Coastal Resource Guide Pleasant Bay and ... - Town to Chatham

More documents

Recommendations

Info

Coastal Resource Guide for Pleasant Bay and Chatham Harborwinter months, while during summer months this sand is returnedto the beach. In general, steeper, high-energy waves during thewinter months cause sediment to move seaward and the milderlate spring through fall wave climate causes sand to migrateback onto the beach face. The movement of sand back and forthperpendicular to the shoreline is called cross-shore sedimenttransport. This process can be dominant on relatively short beachesbetween sections of erosion-resistant coast, where there is littleopportunity for a strong longshore current to be generated. Anexample of an area dominated by this type of transport can bethe coves and ponds throughout the bay, or the summer/winterprofiles of the ocean-facing barrier beach.A widened “summer” beach profile at Scatteree will narrow as onshore sediments are moved offshore by winter storms. Photo: GregBerman4.3.5 Cross-Shore Sediment TransportIn addition to sand moving parallel to the coast, there is alsoa component of transport that moves sediment onshore andoffshore (i.e., cross-shore transport). A familiar example of this isthe formation of a winter beach profile, where sand is moved fromthe dry beach to shallow water areas offshore, typically forming anearshore bar. Offshore sand migration typically occurs during the4.3.6 Aeolian TransportUnder strong enough winds, the sand along the dry beach canbe mobilized and carried away from its original location. Thistransport of dry sand by wind forces, called aeolian transport, istypically less dominant on an estuarine shoreline due to reducedfetch, availability of sediments, and dense vegetation. Anyimpediment to the sand’s movement along the beach can serve tolimit windblown transport. Fencing and beach grass planting arecommon examples of such efforts to limit aeolian transport and/orencourage the deposition of wind blown sands in specific locationssuch as on an existing dune. An example of an area dominatedby this type of natural transport is the extensive dune system onNauset Beach.17The extensive dune system on Nauset Beach is an example of an area dominated by aeolian transport. Photo by Greg BermanPleasant Bay Alliance 2011
Coastal Resource Guide for Pleasant Bay and Chatham HarborSection 5Coastal Structures5.1 PurposeThe purpose of this section is to describe and illustrate the typeand distribution of coastal structures within the Pleasant Baysystem. The function of coastal structures and their potentialimpacts to the coastal zone also are described.5.2 MethodologyThe type, number and distribution of coastal structures in PleasantBay were derived from a combination of existing geospatialdata and local knowledge. In 1996, large-scale base maps withparcel boundaries produced by the Cape Cod Commission wereused by local resource managers (Harbormasters, Conservation,Environmental Staff) to map the approximate locations of coastalstructures around the Bay. The locations were then digitized by theCape Cod Commission for mapping purposes and a GIS databasewas created for the 1998 Pleasant Bay Resource ManagementPlan. The 1996 data was augmented with more recent datataken from field observations by local resource managers involvedwith the 2008 plan update. The location of many of the softshoreline structures were provided by conservation permittingrecords. Shoreline structures in the Chatham section are currentlybeing updated using information derived from aerial photography.5.3 Coastal StructuresCoastal structures in Pleasant Bay include shorefront protectionstructures, as well as piers, docks, floats, and elevated walkways,etc. Shorefront protection structures (“hard structures”) and otherapproaches (“soft solutions” such as fiber rolls, pictured right)are used to manage shoreline erosion, especially on developedcoasts. Revetments, bulkheads, and gabions are examples of hardstructures, while soft structures or soft stabilization techniquesinclude fiber rolls, artificial dunes with beach grass plantings orfencing, and beach nourishment.Section HighlightsCoastal structures in Pleasant Bay include shorefrontprotection structures to manage coastal erosion anddocks and piers to provide water access. In 2007,approximately 160 piers and docks were locatedaround the Bay. These structures may impact coastalenvironments by altering water circulation andcausing scour, or by shading vegetation.“Hard” shorefront protection structures includerevetments, bulkheads, and gabions. In 2007, therewere 132 hard structures around the Bay. Thesemostly permanent structures may affect sedimentdynamics along the shore by inhibiting bankerosion, causing scour near the base and/or end ofthe structure and lowering of beach profile on thefronting beach.Soft stabilization structures or solutions around theBay include fiber rolls, artificial dunes with plantingsor fencing, and beach nourishment. They are fewer innumber (28), but have become increasingly common.Regulatory agencies typically prefer soft shoreprotection solutions since they are less permanentand typically cause fewer impacts to the shore.The growing number of docks and piersin Pleasant Bay was a major impetusfor the Bay’s designation as an ACECand the subsequent developmentof a resource management plan forthe Bay. In an effort to assist townsaround the Bay in developing specificregulatory or bylaw changes relativeto the permitting of docks, piers,walkways and stairways, the PleasantBay Resource Management Allianceissued Guidelines and PerformanceStandards for Permitting Docks and Piersin Pleasant Bay in 1999 and Guidelinesfor Private Walkways and Stairways inFresh and Marine Resource Areas inPleasant Bay in 2002. These documentsrecommend design criteria andperformance standards for constructionof these structures in order to minimizeFiber rolls, considered a “soft solution,” can be covered over with vegetation to restore a naturalappearance and functioning of a coastal bank. Photo: Kristin Andres 18Pleasant Bay Alliance 2011
Page 1 and 2: Coastal Resource Guide for Pleasant
Page 21: Coastal Resource Guide for Pleasant
Page 72 and 73:
Coastal Resource Guide for Pleasant
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82:
show all

Coastal Resource Guide Pleasant Bay and ... - Town to Chatham

Create successful ePaper yourself

Delete template?

Save as template?