<figure><img src="image_1.png" /></figure>

HAL
open science

CARTOGRAPHIC APPROACH APPLIED TO THE
COASTLINE CHANGES RISKS IN SAFI COASTAL
AREA ON ATLANTIC OCEAN IN MOROCCO. El
enfoque cartográfico aplicado a los riesgos de cambio
costero en Safi, Marruecos, permite visualizar y analizar
los cambios que ocurren a lo largo de la costa.
Utilizando técnicas de cartografía, es posible representar
los riesgos asociados al cambio climático, como el
aumento del nivel del mar, la erosión costera y las
tormentas, así como otros factores como la presión
demográfica y la contaminación. Este enfoque
cartográfico puede ayudar a identificar las áreas más
vulnerables y tomar medidas preventivas para mitigar
los riesgos. También permite monitorear los cambios a
lo largo del tiempo y evaluar la efectividad de las
medidas de adaptación implementadas.
<figure><img src="image_1.png" /></figure>

HAL
open science

CARTOGRAPHIC APPROACH APPLIED TO THE COASTLINE CHANGES RISKS IN SAFI COASTAL AREA ON ATLANTIC OCEAN IN MOROCCO. El enfoque cartográfico aplicado a los riesgos de cambio costero en Safi, Marruecos, permite visualizar y analizar los cambios que ocurren a lo largo de la costa.

Utilizando técnicas de cartografía, es posible representar los riesgos asociados al cambio climático, como el aumento del nivel del mar, la erosión costera y las tormentas, así como otros factores como la presión demográfica y la contaminación. Este enfoque cartográfico puede ayudar a identificar las áreas más vulnerables y tomar medidas preventivas para mitigar los riesgos. También permite monitorear los cambios a lo largo del tiempo y evaluar la efectividad de las medidas de adaptación implementadas.
<figure><img src="image_2.png" /></figure>

To cite this version:

Sara Louraibi. CARTOGRAPHIC APPROACH APPLIED TO THE COASTLINE CHANGES RISKS IN SAFI COASTAL AREA ON ATLANTIC OCEAN IN MOROCCO. El enfoque cartográfico aplicado a los riesgos de cambio costero en Safi, Marruecos, permite visualizar y analizar los cambios que ocurren a lo largo de la costa. Utilizando técnicas de cartografía, es posible representar los riesgos asociados al cambio climático, como el aumento del nivel del mar, la erosión costera y las tormentas, así como otros factores como la presión demográfica y la contaminación. Este enfoque cartográfico puede ayudar a identificar las áreas más vulnerables y tomar medidas preventivas para mitigar los riesgos. También permite monitorear los cambios a lo largo del tiempo y evaluar la efectividad de las medidas de adaptación implementadas.. 2024. hal-04553836

HAL Id: hal-04553836

https://hal.science/hal-04553836

Preprint submitted on 30 Apr 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
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émanant des établissements d'enseignement et de
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publics ou privés.

<figure><img src="image_3.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
► To cite this version:

Sara Louraibi. CARTOGRAPHIC APPROACH APPLIED TO THE COASTLINE CHANGES RISKS IN SAFI COASTAL AREA ON ATLANTIC OCEAN IN MOROCCO. El enfoque cartográfico aplicado a los riesgos de cambio costero en Safi, Marruecos, permite visualizar y analizar los cambios que ocurren a lo largo de la costa. Utilizando técnicas de cartografía, es posible representar los riesgos asociados al cambio climático, como el aumento del nivel del mar, la erosión costera y las tormentas, así como otros factores como la presión demográfica y la contaminación. Este enfoque cartográfico puede ayudar a identificar las áreas más vulnerables y tomar medidas preventivas para mitigar los riesgos. También permite monitorear los cambios a lo largo del tiempo y evaluar la efectividad de las medidas de adaptación implementadas.. 2024. hal-04553836

HAL Id: hal-04553836

https://hal.science/hal-04553836v1

Preprint submitted on 30 Apr 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
CARTOGRAPHIC APPROACH APPLIED TO THE
COASTLINE CHANGES RISKS IN SAFI COASTAL
AREA ON ATLANTIC OCEAN IN MOROCCO

**RESUMO** – A abordagem cartográfica aplicada aos riscos de mudanças costeiras em Safi, Marrocos, permite visualizar e analisar as mudanças que ocorrem ao longo da costa. Utilizando técnicas de cartografia, é possível representar os riscos relacionados às mudanças climáticas, como o aumento do nível do mar, a erosão costeira e as tempestades, bem como outros fatores como pressão demográfica e poluição. Essa abordagem cartográfica pode ajudar a identificar as áreas mais vulneráveis e tomar medidas preventivas para mitigar os riscos. Também permite acompanhar as mudanças ao longo do tempo e avaliar a eficácia das medidas de adaptação implementadas.

Este artigo tem como objetivo analisar a dinâmica da linha de costa em Safi, mapeando a dinâmica e avaliando as taxas de variação associadas por meio de Ferramentas SIG para mapeamento a fim de fazer a previsão associada para melhor mitigação.

