Alexandria-Nile Delta coast, Egypt: update and future projection of relative sea-level rise

Abstract

Previous studies have indicated that the Nile River deltaic plain is vulnerable to a number of aspects, including beach erosion, inundation, and relatively high rates of land subsidence. This issue motivates an update and analysis of new tide-gauge records, from which relative sea-level changes can be obtained. Estimated rates from five tide gauges are variable in terms of magnitude and temporal trend of rising sea level. Analysis of historical records obtained from tide gauges at Alexandria, Rosetta, Burullus, Damietta, and Port Said show a continuous rise in mean sea level fluctuating between 1.8 and 4.9 mm/year; the smaller rate occurs at the Alexandria harbor, while the higher one at the Rosetta promontory. These uneven spatial and temporal trends of the estimated relative sea-level rise (RSLR) are interpreted with reference to local geological factors. In particular, Holocene sediment thickness, subsidence rate and tectonism are correlated with the estimated rates of relative sea-level change. From the relatively weak correlation between them, we presume that tectonic setting and earthquakes, both recent and historical ones, contribute more to accelerated RSLR than that of dewatering and compression/ dewatering of Holocene mud underlying the Nile Delta plain. As a result, large areas of the coastal plain have been subsided, but some sectors have been uplifted in response to tectonic activities of thick underlying older strata. Projection of averaged sea-level rise trend reveals that not all the coastal plain of the Nile Delta and Alexandria is vulnerable to accelerated sea-level rise at the same level due to wide variability of the land topography, that includes low-lying areas, high-elevated coastal ridges and sand dunes, accretionary beaches, and artificially protective structures. Interaction of all aspects (tectonic regime, topography, geomorphology, erosion rate, and RSLR rate) permitted to define risk areas much vulnerable to impacts of sea incursion due to accelerated sea-level rise.

Assessing Land Deformation and Sea Encroachment in the Nile Delta: A Radar Interferometric and Inundation Modeling Approach

“…There are almost no natural protective cover/elevated areas near the coast, and only an area 1-km wide with a maximum elevation of 2 m separates this large swath of lands with below sea level elevations from the coast. The government of Egypt has constructed sea walls in some sections of this possible inlet (Frihy et al, 2010), but more work still needs to be done to avert this impending catastrophe.…”

Vulnerability assessments of coastal river deltas - categorization and review

“…Examples of assessments that use multispectral EO data for LULC purposes are Jiang et al (2005), Kleinosky et al (2006), Rao et al (2009), De Andrade et al (2010), IMHEN et al (2011), Xu et al (2011. Examples of assessments that use EO data for shoreline change rate estimation are Frihy et al (2010), Elewa et al (2012). Assessments that used EO DEM data are Mount and Twiss (2005), Rao et al (2009), Woodroffe (2010), Gesch (2013, Liersch et al (2013), andIMHEN et al (2011).…”

“…4a), all of which use tidal gauge data, such as Frihy et al (2010), Boori et al (2010), and Marriner et al (2013). Using the results of previous studies as well as data from 105 core samples, Marriner et al (2013) investigated the rate of subsidence of the Nile River Delta.…”

“…Others have used in-situ datasets to acquire a greater insight in the geophysical properties of a study area, such as Frihy and El-Sayed (2013). The focus of Frihy and El-Sayed (2013) was the vulnerability to RSLR of social and economic activities in the Nile River delta, using a variety of data, such as transects (detailing geomorphologic aspects of the coast), a digitized topographic map (for elevation data of the study area (Frihy 2003)), census data (for socio-economic parameters such as population density, economic activity), in-situ measurement data (to identify and locate coastal protection infrastructure (Frihy 2003)), core samples (to estimate subsidence in the study area), measurement stations (for measuring tide gauge in different areas of the study area to identify spatial variability (Frihy et al 2010)), and data as extracted from previous/other literature or assessments, such as soil accretion and erosion rates (extracted through EO data), predicted changes in sea level, tectonic faults and earthquake locations and severity. The vulnerability of the coastline and the inland areas of the Nile River delta and its surrounding Mediterranean coastal sections were then ranked in a scorecard as high, moderate, and low, only during extreme events, or areas that are safe.…”

“…The vulnerability of the coastline and the inland areas of the Nile River delta and its surrounding Mediterranean coastal sections were then ranked in a scorecard as high, moderate, and low, only during extreme events, or areas that are safe. This ranking has been performed for a variety of coastal features and locations within those sections (Frihy 2003;Frihy et al 2010;Frihy and El-Sayed 2013).…”