Résumé
195
by selecting transects spaced 25 m apart; with automatic computational tools (DSAS) to
calculate shoreline changes.
4.Conclusion
The analysis of shoreline position variations over a period of 60 years requires the use of both
modern and classical techniques (aerial photography, satellite images and DGPS topographic
surveys). Theoretical concepts are presented in this study because we have little climatic and
hydrodynamic data that can interpret the historical variations of the coastline.
The study of the evolution of the coastline between 1957 and 2017 has allowed us to identify
three distinct sectors:
The first sector includes the western part of the beach Tamaris to the beach of
Boudouaou el bahri recorded the highest rates of recession reaching -1.66m / year.
This same sector has experienced stabilization or even a small increase in size from
the year 2003, just after the the implantation of the two breakwaters.
On its side, the sector of the left bank of the oued Réghaia underwent, during this
same period, considerable retreats in the position of the coastline. This recession is
due. This retreat is due practically to the weak contributions carried by the oued
Réghaia and the aggressiveness of the waves.
Finally the third sector including the beach of Cap Djinet and the eastern part of Oued
Isser Beach, has recorded the lowest rate of recession compared to the other two
sectors. The values of the net rate obtained fluctuate between -0.17 to -0.64m/year.
To better interpret the changes in the coastline, we chose the most determining hydrodynamic
factor hydrodynamic factor. Indeed, the different swells of the area show that the swells,
which are that the northeast swells are the most determining, they generate sedimentary losses
in the they generate sedimentary losses in the profile towards the open sea. The changes of the
littoral along the coast of the bay of Zemmouri during the last 60 years depend also on the
human intervention notably the illegal extraction of sand at the level of the beaches of Tarfaia,
Kaddous..., but also the implantation of the coastal engineering works and the occupation of
the back beaches. From the obtained results, the morphodynamic classification of the sandy
beaches was carried out on our site of study while being based on Wright and short (1984),
which makes reference in the field of the morphodynamic classification of the beaches the
sandy bars. The results obtained from this classification show a sectorial organization of the
morphology and morphodynamics along this coastal fringe. This image highlights the distinct
functioning between three parts separated by the wadi Réghaia in the West and wadi Isser in
the East, whose beach slopes and morphodynamic indices are different. From a
methodological point of view, the results obtained show that the detailed analysis, assisted by
GIS, of the position of the coastline on aerial photographs and satellite images is a handy tool
for the study of coastal evolution in the medium and long term, showing in most cases a
general agreement with the results of short-term topographic surveys. However, it should be
kept in mind that modeling as a type of approach would not be entirely satisfactory but would
support the detailed analysis of aerial photographs as an essential means to understand the
general evolution and dynamics of coastal areas.
The results of this article also confirmed that the use of digital aerial photographs, satellite
images (high resolution), geospatial techniques (GIS software), and automatic calculation
code (DSAS) could be a tool to help the decision in the management against coastal risks.
This study provides decision-makers with a reliable decision support tool that can help them
195
by selecting transects spaced 25 m apart; with automatic computational tools (DSAS) to
calculate shoreline changes.
4.Conclusion
The analysis of shoreline position variations over a period of 60 years requires the use of both
modern and classical techniques (aerial photography, satellite images and DGPS topographic
surveys). Theoretical concepts are presented in this study because we have little climatic and
hydrodynamic data that can interpret the historical variations of the coastline.
The study of the evolution of the coastline between 1957 and 2017 has allowed us to identify
three distinct sectors:
The first sector includes the western part of the beach Tamaris to the beach of
Boudouaou el bahri recorded the highest rates of recession reaching -1.66m / year.
This same sector has experienced stabilization or even a small increase in size from
the year 2003, just after the the implantation of the two breakwaters.
On its side, the sector of the left bank of the oued Réghaia underwent, during this
same period, considerable retreats in the position of the coastline. This recession is
due. This retreat is due practically to the weak contributions carried by the oued
Réghaia and the aggressiveness of the waves.
Finally the third sector including the beach of Cap Djinet and the eastern part of Oued
Isser Beach, has recorded the lowest rate of recession compared to the other two
sectors. The values of the net rate obtained fluctuate between -0.17 to -0.64m/year.
To better interpret the changes in the coastline, we chose the most determining hydrodynamic
factor hydrodynamic factor. Indeed, the different swells of the area show that the swells,
which are that the northeast swells are the most determining, they generate sedimentary losses
in the they generate sedimentary losses in the profile towards the open sea. The changes of the
littoral along the coast of the bay of Zemmouri during the last 60 years depend also on the
human intervention notably the illegal extraction of sand at the level of the beaches of Tarfaia,
Kaddous..., but also the implantation of the coastal engineering works and the occupation of
the back beaches. From the obtained results, the morphodynamic classification of the sandy
beaches was carried out on our site of study while being based on Wright and short (1984),
which makes reference in the field of the morphodynamic classification of the beaches the
sandy bars. The results obtained from this classification show a sectorial organization of the
morphology and morphodynamics along this coastal fringe. This image highlights the distinct
functioning between three parts separated by the wadi Réghaia in the West and wadi Isser in
the East, whose beach slopes and morphodynamic indices are different. From a
methodological point of view, the results obtained show that the detailed analysis, assisted by
GIS, of the position of the coastline on aerial photographs and satellite images is a handy tool
for the study of coastal evolution in the medium and long term, showing in most cases a
general agreement with the results of short-term topographic surveys. However, it should be
kept in mind that modeling as a type of approach would not be entirely satisfactory but would
support the detailed analysis of aerial photographs as an essential means to understand the
general evolution and dynamics of coastal areas.
The results of this article also confirmed that the use of digital aerial photographs, satellite
images (high resolution), geospatial techniques (GIS software), and automatic calculation
code (DSAS) could be a tool to help the decision in the management against coastal risks.
This study provides decision-makers with a reliable decision support tool that can help them