Coastal Processes within a Coral Reef Lagoon System: Erakor Lagoon, Efate Island, Vanuatu

Abstract

Small Island Developing States (SIDS) in the South Pacific are highly vulnerable to climate change and development pressure due to their small size, isolation and exposure to natural hazards. Much of the Pacific SIDS population reside within the coastal zone as does the majority of critical infrastructure where resilience is challenged by exposure to natural hazards including inundation and erosion, and impacts from cyclones and tsunamis,. During extreme events, wave energy is a significant damage vector whose impact on populations and infrastructure is mediated by the presence and structural characteristics of adjacent coral reefs. Understanding the role of the structural characteristics of reefs in the dissipation of wave energy is critical to planning climate change resilience for SIDS given climate change will alter water levels, waves climates and the condition of coral reefs. The aims of this paper are to understand (1) the wave dissipation over a coral reef and hydrodynamic circulation within a coral reef lagoon in Erakor lagoon, Port Vila the capital of Vanuatu, and (2) the impact of sea level rise on the wave energy, wave runup and impacts to the shoreline. The information from this assessment can help inform coastal adaptation planning in response to climate change and rising sea levels. The approach is based on using field data to calibrate a numerical model of coastal processes. A wave buoy and five pressure sensors were deployed to measure wave dissipation over the Erakor lagoon's reef and current meters used in the lagoon to measure circulation and residential time. Data processing shows the importance of the reef geomorphology and water levels on wave dissipation.