Gaining insights into the behaviour of inlet-interrupted coasts
Sandy coastlines adjacent to tidal inlets are highly dynamic and widespread landforms that evolve in time due to the supply or removal of sand, making them vulnerable to changes in sediment budget. These systems are affected by the combined effects of terrestrial (e.g., river sand supply) and oceanic (e.g., sea-level rise) processes, making their behaviour even more complex, especially with the significant changes expected in climate conditions (as early as the mid-century) and anthropogenic influences. For example, an increase in rainfall over land will not only increase the river flow but will also increase the volume of sand carried by the river. Such a variation will result in a larger supply of sediment to the coast, which may result in an outbuilding (known as progradation) of the coastline. Another significant consequence of climate change is an acceleration of sea-level rise, which will also impact the coast. A higher sea level creates a need for more sand to maintain the position of the coastline. If that extra sand is not available, the shoreline will retreat (i.e., shoreline erosion), with serious consequences for communities, developments, and infrastructure. While such terrestrial and oceanic processes affect the sand budget of the coastal inlet system, until now, their combined effect has not been adequately investigated. Accordingly, Janaka Bamunawala, has developed and piloted a fully probabilistic numerical model (named G-SMIC) that accounts for the combined effect of such terrestrial and oceanic processes and provides rapid, probabilistic projections of changes in the sand budget and the shoreline at coastal inlets as a part of his doctoral degree at IHE Delft/University of Twente (The Netherlands) with financial support from Deltares (The Netherlands).
A part of this research is published in Scientific Reports, describing novel projections of shoreline change adjacent to 41 tidal inlets worldwide. The results for the most extreme IPCC climate scenario (i.e., RCP 8.5) show that ~90% of the studied coasts may retreat in the 21st century, where two-thirds of them are projected to erode by more than 100 m. However, the other coasts are projected to prograde due to rivers’ increased sand supply. The distinction between retreating and prograding coasts is an important step forward in assessing climate-change impacts on coastal areas worldwide, compared to the projections made hitherto that have only been able to project shoreline retreat. G-SMIC may be widely applied to support evidence-based coastal adaptation for the coming century. Prior to this global application of the model, its concept was first presented and verified at case study sites.
Further information can be found via following publications
- Read the article on the Nature Scientific Reports
- Read the model concept on the Frontiers in Marine Science
- Read the model development and case study applications on the Frontiers in Marine Science