where the practice of restoring tidal flow to salt marshes has been ongoing for decades, and shows how that experience can inform restoration efforts around the world. Students and researchers involved in restoration science will find the technical syntheses, presentation of new concepts, and identification of research needs to be especially useful as they formulate research and monitoring questions, and interpret research findings. Tidal Marsh Restoration is an essential work for managers, planners, regulators, environmental and engineering consultants, and others engaged in planning, designing, and implementing projects or programs aimed at restoring tidal flow to tide-restricted or diked salt marshes.
|Series:||The Science and Practice of Ecological Restoration Series Series|
|Product dimensions:||6.90(w) x 10.10(h) x 1.10(d)|
About the Author
Charles T. Roman is a coastal ecologist with the US National Park Service and professor-in-residence at the University of Rhode Island Graduate School of Oceanography. David M. Burdick is Research Associate Professor of Coastal Ecology and Restoration in the Department of Natural Resources and the Environment at the University of New Hampshire.
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Tidal Marsh Restoration
A Synthesis of Science and Management
By Charles T. Roman, David M. Burdick
ISLAND PRESSCopyright © 2012 Island Press
All rights reserved.
A Synthesis of Research and Practice on Restoring Tides to Salt Marshes
CHARLES T. ROMAN AND DAVID M. BURDICK
The structure and ecological function of salt marshes are defined by many interacting factors, including salinity, substrate, nutrient and oxygen availability, sediment supply, and climate, but hydrology (the frequency and duration of tidal flooding) is a dominating factor (e.g., Chapman 1960; Ranwell 1972; Daiber 1986). When tidal flow is restricted there can be dramatic changes to physical and biological processes that affect vegetation patterns, fish and avian communities, and biogeochemical cycling, among others. Throughout the developed coastal zone, roads and railroads that cross salt marshes often have inadequately sized bridges and culverts that restrict tides (fig. 1.1). Tide gates are also a common feature, eliminating or dramatically restricting flood tides from entering salt marshes but allowing for some drainage on the ebb tide. Other tide-restricting practices that have been ongoing for centuries include impoundments for wildlife management purposes (Montague et al. 1987) and diking and draining to facilitate grazing and agriculture (Daiber 1986; Doody 2008). Diking is particularly extensive in Atlantic Canada (Ganong 1903), Europe (Davy et al. 2009), and the United States (e.g., Delaware Bay, Sebold 1992; San Francisco Bay, Nichols et al. 1986).
With tidal restriction there are often dramatic changes in vegetation as salt and flood-tolerant species of the salt marsh are displaced by plants typically found in fresher and drier conditions. Under regimes of tidal restriction, Spartina-dominated (cordgrass) marshes in the northeastern United States have been invaded by the aggressive Phragmites australis (common reed), often in dense monocultures, and other less salt-tolerant herbaceous and woody species (e.g., Roman et al. 1984; Burdick et al. 1997; Crain et al. 2009). Phragmites marshes, when compared to short-grass Spartina meadows, reportedly do not provide suitable habitat for birds, especially those that typically nest in salt marshes (Benoit and Askins 1999; DiQuinzio et al. 2002). Fish abundance, species composition, and food web support functions are altered by tidal restriction when compared to tide-unrestricted systems (e.g., Dionne et al. 1999; Able et al. 2003; Raposa and Roman 2003; Wozniak et al. 2006). Feeding, reproduction, and nursery function can be much reduced or eliminated based on studies documenting the response of the dominant East Coast marsh fish, Fundulus heteroclitus (mummichog), to Phragmites invasions (Able and Hagan 2000; Able et al. 2003; Hunter et al. 2006). Tidal restriction can result in significant subsidence of the sediment surface and acidification of salt marsh soils, with subsequent declines in marsh primary production and export (e.g., Anisfeld and Benoit 1997; Portnoy 1999). Water quality concerns, especially low levels of dissolved oxygen in tide-restricted marshes, have been reported with detrimental effects on estuarine fauna (Portnoy 1991).
