Molly Mitchell
Virginia Institute of Marine Science, Ccrm, Department Member
Research Interests:
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... 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.
Research Interests:
Low elevation coastal zones (LECZ) are extensive throughout the southeastern United States. LECZ communities are threatened by inundation from sea level rise, storm surge, wetland degradation, land subsidence, and hydrological flooding.... more
Low elevation coastal zones (LECZ) are extensive throughout the southeastern United States. LECZ communities are threatened by inundation from sea level rise, storm surge, wetland degradation, land subsidence, and hydrological flooding. Communication among scientists, stakeholders, policy makers and minority and poor residents must improve. We must predict processes spanning the ecological, physical, social, and health sciences. Communities need to address linkages of (1) human and socioeconomic vulnerabilities; (2) public health and safety; (3) economic concerns; (4) land loss; (5) wetland threats; and (6) coastal inundation. Essential capabilities must include a network to assemble and distribute data and model code to assess risk and its causes, support adaptive management, and improve the resiliency of communities. Better communication of information and understanding among residents and officials is essential. Here we review recent background literature on these matters and off...
Research Interests:
Building flood resilience in coastal communities requires a precise understanding of the temporal and spatial scales of inundation and the ability to detect and predict changes in flooding. In Hampton Roads, the Intergovernmental Pilot... more
Building flood resilience in coastal communities requires a precise understanding of the temporal and spatial scales of inundation and the ability to detect and predict changes in flooding. In Hampton Roads, the Intergovernmental Pilot Project's Scientific Advisory Committee recommended an integrated network of ocean, earth, and atmospheric data collection from both private and public sector organizations that engage in active scientific monitoring and observing. Since its establishment, the network has grown to include monitoring of water levels, land subsidence, wave measurements, current measurements, and atmospheric conditions. High-resolution land elevation and land cover data sets have also been developed. These products have been incorporated into a number of portals and integrated tools to help support resilience planning. Significant challenges to building the network included establishing consistent data standards across organizations to allow for the integration of th...
Research Interests:
Nature-based shoreline protection provides a welcome class of adaptations to promote ecological resilience in the face of climate change. Along coastlines, living shorelines are among the preferred adaptation strategies to both reduce... more
Nature-based shoreline protection provides a welcome class of adaptations to promote ecological resilience in the face of climate change. Along coastlines, living shorelines are among the preferred adaptation strategies to both reduce erosion and provide ecological functions. As an alternative to shoreline armoring, living shorelines are viewed favorably among coastal managers and some private property owners, but they have yet to undergo a thorough examination of how their levels of ecosystem functions compare to their closest natural counterpart: fringing marshes. Here, we provide a synthesis of results from a multi-year, large-spatial-scale study in which we compared numerous ecological metrics (including habitat provision for fish, invertebrates, diamondback terrapin, and birds, nutrient and carbon storage, and plant productivity) measured in thirteen pairs of living shorelines and natural fringing marshes throughout coastal Virginia, USA. Living shorelines were composed of mars...
Research Interests:
Accelerating sea level rise in Virginia, United States, will significantly increase the flooding threat to low-lying roads, residences, and critical infrastructure as well as raise the water table, allowing saltwater intrusion into well... more
Accelerating sea level rise in Virginia, United States, will significantly increase the flooding threat to low-lying roads, residences, and critical infrastructure as well as raise the water table, allowing saltwater intrusion into well water and threatening the function of septic fields. Although most of the adaptation work in Virginia has focused on urban economic centers, the majority of the coastline is rural and faces different threats and opportunities to address them compared to urban areas due to their reduced economic assets and their reliance on private infrastructure. In this case study, we assess the potential for geospatially quantifying impact to septic systems and adjacent water ways due to sea level rise. The case study found that the data necessary to reliably quantify these impacts on a state-wide scale are lacking and collection of that information needs to be prioritized given the potential for extensive sea level impacts.
Research Interests:
Research Interests:
Changes in the eustatic sea level have enhanced the impact of inundation events in the coastal zone, ranging in significance from tropical storm surges to pervasive nuisance flooding events. The increased frequency of these inundation... more
Changes in the eustatic sea level have enhanced the impact of inundation events in the coastal zone, ranging in significance from tropical storm surges to pervasive nuisance flooding events. The increased frequency of these inundation events has stimulated the production of interactive web-map tracking tools to cope with changes in our changing coastal environment. Tidewatch Maps, developed by the Virginia Institute of Marine Science (VIMS), is an effective example of an emerging street-level inundation mapping tool. Leveraging the Semi-implicit Cross-scale Hydro-science Integrated System Model (SCHISM) as the engine, Tidewatch operationally disseminates 36-h inundation forecast maps with a 12-h update frequency. SCHISM’s storm tide forecasts provide surge guidance for the legacy VIMS Tidewatch Charts sensor-based tidal prediction platform, while simultaneously providing an interactive and operationally functional forecast mapping tool with hourly temporal resolution and a 5 m spati...
