A global assessment of estuarine tidal response to sea level rise

Climate change induced sea level rise (SLR) is one of the greatest challenges threatening the sustainable management of estuaries worldwide. Current knowledge regarding SLR and estuarine hydrodynamics is primarily focused on individual case studies, which provides limited guidance on how different estuary typologies will respond to SLR. To expand the current knowledge, this research used an idealised hydrodynamic approach to analyse the tidal range dynamics of 25 real-world estuaries with diverse shapes and boundary conditions, providing insights into estuarine response to SLR-induced tidal variations. Under present-day conditions, short length estuaries with wide entrances, deep waters, strong convergence, macro-tidal conditions, low values of roughness, and low upland river inflows are likely to experience amplified tidal range patterns; whereas lengthy estuaries with narrow entrances, shallow water depths, micro/meso-tidal conditions, high values of roughness, and high upland river inflows often exhibit a mix of dampened-amplified or fully dampened tidal range patterns. Under the effects of SLR, estuarine tidal range dynamics change depending on their present-day tidal range patterns. Where the present-day tidal range pattern is either dampening, a mix of dampening/amplification, or amplification, SLR increases (up to 61 %), moderately increases (up to 26 %), and slightly decreases/increases (up to 5 %) the tidal range of estuaries, respectively. Considering the relationship between an estuary's present-day tidal range pattern and its response to SLR, the presented approach may be useful in providing an initial assessment of SLR effects in estuaries worldwide. This may help to identify sites most impacted by future SLR, and to direct decision-making towards evidence-based management approaches.