Effects of Near-Term Sea-Level Rise on Coastal Infrastructure
Dr. Joseph Donoghue | Oklahoma State University
The objective of this project was to develop new methods for comprehensive modeling of the effects and potential risk of projected sea-level rise, and increased storminess, on coastal environments and infrastructure. The project focused on the Eglin Air Force Base (EAFB) region on the northwest Florida coast; however, the methods that have been developed are applicable to military installations in similar coastal settings.
The project had six major components: (1) analyzing historic coastal change and remote sensing data; (2) modeling future storms; (3) analyzing the paleostorm history in coastal sediments; (4) modeling coastal wetlands; (5) modeling coastal groundwater; and (6) modeling morphologic change and analyzing uncertainty. The modeling efforts employed various sea-level rise scenarios, ranging from 0.5 meters to 2.0 meters by the year 2100.
This project developed one of the most comprehensive databases ever assembled on historic changes in shorelines and barrier island morphology. By combining remote sensing and survey data, a unique time series of shorelines and barrier evolution was created. This robust data set informed model development and enabled the creation of a conceptual model for the evolution of the Santa Rosa Island barrier plus a purpose-built numerical model. Santa Rosa is important as the site of substantial EAFB infrastructure.
A regional storm history was developed for use in the modeling effort, both for historic and prehistoric time. The historic database encompasses approximately 150 years. The prehistoric record, from coastal sediment cores, extends back over approximately four millennia. A storm model incorporates this history to create an ensemble of future storm tracks and potential storm effects for the region. Changes in future storm wind and storm surge damage from more common large hurricanes can thereby be assessed.
A purpose-built numerical model of coastal morphology was also developed, incorporating morphological, sea-level, and storm climatology data to predict changes over the next century. This Model of Complex Coastal Systems (MOCCS) includes representations of the shoreline position and coastal landform changes caused by periods of both ordinary weather and storm events. The system components include the beach and surf-zone, the adjoining shoreface and inner continental shelf, the tidal inlet and adjacent bay, along with the coastal dune system and the overwash deposits that affect the freeboard of the barrier island and the position of its bay shoreline. All components respond to variations in the major forcing parameters, which include the sediment supply, wave climate and changing sea level. The model represents the complex non-linear interactions between these system components in response to five different sea-level rise scenarios. Uncertainty analyses are employed to characterize uncertainty sources and to quantify propagation of the uncertainty through numerical models. In particular, the scenario uncertainty of sea-level rise is quantified using a scenario averaging method. Results regarding barrier island shoreline and morphologic changes are stated probabilistically and are suitable for use by base planners and managers.
Outcomes of this study can be used to evaluate how to make reliable predictions of the effects of future climate change on coastal infrastructure and natural coastal systems. The expected result will be to enable cost-effective mitigation and adaptation strategies to prepare for a warmer future.