Summary/Abstract
Coastal lagoons are known to reduce extreme water levels compared to the open sea due to their narrow and shallow connections to the ocean. However, the rising mean sea level will decrease this protective property. In this study, the authors investigate lagoons using a simple box model to explore how combinations of tides, storm surges, river discharge, and sea-level rise will change water levels inside lagoons. The study aims to provide an overview of potentially affected lagoons and to highlight the importance of these processes. Due to sea-level rise, water from the ocean can more easily flow into the lagoon. Therefore, the study’s results show that maximum water levels inside a lagoon can rise faster than sea-level rise. On the other hand, river discharge can exit the lagoon more easily at the same time. For this case, the study finds that water levels inside a lagoon rise slower than sea-level rise. For events where tides, storm surges, and river discharge are all present, the study finds that maximum water level may rise either slower or faster than sea-level rise, depending on the properties of the lagoon.