The practice of restoring tidal flow to degraded tide-restricted salt marshes has been actively pursued for decades. In Delaware Bay (New Jersey) over 1700 hectares of salt marsh that had been diked and cultivated for salt hay are now undergoing tidal restoration (Weinstein et al. 1997; Philipp 2005). Similarly, restoration efforts through the natural or deliberate breaching of dikes are under way in the United Kingdom and other parts of Europe (Pethick 2002; Wolters et al. 2005; Davy et al. 2009), Bay of Fundy (Byers and Chmura 2007), San Francisco Bay (Williams and Faber 2001; Williams and Orr 2002), the Pacific Northwest (Thom et al. 2002), and elsewhere. Along populated coasts, managers are also engaged in programs to restore tidal flow to degraded salt marshes by removing tide gates and enlarging culverts, bridge openings, and other flow restrictions, with numerous examples from the northeastern United States (Warren et al. 2002; Crain et al. 2009), southeastern US (NOAA Restoration Center and NOAA Coastal Service Center 2010), Pacific US (Zedler 2001; Callaway and Zedler 2004), Australia (Williams and Watford 1996; Thomsen et al. 2009), and other regions.
Purpose and Book Organization
To help guide future restoration efforts throughout the coastal zones of the world and to advance restoration science and management, this edited volume compiles, synthesizes, and interprets the current state of knowledge on the science and practice of restoring tidal flow to salt marshes. This book focuses on the New England and Atlantic Canada region, where the practice of restoring tidal flow to salt marshes has been ongoing for decades, accompanied by extensive multidisciplinary research efforts. However, the book is far from limited in regional scope; the contributing authors incorporate relevant literature from other regions to complement and support the information base developed in New England and Atlantic Canada.
This book will serve as a valuable reference to guide managers, planners, regulators, environmental and engineering consultants, and others engaged in planning, designing, and implementing individual projects or programs to restore tidal flow to tide-restricted or diked salt marshes. Those involved in restoration science will find the technical syntheses, presentation of new concepts, and identification of research needs to be especially useful as research and monitoring questions are formulated and as research findings are analyzed, interpreted, and reported. Perhaps this book will inspire undergraduate and graduate students to pursue careers in coastal habitat restoration from the restoration science or resource management perspective.
The book is divided into six major parts—Introduction, Synthesis of Tidal Restoration Science, The Practice of Restoring Tide-Restricted Marshes, Integrating Science and Practice, Communicating Restoration Science, and a Summary. Following this introductory chapter, the second part of the book synthesizes the extensive literature that is available on the hydrologic, biogeochemical, and biological (vegetation, nekton, birds) responses of salt marshes to tidal restoration. The focus is on the New England and Atlantic Canada region, but, as noted, the chapters also provide broader geographic perspectives. There is an emphasis on trajectories of change throughout the restoration process. Each chapter closes with recommended research needs aimed at improving our understanding of marsh responses to tidal restoration.
Coastal managers from local, state, and federal agencies and conservation organizations have an extraordinary knowledge base on the practice of salt marsh tidal restoration. The third part of the book provides a rather unique opportunity for those at the forefront of facilitating tidal restoration projects to offer insight on the challenges of developing and maintaining salt marsh restoration programs, to highlight project achievements, identify monitoring and adaptive management approaches, and discuss the essential role of partnerships. Some agencies in the New England and Atlantic Canada region have been engaged in tidal restoration projects, with dedicated programs, for over two decades. Other programs are newly emerging, and some offer no formal restoration program but present the structure used to implement successful projects. The chapters present a broad range of lessons learned, which are transferable to agencies or organizations that are developing programs (or leading individual projects) aimed at tidal restoration of coastal wetlands.
Part IV of the book integrates science and practice, with chapters on the role of monitoring, adaptive management, and documentation of ecosystem services as multiparameter tools to evaluate trajectories of restoration. Another chapter offers ecosystem-based simulation models—that go beyond predicting hydrologic responses to restoration—as an informative methodology to aid in the regional prioritization of restoration sites, to guide the design of projects, and to facilitate communication of restoration objectives and anticipated outcomes. The final chapter in part IV presents modifications to tide-restricting infrastructure (e.g., modified tide gates) that can be used to achieve a desired hydrologic condition.
Part V contains four case studies focused on successes and challenges associated with advancing tidal restoration projects to the public, regulatory, and stakeholder audiences. Each chapter discusses the role of interdisciplinary science, hydrologic and ecological modeling, and effective communication to address societal concerns (e.g., flood protection, mosquito control, water quality, altered habitat) that are associated with tidal restoration projects.
