The Role of Sea State to the Morphological Changes of Prasonisi Tombolo, Rhodes Island, Greece

Wave-induced morphodynamic processes that cause formation, preservation, and destruction of the Prasonisi tombolo in Rhodes Island are investigated, based on satellite image analysis and numerical modeling. A new method is developed for extracting wave events that consist of successive wave data of similar characteristics. The wave events refer either to wind seas or swell seas. This process combined with the satellite image analysis is then utilized for the derivation of the most representative wave scenarios that affect tombolo and salient formation. In particular, the main factors that play a significant role in tombolo and salient evolution are the offshore wave conditions, the location and width of the surf zone, the maximum value of the wave breaking index in the study area, and the initial bottom bathymetry before the study area is exposed to a new sea state. In general, the proposed method provides a realistic insight into tombolo morphodynamics and can be used to provide a cost-effective approach and a wave data-reduction technique for coastal engineering studies

Assessment of the physical impact of a short-term dredging operation on a semi-enclosed environment: South Euboean Gulf, Greece

The potential influence of short-period (May-June 2012) dredging activities (for the installation of a submarine gas pipeline) on physical properties of the marine environment of two shallow-water sites in the Aliveri and Varnavas areas of South Euboean Gulf (Greece) has been evaluated. During the dredging operation in Varnavas, the induced dredge plume traveled up to 750 m from the shoreline, featured by light attenuation coefficient (c(p)) maxima of 4.01-4.61 m(-1) and suspended particulate matter (SPM) concentrations up to 6.01 mg L-1. After dredging the previous parameters reduced to the ambient seawater condition, 0.45 m(-1) and < 2.8 mg L-1 on average, respectively. Likewise in Aliveri, the dredging-associated sediment plume drifted offshore up to 400 m from the shoreline, characterized by c(p) maxima of 2.11-4.86 m(-1) and SPM concentrations up to 13.07 mg L-1. After the completion of the excavation and trenching activities, the c(p) and SPM values were restored to the pre-disturbance condition, 0.6 m(-1) and < 2.2 mg L-1 on average, respectively. The migration of the dredge plume in both dredging sites was accomplished through the formation of intermediate and benthic nepheloid layers, whose development and evolution were governed by seawater stratification and flow regime. The dredging-derived SPM levels appeared to increase within a distance of no more than 300 m from the shoreline (near-field zone). Based on data from the literature, this SPM enhancement together with the deposition of a post-dredging residual mud veneer in the near-field zone could deteriorate local marine biota, but in a reversible way

Assessment of the Coastal Vulnerability to the Ongoing Sea Level Rise for the Exquisite Rhodes Island (SE Aegean Sea, Greece)

The foreseeable acceleration of global sea level rise could potentially pose a major threat to the natural charm and functional integrity of the world-renowned tourist coastal attractions of Rhodes Island, as a result of the anticipated increasing frequency of flooding and erosion events. Hence, this study aims to determine the most vulnerable segments (in terms of physical impact) of the Rhodes coastline through the widely accepted coastal vulnerability index (CVI), applying a combination of well-known, broadly used approaches and methods. The frequency distribution of the current CVI along the island’s coastline suggests a rather worrying high to very high vulnerability of 40%. In addition, a CVI projection to the end of the 21st century (based on the Intergovernmental Panel on Climate Change predictive scenarios) indicates an enhancement of the total vulnerability by 48%, mainly focused on the majority of the western coastline. Hence, a considerable number of popular coastal destinations in the island shall remain under unignorable threat and, therefore, coastal managers and decision-makers need to hatch an integrated plan to minimize economic and natural losses, private property damage and tourism infrastructure deterioration from flooding and erosion episodes, which will most likely be intensified in the future