**Palavras-chave:** Litoral, Erosão, Submersão costeira, GIS, Safi, Marrocos.

**ABSTRACT** – Climate change, demographic pressure, polluting discharges, and overexploitation are indeed major factors that impact the coastline area on the Atlantic Ocean in Safi, Morocco. Climate change can lead to rising sea levels, increased storm intensity, and coastal erosion, which can negatively affect the coastline. Demographic pressure can result in increased urbanization and infrastructure development along the coast, leading to habitat destruction and increased pollution. Polluting discharges, such as industrial waste and untreated sewage, can contaminate the coastal waters and harm marine ecosystems. Overexploitation of coastal resources, such as overfishing or excessive sand mining, can also degrade the coastline's ecological balance. These factors collectively pose significant challenges to the coastal area in Safi, Morocco. The cartographic approach applied to coastal change risks in Safi, Morocco allows for visualizing and analyzing the changes occurring along the coastline. By using mapping techniques, it is possible to represent risks related to climate change, such as sea-level rise, coastal erosion, storms, as well as other factors like demographic pressure and pollution. This cartographic approach can help identify the most vulnerable areas and take preventive measures to mitigate risks. It also enables tracking changes over time and assessing the effectiveness of adaptation measures implemented.

**Keywords:** Coastline, Erosion, Coastal submergence, GIS, Morocco.
CARTOGRAPHIC APPROACH APPLIED TO THE
COASTLINE CHANGES RISKS IN SAFI COASTAL
AREA ON ATLANTIC OCEAN IN MOROCCO

**RESUMO** – A abordagem cartográfica aplicada aos riscos de mudanças costeiras em Safi, Marrocos, permite visualizar e analisar as mudanças que ocorrem ao longo da costa. Utilizando técnicas de cartografia, é possível representar os riscos relacionados às mudanças climáticas, como o aumento do nível do mar, a erosão costeira e as tempestades, bem como outros fatores como pressão demográfica e poluição. Essa abordagem cartográfica pode ajudar a identificar as áreas mais vulneráveis e tomar medidas preventivas para mitigar os riscos. Também permite acompanhar as mudanças ao longo do tempo e avaliar a eficácia das medidas de adaptação implementadas.

Este artigo tem como objetivo analisar a dinâmica da linha de costa em Safi, mapeando a dinâmica e avaliando as taxas de variação associadas por meio de Ferramentas SIG para mapeamento a fim de fazer a previsão associada para melhor mitigação.

**Palavras-chave:** Litoral, Erosão, Submersão costeira, GIS, Safi, Marrocos.

**ABSTRACT** – Climate change, demographic pressure, polluting discharges, and overexploitation are indeed major factors that impact the coastline area on the Atlantic Ocean in Safi, Morocco. Climate change can lead to rising sea levels, increased storm intensity, and coastal erosion, which can negatively affect the coastline. Demographic pressure can result in increased urbanization and infrastructure development along the coast, leading to habitat destruction and increased pollution. Polluting discharges, such as industrial waste and untreated sewage, can contaminate the coastal waters and harm marine ecosystems. Overexploitation of coastal resources, such as overfishing or excessive sand mining, can also degrade the coastline's ecological balance. These factors collectively pose significant challenges to the coastal area in Safi, Morocco. The cartographic approach applied to coastal change risks in Safi, Morocco allows for visualizing and analyzing the changes occurring along the coastline. By using mapping techniques, it is possible to represent risks related to climate change, such as sea-level rise, coastal erosion, storms, as well as other factors like demographic pressure and pollution. This cartographic approach can help identify the most vulnerable areas and take preventive measures to mitigate risks. It also enables tracking changes over time and assessing the effectiveness of adaptation measures implemented.

**Keywords:** Coastline, Erosion, Coastal submergence, GIS, Morocco.
**RÉSUMÉ** – L'APPROCHE CARTOGRAPHIQUE APPLIQUÉE AUX RISQUES DE CHANGEMENT CÔTIER À SAFI, AU MAROC.

Les changements climatiques, la pression démographique, les rejets polluants et la surexploitation sont les principaux facteurs qui impactent la zone côtière de l'océan Atlantique à Safi, au Maroc. Le changement climatique peut entraîner une élévation du niveau de la mer, une intensification des tempêtes et une érosion côtière, ce qui peut avoir des conséquences négatives sur la côte. La pression démographique peut entraîner une urbanisation croissante et un développement d'infrastructures le long de la côte, ce qui peut entraîner la destruction des habitats et une augmentation de la pollution. Les rejets polluants, tels que les déchets industriels et les eaux usées non traitées, peuvent contaminer les eaux côtières et nuire aux écosystèmes marins. La surexploitation des ressources côtières, telle que la surpêche ou l'exploitation excessive du sable, peut également perturber l'équilibre écologique de la côte. Ces facteurs constituent collectivement des défis importants pour la zone côtière à Safi, au Maroc.

L'approche cartographique appliquée aux risques de changement côtier à Safi, au Maroc, permet de visualiser et d'analyser les changements qui se produisent le long de la côte. En utilisant des techniques de cartographie, il est possible de représenter les risques liés au changement climatique, tels que l'élévation du niveau de la mer, l'érosion côtière et les tempêtes, ainsi que d'autres facteurs tels que la pression démographique et les pollutions.

