Climate Change Induced Coastline Change Adjacent to Small Tidal Inlets

Abstract

The many thousands of small tidal inlets (STIs), and their adjacent coastlines, are almost certain to be affected by climate change in multiple ways, due to their behaviour being closely linked to both oceanic and terrestrial drivers such as riverflow, sea level, and ocean waves, all which are projected to change over the 21st century. Development of risk informed adaptation strategies for these highly utilized and inhabited inlet-interrupted coast zones requires projections of both alongshore average coastline recession and alongshore variability in coastline position along the coast under future forcing conditions, the latter being an aspect that has not received much attention to date. Here, a combination of a process-based morphodynamic model (Delft3D) and the reduced complexity coastline model (SMIC), concurrently forced with tides, waves, riverflows, and sea level rise, is used to investigate both of these phenomena at STI-interrupted coasts. The models are here applied to schematised conditions representing two systems in Sri Lanka, representing two of the three main Types of STIs: Negombo lagoon – permanently open, locationally stable inlet (Type 1), and Kalutara lagoon – permanently open, alongshore migrating inlet (Type 2). Results indicate that, under a high emissions climate scenario following RCP 8.5, by end-century, the coastline adjacent to the Type 1 STI may experience an alongshore average recession as large as 200 m, and that the alongshore variability in coastline position may be up to twice that at present. The Type 2 STI is projected to experience an alongshore average coastline recession of about 120 m, and up to a 75% increase in alongshore variability in coastline position by end-century, relative to the present. Thus, both the alongshore average coastline recession and the increase in the alongshore variability in coastline position are greater at the Type 1 STI, compared to at the Type 2 STI. These findings highlight the importance of accounting for both alongshore average coastline recession and future changes in alongshore variability in coastline position when assessing coastal hazards and risk on inlet-interrupted coasts to adequately inform climate adaptation strategies.

Mediterranean Coastal Lagoons Review: Sites to Visit before Disappearance

“…Climate change has as a consequence on sea level rise and with it the disappearance of the sandbars due to shoreline recession [67]. These studies are the most recent on coastal lagoons, and in our study area have dealt especially with Venice [68], but are of concern in general in all coastal lagoons, especially those with urban settlements on their shores [69].…”

Numerical assessment of hydro‐morphodynamics affected by altered upstream discharge in the Dujiangyan reach of the Min River, China

“…The governing equation was expressed in orthogonal curvilinear coordinates, discretized by a 2D finite‐difference grid, and solved by an alternating‐direction implicit scheme. The horizontal advection terms were spatially discretized using a cyclic method (Crosato et al, 2012; Duong, 2021; Vona et al, 2021).…”

“…where t is time (s); x and y are the downstream and lateral coordinates (m), respectively; ζ is the water level with respect to the datum (m); The horizontal advection terms were spatially discretized using a cyclic method (Crosato et al, 2012;Duong, 2021;Vona et al, 2021).…”

Detecting the Effects of Extreme Events on Estuarine Suspended Particulate Matter Using Satellite Remote Sensing (Scheldt Estuary): Challenges and Opportunities

“…In contrast, reference [51] observed a sharp loss of turbidity in the occurrence of flood events (river discharge above the 75th percentile) in the macrotidal Gironde Estuary (France), and reference [16] observed lower turbidity in the microtidal estuary of Río de la Plata (Uruguay) caused by periods of intensified river discharge due to excessive rain. However positive (i.e., increase in turbidity with extreme events) or negative (i.e., turbidity dilution) the trend with SPM, it is rational to expect that extreme events represent changes in the local SPM dynamics and that these changes likely also affect other aspects of the estuary (e.g., changes in water quality and sediment-related biota [21], or shoreline recession of tidal flats [52]). We also speculate that the effects of extreme events in the diverse biogeochemical aspects of the estuary are not uniform along the estuary, e.g., reference [53], thus affecting more the sites and regions that are not used to large variability in SPM.…”