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HomeMy Public PortalAboutPreserving The Values And Services Provided By Healthy Coastal WetlandsBrewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 1 #2 Preserving The Values And Services Provided By Healthy Coastal Wetland Resources Introduction The Town of Brewster Coastal Committee is charged with developing a management plan to provide vision and direction for the future management of Brewster’s coastal resources. The Brewster Coastal Resources Management Plan will build on the Coastal Adaptation Strategy (CAS) developed by the Brewster Coastal Advisory Group and written by the Horsley Witten Group. The CAS assessed impacts to town landings and beaches from sea level rise and storm surge, and provided guiding principles for assessing future management actions. This discussion paper is one of a series designed to highlight management issues that will be addressed in the Brewster Coastal Resource Management Plan. Each paper will be presented at a community workshop to engage stakeholders in discussing management issues and trends, and evaluating potential strategies and action items. The discussion paper topics and workshop dates are: 1. Sustaining our public beaches and landings in the face changing shoreline conditions Community workshop: May 17 2. Preserving the values and services provided by healthy coastal wetlands Community workshop: June 14 3. Providing access for water-dependent activities Community workshop: July 19 4. Preserving access to beach and landings for residents and visitors Community workshop: August 16 5. Protecting vulnerable infrastructure, visual access, cultural & historical resources Community workshop: September 13 Each paper discusses current conditions and future trends, and explores a range of potential management strategies and actions. Proposed strategies and actions could encompass physical improvements, policies and regulations, management practices, technical studies/analyses, or communications measures. This paper will discuss the beneficial ecosystem services provided by salt marshes and other coastal wetland resources, the threats to those resources resulting from sea level rise and storm surges, and the measures and strategies available to the community to protect or, where necessary, restore the functioning of these wetland resources. Along with white paper #1, this paper provides important baseline information for assessing management issues covered in subsequent white papers. Subsequent discussion papers will address issues of public beach access; access to town landings for activities such as shellfishing/aquaculture; public infrastructure; and visual, historical and cultural resources. Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 2 Summary of Coastal Wetland Resources and Potential Impacts Stony Brook Marsh, south Photo courtesy of C Miller While walking on the flats or enjoying a day at the beach, we don’t often think about the natural processes constantly shaping and sustaining these special resource areas. Tidal flats, beaches, dunes and other shoreline features each play a role in sustaining a healthy coastal system. The ongoing health and functioning of a variety of coastal wetland resources along Brewster’s shoreline is essential to sustaining our enjoyment of beaches and flats, and the extensive wildlife and other benefits these resources provide to the community. The primary types of coastal landforms along Brewster’s shoreline include land under the ocean, salt marshes, dunes, tidal flats, coastal banks, and coastal beaches. Even though these areas are not “wet” all the time, they are considered wetland resources and are protected under local and state wetland protection regulations. The descriptions and significance of these coastal wetland resources are summarized below.1 Land under the Ocean means land extending from the mean low water line seaward to the boundary of the Town's jurisdiction (three miles). Land under the ocean is provides important habitat for fish and shellfish, and is likely to help prevent storm damage and flood control. 