Abstract
Barrier islands characterize up to an eighth of the global coastlines. They buffer the mainland coastal areas from storm surge and wave energy from the open ocean. Changes in their shape or disappearance due to erosion may lead to an increased impact of sea level extremes on the mainland. A barrier island threatened by erosion is Egmont Key which is located in the mouth of the Tampa Bay estuary at the west-central coast of Florida. In this sensitivity study we investigate the impact a loss of Egmont Key would have on storm surge water levels and wind waves along the coastline of Tampa Bay. We first simulate still water levels in a control run over the years 1948-2010 using present-day bathymetry and then in a scenario run covering the same period with identical boundary conditions but with Egmont Key removed from the bathymetry. Return water levels are assessed for the control and the scenario runs using the Peak-over-threshold method along the entire Tampa Bay coastline. Egmont Key is found to have a significant influence on the return water levels in the Bay, especially in the northern, furthest inland parts where water levels associated with the 100-year return period increase between 5 cm and 15 cm. Additionally, wind wave simulations considering all 99.5th percentile threshold exceedances in the years 1980-2013 were conducted with the same control and scenario bathymetries. Assessing changes in return levels of significant wave heights due to the loss of Egmont Key revealed an increase of significant wave heights around today's location of the island.
Highlights
Barrier islands are located near the mainland coast, often forming lagoons which are connected to the ocean by small tidal inlets. Oertel (1985) describes that coastal areas around and behind a barrier island are not merely independent from each other but rather part of an interrelated barrier island system with regard to hydrodynamic, hydrological, and geological processes
This study aims at investigating the effect of a barrier island loss on extreme still water levels and wind waves in the Tampa Bay
We focus on the 99.8th percentile of threshold exceedances since only these data are used in the following extreme value analysis (EVA)
Summary
Barrier islands are located near the mainland coast, often forming lagoons which are connected to the ocean by small tidal inlets. Oertel (1985) describes that coastal areas around and behind a barrier island are not merely independent from each other but rather part of an interrelated barrier island system with regard to hydrodynamic, hydrological, and geological processes. Barrier islands are located near the mainland coast, often forming lagoons which are connected to the ocean by small tidal inlets. Barrier islands can be found along 6.5% (Stutz and Pilkey, 2001) to 13% (Cromwell, 1973) of the coastlines. Examples in Europe are the Frisian Islands protecting the Wadden Sea (North Sea) or the barrier island system forming the Venice Lagoon (Mediterranean Sea). In the United States barrier island systems span large coastal areas along the Atlantic Ocean and Gulf of Mexico. Due to marked interdependency between barrier islands, the mainland coast, and adjacent waters, changes in individual parts may have an effect on the entire system (Oertel, 1985)
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