Abstract
Located south of the western Mediterranean, in the central Algerian region, Cherchell
coastline has participated over time in the economic development of the region (agriculture
and seaside tourism). During the last decades this coastline has suffered several threats due to
human interventions such as the construction of the Boukerdene dam in the region's
watershed (trapping sediments and water coming down from the foothills), the abusive
extraction of sand from beaches and from the wadi bed in order to satisfy the construction
demand, as well as the exploitation of the aquifer. This makes the coastline more vulnerable
to accelerated sea level rise. The goal of this thesis work is to use geomatics for the study of
coastal hazards in Cherchell coastline, such as coastal kinematics, marine flooding due to
extreme storm swells, marine intrusion, and the coastal vulnerability index. Using aerial
photos, satellite images, digital terrain models combined with geographic information systems
(GIS).
The historical evolution of the shoreline, allows to have a real observation on the evolution of
the beaches studied (Hamdania, Tizirine and the Center beach). In order to fully understand
the phenomena at the origin of the erosion of Hamdania beach, a study of the hydrosedimentary functioning was carried out to identify the presence of a back current in the
region. A trend scenario has been projected over the next 50 years, in order to get an idea of
the future of these beaches. For a period of 58 years. The erosion affecting the Cherchell
shoreline is greater than the accumulation, the recession is almost three times greater than the
accretion.
The assessment of land to be lost due to flood risk is based on annual, decadal, five-year and
centennial extreme storm swell data. The results we have reached indicate that most of the
flooded land is with annual storm swells, which is explained by the low topography of the
beaches (Hamdania and Bella) and the wadi plains (El Hachem and El Bellaa) near the coast.
The mapping of the vulnerability of the Cherchell Coastal Aquifer to marine intrusion, based
on the established methodology of the GALDIT model for coastal aquifers, shows low to
moderate vulnerability upstream and high vulnerability downstream. This high vulnerability
can reach 800 m inland perpendicular to the shoreline. This vulnerability is mainly due to the
hydrological imbalance caused by the construction of the Boukerdene Dam, which reduces
surface water inflows.
The assessment of the physical and socio-economic vulnerability of the Cherchell coast and
sea level rise provides a snapshot of the state of vulnerability of the coast. In terms of physical
vulnerability, one third (33%) of Cherchell coastline is vulnerable to sea level rise, consisting
mainly of areas of sand accumulation. This is explained by the presence of densely populated
urban areas with developed road networks, with an important heritage and cultural heritage.
Keywords
Geomatics, coastal risk, coastal kinematics, hydro-sedimentary functioning, marine flooding,
marine intrusion, physical and socio-economic vulnerability. western Mediterranean, central
Algerian region, Cherchell, Hamdania.
Located south of the western Mediterranean, in the central Algerian region, Cherchell
coastline has participated over time in the economic development of the region (agriculture
and seaside tourism). During the last decades this coastline has suffered several threats due to
human interventions such as the construction of the Boukerdene dam in the region's
watershed (trapping sediments and water coming down from the foothills), the abusive
extraction of sand from beaches and from the wadi bed in order to satisfy the construction
demand, as well as the exploitation of the aquifer. This makes the coastline more vulnerable
to accelerated sea level rise. The goal of this thesis work is to use geomatics for the study of
coastal hazards in Cherchell coastline, such as coastal kinematics, marine flooding due to
extreme storm swells, marine intrusion, and the coastal vulnerability index. Using aerial
photos, satellite images, digital terrain models combined with geographic information systems
(GIS).
The historical evolution of the shoreline, allows to have a real observation on the evolution of
the beaches studied (Hamdania, Tizirine and the Center beach). In order to fully understand
the phenomena at the origin of the erosion of Hamdania beach, a study of the hydrosedimentary functioning was carried out to identify the presence of a back current in the
region. A trend scenario has been projected over the next 50 years, in order to get an idea of
the future of these beaches. For a period of 58 years. The erosion affecting the Cherchell
shoreline is greater than the accumulation, the recession is almost three times greater than the
accretion.
The assessment of land to be lost due to flood risk is based on annual, decadal, five-year and
centennial extreme storm swell data. The results we have reached indicate that most of the
flooded land is with annual storm swells, which is explained by the low topography of the
beaches (Hamdania and Bella) and the wadi plains (El Hachem and El Bellaa) near the coast.
The mapping of the vulnerability of the Cherchell Coastal Aquifer to marine intrusion, based
on the established methodology of the GALDIT model for coastal aquifers, shows low to
moderate vulnerability upstream and high vulnerability downstream. This high vulnerability
can reach 800 m inland perpendicular to the shoreline. This vulnerability is mainly due to the
hydrological imbalance caused by the construction of the Boukerdene Dam, which reduces
surface water inflows.
The assessment of the physical and socio-economic vulnerability of the Cherchell coast and
sea level rise provides a snapshot of the state of vulnerability of the coast. In terms of physical
vulnerability, one third (33%) of Cherchell coastline is vulnerable to sea level rise, consisting
mainly of areas of sand accumulation. This is explained by the presence of densely populated
urban areas with developed road networks, with an important heritage and cultural heritage.
Keywords
Geomatics, coastal risk, coastal kinematics, hydro-sedimentary functioning, marine flooding,
marine intrusion, physical and socio-economic vulnerability. western Mediterranean, central
Algerian region, Cherchell, Hamdania.