Cette approche cartographique peut aider à identifier les zones les plus vulnérables et à prendre des mesures préventives pour atténuer les risques. Elle permet également de suivre les changements au fil du temps et d'évaluer l'efficacité des mesures d'adaptation mises en place.

*Mots clés:* Littoral, Erosion, Submersion côtière, SIG, Maroc.

**RESUMEN** – EL ENFOQUE CARTOGRAFICO APLICADO A LOS RIESGOS DE CAMBIO COSTERO EN SAFI, MARRUECOS.

Los cambios climáticos, la presión demográfica, los vertidos contaminantes y la sobreexplotación son los principales factores que impactan en la zona costera del océano Atlántico en Safi, Marruecos. El cambio climático puede provocar el aumento del nivel del mar, intensificar las tormentas y erosionar la costa, lo que puede tener un impacto negativo en la zona costera. La presión demográfica puede resultar en un aumento de la urbanización y el desarrollo de infraestructuras a lo largo de la costa, lo que conlleva la destrucción del hábitat y un aumento de la contaminación. Los vertidos contaminantes, como los residuos industriales y las aguas residuales no tratadas, pueden contaminar las aguas costeras y dañar los ecosistemas marinos. La sobreexplotación de los recursos costeros, como la pesca excesiva o la extracción excesiva de arena, también puede alterar el equilibrio ecológico de la costa. Estos factores representan desafíos significativos para la zona costera de Safi, Marruecos.
**RÉSUMÉ** – L'APPROCHE CARTOGRAPHIQUE APPLIQUÉE AUX RISQUES DE CHANGEMENT CÔTIER À SAFI, AU MAROC.

Les changements climatiques, la pression démographique, les rejets polluants et la surexploitation sont les principaux facteurs qui impactent la zone côtière de l'océan Atlantique à Safi, au Maroc. Le changement climatique peut entraîner une élévation du niveau de la mer, une intensification des tempêtes et une érosion côtière, ce qui peut avoir des conséquences négatives sur la côte. La pression démographique peut entraîner une urbanisation croissante et un développement d'infrastructures le long de la côte, ce qui peut entraîner la destruction des habitats et une augmentation de la pollution. Les rejets polluants, tels que les déchets industriels et les eaux usées non traitées, peuvent contaminer les eaux côtières et nuire aux écosystèmes marins. La surexploitation des ressources côtières, telle que la surpêche ou l'exploitation excessive du sable, peut également perturber l'équilibre écologique de la côte. Ces facteurs constituent collectivement des défis importants pour la zone côtière à Safi, au Maroc.

L'approche cartographique appliquée aux risques de changement côtier à Safi, au Maroc, permet de visualiser et d'analyser les changements qui se produisent le long de la côte. En utilisant des techniques de cartographie, il est possible de représenter les risques liés au changement climatique, tels que l'élévation du niveau de la mer, l'érosion côtière et les tempêtes, ainsi que d'autres facteurs tels que la pression démographique et les pollutions.

Cette approche cartographique peut aider à identifier les zones les plus vulnérables et à prendre des mesures préventives pour atténuer les risques. Elle permet également de suivre les changements au fil du temps et d'évaluer l'efficacité des mesures d'adaptation mises en place.

*Mots clés:* Littoral, Erosion, Submersion côtière, SIG, Maroc.

**RESUMEN** – EL ENFOQUE CARTOGRÁFICO APLICADO A LOS RIESGOS DE CAMBIO COSTERO EN SAFI, MARRUECOS.

Los cambios climáticos, la presión demográfica, los vertidos contaminantes y la sobreexplotación son los principales factores que impactan en la zona costera del océano Atlántico en Safi, Marruecos. El cambio climático puede provocar el aumento del nivel del mar, intensificar las tormentas y erosionar la costa, lo que puede tener un impacto negativo en la zona costera. La presión demográfica puede resultar en un aumento de la urbanización y el desarrollo de infraestructuras a lo largo de la costa, lo que conlleva la destrucción del hábitat y un aumento de la contaminación. Los vertidos contaminantes, como los residuos industriales y las aguas residuales no tratadas, pueden contaminar las aguas costeras y dañar los ecosistemas marinos. La sobreexplotación de los recursos costeros, como la pesca excesiva o la extracción excesiva de arena, también puede alterar el equilibrio ecológico de la costa. Estos factores representan desafíos significativos para la zona costera de Safi, Marruecos.
El enfoque cartográfico aplicado a los riesgos de cambio costero en Safi, Marruecos, permite visualizar y analizar los cambios que ocurren a lo largo de la costa. Utilizando técnicas de cartografía, es posible representar los riesgos asociados al cambio climático, como el aumento del nivel del mar, la erosión costera y las tormentas, así como otros factores como la presión demográfica y la contaminación. Este enfoque cartográfico puede ayudar a identificar las áreas más vulnerables y tomar medidas preventivas para mitigar los riesgos. También permite monitorear los cambios a lo largo del tiempo y evaluar la efectividad de las medidas de adaptación implementadas.

