Numerical modeling of the impact of sea-level rise on fringing coral reef hydrodynamics and sediment transport

Abstract

Most climate projections suggest that sea level may rise on the order of 0.5-1.0 m by 2100; it is not clear, however, how fluid flow and sediment dynamics on exposed fringing reefs might change in response to this rapid sea-level rise. Coupled hydrodynamic and sedimenttransport numerical modeling is consistent with recent published results that suggest that an increase in water depth on the order of 0.5-1.0 m on a 1-2 m deep exposed fringing reef flat would result in larger significant wave heights and setup, further elevating water depths on the reef flat. Larger waves would generate higher near-bed shear stresses, which, in turn, would result in an increase in both the size and the quantity of sediment that can be resuspended from the seabed or eroded from adjacent coastal plain deposits. Greater wave-and wind-driven currents would develop with increasing water depth, increasing the alongshore and offshore flux of water and sediment from the inner reef flat to the outer reef flat and fore reef where coral growth is typically greatest. Sediment residence time on the fringing reef flat was modeled to decrease exponentially with increasing sea-level rise as the magnitude of sea-level rise approached the mean water depth over the reef flat. The model results presented here suggest that a 0.5-1.0 m rise in sea level will likely increase coastal erosion, mixing and circulation, the amount of sediment resuspended, and the duration of high turbidity on exposed reef flats, resulting in decreased light availability for photosynthesis, increased sediment-induced stress on the reef ecosystem, and potentially affecting a number of other ecological processes.

Global changes of extreme coastal wave energy fluxes triggered by intensified teleconnection patterns

“…Such an increase, combined with anticipated RSLR of 0.5-1.5 m [Church et al, 2013;Hinkel et al, 2014], and fast-growing population trends [Zinkina and Korotayev, 2014], can lead to higher wave-induced water levels, energy, and thus coastal impacts. Small Island Developing States located in the tropical southern Pacific are known for their limited and low-lying areas and their strong exposure to coastal hazard [Strolazzi et al, 2011;Duvat et al, 2013]. An increase of extreme WEF of about 10% by the end of the century, together with the effects of RSLR, could compromise a significant portion of their surface and even threaten the existence of some atolls.…”

Long-Distance Interactions Regulate the Structure and Resilience of Coastal Ecosystems

“…Seagrasses and mangroves provide an important reciprocal service to the corals by trapping sediments and absorbing nutrients (Christianen et al 2013, Storlazzi et al 2011). These effects have important implications for corals because they decrease sediment and nutrient fluxes from the hinterland toward the reef.…”

“…These effects have important implications for corals because they decrease sediment and nutrient fluxes from the hinterland toward the reef. Especially during siltation events, these mechanisms may act as buffers against excess sedimentation, thereby preventing the burial and suffocation of both the seagrass meadows and the coral reefs (Christianen et al 2013, Rogers 1990, Storlazzi et al 2011. Because tolerance of high nutrient and sediment loading progressively decreases from mangrove forests to seagrass meadows to coral reefs, a protective cascade forms across these three habitats against algal overgrowth and sediment burial (Gillis et al 2014).…”

An AHP-derived method for mapping the physical vulnerability of coastal areas at regional scales

“…We were also lacking data to analyse the consequences of fringing coral reef degradation and sea level rise on lagoon waves, currents, and shoreline dynamics (e.g. Storlazzi et al, 2011). In some cases, existing data presented some spatial inconsistencies: for example, the actual shoreline position differs between various GIS shoreline datasets in Languedoc-Roussillon.…”