Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise
Wetlands
Tidal marshes are important ecological systems that are responding to sea level rise-driven chang... more Tidal marshes are important ecological systems that are responding to sea level rise-driven changes in tidal regimes. Human development along the coastline creates barriers to marsh migration, moderating tidal marsh distributions. This study shows that in the Chesapeake Bay, USA an estuarine system with geographic and development variability, overall estuarine tidal marshes are projected to decline by approximately half over the next century. Tidal freshwater and oligohaline habitats, which are found in the upper reaches of the estuary and are typically backed by high elevation shorelines are particularly vulnerable. Due to their geological setting, losses of large extents of tidal freshwater habitat seem inevitable under sea level rise. However, in the meso/poly/euhaline zones that (in passive margin estuaries) are typically low relief areas, tidal marshes are capable of undergoing expansion. These areas should be prime management targets to maximize future tidal marsh extent. Redirecting new development to areas above 3 m in elevation and actively removing impervious surfaces as they become tidally inundated results in the maximum sustainability of natural coastal habitats. Under increasing sea levels and flooding, the future of tidal marshes will rely heavily on the policy decisions made, and the balance of human and natural landscapes in the consideration of future development.
Review of boat wake wave impacts on shoreline erosion and potential solutions for the Chesapeake ... more Review of boat wake wave impacts on shoreline erosion and potential solutions for the Chesapeake Bay Donna M. Bilkovic Virginia Institute of Marine Science Molly Mitchell Virginia Institute of Marine Science Jenny Davis NOAA Center for Coastal Fisheries and Habitat Research Elizabeth Andrews Virginia Coastal Policy Center (VCPC), College of William & Mary Law School Angela King Virginia Coastal Policy Center (VCPC), College of William & Mary Law School
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This report examines mounting evidence of human influence on the earth and its environmental proc... more This report examines mounting evidence of human influence on the earth and its environmental processes as measured by a suite of water level sensors in operation throughout the U.S. during the Anthropocene, a proposed new geologic epoch following the Holocene, the latest interglacial epoch that began nearly 12,000 years ago. A review of recent relative sea level (RSL) observations at U.S. tide stations since 1969 examines trends in RSL rise rate and acceleration that vary in response to both global and regional processes. Trend histories at 32 coastal locations selected for study display a high degree of similarity between locations in regions that are experiencing similar processes. With the exception of the U.S. Northeast Coast and Alaska, every other location in the continental U.S. has experienced an upturn in RSL rise rate since 2014 despite wide differences in the magnitude and trending direction of RSL acceleration. High RSL acceleration along the U.S. Northeast Coast has trended downward since 2011 while low RSL acceleration along the U.S Southeast Coast has recently trended upward in response to changes likely associated with ocean dynamics and ice sheet loss. RSL change in the sedimentary basins of the central U.S. Gulf Coast region is highly dependent on local rates of vertical land movement (VLM). VLM here varies over relatively short time scales amid changing patterns of subsurface water and hydrocarbon extraction. RSL rise rates of 5 mm/year or more aided by weak acceleration in Louisiana and Texas project a total RSL rise of between 0.4 and 0.5 meters above 1992 MSL by the year 2050; other Gulf and East Coast locations will experience equal or greater rise if upward trends in acceleration continue. Low and mostly downward trends in RSL rise rate at central U.S. West Coast locations have recently reverted to a pattern of upward trends with higher rise rates. Rise rates prior to 2013 appear to have been restrained by deceleration now trending toward acceleration. A combination of tectonic plate convergence and glacial isostatic adjustment makes the non-contiguous U.S. coastal state of Alaska unique with regard to RSL trends. Land emergence, rather than subsidence, produces consistent trends of falling RSL in Alaska. With these observed trends in mind, RSL rise rate and acceleration patterns elucidated within the proposed Anthropocene epoch (here 1969 through 2017) are presented for U.S. coastal locations with analogous 'report cards' displaying nearly fifty years of RSL heights projected forward to the mid-point of the present century. Factors contributing to RSL acceleration include: 1) steric expansion, 2) ocean dynamics, 3) Greenland and Antarctic ice sheet melting, 4) glacial isostatic adjustment, 5) groundwater and hydrocarbon storage changes, 6) inverted barometer, and 7) atmospheric cycles. With these contributing factors in mind, the report concludes with a broad summary of management recommendations applicable in regions experiencing the effects of these change-producing factors, as human populations look to better understand, quantify, and mitigate adverse effects on the increasingly inhabited coastal zone.
Banks (DEQ) and Richard Sobota (FEMA, DHS) for their efforts to finding and consolidating informa... more Banks (DEQ) and Richard Sobota (FEMA, DHS) for their efforts to finding and consolidating information on Virginia Repetitive Loss properties; Kelly Burkes-Copes (USACE, ERDC) and Jay Ratcliff (USACE, ERDC) for sharing data from their sea level rise/storm surge project, Tonya Denckla Cobb (UVA, IEN) for sharing the outcomes of their stakeholder groups on sea level rise, John Scrivani (VITA) for helping acquire LiDAR data, Keil Schmid (NOAA) for helping with GIS data corrections, Rose Lawson (VDOT) for providing VDOT flooding records, and David Wilcox for help with GIS manipulations. We would like to acknowledge all the participants in the stakeholder advisory group, many of whom traveled far distances to attend the meeting and who all contributed unique perspectives which helped shape the report.
Road accessibility from county seat under flooding: Hampton, Newport News, James City, Poquoson, Williamsburg, York, Accomack, Northampton, Alexandria, Fairfax, Gloucester, Mathews, Middlesex
Molly Mitchell Introduction Over the past few decades, the Hampton Roads region, with its extensi... more Molly Mitchell Introduction Over the past few decades, the Hampton Roads region, with its extensive coastline, has been experiencing more frequent flooding from surges and precipitation caused by tropical storms, nor’easters and heavy thunderstorms (Figure 1). Recurrent flooding is “flooding that occurs repeatedly in the same area over time due to precipitation events, high tides or storm surge.” 1 The recurrence of tidal/surge flooding in Hampton Roads has increased from 1.7 days of “nuisance” flooding per year in 1960 to 7.3 days per year in 2014.2 Although there is no definitive region-wide data to document the increases in precipitation-induced flooding, there is much anecdotal, locality-specific evidence. With continued land subsidence and the projected increase in sea level rise, it is reasonable to expect that flooding events may become even more common.
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