**Palabras clave:** Litoral, Erosión, Inmersión Còtière, SIG, Marruecos.

# I. INTRODUCTION

Coastal area constitutes a zone of transition between the marine and terrestrial ecosystems by providing fundamental ecosystem services. It attracts large populations. These areas of great interest for the well-being of humans are under increasing pressure with the population growth.

In coastal environments human interventions contribute to disruption coastal regimes by reducing or increasing the volumes of sediment transits coasts. This imbalance modifies the stability of the coastline (Paskoff, 1998; Schoonees et al., 2006; Samat, 2007). Also, these areas are generally subject to various risks such as submersion and coastal erosion.

Coastal erosion is a natural phenomenon that can be observed in the Safi coastline. The populations settled in these environments are then exposed to these risks with a level of vulnerability that could be more or less high according to their sensitivity and ability to be adapted. Also, the erosion is also linked to the rise in relative sea level.

Sea level has always evolved and sometimes very rapidly, 130 m between the last ice age about 21,000 years ago and the start of the current interglacial period, or about 1 m per century. This evolution then slowed down about 6,000 years ago and has stabilized around only 5 cm per century on average over the last 2 to 3 millennia. Such changes can only be explained by natural variations. However, during the 20th century, the sea level has risen by around 20 cm. The latest Intergovernmental Panel on Climate Change (IPCC) report predicts an increase of nearly one meter in 2100 in the most extreme scenario.

The application of GIS to produce shoreline maps has an important role in managing coastal resources for sustainable development in the coastal areas in the study area.
El enfoque cartográfico aplicado a los riesgos de cambio costero en Safi, Marruecos, permite visualizar y analizar los cambios que ocurren a lo largo de la costa. Utilizando técnicas de cartografía, es posible representar los riesgos asociados al cambio climático, como el aumento del nivel del mar, la erosión costera y las tormentas, así como otros factores como la presión demográfica y la contaminación. Este enfoque cartográfico puede ayudar a identificar las áreas más vulnerables y tomar medidas preventivas para mitigar los riesgos. También permite monitorear los cambios a lo largo del tiempo y evaluar la efectividad de las medidas de adaptación implementadas.

**Palabras clave:** Litoral, Erosión, Inmersión Còtière, SIG, Marruecos.

# I. INTRODUCTION

Coastal area constitutes a zone of transition between the marine and terrestrial ecosystems by providing fundamental ecosystem services. It attracts large populations. These areas of great interest for the well-being of humans are under increasing pressure with the population growth.

In coastal environments human interventions contribute to disruption coastal regimes by reducing or increasing the volumes of sediment transits coasts. This imbalance modifies the stability of the coastline (Paskoff, 1998; Schoonees et al., 2006; Samat, 2007). Also, these areas are generally subject to various risks such as submersion and coastal erosion.

Coastal erosion is a natural phenomenon that can be observed in the Safi coastline. The populations settled in these environments are then exposed to these risks with a level of vulnerability that could be more or less high according to their sensitivity and ability to be adapted. Also, the erosion is also linked to the rise in relative sea level.

Sea level has always evolved and sometimes very rapidly, 130 m between the last ice age about 21,000 years ago and the start of the current interglacial period, or about 1 m per century. This evolution then slowed down about 6,000 years ago and has stabilized around only 5 cm per century on average over the last 2 to 3 millennia. Such changes can only be explained by natural variations. However, during the 20th century, the sea level has risen by around 20 cm. The latest Intergovernmental Panel on Climate Change (IPCC) report predicts an increase of nearly one meter in 2100 in the most extreme scenario.

The application of GIS to produce shoreline maps has an important role in managing coastal resources for sustainable development in the coastal areas in the study area.
## II. STUDY AREA

The study took place along the coast of Safi city (Morocco). It localized in western Morocco on the Atlantic Ocean, between 32°17′57″North latitude and 9°14′13″ West longitude (fig. 1).

<figure><img src="image_4.png" /><figcaption>Fig. 1 -Geographical location of the study area</figcaption></figure>

### 1. Climate

The climate in Safi is semi-arid to mild temperate winter with generally hot and dry summer and the oceanic influences of the coast area.

### 2. Temperature

The temperatures are moderate in the areas close to the ocean and more contrasted in the interior part.

This parameter shows interannual variability, but it varies little from one year to another. The coldest months are December, January and February which the annual average is 6 °C To 8 °C. The Data relating to the level of Safi station covering around 30 years indicates that the temperatures are little variable from year to year with an annual average varying From 17 °C to 19 °C (MARRAKECH SAFI REGION MONOGRAPHIE 2022).
## II. STUDY AREA

The study took place along the coast of Safi city (Morocco). It localized in western Morocco on the Atlantic Ocean, between 32°17′57″North latitude and 9°14′13″ West longitude (fig. 1).

<figure><img src="image_3.png" /><figcaption>Fig. 1 -Geographical location of the study area</figcaption></figure>

### 1. Climate

The climate in Safi is semi-arid to mild temperate winter with generally hot and dry summer and the oceanic influences of the coast area.

### 2. Temperature

The temperatures are moderate in the areas close to the ocean and more contrasted in the interior part.

