Building an agent-based model to explore the interactions between human activities and vegetation cover on sandy anthropogenic shores (SAS) in the Netherlands

Abstract

Coastal dunes play an essential role in defence against the sea in many countries, including the Netherlands. Sandy Anthropogenic Shores (SAS) is the recent nature-based human intervention for dune reinforcement. SAS are coastal zones (including shores, dunes, lagoons, etc.) that are created or heavily modified by moving large amounts of dredged sand from offshore to near the coast. This allows natural processes (waves, winds, and currents) to spread the sand and reinforce the foredune for longer-term coastal safety. Not only the natural processes but also vegetation cover near the dune foot and on the foredune play essential roles in trapping windblown sand from the coast, steering embryo dune development and dune growth. The Sand Motor and Hondsbossche Dunes are two examples of SAS in the Netherlands. Previous studies of vegetation on SAS have mainly assessed the influence of natural conditions such as climate change, nutrient availability, sand burial, beach shape (morphology and width), hydrodynamic wave characteristics, etc., on vegetation propagation. The impacts of short-term human management of the coast and recreational activities still need to be addressed. We chose an agent-based model (ABM) approach to simulate human activities, including management and use of SAS and coupled it with a biophysical model similar to DUBEVEG. DUBEVEG is a biophysical model simulating the interactions between natural processes caused by wind, wave and tide, vegetation cover, and beach-dune sediment dynamics. We conducted several interviews and workshops with stakeholders from the management sectors. We also surveyed the beach users to elicit knowledge about social dynamics and their interaction with the biophysical system (morphology and vegetation). Using NetLogo, we developed an ABM, translating the elicited knowledge into a quantitative model. The developed ABM was used to analyse how various landscape designs of the modified coast (e.g., types and locations of recreational facilities such as restaurants, beach houses, artificial lagoons, entrances, car parking, etc.) influence human activities. Then, we used the model to explore the impact of human dynamics on vegetation growth and embryo dune development in the long term. The developed ABM model improves the sustainable design and management of the SAS by exploring the influence of SAS's initial design and short-term decisions about recreational activities and flood safety measures on the long-term evolution of the landscape (vegetation and morphology).