Abstract
An agent-based model (ABM) is developed to explore the effects of storms and sea level rise (SLR) on soft-engineered coastal management actions and households’ housing decisions at the coastal town of Nags Head in North Carolina, USA. The ABM links the behavior of household agents (individual homeowners) and town agents (coastal managers) with morphological coastal evolution caused by long-term erosion, sea level rise, and storms. Storm impacts are determined by combining the process-based model XBeach (Roelvink, 2009) outputs with the ABM framework. The integrated ABM framework is applied to simulate occupation dynamics and community viability under forcing from storms and sea level rise over a time frame of 50 years. A timeline with storm events was created using historical data and the intensity of the storm in the midpoint of the timeline was varied to explore the effect of storm intensity on the community. Simulations demonstrated a strong link between the intensity of storms and household occupancy. Results suggest that increased storm intensity hinders development and in some cases can cause community occupation growth to stagnate or decline. The results also indicate a feedback loop between the natural processes, management decisions, and household decisions. After a severe storm, buildings are damaged, expenses are increased, and occupation declines. A diminished community cannot invest in protection measures and in turn becomes more vulnerable to future storms. A tipping point may occur, where the community stagnates with respect to its household occupation. To investigate the influence of varying sea level rise rates on community occupancy dynamics, the model was forced with different sea level rise scenarios, including no sea level rise, a constant rate of sea level rise, and two scenarios with accelerated sea level rise. The scenario with no sea level rise showed a considerably more attractive community than the scenarios with sea level rise. This was attributed to (1) absence of expenses incurred in other scenarios to mitigate recession caused by sea level rise and (2) lower flooding risk.
Highlights
Coastal town managers have to develop efficient coastal management plans to address climate change
Communities might be able to buffer the challenges arising from these changes, abrupt disturbances such as damaging storms might push a community over the tipping point and cause it to lose its vitality
The study examined the changes in household occupation dynamics due to storms and sea level rise by simulating plausible scenarios
Summary
The second objective is to use the updated version of the ABM including XBeach to explore the influence of storm intensity and sea level rise by modelling the response of households and town managers under alternative scenarios for the coastal town of Nags Head, North Carolina, USA. The general model structure including the representation of the coastal community and data requirements are explained This is followed by a detailed description of each process and decision in the model, including the integration of XBeach into the ABM framework to simulate morphological changes. To simulate the morphological changes through time, the ABM requires a characterization of the profile extending from closure depth to the heel of the dune for each alongshore cell that includes the key features for natural processes and manipulations due to soft engineered coastal protection projects: beach nourishment and dune replenishment. The representative subaerial profile consists of the following shore features: 1. Beach slope: The beach slope from the berm to mean sea level
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