This parameter shows interannual variability, but it varies little from one year to another. The coldest months are December, January and February which the annual average is 6 °C To 8 °C. The Data relating to the level of Safi station covering around 30 years indicates that the temperatures are little variable from year to year with an annual average varying From 17 °C to 19 °C (MARRAKECH SAFI REGION MONOGRAPHIE 2022).
**3. Precipitation**

The rainy season covers on average the period from October to May; the rains fall regularly in Autumn and Winter. The rainfall in the annual average is estimated at 300 mm decreases from the coast towards the interior of the city.

**4. Relative Air Humidity**

The relative humidity of the air in the city, especially in the littoral fringe, remains consistently high. On average, it ranges between 70% and 80%. In the morning, it can exceed 90%, while it may decrease to around 60% by noon. The high air humidity plays a significant role in compensating for aridity in the region.

**5. Winds**

The winds in the Sahel region are characterized by frequent occurrence and are particularly strong in the coastal zone. These winds predominantly blow from the northwest direction and often intensify towards the late afternoon. Additionally, hot winds known as Charguis are occasionally observed in April and May.

### III. ASSESSMENT OF THE COAST SUBMERGENCE

The methodological steps proposed by HOOZEMANS and *al*. (1993) and applied by SNOUSSI and *al*. (2008) are applied to determine the flood levels by the sum of the factors involved in the rise in sea level.

Elevation data was taken from the 2018 aerial restitution. A digital elevation model (DEM) was produced from the interpolation of the elevation data by triangular irregular network (TIN), and a database. Ground control point data was measured by a global positioning system (GPS). The horizontal resolution of the DEM is a few centimeters, which makes it possible to correctly represent narrow lines such as roads, dunes and buildings. These data have been integrated into a GIS (ArcGIS) database.

The assessments presented (Figure 2) estimate that the areas of potential coast submergence in the studied area are larger due to future socio-economic Development and the current morphodynamic evolution. As for the impact on the Environment, we point out that significant ecological losses can occur.
**3. Precipitation**

The rainy season covers on average the period from October to May; the rains fall regularly in Autumn and Winter. The rainfall in the annual average is estimated at 300 mm decreases from the coast towards the interior of the city.

**4. Relative Air Humidity**

The relative humidity of the air in the city, especially in the littoral fringe, remains consistently high. On average, it ranges between 70% and 80%. In the morning, it can exceed 90%, while it may decrease to around 60% by noon. The high air humidity plays a significant role in compensating for aridity in the region.

**5. Winds**

The winds in the Sahel region are characterized by frequent occurrence and are particularly strong in the coastal zone. These winds predominantly blow from the northwest direction and often intensify towards the late afternoon. Additionally, hot winds known as Charguis are occasionally observed in April and May.

### III. ASSESSMENT OF THE COAST SUBMERGENCE

The methodological steps proposed by HOOZEMANS and *al*. (1993) and applied by SNOUSSI and *al*. (2008) are applied to determine the flood levels by the sum of the factors involved in the rise in sea level.

Elevation data was taken from the 2018 aerial restitution. A digital elevation model (DEM) was produced from the interpolation of the elevation data by triangular irregular network (TIN), and a database. Ground control point data was measured by a global positioning system (GPS). The horizontal resolution of the DEM is a few centimeters, which makes it possible to correctly represent narrow lines such as roads, dunes and buildings. These data have been integrated into a GIS (ArcGIS) database.

The assessments presented (Figure 2) estimate that the areas of potential coast submergence in the studied area are larger due to future socio-economic Development and the current morphodynamic evolution. As for the impact on the Environment, we point out that significant ecological losses can occur.
<figure><img src="image_5.png" /><figcaption>Fig 2– Coast submergence in Safi-Morocco</figcaption></figure>

With the future rise in sea level, a significant portion of the rear littoral grasslands would be affected by submersion and increased salinity of groundwater. Consequently, the grassland vegetation in these areas would undergo a regressive evolution, leading to the return of species characteristic of the schorre.

## 1.1 Evolution of the Coastline of Safi

The analysis of the Safi coastline was conducted by interpreting cartographic documents, including topographic maps and aerial photography (Figure 3). The method employed for this analysis involved several steps. Firstly, data acquisition and preprocessing were carried out to gather relevant information and prepare it for further analysis. Next, the location of the coastline was identified, and digitization techniques were employed to convert the physical coastline into a digital format. Finally, the kinematics of the coastline were studied, which involved analyzing the changes and movements of the coastline over time. This analysis helps in understanding the dynamic nature of the Safi coastline.
<figure><img src="image_4.png" /><figcaption>Fig 2– Coast submergence in Safi-Morocco</figcaption></figure>

With the future rise in sea level, a significant portion of the rear littoral grasslands would be affected by submersion and increased salinity of groundwater. Consequently, the grassland vegetation in these areas would undergo a regressive evolution, leading to the return of species characteristic of the schorre.

