Coastal inundation scenarios in the north-eastern sector of the Island of Gozo (Malta, Mediterranean Sea) as a response to sea level rise

Figures & data

Figure 1. Geographic setting of Gozo within the Maltese Islands (central Mediterranean Sea). Satellite images are derived from Google Earth (map data: SIO, NOAA, US Navy, NGA, GEBCO, Landsat/Copernicus). The map data of Gozo and Comino islands (upper right corner) are derived from OpenStreetMap database (2022). Geographic coordinates are represented in the WGS84 reference system.

On the left upper corner, an image of the Globe is shown illustrating with a red square the approximate location of the Maltese Islands in the world. Moreover, on the same left upper corner, a sketch of the Mediterranean region is shown illustrating with a red circle the location of the Maltese Islands. In the right upper corner, a map of Gozo Island is reported including geographic coordinates and main toponyms. In the central part of the figure, a satellite image shows the location of the Maltese Islands between Tunisia and Italy (Sicily region).

Figure 2. Physical setting of the study area (geographic coordinates are expressed in WGS84).

A map of the study area is shown. It includes information about the elevation (ranging from 0 m above the sea level to 139 m), main localities (among which Marsalforn and Ramla bays that are the most cited in the text) and main water courses.

Figure 3. Coastal landscapes of the north-eastern sector of the Island of Gozo: (a) the densely inhabited Marsalforn Bay; (b) the gold-reddish sands of Ramla Bay; (c) coastal clay slopes east of Marsalforn Bay within the Għajn Barrani protected area; (d) traditional boat houses at Dahlet Qorrot Bay.

The figure is a mosaic of pictures representing some of the landscapes that can be seen within the study area. The first picture (a) represents the densely inhabited Marsalforn Bay including many high-rise buildings close to the seaside; the second picture (b) shows a view of the gold-reddish sands of Ramla Bay with people gathered on the beach; the third picture (c) shows coastal clay slopes reaching the sea; the fourth picture (d) depicts traditional boat houses at Dahlet Qorrot Bay.

Table 1. Sea level values used in this study for the evaluation of potential coastal inundation and coastline retreat under different scenarios.

Sea level (IPCC, 2021)	Projections (vs. 1995–2014)	Scenario SSP1-2.6 (m)	Scenario SSP5-8.5 (m)
Local	2050	0.19 (0.11–0.28)	0.23 (0.14–0.33)
Local	2100	0.40 (0.22–0.62)	0.73 (0.52–1.03)

Note: The median values are represented in bold while the likely ranges are in parenthesis.

Table 2. Storm surge values referred to return periods of 10 and 100 years which were used in this study for the evaluation of potential coastal inundation and coastline retreat under different scenarios.

Storm surge level (CDS, 2020)	Projections	10 years return period (m)	100 years return period (m)
Local	2041–2070	0.34	0.45
Local	2071–2100	0.33	0.45

Table 3. Extent of the areas potentially inundated by sea level rise under the scenarios SSP1-2.6 and SSP5-8.5.

Year	Scenario SSP1-2.6	Scenario SSP5-8.5
	Potentially inundated area (km^2)	Potentially inundated area (km^2)
2030	0.02	0.02
2040	0.03	0.04
2050	0.04	0.05
2060	0.05	0.06
2070	0.06	0.07
2080	0.06	0.08
2090	0.07	0.09
2100	0.07	0.10

Note: Values in bold refer to the scenarios used to depict the inundation map.

Figure 4. Percentage of area potentially inundated resulting from the analysis of the extent of the low-lying areas (a, c) and of the area within 5 m above sea level (b, d). Upper panels (green dots) refer to SSP1-2.6 scenarios while lower panels (blue dots) refer to SSP5-8.5 scenarios.

Results from the analysis of the extent of potentially inundated areas. The percentage of the potentially inundated low-lying areas considering the SSP1-2.6 and the SSP5-8.5 scenarios respectively corresponds to 60% for the first scenario and 80% for the second scenario in 2100. The percentage of the potentially inundated areas within 5 m a.s.l., considering SSP1-2.6 and the SSP5-8.5 scenarios respectively, corresponds to approximately 20% for the first scenario and 25% for the second scenario in 2100.

Figure 5. Numbers of buildings potentially inundated considering the SSP5-8.5 scenario for the year 2050 (first column), 2100 (second column) and with the contribution of storm surge with a return period of 100 years (third column).

OpenStreetMap database. (2022). https://www.openstreetmap.or.

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IPCC. (2021). IPCC AR6 sea level projection tool. Retrieved October 10, 2021, from https://sealevel.nasa.gov/data_tools/17

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Data availability statement

The base map of the marine areas is a 5-m resolution Digital Terrain Model (DTM) resulting from the merge of bathymetric data acquired during different oceanographic surveys:

• MEDCOR2009 carried out on board the R/V Urania of the CNR using the Kongsberg Simrad multibeam EM3002D and processed using CARIS HIPS & SIPS;

• ERDF156 carried out by Malta Environment and Planning Authority (MEPA) on board the ISIS catamaran of the AquaBioTech Group using the SEA Company interferometric system SWATHplus-L.

Bathymetry from MEDCOR2009 is available for public consultation and downloadable at the resolution 1/16 * 1/16 arc minutes from the EMODnet Bathymetry Portal (https://portal.emodnet-bathymetry.eu/). The DTM of the Island of Gozo is 1 m-resolution and it is provided by the Malta Planning Authority. The data obtained in this study are available from the corresponding author [NS], upon reasonable request.