1 Resource definitions excerpted from the Massachusetts Wetlands Protection Act Regulations (310 CMR 10.00) Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 3 Coastal Dune means any natural hill, mound or ridge of sediment landward of a coastal beach deposited by wind action or storm overwash. Coastal dune also means sediment deposited by artificial means and serving the purpose of storm damage prevention or flood control. Coastal dunes help to prevent storm damage and control flooding by supplying sand to coastal beaches. Coastal dunes protect inland coastal areas from storm damage and flooding by storm waves and storm-elevated seas because the dunes are higher than the coastal beaches which they border. Coastal dunes are a sediment source in that wind, waves and currents move sediment from coastal dunes on to coastal beaches. Coastal Bank means the seaward face or side of any elevated landform, other than a coastal dune, which lies at the landward edge of a coastal beach, land subject to tidal action, or other wetland. Coastal banks composed of loose sediment and exposed to vigorous wave action serve as a major continuous source of sediment for beaches, dunes, and barrier beaches. Coastal banks that supply sediment to coastal beaches, coastal dunes and barrier beaches are assumed to be significant to storm damage prevention and flood control. In addition to being a sediment source, coastal banks, because of their height and stability, may act as a buffer or natural wall, which protects upland areas from storm damage and flooding. Coastal Beach means unconsolidated (loose) sediment subject to wave, tidal and coastal storm action which forms the gently sloping shore of a body of salt water and includes tidal flats. Coastal beaches extend from the mean low water line landward to the dune line, coastal bankline or the seaward edge of existing human-made structures, when these structures replace one of the above lines, whichever is closest to the ocean. Coastal beaches, including tidal flats, are significant to help to prevent storm damage, control flooding and protect wildlife habitat. Coastal beaches dissipate wave energy because of their gentle slope, and their granular, permeable sandy sediment. These characteristics allow beaches to change form in response to wave conditions. That is why a beach can look very different in the winter compared to summer. Coastal beaches serve as a sediment source for dunes and offshore subtidal areas. Vegetative debris found in the drift line of coastal beaches is consumed by invertebrates, which in turn are a food source for resident and migratory shorebirds. Tidal Flat means any nearly level part of a coastal beach which usually extends from the mean low water line landward to the more steeply sloping face of the coastal beach or which may be separated from the beach by land under the ocean. Tidal flats provide habitats for marine organisms such as worms and mollusks (shellfish), which in turn are food sources for fishes and migratory and wintering birds. Tidal flats are also sites where organic and inorganic materials may become entrapped and then returned to the photosynthetic zone of the water column to support algae and other primary producers of the marine food web. Salt marsh means a coastal wetland that extends landward up to the highest high tide line (ie, highest spring tide of the year), and is characterized by plants that are well adapted to or prefer living in saline soils, such as salt meadow cord grass (Spartina patens) and/or salt marsh cord grass (Spartina alterniflora), spike grass (Distichlis spicata), high-tide bush (Iva frutescens), and black grass (Juncus gerardii). A salt marsh may contain tidal creeks, ditches and pools. Salt marshes are significant to protection of marine fisheries, wildlife habitat, and shellfish. Salt marshes absorb wave energy and floodwaters, which helps to prevent storm damage and flooding during coastal storms. Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 4 Salt marshes are among the most productive ecosystems on the planet, rivaling rain forests in their diversity and productivity. A salt marsh produces large amounts of organic matter. A significant portion of this material enters coastal waters where it provides the basis for a large food web that supports many marine organisms, including finfish and shellfish and many bird species. Salt marshes also provide a spawning and nursery habitat for several important estuarine forage fish as well as important food, shelter, breeding areas, and migratory and overwintering areas for many wildlife species. Salt marsh plants and substrate remove pollutants from surrounding waters. The sediments absorb chlorinated hydrocarbons and heavy metals such as lead, copper, and iron. The marsh also retains nitrogen and phosphorous compounds, which in large amounts can lead to algal blooms in coastal waters. The underlying peat also serves as a barrier between fresh ground water landward of the salt marsh and the ocean, thus helping to maintain the level of such ground water. A more recently acknowledged benefit of salt marshes is their ability to store carbon. Salt marsh plants remove carbon dioxide from the atmosphere. Some of the carbon is stored for centuries as soil carbon. Why do marshes store so much carbon? They grow upward every year at about the same rate as sea level rise, roughly ¼ inch. The soil is composed of plant