Satellite images survey for the identification of the coastal sedimentary system changes and associated vulnerability along the western bay of the Gulf of Tunis (northern Africa)

Abderraouf Hzami,Abdeljaouad Saâdi,Gheorghe Romanescu,Alin Mihu-Pintilie,Cristian Constantin Stoleriu,Oula Amrouni

doi:10.5194/piahs-377-83-2018

Abstract

Abstract. The aim of this study consists in testing the effectiveness of satellite data in order to monitoring shoreline and sedimentary features changes, especially the rapidly changing of Gulf of Tunis coast. The study area is located in the Gulf of Tunis western bay (Southern Mediterranean Sea) which is characterized by sandy beaches of Ghar Melah and Raoued (Medjerda Delta area). The aerial photographs and satellite imageries were used for mapping the evolution of shoreline. Diachronic data (satellite imagery, aerial photography and topographic maps) were used to monitor and to quantify, the evolution of the coastal areas. These thematic data were digitally overlaid and vectorised for highlighting the shoreline changes between 1936 and 2016, in order to map the rate of erosion and accretion along the shoreline. Results show that the accretion and degradation are related to the Medjerda: change of outlet in 1973 and impoundment of the Sidi Salem dam in 1982. We found that the general trend of the coastal geomorphic processes can be monitored with satellite imageries (such as Sentinel A2, Spots 4 and 5), due to its repetitive coverage along the time and their high quality concerning the spectral contrast between land and sea areas. Improved satellite imageries with high resolution should be a valuable tool for complementing traditional methods for mapping and assessing the sedimentary structures (such as shoreline, delta, marine bars), and monitoring especially the lowlands coastal areas (slightly eroded).

Highlights

The general characteristics of coastal erosion worldwide are described in terms of geography by the types of erosion, the causes which starts the erosion processes, and the effects generated by erosion processes
The all graphical data were used to calculate the spatial shoreline evolution using statistics provided by Digital Shoreline Analysis System (DSAS) (Thieler et al, 2009) in order to highlighting the differences between Proc
Tion using Net Shoreline Movement (NSM) and End Point Rate (EPR) statistical technics shows the importance of the different periods in this study

Summary

Introduction

The general characteristics of coastal erosion worldwide are described in terms of geography by the types of erosion, the causes which starts the erosion processes, and the effects generated by erosion processes. Shoreline is an element with a high spatial variability which imposes a rapidly changing for coastal landforms (Mujabar and Chandrasekar, 2013). The efficient methods are needed to handle the spatial and temporal variability of coastal shoreline using GIS techniques. Many researches utilized remote sensing data to analyse coastal environments: Louati et al (2014), Oyedotun (2014, 2017), Thinh and Hens (2017). Many studies in Tunisia have shown the effect of coastal degradation related to different natural and anthropogenic factors 2010; Halouani et al, 2011, 2013; Saïdi et al, 2012, 2013; Louati and Zargoun, 2013; Louati et al, 2014)

Study area

Material and methods

Results and discussion

Conclusion