Evaluating the fate of freshwater lenses on atoll islands after eustatic sea-level rise and cyclone-driven inundation: A modelling approach

Terry, James P.; Chui, Ting Fong May

doi:10.1016/j.gloplacha.2012.03.008

Cited by 72 publications

(64 citation statements)

References 28 publications

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“…On the same atoll, motu can stretch for tens of kilometers long on one side but less than a half kilometer elsewhere (Figure 1c and 1d). Motu may provide the only emergent land for atoll island nations (Kench et al, 2014b) and hold the majority of freshwater available on atolls, as rainwater infiltrates through the partially lithified rubble and sand and then sits above the saltwater in an unconfined aquifer (Terry and Chui, 2012). Motu and atolls are morphologically dynamic landforms that respond to external forcing like sea-level change or a change in wave climate.…”

Section: Atolls Reef Flats and Motumentioning

confidence: 99%

Investigating the evolution and formation of coastlines and the response to sea-level rise

Ortiz¹

2015

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To understand how waves and sea level shape sandy shoreline profiles, I use existing energetics-based equations of cross-shore sediment flux to describe shoreface evolution and equilibrium profiles, utilizing linear Airy wave theory instead of shallow-water wave assumptions. By calculating a depth-dependent characteristic diffusivity timescale, I develop a morphodynamic depth of shoreface closure for a given time envelope, with depth increasing as temporal scale increases. To assess which wave events are most important in shaping the shoreface in terms of occurrence and severity, I calculate the characteristic effective wave conditions for both cross-shore and alongshore shoreline evolution. Extreme events are formative in the cross-shore shoreface evolution, while alongshore shoreline evolution scales linearly with the mean wave climate. Bimodal distributions of weighted wave heights are indicative of a site impacted more frequently by tropical storms rather than extra-tropical storms.To understand how offshore wave climate and underlying geometry of a carbonate reef platform shapes evolution of atolls, I simulate the hydrodynamics of a simplified reef flat, using XBeach, a two-dimensional model of infragravity wave propagation. The reef flat self-organizes to a specific width and water depth depending on the offshore wave climate and characteristics of the available sediment. Formation of a sub-aerial landmass, like a motu, can be initiated by a change in offshore wave climate (like a storm), which can create a nucleation site from mobilization and deposition of coarse sediment on the reef flat. Once a motu is present, the shoreline should prograde until reaching a critical reef-flat width. Our conceptual model of reefflat evolution and motu formation is governed by understanding the hydrodynamics of the system and subsequent response of sediment transport. 4 Chapter 1 -IntroductionClimate change has many diverse and severe impacts on our planet, including accelerated rates of sea-level rise. Over the past twentieth century, eustatic sea level rose around 1.5 -2.0 mm/yr (IPCC, 2013; Cazenave et al., 2014; Hay et al., 2015), and predicted rates of eustatic sealevel could far exceed 5 mm/yr in by the end of coming century (IPCC, 2013;Horton et al., 2014;Kopp et al., 2014). Understanding the response of coastal systems to increased rates of sea-level rise is important; 10% of the world's population lives in the Low Elevation CoastalZone (IPCC, 2014; Wong et al., 2014). My research has focused on understanding the processes that shape different coastal systems and how these systems evolve. I am interested in the response of coastal sandy and carbonate sedimentary systems to changes in sea level and predicting how future climate might impact coastal evolution.Geomorphology is the study of landscape evolution through time: by understanding the processes that shape the landscape, it is possible to predict how a landscape may respond to changing forces. Changes in sediment flux can be a primary driver of coast...

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Section: Atolls Reef Flats and Motumentioning

confidence: 99%

Investigating the evolution and formation of coastlines and the response to sea-level rise

Ortiz¹

2015

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“…J. P. Terry and Chui () and T. F. Chui and Terry () also simulated the effect of sea level rise on the extent of salinization from the overwash event. T. F. Chui and Terry () also included the central topographic depression in their model, which often is observed on atoll islands in the Pacific (Ayers & Vacher, ; Hamlin & Anthony, ) and found that the central topographic depression can be a significant source of seawater infiltration even after the overwash event has occurred.…”

Section: Introductionmentioning

confidence: 99%

Quantifying threats to groundwater resources in the Republic of Maldives Part II: Recovery from tsunami marine overwash events

Alsumaiei

Bailey

2018

Hydrological Processes

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Marine overwash events are among the most serious short‐term threats to groundwater supply of small coral islands. During such events, seawater can inundate small islands partially or completely, causing salinization of the aquifer. A comprehensive knowledge of freshwater lens recovery is essential for water planners on these islands. In this study, a numerical modelling approach is used to quantify recovery of the freshwater lens on 4 islands of the Maldives after a tsunami‐induced overwash event similar to that experienced from the Indian Ocean earthquake in December 2004. The islands vary in size (0.2 to 10.1 km2) and span the climatic regions of the Maldives. A tested 3‐dimensional SEAWAT groundwater model for each island is used to simulate the recovery process. Recharge rates from historical rainfall data and from global climate models are imposed on each island during the post‐overwash recovery period. The effect of groundwater pumping on lens recovery also is examined. Results show abrupt decrease in fresh groundwater volumes for each island, followed by recovery that is significantly influenced by island size and recharge patterns. Overall, salinization is more widespread on small islands (<1 km2), but recovery is more rapid than for large islands. Between 50% and 90% of lens recovery occurs after 2 years for small islands (<1 km2) whereas only 35% and 55% for large islands. Imposing pumping rates required to sustain the local population lengthened the recovery time between 5% and 15%, with smaller islands having the higher percentage. However, the governing factor on recovery time is the spatial extent of land surface inundation by the overwash event, with wave height and duration of the event having a negligible impact. A strong relationship exists between required recovery time and island surface area, thereby providing a method to determine recovery time for other atoll islands not investigated in this study with similar geologic structure. Our results can be used to aid in managing water resources during the post‐overwash period.

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“…Coastal plant communities around the world are threatened by halophytic movement into upland glycophytic communities (1)(2)(3)56). Sea level rise coupled with anthropogenic disturbance has been found to be the major contributors to the loss of coastal communities (3).…”

Section: Discussionmentioning

confidence: 99%

“…Increasing sea levels and anthropogenic disturbances are causing changes in coastal plant communities around the world (1)(2)(3). Shifts from less salt-and lower inundation-tolerant to more salt-and higher inundation-tolerant community types or to open water have been documented (1,(3)(4)(5)(6)(7).…”

Section: Introductionmentioning

confidence: 99%

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Evaluating plant community response to sea level rise and anthropogenic drying: Can life stage and competitive ability be used as indicators in guiding conservation actions?

Wendelberger¹

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Evaluating the fate of freshwater lenses on atoll islands after eustatic sea-level rise and cyclone-driven inundation: A modelling approach

Cited by 72 publications

References 28 publications

Investigating the evolution and formation of coastlines and the response to sea-level rise

Investigating the evolution and formation of coastlines and the response to sea-level rise

Quantifying threats to groundwater resources in the Republic of Maldives Part II: Recovery from tsunami marine overwash events

Evaluating plant community response to sea level rise and anthropogenic drying: Can life stage and competitive ability be used as indicators in guiding conservation actions?

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