roots and trapped sediment, and so as they grow upward, they build large carbon stores over many centuries, keeping CO2 out of the atmosphere. This “ecosystem service” is referred to as “Blue Carbon.”2 Coastal Processes and Threats to Coastal Wetland Resources Coastal shorelines such as Brewster’s are dynamic systems subject to the constant influences of tides, waves, storm and tidal surges, currents and wind. Erosion occurs when these natural forces move coastal sediments, particularly from eroding coastal banks and dunes. Eroded sediments are then transported by wind, waves and currents and are deposited on beaches, dunes, marshes or offshore on tidal flats in a process referred to as deposition. These resource areas rely on a supply of sediment to maintain elevation. Without the processes of sediment erosion, transport and deposition to counteract sea level rise and subsidence, beaches, dunes, marshes, and tidal flats would eventually disappear. Erosion management measures on public and private property can interfere with natural coastal processes and the beneficial movement of sediment. Hard structures such as revetments, bulkheads, groins and gabions are designed to prevent the process of sediment erosion, transport and deposition. Even with regular beach nourishment, resource areas adjacent and downdrift of hard structures can experience a loss of sediment supply resulting in loss of resource area. In the extreme, beach area and marsh is lost at all levels of the tide. Salt marshes are naturally extremely adaptable. As noted in the Coastal Adaptation Strategy, salt marshes can contract or expand depending on the frequency and depth of flooding. The pattern of inundation in turn dictates vegetation coverage and the overall marsh ecosystem.3 When rising sea level or increased erosive forces outpace the ability of a salt marsh to increase in elevation, the marsh would naturally seek to migrate 2 Kroeger, Kevin D., USGS Woods Hole Coastal and Marine Science Center. Blue Carbon in the Herring River: Can We Reduce Greenhouse Gas Emissions through Wetland Restoration? Paragraph excerpted from presentation to Friends of Herring River. March 29, 2018. 3 CAS p 26 Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 5 landward. However, the presence of development or other geographic features can reduce or eliminate opportunities for landward migration of salt marsh. A marsh that experiences loss of elevation without the ability to migrate landward eventually will drown in place resulting in a loss of salt marsh resource area. Brewster’s shoreline resources are anchored by two large marsh systems: the Quivett Creek-Paine’s Creek marsh system shared with Dennis, and the Namskaket Creek marsh system shared with Orleans. Each of these extensive marsh systems provides a wide variety of ecosystem services: wildlife habitat, nursery and forage areas for fish and shellfish, storm and flood protection, pollution filtration and carbon storage. If all or portions of these systems are lost, the ecological and other public benefits they provide also would be lost. Man-mad replication of these naturally occurring ecosystem services, if even possible, can be extremely costly and difficult to achieve. Actions Taken by the Town to Preserve Coastal Wetland Resources The Town purchased and protected the two major salt marshes located at either end of Brewster’s shoreline. The Namskaket Creek is a 200-acre tidal creek and marsh located adjacent to Crosby Landing and extends into the Town of Orleans. According to a report by the Massachusetts Estuaries Project, the Namskaket Marsh system is a typical New England salt marsh dominated by a central tidal creek and emergent marsh colonized by low marsh (Spartina alterniflora) and high marsh (Spartina patens, Distichlis spicata) with some more brackish marsh plants found in the upper most regions and limited bordering patches of Phragmites. The marsh is regularly flushed with high quality waters of Cape Cod Bay, with near complete drainage at low tide. As a result Namskaket Marsh has a relatively high tolerance for nitrogen inputs from its watershed. Observations by the USGS and the MEP indicate a healthy functioning New England salt marsh.4 Namskaket Marsh provides both wildlife habitat and a nursery to offshore fisheries, as well as serving as a storm buffer and nutrient sink for watershed nitrogen from septic systems, road runoff and fertilizers. A heavily used bicycle trail is located in the upper reaches of the marsh.5 In recognition of its natural beauty and critical environmental value, Namskaket Marsh is included in the state-designated Inner Cape Cod Bay Area of Critical Environmental Concern (ACEC). ACEC’s are classified as Outstanding Resource Waters by the Commonwealth of Massachusetts. The ACEC affords a higher level of regulatory protection for wetland resources, and provides a framework for developing a management plan to guide coordinated resource management actions.6 Quivett Creek-Paine’s Creek Marsh is a 190-acre area surrounding Wing Island owned by the Town of Brewster and protected by a Conservation Restriction held by the Massachusetts Department of Conservation and Recreation. MassDCR has developed a base line documentation report for the land area 4 Howes, B., et al. Massachusetts Estuaries Project Linked Watershed-Embayment Model to Determine Critical Nitrogen Loading Thresholds for the Namskaket Marsh Estuarine System, Orleans, MA. 2008 5 op. cit. 6 op. cit. Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 6 covered under the Conservation Restriction. Additional marsh areas are protected through the joint efforts of the Brewster and Dennis Conservation Trusts, In 2009, the Town of Brewster purchased the 3.8 Quivett Marsh Vista Conservation Area and commissioned a Land Use and Management Plan for the property. The Town of Dennis Crowes Pasture property directly abuts this marsh to the west. The Quivett Marsh and Crowes Pasture comprise more than 570 contiguous acres, of which 300 acres are classified as a nationally declining coastal wetland type. The US Fish & Wildlife Service identifies the area as significant habitat for a number of species of federal concern, including piping plovers, American black ducks and other migratory waterfowl and shore birds, river herring, striped bass and state-threatened northern harriers and osprey.7 These salt marsh systems are valuable for their ecosystem services, including the ability to absorb storm surge and floodwaters. Salt marshes require a steady supply of sediment to maintain their elevation in the face of sea level rise. To the extent that an area of salt marsh is unable to keep pace with sea level rise, the marsh will naturally migrate landward. Development or hardening along the shoreline can prevent opportunities for the landward migration of salt marshes. 7 DeTour, D. Baseline Documentation Report for Quivet Creek/Paines Creek Marsh Conservation Restriction. June 30, 2006. Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 7 Other recent management actions undertaken by the Town to maintain wetland resources include the following: • Restored tidal flow to a salt pond and surrounding tidal wetland and salt marsh by replacing the undersized culvert at Paine’s Creek leading to Freemans Pond; • Restored tidal flow to Stony Brook and surrounding salt marsh and restored a diadromous fish run by replacing the undersized culvert under Route 6A at Stony Brook with a much larger box culvert; • Improved drainage at Saint’s landing, eliminating direct discharge onto the beach and erosion down the path; • Relocated parking lot at Paine’s Creek; parking lot replaced with sacrificial sand and beach; • Stormwater controls throughout the Stony Brook valley, including Paine’s Creek Road, Stony Brook Road, and replacement of the dam at the Stony Brook Mill; • Relocated parking spaces, restored and protected dune at Breakwater, including a sturdy sand fence at the beach side of the dune. Implemented green infrastructure (vegetated swale) to absorb stormwater and pollutants to eliminate a direct discharge onto the beach; • Stairs and sand nourishment at Little Breakwater to replace a degraded path/gulley down the coastal bank; • Replaced stairs at Spruce Hill with a raised structure that allows dune migration. Stairs damaged in storm, to be replaced Spring 2018; • Ellis Landing stormwater and beach restoration: removed non-functional stormwater structures from beach, installed a resilient mat, nourished beach, installed stormwater controls in roadway and parking area, eliminating a direct stormwater discharge to the beach; • Linnell Landing stormwater project: Installed stormwater control structures throughout parking lot and roadway, pitched parking lot back from beach, repaved; Eliminated a direct stormwater discharge onto the beach; • Regular sand nourishment at Breakwater Landing, Ellis Landing, and Paine’s Creek; • Sand nourishment at Mant’s Landing, sacrificial dune and sturdy sand fence; • Developed the Century Scale Sediment Budget and Brewster Coastal Adaptation Strategy; • Notice of Intent/Order of Conditions developed for all landings except Mant’s, allowing regular maintenance and nourishment as required; For Mant’s Landing, a conceptual study was completed to evaluate removal of pavement with replacement by a resilient pervious surface, with grade changes to address stormwater concerns from flooding beach side and from the marsh at the back; • Culvert to be replaced under Crosby Lane Fall 2018. Summary of Management Issues