Saltwater intrusion is the leading edge of sea-level rise, preceding tidal inundation, but leaving its salty signature far inland. With climate change, saltwater is shifting landward into regions that previously have not experienced or... more
Saltwater intrusion is the leading edge of sea-level rise, preceding tidal inundation, but leaving its salty signature far inland. With climate change, saltwater is shifting landward into regions that previously have not experienced or adapted to salinity, leading to novel transitions in biogeochemistry, ecology, and human land uses. We explore these changes and their implications for climate adaptation in coastal ecosystems. Biogeochemical changes, including increases in ionic strength, sulfidation, and alkalinization, have cascading ecological consequences such as upland forest retreat, conversion of freshwater wetlands, nutrient mobilization, and declines in agricultural productivity. We explore the trade-offs among land management decisions in response to these changes and how public policy should shape socioecological transitions in the coastal zone. Understanding transitions resulting from saltwater intrusion—and how to manage them—is vital for promoting coastal resilience.
Research Interests:
Relative sea level (RSL) observations since 1969 at U.S. tide stations exhibit trends in RSL rise rate and acceleration that vary in response to both global and regional processes. Trend histories display a high degree of similarity... more
Relative sea level (RSL) observations since 1969 at U.S. tide stations exhibit trends in RSL rise rate and acceleration that vary in response to both global and regional processes. Trend histories display a high degree of similarity between locations in coastal regions that are experiencing similar processes. With the exception of the U.S. Northeast Coast and Alaska,every other coastal location in the continental U.S. has experienced an upturn in RSL rise rate since 2013-2014 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 hydrocarbons 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.
Research Interests:
Globally, shoreline protection approaches are evolving towards the incorporation of natural and nature-based features (living shorelines henceforth) as a preferred alternative to shoreline armoring. Emerging research suggests that living... more
Globally, shoreline protection approaches are evolving towards the
incorporation of natural and nature-based features (living shorelines
henceforth) as a preferred alternative to shoreline armoring. Emerging
research suggests that living shorelines may be a viable approach to
conserving coastal habitats (marshes, beaches, shallows, seagrasses)
along eroding shorelines. Living shorelines typically involve the use of
coastal habitats, such as wetlands, that have a natural capacity to
stabilize the shore, restore or conserve habitat, and maintain coastal
processes. They provide stability while still being dynamic components
of the ecosystem, but due to their dynamic nature, careful designs and
some maintenance will be required if habitat conservation is a goal.
Living shorelines may represent a singular opportunity for habitat
conservation in urban and developing estuaries because of their value
to society as a shoreline protection approach and resilience to sea
level rise. However, enhanced public acceptance and coordination
among regulatory and advisory authorities will be essential to expand
their use. To fully understand their significance as habitat conservation
strategies, systematic and standardized monitoring at both regional
and national scales is vital to evaluate the evolution, persistence, and
maximum achievable functionality (e.g., ecosystem service provision)
of living shoreline habitats.
incorporation of natural and nature-based features (living shorelines
henceforth) as a preferred alternative to shoreline armoring. Emerging
research suggests that living shorelines may be a viable approach to
conserving coastal habitats (marshes, beaches, shallows, seagrasses)
along eroding shorelines. Living shorelines typically involve the use of
coastal habitats, such as wetlands, that have a natural capacity to
stabilize the shore, restore or conserve habitat, and maintain coastal
processes. They provide stability while still being dynamic components
of the ecosystem, but due to their dynamic nature, careful designs and
some maintenance will be required if habitat conservation is a goal.
Living shorelines may represent a singular opportunity for habitat
conservation in urban and developing estuaries because of their value
to society as a shoreline protection approach and resilience to sea
level rise. However, enhanced public acceptance and coordination
among regulatory and advisory authorities will be essential to expand
their use. To fully understand their significance as habitat conservation
strategies, systematic and standardized monitoring at both regional
and national scales is vital to evaluate the evolution, persistence, and
maximum achievable functionality (e.g., ecosystem service provision)
of living shoreline habitats.
