Pennsylvania By Chris Linn The following document can be cited as: Chris Linn. 2010. “Pennsylvania.” In James G. Titus and Daniel Hudgens (editors). The Likelihood of Shore Protection along the Atlantic Coast of the United States. Volume 1: Mid- Atlantic. Report to the U.S. Environmental Protection Agency. Washington, D.C. This report has undergone peer review as required by the Peer Review Handbook of the US Environmental Protection Agency for influential scientific information under the direction of Karen Scott, peer review leader for all products associated with Climate Change Science Program Synthesis and Assessment Product 4.1. The opinions expressed herein are solely those of the authors and do not necessarily represent the official opinion of the Environmental Protection Agency. The primary referring page for this document is http://risingsea.net/ERL/PA.html CHAPTER 4 PENNSYLVANIA Chris Linn Delaware Valley Regional Planning Commission [ 388 THE LIKELIHOOD OF SHORE PROTECTION IN PENNSYLVANIA] CONTENTS Summary ......................................................................................................................... 390 Introduction..................................................................................................................... 394 Purpose of this Study .................................................................................................. 394 1 Caveats ....................................................................................................................... 396 1 How to Read this Report ............................................................................................. 397 Existing Conditions in the Delaware Estuary............................................................... 398 Sea Level Rise in the Delaware Estuary ..................................................................... 398 Physical Conditions in the Estuary .............................................................................. 399 Methods........................................................................................................................... 401 Study Area .................................................................................................................. 401 Protection Categories.................................................................................................. 402 Basis for Category Delineations .................................................................................. 403 Creation of Sea Level Rise Response Maps............................................................... 406 Additional Considerations............................................................................................ 407 Map Scale ................................................................................................................... 408 Use of Experts............................................................................................................. 409 Pennsylvania State Policies .......................................................................................... 410 Wetlands and Floodplains ........................................................................................... 410 Pennsylvania Coastal Zone Management Program .................................................... 412 Municipal and County Policies...................................................................................... 414 County-Specific Responses to Sea Level Rise............................................................ 415 Delaware County ............................................................................................................ 416 Discussion Summary................................................................................................... 416 Anticipated Response Scenarios ................................................................................ 418 County Review ............................................................................................................ 420 Philadelphia County ....................................................................................................... 424 Discussion Summary................................................................................................... 424 Anticipated Response Scenarios ................................................................................ 425 County Review ............................................................................................................ 426 [ CONTENTS 389 ] Bucks County ..................................................................................................................429 Discussion Summary ...................................................................................................429 Anticipated Response Scenarios .................................................................................430 County Review.............................................................................................................431 Appendix A: Length of Shorelines by Likelihood of Shore Protection ......................434 Appendix B: Area of Land by Likelihood of Shore Protection ....................................437 Appendix C: Elevation Uncertainty................................................................................441 Appendix D. Stakeholder Comments ............................................................................445 ACKNOWLEDGEMENTS.................................................................................................448 MAPS Map 4-1. Study Results for Coastal Region of Pennsylvania ............................................392 Map 4-2. Delaware County: Likelihood of Shore Protection ..............................................422 Map 4-3. Philadelphia County: Likelihood of Shore Protection..........................................428 Map 4-4. Bucks County: Likelihood of Shore Protection ...................................................433 FIGURE Figure 4-1. Land Vulnerable to Sea Level Rise in Pennsylvania.......................................400 TABLES Table 4-1: Area of Land by Likelihood of Shore Protection ...............................................393 Table 4-2: Shoreline Length by Major Body of Water and Likelihood of Shore Protection 393 Table 4-3. Area of Land Vulnerable to Sea Level Rise in Pennsylvania............................399 Table 4-4: Government Participants and Reviewers .........................................................403 Table 4-5: Statewide Sea Level Rise Shore Protection Categories by Land Use .............418 Table 4-4: Delaware County Land Use Shore Protection Categories ...............................421 Table 4-5: Philadelphia Land Use Shore Protection Categories .......................................427 Table 4-6: Bucks County Land Use Shore Protection Categories.....................................432 [ 390 THE LIKELIHOOD OF SHORE PROTECTION IN PENNSYLVANIA] SUMMARY Sea level is rising about 1 inch every 9 years (2.7 millimeters per year) along the coast of Pennsylvania. Sea level rise in this area will continue to be approximately 0.05 inches per year (1.2 mm/year) greater than the global rise in sea level because of land subsidence in the Mid-Atlantic region. Given the small amount of low-lying land along Pennsylvania’s coast, rising seas threaten only a relatively small portion of the state’s coastal communities. However, the impacts of sea level rise go beyond inundation to include increased erosion, increased flooding, and the migration of the salt line farther up tidal rivers and streams. Land use is diverse along the Pennsylvania portion of the Delaware Estuary. Most of the coast is heavily developed; only about 18 percent of the coastal area is classified as undeveloped. Much of the natural shoreline has already been filled in or modified many times over with bulkheads, docks, wharfs, piers, riprap shorelines, and other hard structures during the past two centuries. As a result of the developed and altered character of the Delaware Estuary, the natural ebb and flow of the tide is, in many places, already restricted by hard edges and vertical structures. Shoreline armoring with bulkheads establishes a vertical boundary that separates uplands on one side from open water, wetlands, or mudflats on the other. As the sea rises, these armoring structures prevent the high protected uplands from becoming progressively transformed into a wetlands or intertidal environment. If fronting marshes or tidal flats do not accrete enough sediment to keep pace with rising sea level, they will drown. This report develops maps that distinguish shores that are likely to be protected from the sea from those areas that are likely to be submerged, assuming current coastal policies, development trends, and shore protection practices. Our purpose is primarily to promote the dialogue necessary to decide where people will yield the right of way to the inland migration of wetlands and beaches, and where we will hold back the sea. A key step in evaluating whether new policies are needed is to evaluate what would happen under current policies. The maps in this report represent neither a recommendation nor an unconditional forecast of what will happen, but simply the likelihood that shores would be protected if current trends continue. The author obtained land use and planning data from Delaware, Philadelphia, and Bucks County and consulted with county planners as well as participating agencies