Allowing sand to move freely through the natural coastal processes of sediment erosion, transport and deposition is essential to the long-term sustainability of beaches, tidal flats, dunes and salt marshes. In addition to the visual beauty, recreational opportunities and economic value, these resources provide important ecosystem services including storm damage protection, erosion control, pollution filtration, wildlife habitat, and carbon storage. These natural services are difficult and expensive to replicate if the resource areas providing them are lost. Shoreline structures such as revetments and groins are intended to prevent erosion by interfering with the natural coastal processes of erosion, transport and deposition. These structures can starve adjacent and downdrift beaches, dunes and salt marshes of sediment they need to maintain elevation. Any effort to Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 8 manage erosion on public and private property needs to be conducted in balance with the need for a steady supply of sediments to maintain the elevation of salt marshes, beaches, dunes and tidal flats. Through a process of sediment transport and accretion, Brewster’s expansive tidal flats have kept up with sea level rise. However it is not clear whether the flats will be able to keep pace if sea level rise accelerates, as is anticipated. The elevation of Brewster’s marshes, notably Namskaket and Quivett marshes, also has kept pace with sea level rise. However it is not clear whether the marshes will be able to keep pace if sea level rise accelerates, as is anticipated. There are opportunities for active management of these resource areas in coordination with adjoining towns of Dennis and Orleans, respectively. Quivett Marsh Vista Photo courtesy of C Miller Management Concepts 1. Use the state of the art wetland modeling to assess patterns of salt marsh retreat in Brewster. Model results could then be used to develop salt marsh management plans to counteract loss of marsh due to subsidence or inundation. Management actions could include: a. Channel drainage improvements; b. Piloting of thin layer deposition, based on MassDEP permitting guidance. Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 9 2. Removal of tidal restrictions (e.g., Crosby salt marsh restoration project)Identify opportunities to accommodate landward migration of wetlands: a. Identify key parcels for acquisition; b. Work with the Town’s Open Space Committee and Community Preservation Committee and the Brewster Conservation Trust to develop a funding strategy for acquisition of these properties; c. Seek conservation restrictions on select parcels to limit development. 3. Revise or implement planning and zoning measures: a. Review/update wetlands conservancy district; b. Review/update flood plain bylaw; c. Evaluate Coastal District of Critical Planning Concern designation. 4. Develop and Implement Land Use and Management Plans for Quivett Creek/Paine’s Creek Marsh and Namskaket Marsh. 5. Develop an Inner Cape Cod Bay ACEC management Plan in coordination with the Towns of Eastham and Orleans. 6. Adopt permitting guidance for shoreline structures and other development a. Permitting guidelines for erosion management structures; b. Site plan review or other measures for residential development. 6. Adopt changes to local wetlands protection bylaw or regulation to enhance wetland resource protection. 7. Develop public informational materials to educate shoreline property owners about best practices for vegetation management, erosion management, and buffer protection, etc. Discussion Questions Do you support use of town land currently devoted to parking for purposes of allowing opportunities for wetland resources to migrate landward? Do you support use of town funds to acquire property for purposes of allowing opportunities for wetland resources to migrate landward? Do you support increased regulation of residential development along the shoreline to prevent building in low-lying areas and protect coastal wetland resources? Brewster Coastal Resource Management Plan June 2018 Preserving Coastal Wetland Resources 10 Resources (hyperlinks provided where available) Coastal Adaptation Strategy, Brewster Coastal Advisory Group, 2016 Assessment of the Century Scale Sediment Budget of the Brewster Coast Howes, B., et al. Massachusetts Estuaries Project Linked Watershed-Embayment Model to Determine Critical Nitrogen Loading Thresholds for the Namskaket Marsh Estuarine System, Orleans, MA. 2008 Massachusetts Wetland Protection Act Regulations, 310 CMR 10.00 DeTour, Darrell. Baseline Documentation Report for Quivet Creek-Paines Creek Marsh Conservation Restriction. CR Holder: Massachusetts Department of Conservation and Recreation. June 30, 2006.