## 1.1 Evolution of the Coastline of Safi

The analysis of the Safi coastline was conducted by interpreting cartographic documents, including topographic maps and aerial photography (Figure 3). The method employed for this analysis involved several steps. Firstly, data acquisition and preprocessing were carried out to gather relevant information and prepare it for further analysis. Next, the location of the coastline was identified, and digitization techniques were employed to convert the physical coastline into a digital format. Finally, the kinematics of the coastline were studied, which involved analyzing the changes and movements of the coastline over time. This analysis helps in understanding the dynamic nature of the Safi coastline.
<figure><img src="image_6.png" /><figcaption>Fig 3– Aspect of the Safi Coastline 03/05/2018</figcaption></figure>

1.1.2 *The coastline variation rates*

To understand the changing coastline in Safi, a digitized approach is employed, which involves using multiple dates to analyze reference lines obtained for different periods (1984-2018). The analysis of coastal dynamics involves several steps. Firstly, selecting a coastline indicator, followed by extracting this indicator. The method is then replicated for each period under consideration, and finally, a comparison is made to evaluate the changes that have occurred. This comprehensive approach allows for a thorough assessment of the evolution of the coastline in Safi over time.

2.1.2 *Coastline Indicator*

The concept of the coastline, which serves as the boundary between terrestrial and marine ecosystems, can be somewhat ambiguous due to the gradual transition between these ecosystems. As a result, multiple linear representations can be proposed for the same coastline, leading to the necessity of selecting a reference line. Based on various literature reviews (Boak and Turner, 2005; Faye, 2010), several reference lines have been identified. In our study, we have chosen a
<figure><img src="image_5.png" /><figcaption>Fig 3– Aspect of the Safi Coastline 03/05/2018</figcaption></figure>

1.1.2 *The coastline variation rates*

To understand the changing coastline in Safi, a digitized approach is employed, which involves using multiple dates to analyze reference lines obtained for different periods (1984-2018). The analysis of coastal dynamics involves several steps. Firstly, selecting a coastline indicator, followed by extracting this indicator. The method is then replicated for each period under consideration, and finally, a comparison is made to evaluate the changes that have occurred. This comprehensive approach allows for a thorough assessment of the evolution of the coastline in Safi over time.

2.1.2 *Coastline Indicator*

The concept of the coastline, which serves as the boundary between terrestrial and marine ecosystems, can be somewhat ambiguous due to the gradual transition between these ecosystems. As a result, multiple linear representations can be proposed for the same coastline, leading to the necessity of selecting a reference line. Based on various literature reviews (Boak and Turner, 2005; Faye, 2010), several reference lines have been identified. In our study, we have chosen a
reference line that is easily identifiable on images covering the entire study area and all the periods under investigation. This reference line is defined as the boundary on the land side of protective structures, if present, or in the absence of such structures, the limit between dry sand and wet sand, which is considered as the boundary between the high seas and the coastline.

### 3.1.2 Extraction of Reference Lines and Integration into GIS

The process of reference line extraction involved manual digitization using a 1984 corrected aerial photograph of the study area and a Google Earth image from 2018. The digitized lines were saved in .kml format and imported into ArcGIS 10.4. Using ArcGIS's conversion tool, the coastlines digitized in Google Earth were converted into shapefiles. These shapefiles were then integrated into a geodatabase and used as input data in the Digital Shoreline Analysis System (DSAS).

### 4.1.2 Comparison of the Reference Lines

The Digital Shoreline Analysis System (DSAS) is a plugin developed by the United States Geological Survey (USGS) that operates within the ArcGIS software provided by Environmental Systems Research Institute (ESRI). DSAS is designed to calculate rate of change statistics for a time series of coastline vector data. It has been widely utilized for measuring and monitoring the dynamics of coastlines. Specifically, DSAS version 4.3 on ArcGIS 10.4 measures changes in reference lines by comparing them to transects spaced 10 meters apart, which are generated from a baseline (Figure 4).
reference line that is easily identifiable on images covering the entire study area and all the periods under investigation. This reference line is defined as the boundary on the land side of protective structures, if present, or in the absence of such structures, the limit between dry sand and wet sand, which is considered as the boundary between the high seas and the coastline.

### 3.1.2 Extraction of Reference Lines and Integration into GIS

The process of reference line extraction involved manual digitization using a 1984 corrected aerial photograph of the study area and a Google Earth image from 2018. The digitized lines were saved in .kml format and imported into ArcGIS 10.4. Using ArcGIS's conversion tool, the coastlines digitized in Google Earth were converted into shapefiles. These shapefiles were then integrated into a geodatabase and used as input data in the Digital Shoreline Analysis System (DSAS).

### 4.1.2 Comparison of the Reference Lines

The Digital Shoreline Analysis System (DSAS) is a plugin developed by the United States Geological Survey (USGS) that operates within the ArcGIS software provided by Environmental Systems Research Institute (ESRI). DSAS is designed to calculate rate of change statistics for a time series of coastline vector data. It has been widely utilized for measuring and monitoring the dynamics of coastlines. Specifically, DSAS version 4.3 on ArcGIS 10.4 measures changes in reference lines by comparing them to transects spaced 10 meters apart, which are generated from a baseline (Figure 4).
<figure><img src="image_7.png" /><figcaption>Fig 4– Example of transects and baseline, created by the DSAS to measure the evolution of the coastline between 1984-2018.</figcaption></figure>

5.1.2 Determination of the associated uncertainties

In the given context, uncertainty statistics are derived from a margin of error table integrated into the program. By default, a margin of error of 10 meters is used for each reference line. The errors in the case study can arise from natural factors affecting the position of the reference line (such as winds and tides), uncertainties related to image processing (including rectification, mosaic, and precision between historical images), and measurement uncertainties during digitization.

