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3 Research Gaps
Pages 61-84

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From page 61...
... Understanding long-term coastal zone dynamics under changing conditions within the coupled natural-human coastal system will require addressing research gaps related to (1) the physical and ecological components of the natural system (as well as interactions and feedbacks among these components)
From page 62...
... This leads to varying levels of granularity in the questions related to different research gaps. THE COUPLED NATURAL-HUMAN SYSTEM Physical drivers (e.g., sea level rise, episodic storms)
From page 63...
... to track rates of relative sea level rise in a meaningful way. Perhaps the greatest challenge to monitoring sea level rise in coastal zones is that current space-based sensors are unable to produce meaningful signals of sea level change in the 63
From page 64...
... satellite mission, scheduled to be launched in April 2021, may offer a new means to monitor climate-driven sea level rise near the coastline. Research Gap 1: Current datasets, monitoring systems, and approaches are insufficient to track and understand how the oceanic component of sea level (i.e., excluding subsidence)
From page 65...
... In addition, because shallow subsidence due to compaction of Holocene sediments is a dominant process in many portions of the Gulf Coast (notably in coastal Louisiana; Törnqvist et al., 2008) , there is a particularly great need for geotechnical models that include loading, dewatering, and other compaction processes in the prediction of subsidence rates.
From page 66...
... Episodic Coastal and Riverine Flooding Flooding events along the Gulf Coast are related to the effects of major landfalling hurricanes and other storms, but are also affected by precipitation and related changes in river discharge. Storms can cause major devastation and their flood damage potential will increase in the future due to concomitant sea level rise.
From page 67...
... Research Gap 3: The combined effects of freshwater input from Gulf Coast watersheds, storm surge, sea level rise, and development on coastal flood hazards are not well understood, thereby limiting the capacity to include and model these effects in predictions of Gulf Coast dynamics. • How is storm surge affected as the coastal landscape (e.g., landforms, ecosystems, land use)
From page 68...
... . Resolving this uncertainty would contribute to a better understanding of sediment management within this large region, because it would help clarify the degree to which current landform change is a response to historic changes in sediment supply, current changes in hydrodynamics, or relative sea level rise.
From page 69...
... • How will the availability of sediment to wetlands and barrier islands change in the future, and what will be the likely effect of these changes on coastal evolution? Coastal Sediment Transport and Hydrodynamics The fate, delivery, and transport of sediments exert major control on the evolution of the coastal landscape.
From page 70...
... As sea level rise accelerates and environmental conditions such as storminess, precipitation, and temperature shift in the future, the dynamic coastal landforms and embayments of the Gulf Coast will respond by evolving even more rapidly than they have in the recent past. The ability to simulate and forecast the long-term evolution of coastal landforms and embayments is critical to understanding the coupled natural-human system and would draw directly from progress toward addressing Research Gaps 1 to 5 (described in previous sections)
From page 71...
... . The amount of sediment supplied to wetlands and barrier islands is especially critical in determining whether they can accrete and maintain their position and function as sea level rises.
From page 72...
... , and landform evolution models (e.g., of barrier islands, wetlands, estuaries) by coupling them in appropriate ways.
From page 73...
... They can also result in an understanding of crucial observations and can therefore inform the design of long-term observational programs. Research Gap 6: There is a critical need to understand and project the future response of coastal landforms and embayments to changing climate and the conditions under which they will no longer be able to keep pace with relative sea level rise.
From page 74...
... However, the impacts of physical temporal variability on the dynamics and function of coastal ecosystems are not fully understood. For instance, more research is needed on how Gulf Coast ecosystems respond to rising water levels driven by global sea level rise and subsidence, which takes place over years to decades; changes in wind-driven setup, which take place over hours to days (but also have a multi-decadal component)
From page 75...
... • How prominent will the effects of relative sea level rise be in relation to other stressors such as coastal development, and what are the interactions among these processes and the consequences for ecosystem survivability? • What are the most important interactions between and among physical forcing, coastal development, and climate change driving changes in environmental condi tions and ecosystem response, both in terms of their structure and function?
From page 76...
... Research Gap 8: The understanding of strategic natural resource conservation and restoration activities for effective coastal management is limited. • Which functional hot spots best contribute to the preservation of ecosystem re sources, function, and services in developed coasts under current and future climate conditions?
From page 77...
... Households might purchase high-clearance cars or trucks to transit areas of minor flooding, replace carpet with tile to deal with nuisance flooding, or raise homes on pilings to avoid damages from storm surge. Governments might build a seawall or fund a beach nourishment project to mitigate against storm risk or erosion associated with sea level rise.
From page 78...
... , datasets that compile federal, state, and local decisions about defensive capital expenditures and local development restrictions are sparse and not uniformly tracked over time and space. Research Gap 9: There is a need to understand how decisions about the built environment will be affected by coastal change and how these decisions create feedbacks between the natural and human systems.
From page 79...
... Energy-Related Infrastructure Given that a large percentage of the U.S. energy infrastructure lies along the Gulf Coast, sea level rise, subsidence, increased hurricane intensity, and loss of wetlands and other ecosystems could lead to direct impacts on infrastructure, such as damage to equipment from coastal erosion or flooding.
From page 80...
... Recognizing its vulnerability to storm surge and erosion, energy companies dependent on that infrastructure have previously invested in engineered protection, as well as beach and dune nourishment. In addition, Port Fourchon is conducting feasibility studies of a major expansion that would include deeper draft navigation channels, and beneficial use of the dredged sediment has been proposed to create wetland habitat areas and reduce storm surge impacts (Guidry, 2016, 2018; Duchmann, 2018)
From page 81...
... • What strategies for coastal development are most cost-effective when considering future climate change, relative sea level rise, and episodic events? • How do coastal engineering approaches or development restrictions feed back on continued coastal development and the tax base that supports engineering interventions?
From page 82...
... . Complicating the problem further are the compounding effects of economic and social stressors and multiple interactive and simultaneous sources of environmental change (e.g., sea level rise over the long term, increasing frequency of nuisance flooding, the sudden shock of a major storm)
From page 83...
... As such, these research gaps can be addressed while being viewed primarily through the lens of a specific component. In contrast, this research gap involves the consideration of the entire coupled system.
From page 84...
... • How can models account for household decisions in response to novel environ mental changes (e.g., types or magnitude of changes that households have not yet experienced, such as unprecedented levels of sea level rise)


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