Numerical Modelling of Arctic Coastal Erosion Due to Breaking Waves Impact Using REEF3D

Ahmad, Nadeem (Norwegian University of Science and Technology) | Bihs, Hans (Norwegian University of Science and Technology) | Chella, Mayilvahanan Alagan (Norwegian University of Science and Technology) | Arntsen, Øivind A. (Norwegian University of Science and Technology) | Aggarwal, Ankit (Norwegian University of Science and Technology)

OnePetro 

ABSTRACT

In the present study, numerical modelling breaking waves over a slope and the resulting erosion in the arctic region is presented. The study is performed with the open-source computational fluid dynamics (CFD) model REEF3D. First, the numerical model results are validated with experimental data for breaking waves and sediment transport over a sloping seabed with the seawall. Good agreement with experimental data is achieved. Further, a real case study is carried out to investigate the breaking wave impact on a vertical bluff in combination with the arctic coastal morphodynamics. For this case study, the Bjørndalen location in the Isfjorden, Svalbard is chosen, where significant coast erosion was observed during a storm event in September 2015.

INTRODUCTION

Much of the arctic coastline is susceptible to climate change. Due to the global warming and additional heat fluxes transferred to the arctic coasts, their period of the frozen state is reduced. Consequently, during the extended warmer periods, the active sediment layer in the Arctic coastline can be advesrly affected. The active sediment layer consists of coarse-grained sandy soil with high moisture content (90% sand and 10% silt: data specific to Svalbard, Norway (Fromreide, 2014)). The average thickness of the active layer varies between 1 to 10 m (Huggett, 2003) which highly influence the arctic coastline. Hence, the climatic change might affect the arctic coastline in two ways. Firstly, the extended warmer period would result in the formation of deeper and weaker active sediment layers (IPCC, 2007). Secondly, the melting of Arctic ice sheets would rise sea level, which results in high tides approaching the arctic coastlines (Thompson et al., 2016) and eroding the weaker active sediment layer. There, it would influence sediment transport processes, coastline profiles, the stability of the permafrost bluff and foundations.

A recent example of the impact of climate change on the arctic coastline is the Bjørndalen location at the Isfjorden coastline in Svalbard, where significant coastal erosion took place during a storm event in September 2015. Devastating waves reached cabin areas near the Isfjorden and resulted in almost 1 m deep erosion (SvalbardPosten, 2015). Therefore, In order to better understand the coastline erosion phenomena in the arctic regions, the physical processes such as wave propagation, shoaling and wave breaking and the resulting sediment transport have to be investigated in detail. The study is also important for the design of new foundations and suitable mitigation measures at the arctic coastlines.