Salt marsh ecosystems have declined globally and are increasingly threatened by erosion, sea level rise, and urban development. These highly productive, physically demanding ecosystems are populated by core species groups that often have... more
Salt marsh ecosystems have declined globally and are increasingly threatened by erosion, sea level rise, and urban development. These highly productive, physically demanding ecosystems are populated by core species groups that often have strong trophic interactions with implications for ecosystem function and service provision. Positive interactions occur between ribbed mussels (Geukensia demissa) and cordgrass (Spartina alterniflora). Mussels transfer particulate nitrogen from the water column to the marsh sediments, which stimulates cordgrass growth, and cordgrass provides predator and/or heat stress refuge for mussels. Here, we test mussel facilitation of two functions in salt marshes that relate to N removal: microbial denitrification and water filtration. Microcosm experiments revealed that the highest rates of N 2 production and nitrification occurred when mussels were present with marsh vegetation, suggesting that mussels enhanced coupling of the nitrification–denitrification. Surveys spanning the York River Estuary, Chesapeake Bay, showed that the highest densities of mussels occurred in the first meter for all marsh types with mainstem fringing (1207 AE 265 mussels/m 2) being the most densely populated. The mussel population was estimated to be ~197 million animals with a water filtration potential of 90–135 million L/hr. Erosion simulation models demonstrated that suitable marsh habitat for ribbed mussels along the York River Estuary would be reduced by 11.8% after 50 years. This reduction in mussel habitat resulted in a projected 15% reduction in ribbed mussel abundance and filtration capacity. Denitrification potential was reduced in conjunction with projected marsh loss (35,536 m 2) by 205 g N/hr, a 16% reduction. Because of the predominant occurrence of ribbed mussels at the marsh seaward edge and because the highest proportional loss will occur for fringing marshes (20%), shoreline management practices that restore or create fringing marsh may help offset these projected losses.
Research Interests:
John D. Boon and Molly Mitchell (2015) Nonlinear Change in Sea Level Observed at North American Tide Stations. Journal of Coastal Research: Volume 31, Issue 6: pp. 1295 – 1305. The rate at which coastal sea level is expected to rise or... more
John D. Boon and Molly Mitchell (2015) Nonlinear Change in Sea Level Observed at North American Tide Stations. Journal of Coastal Research: Volume 31, Issue 6: pp. 1295 – 1305.
The rate at which coastal sea level is expected to rise or fall is of considerable interest to coastal residents and managers who view changes on the time scale of a 30-year mortgage. Analysis of historical records at North American tide stations provides evidence of recent nonlinear sea-level change at this scale using relative mean sea-level (RMSL) observations. RMSL tracks local inundation risk directly without the need to correct an accepted worldwide geocentric measure—e.g., global mean sea-level rise—with locally estimated vertical rate adjustments. Published RMSL linear trends provide essential information but are routinely compared between tide stations with widely varying record lengths, thereby obfuscating nonlinear change (acceleration or deceleration) over a specific period of time. Here monthly averaged RMSL data from 45 U.S. tide stations and one Canadian tide station are analyzed from 1969 through 2014, extending a definitive period of acceleration previously noted along the U.S. NE Coast. Using a Bayesian approach to determine the joint probability of paired regression parameters for RMSL quadratic trends, probabilities for forward projections to the year 2050 based on these trends suggest continued sea-level rise will be aided by acceleration presently on the order of 0.1 to 0.2 mm/y2 in the U.S. NE and Gulf Coast regions. Deceleration ranging from −0.1 to −0.4 mm/y2 is likely to reinforce falling sea levels at specific locations on the U.S. West Coast in the near term.
The rate at which coastal sea level is expected to rise or fall is of considerable interest to coastal residents and managers who view changes on the time scale of a 30-year mortgage. Analysis of historical records at North American tide stations provides evidence of recent nonlinear sea-level change at this scale using relative mean sea-level (RMSL) observations. RMSL tracks local inundation risk directly without the need to correct an accepted worldwide geocentric measure—e.g., global mean sea-level rise—with locally estimated vertical rate adjustments. Published RMSL linear trends provide essential information but are routinely compared between tide stations with widely varying record lengths, thereby obfuscating nonlinear change (acceleration or deceleration) over a specific period of time. Here monthly averaged RMSL data from 45 U.S. tide stations and one Canadian tide station are analyzed from 1969 through 2014, extending a definitive period of acceleration previously noted along the U.S. NE Coast. Using a Bayesian approach to determine the joint probability of paired regression parameters for RMSL quadratic trends, probabilities for forward projections to the year 2050 based on these trends suggest continued sea-level rise will be aided by acceleration presently on the order of 0.1 to 0.2 mm/y2 in the U.S. NE and Gulf Coast regions. Deceleration ranging from −0.1 to −0.4 mm/y2 is likely to reinforce falling sea levels at specific locations on the U.S. West Coast in the near term.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
This thesis or dissertation is not available through the W&M Digital Archive at this time. The item is available in Swem Library and electronic access is possible for some items through the database ProQuest Dissertations and... more
This thesis or dissertation is not available through the W&M Digital Archive at this time. The item is available in Swem Library and electronic access is possible for some items through the database ProQuest Dissertations and Theses--Full Text. Consult the Swem Library ...