QUANTITATIVE ASSESSMENT OF SHORELINE CHANGE AND POTENTIAL LAND LOSS DUE TO SEA LEVEL RISE IN THE ROSETTA PROMONTORY, NILE DELTA, EGYPT

The coastline of the Nile Delta has suffered greatly from accelerated erosion since the construction of the Aswan High Dam in 1964 and, consequently, the entrapment of a large amount of the river sediment behind it. The coastline of the Rosetta Promontory showed the highest erosion in the Delta with an average retreating rate of 100 m/y. In an effort to mitigate erosion, a 5 km long seawall was built on both sides of the outer margin of the promontory in 1991. For additional beach protection, 5 groins were constructed at the eastern end of the seawall and 10 at the western end, in 2003 and 2005, respectively. Although the building of the seawalls has been largely successful in halting the recession with negligible erosion since its construction, it has negatively affected the adjacent, unprotected coastline segments. Most of these groins, however, are not functioning efficiently and are causing serious shoreline erosion. High spatial resolution QuickBird and WorldView-2 imagery of the Rosetta Promontory (31 km²), along with the DSAS extension for ArcGIS were used to precisely measure and statistically analyze changes in shoreline position over an 8 year period (2002 – 2010). Analysis shows that 906,307 m² of land was eroded and the coastline retreated 355 m at an average rate of 44 m/y. A small area of 92.7 m² was deposited during the same period with a rate of 11 m/y. Results reveal that there is little to no elevation in the promontory with areas below sea-level, indicating that a small sea level rise (SLR) would inundate much of the promontory. Based on DEM data (derived from field measurements, topographic maps and satellite images) and a land use/cover map (derived from remote sensing image classification) a SLR scenario of only 1 m would cause two thirds (67.7%) of the study area to become inundated. This would put several coastal villages, 314 acres of productive agricultural land, and 16 km of road network at great risk. Unless action is taken, coastal erosion will steadily ingest the edge of the Nile Delta at an alarming rate. The use of detailed satellite imagery and DEM data has proven to be a quick and cost-effective approach for quantitatively assessing shoreline changes and predicting the amount of coastal areas that could potentially succumb to the sea. Results from such studies could play a vital role in future coastal planning in Egypt.