The DSAS (Digital Shoreline Analysis System) measures the distances between intersection points of transects and shorelines, calculates change rates along each transect, and presents the results in table format (Figure 5). These results can be further analyzed by extracting statistics from the attribute tables and generating coastline variation curves in Excel.
<figure><img src="image_6.png" /><figcaption>Fig 4– Example of transects and baseline, created by the DSAS to measure the evolution of the coastline between 1984-2018.</figcaption></figure>

5.1.2 Determination of the associated uncertainties

In the given context, uncertainty statistics are derived from a margin of error table integrated into the program. By default, a margin of error of 10 meters is used for each reference line. The errors in the case study can arise from natural factors affecting the position of the reference line (such as winds and tides), uncertainties related to image processing (including rectification, mosaic, and precision between historical images), and measurement uncertainties during digitization.

The DSAS (Digital Shoreline Analysis System) measures the distances between intersection points of transects and shorelines, calculates change rates along each transect, and presents the results in table format (Figure 5). These results can be further analyzed by extracting statistics from the attribute tables and generating coastline variation curves in Excel.
<figure><img src="image_8.png" /><figcaption>Fig 5 – Example of transects and baseline, created by the DSAS to measure the evolution of the coastline between 1984-2018.</figcaption></figure>

#### IV. DISCUSSION

Based on the analysis of diachronic study results from aerial photographs taken at 10 measurement points within the study area, it has been observed that the coastline has progressively shifted inland since 1984. The rate of this shift varies between -0.38 and -1.30 meters per year. During the period from 1984 to 2018, there was a general decline in the coastline, except for certain areas located behind the ears and the urban area. This situation can be attributed to two main factors. Firstly, the scale of urbanization has disrupted the natural sediment exchange between the beach, back-beach, and dune. Secondly, the area has experienced strong storms that have contributed to this coastal erosion.
<figure><img src="image_7.png" /><figcaption>Fig 5 – Example of transects and baseline, created by the DSAS to measure the evolution of the coastline between 1984-2018.</figcaption></figure>

## IV. DISCUSSION

Based on the analysis of diachronic study results from aerial photographs taken at 10 measurement points within the study area, it has been observed that the coastline has progressively shifted inland since 1984. The rate of this shift varies between -0.38 and -1.30 meters per year. During the period from 1984 to 2018, there was a general decline in the coastline, except for certain areas located behind the ears and the urban area. This situation can be attributed to two main factors. Firstly, the scale of urbanization has disrupted the natural sediment exchange between the beach, back-beach, and dune. Secondly, the area has experienced strong storms that have contributed to this coastal erosion.
V. CONCLUSION

According to the information provided, the evolution of the Safi coastline has been studied using DSAS (Digital Shoreline Analysis System), which has provided insight into the associated variation rates along the entire coast. The risk of coastal erosion in this area has been influenced by economic factors, primarily the port, as well as governance and social factors such as anarchic occupation of land. To address this issue, the authorities have implemented various coastal protection structures as a management strategy.

While quantitative information on the coast's evolution is currently reassuring, there is a concern that the authorities may have excessive confidence in these structures. It is noted that these protective works are expensive and may not be sustainable in the long term. Additionally, the study suggests that further improvements are necessary. Firstly, the study should be extended to cover the entire area protected by the structures. Secondly, a projection should be made using a compilation of coastlines dating from after the construction of protective works, with a sufficient number of data points to minimize errors in the projection model.
V. CONCLUSION

According to the information provided, the evolution of the Safi coastline has been studied using DSAS (Digital Shoreline Analysis System), which has provided insight into the associated variation rates along the entire coast. The risk of coastal erosion in this area has been influenced by economic factors, primarily the port, as well as governance and social factors such as anarchic occupation of land. To address this issue, the authorities have implemented various coastal protection structures as a management strategy.

While quantitative information on the coast's evolution is currently reassuring, there is a concern that the authorities may have excessive confidence in these structures. It is noted that these protective works are expensive and may not be sustainable in the long term. Additionally, the study suggests that further improvements are necessary. Firstly, the study should be extended to cover the entire area protected by the structures. Secondly, a projection should be made using a compilation of coastlines dating from after the construction of protective works, with a sufficient number of data points to minimize errors in the projection model.
ORCID ID

SARA LOURAIBI https://orcid.org/0000-0001-8779-0161

BIBLIOGRAPHIC REFERENCES

BANQUE MONDIALE, (2011), adaptation au changement, climatique et aux désastres naturels des villes côtières d'afrique du nord, phase1 : évaluation des risques en situation actuelle et a l'horizon 2030, version finale, p 21-22.

Creel, L. Ripple Effects: Population and Coastal Regions. Population Reference Bureau Measure Communications. Available online: http://www.org (accessed on 15 February 2020).

Debaine F., Robin M. (2012): A new GIS modeling of coastal dune protection services Against physical coastal hazards, Ocean&Coastal Management 63 (2012)43-54 Doi:10.1016/j.ocecoman.2012.03.012 (Elsevier).