The book closes with a summary of the state of science with regard to tidal restoration of salt marshes and the application of this knowledge to the implementation or practice of salt marsh restoration. Enhancing our ability to understand, predict, and plan for the response of tide-restored salt marshes to accelerated rates of sea level rise was a recurring theme throughout this edited volume and is appropriately a focus of the final chapter.
A Justification for Tidal Restoration Initiatives
Within coastal zones of the world, salt marshes, mangroves, and other ecosystem types have been destroyed due to filling and dredging operations, sometimes at alarming proportions. In the New England region it is estimated that 37 percent of salt marshes have been lost, while in urban centers, like Boston, salt marsh loss is even greater (81 percent) (Bromberg and Bertness 2005). Within the Canadian Maritimes there has been an estimated 64 percent loss of coastal wetlands, mostly attributed to agricultural reclamation, and along the Pacific US coast there is reportedly a 93 percent loss of coastal marsh, with the urban San Francisco Bay dominating the loss statistic (Gedan and Silliman 2009). In addition to these losses, coastal wetland habitat is degraded by tidal restrictions, impoundments, diking, ditching, invasive species, storm water discharge, nutrient enrichment, and other factors. Combined with losses, habitat degradation has impacted the ability of once vibrant coastal marshlands to support fish and bird populations, provide storm protection, sequester carbon, contribute to water quality maintenance, and provide open space for recreation and aesthetics. Reintroducing tidal flow to tide-restricted salt marshes represents a technique that can be successfully implemented to restore the functions of degraded salt marshes and enhance resilience to climate change effects. It is our hope that this book will provide stewards of the coastal zone with the scientific foundation and practical guidance necessary to implement effective and necessary tidal restoration initiatives.CHAPTER 2
Predicting the Hydrologic Response of Salt Marshes to Tidal Restoration
The Science and Practice of Hydraulic Modeling
JAMES G. MACBROOM AND ROY SCHIFF
The hydraulic gradients caused by tides are the primary source of physical energy in coastal salt marshes. The salt marsh ecosystem is driven by the interaction of tidal and freshwater hydrology, hydraulics, and sediment processes that determine water depth, duration of inundation, and amount of sediment erosion and deposition. The movement of water through tidal creeks and over marshes also establishes local water quality such as salinity, temperature, and dissolved oxygen as freshwater and saltwater mix.
Many tidal marshes have modified hydrologic processes that alter habitat and ecological interactions due to changes in tide levels, tidal prism, and salinity levels (e.g., Roman et al. 1984; Environmental Agency 2008). The origin of degraded salt marshes is often the constriction or blockage of channels that restrict tidal flow and alter tide levels. Tidal barriers modify flow, water surface elevation, flood volume, salinity, sediment transport rates, and the movement of aquatic organisms. The vast storage and conveyance typical of a natural marsh are reduced with increasing frequency and severity of tidal barriers, a common condition in salt marshes, especially within developed watersheds. Tidal barriers can include undersized culverts, tide gates, sluiceways, bridges, and other types of structures.
A key facet of most marsh restoration projects is the return toward natural hydrologic processes; thus hydraulic modeling is an analysis and design element essential to restoring a salt marsh. Modeling of the marsh and structures, in conjunction with investigating marsh channel morphology and equilibrium conditions, enables reduction or elimination of flow restrictions to return the appropriate tide ranges and storm surges, which in turn allow natural (passive) restoration.
The analysis and prediction of hydraulics within a tidal marsh, with its network of channels and complex flow patterns, is one of the most complicated challenges faced by hydraulic engineers. This chapter discusses analysis of tidal marsh hydraulics using analog, empirical, mathematical, and physical models. Important objectives of hydraulic modeling include accurately representing the combination of tidal exchange and storm surge to predict flow depth and velocity over a range of flow magnitudes. Model results may be directly used to identify changes in upland flooding, sediment transport, aquatic habitat, marsh vegetation, salinity levels, and fish passage under a range of restoration alternatives. Many of these challenging tasks require multiple models and interdisciplinary data collection to establish relationships to marsh hydraulics.
