ASSESSING THE RESPONSE OF PRE- AND POST-BEACH PROTECTION AND PROJECTED SHORELINE CHANGE IN THE ROSETTA PROMONTORY, NILE DELTA

The shoreline of the Nile Delta has been suffering from severe erosion since the construction of the Aswan High Dam in the early sixties. In an effort to alleviate sediment loss, two 5 km long seawalls and 15 groins were built along the coastline of the Rosetta Promontory. An analysis to quantify erosion and accretion patterns along the promontory was conducted using 11 Landsat images over a 40 year time span. The positions of the shorelines were automatically extracted from the Landsat images and compared with shorelines from corresponding very high resolution images for data validation. Rates of shoreline change were calculated using the USGS-DSAS software. Analysis showed that construction of the seawalls was largely successful in halting the recession of 137.4 m/y along the promontory’s tip. Conversely, the construction of the 15 groins has negatively affected both sides of the promontory, were some segments have undergone up to 30.8 m/y of erosion. This study estimated that without the construction of the seawalls, the tip of the promontory would have retreated 2.3 km by 2013. Furthermore, without additional protection, the sides of the promontory will lose ~1.3 km² of land and the coastline would recede at an average rate of 200 m by 2020. The newly available Landsat-8 (LDCM) image was used to map the land-use-land-cover (LULC) and calculate the percentage of various types of ground cover facing potential loss to projected coastal erosion and rising sea levels. The Decision Tree Classification (DTC) was utilized to extract the LULC of the area. The DTC was primarily based on three remote sensing indices (NDVI, MNDWI and NDBI) and the thermal infrared band. Based on the LULC map and the topo-map derived DEM, about 129.13 km² of the study area (out of 228 km²) is at or below 1 m above sea level. This implies that a SLR of 1 m would cause about 76.3% of the study area to be flooded, putting several coastal villages and ~ 31,908 acres of productive agricultural lands, including fruit trees and croplands, at great risk. Additionally, 1m of SLR is likely to inundate ~41.2 km² of sandy beaches, including coastal flats and sabkhas, 1.9 km² of inland water bodies, including fish farms, and dense road networks in the area. Unless action is taken, coastal erosion, strengthened by rising sea levels, will steadily consume the Nile Delta at an alarming rate.