Duarte, C.M.; Losada, I.J.; Hendriks, I.E.; Mazarrasa, I.; Marbà, N. (2013), The role of coastal plant communities for climate change mitigation and adaptation. Nat. Clim. Chang, 3, 961-968.

GROSSMAN D, (2016), a renegade biologist is challenging a millennium of German dike-building tradition, Hakai magazine Coastal science and societies, p 5-6.

GUILCHER A, (1966), Les grandes falaises et méga-falaise des côtes sud-ouest et ouest de l'Irlande. Annales de Géographie, Volume 75, Numéro 407, pp 26-38.

GUILCHER A,(1974), Les « rasas » : un problème de morphologie littorale générale. Annales de Géographie, t. 83, n°455, pp 1-33.

J. Tricart, S. Rimbert, G. Lutz,(1970) Introduction à l'Utilisation des Photographies Aériennes en Géographie, Géologie, Ecologie, Aménagement du Territoire. Tome I. Notions Générales, Données Structurales, Géomorphologie. Ed. SEDES, pp 96-97.

Liquete, C.; Zulian, G.; Delgado-Fernandez, I,(2013); Stips, A.; Maes, J. Assessment of coastal protection as an ecosystem service in Europe. Ecol. Indic., 30, 205-217. [CrossRef].

P. Durand,(1988) Cinématique d'un littoral sableux à partir de photographies aériennes et de cartes topographiques. Exemple du littoral d'Argelès-Plage à Saint-Cyprien (Roussillon, France). Géomorphologie : relief, processus, environnement 2155-166.

Spalding, M.D.; Ruffo, S.; Lacambra, C.; Meliane, I.; Zeitlin Hale, L.; Shepard, C.C.; Beck, M.W. (2014) The role of ecosystems in coastal protection: Adapting to climate change and coastal hazards. Ocean Coast. Manag., 90, 50-57.

Weisrock A.(1980): Géomorphologie et paléo environnement de l'atlas atlantique Maroc.

Weisrock A.(1985): Les falaises de la cote atlantique marocaine de Safi à Bedouzza (Cap Cantin).Bull.Assoc.Géo.Franç. 2,Paris, p.94-104.
ORCID ID

SARA LOURAIBI https://orcid.org/0000-0001-8779-0161

BIBLIOGRAPHIC REFERENCES

BANQUE MONDIALE, (2011), adaptation au changement, climatique et aux désastres naturels des villes côtières d'afrique du nord, phase1 : évaluation des risques en situation actuelle et a l'horizon 2030, version finale, p 21-22.

Creel, L. Ripple Effects: Population and Coastal Regions. Population Reference Bureau Measure Communications. Available online: http://www.org (accessed on 15 February 2020).

Debaine F., Robin M. (2012): A new GIS modeling of coastal dune protection services Against physical coastal hazards, Ocean&Coastal Management 63 (2012)43-54 Doi:10.1016/j.ocecoman.2012.03.012 (Elsevier).

Duarte, C.M.; Losada, I.J.; Hendriks, I.E.; Mazarrasa, I.; Marbà, N. (2013), The role of coastal plant communities for climate change mitigation and adaptation. Nat. Clim. Chang, 3, 961–968.

GROSSMAN D, (2016), a renegade biologist is challenging a millennium of German dike-building tradition, Hakai magazine Coastal science and societies, p 5-6.

GUILCHER A, (1966), Les grandes falaises et méga-falaise des côtes sud-ouest et ouest de l'Irlande. Annales de Géographie, Volume 75, Numéro 407, pp 26-38.

GUILCHER A,(1974), Les « rasas » : un problème de morphologie littorale générale. Annales de Géographie, t. 83, n°455, pp 1-33.

J. Tricart, S. Rimbert, G. Lutz,(1970) Introduction à l'Utilisation des Photographies Aériennes en Géographie, Géologie, Ecologie, Aménagement du Territoire. Tome I. Notions Générales, Données Structurales, Géomorphologie. Ed. SEDES, pp 96-97.

Liquete, C.; Zulian, G.; Delgado-Fernandez, I,(2013); Stips, A.; Maes, J. Assessment of coastal protection as an ecosystem service in Europe. Ecol. Indic., 30, 205–217. [CrossRef].

P. Durand,(1988) Cinématique d'un littoral sableux à partir de photographies aériennes et de cartes topographiques. Exemple du littoral d'Argelès-Plage à Saint-Cyprien (Roussillon, France). Géomorphologie : relief, processus, environnement 2155-166.

Spalding, M.D.; Ruffo, S.; Lacambra, C.; Meliane, I.; Zeitlin Hale, L.; Shepard, C.C.; Beck, M.W. (2014) The role of ecosystems in coastal protection: Adapting to climate change and coastal hazards. Ocean Coast. Manag., 90, 50–57.

Weisrock A.(1980): Géomorphologie et paléo environnement de l'atlas atlantique Maroc.

Weisrock A.(1985): Les falaises de la cote atlantique marocaine de Safi à Bedouzza (Cap Cantin).Bull.Assoc.Géo.Franç. 2,Paris, p.94-104.