Hydrologic and Hydraulic Concepts Relevant to Modeling Salt Marshes
Hydraulic modeling of salt marshes includes the characterization of the tidal prism, tidal action, the marsh water budget, and flow types. The tidal prism and runoff are typical inputs to the model, while the model output includes flow types, hydraulics, and the resulting water budget.
Excerpted from Tidal Marsh Restoration by Charles T. Roman, David M. Burdick. Copyright © 2012 Island Press. Excerpted by permission of ISLAND PRESS.
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Table of Contents
Foreword W. Gregory Hood Charles A. Simenstad xiii
Part I Introduction 1
Chapter 1 A Synthesis of Research and Practice on Restoring Tides to Salt Marshes Charles T. Roman David M. Burdick 3
Part II Synthesis of Tidal Restoration Science 11
Chapter 2 Predicting the Hydrologic Response of Salt Marshes to Tidal Restoration: The Science and Practice of Hydraulic Modeling James G. MacBroom Roy Schiff 13
Chapter 3 Biogeochemical Responses to Tidal Restoration Shimon C. Anisfeld 39
Chapter 4 Vegetation Responses to Tidal Restoration Stephen M. Smith R. Scott Warren 59
Chapter 5 Ecology of Phragmites australis and Responses to Tidal Restoration Randolph M. Chambers Laura A. Meyerson Kimberly L. Dibble 81
Chapter 6 A Meta-analysis of Nekton Responses to Restoration of Tide-Restricted New England Salt Marshes Kenneth B. Raposa Drew M. Talley 97
Chapter 7 Avian Community Responses to Tidal Restoration along the North Atlantic Coast of North America W. Gregory Shriver Russell Greenberg 119
Part III The Practice of Restoring Tide-Restricted Marshes 145
Chapter 8 Restoration of Tidal Flow to Degraded Tidal Wetlands in Connecticut Ron Rozsa 147
Chapter 9 Salt Marsh Restoration in Rhode Island Caitlin Chaffee Wenley Ferguson Marci Cole Ekberg 157
Chapter 10 Restoration of Tidal Flow to Salt Marshes: The Massachusetts Experience Hunt Durey Timothy Smith Marc Carullo 165
Chapter 11 Restoration of Tidal Flow to Salt Marshes: The New Hampshire Experience Ted Diers Frank D. Richardson 173
Chapter 12 Restoration of Tidal Flow to Salt Marshes: The Maine Experience Jon Kachmar Elizabeth Hertz 183
Chapter 13 Salt Marsh Tidal Restoration in Canada's Maritime Provinces Tony M. Bowron Nancy Neatt Danika van Proosdij Jeremy Lundholm 191
Part IV Integrating Science and Practice 211
Chapter 14 Adaptive Management and Monitoring as Fundamental Tools to Effective Salt Marsh Restoration Robert N. Buchsbaum Cathleen Wigand 213
Chapter 15 Recovering Salt Marsh Ecosystem Services through Tidal Restoration Gail L. Chmura David M. Burdick Gregg E. Moore 233
Chapter 16 Role of Simulation Models in Understanding the Salt Marsh Restoration Process Raymond A. Konisky 253
Chapter 17 Incorporating Innovative Engineering Solutions into Tidal Restoration Studies William C. Glamore 277
Part V Communicating Restoration Science 297
Chapter 18 Salt Marsh Restoration at Cape Cod National Seashore, Massachusetts: The Role of Science in Addressing Societal Concerns John W. Portnoy 299
Chapter 19 Drakes Island Tidal Restoration: Science, Community, and Compromise Susan C. Adamowicz Kathleen M. O'Brien 315
Chapter 20 Role of Science and Partnerships in Salt Marsh Restoration at the Galilee Bird Sanctuary, Narragansett, Rhode Island Francis C. Golet Dennis H. A. Myshrall Lawrence R. Oliver Peter W. C. Paton Brian C. Tefft 333
Chapter 21 Restoration of Tidally Restricted Salt Marshes at Rumney Marsh, Massachusetts: Balancing Flood Protection with Restoration by Use of Self-Regulating Tide Gates Edward L. Reiner 355
Part VI Summary 371
Chapter 22 Salt Marsh Responses to Tidal Restriction and Restoration: A Summary of Experiences David M. Burdick Charles T. Roman 373
About the Editors and Contributors 383
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