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Monitoring Coastal Erosion and Deposition in Sam Son City, Vietnam – a Contribution from Remote Sensing Data

100%

Pham L. T. , Le D. K. , Tong S. S. , Le H. T. T.

tom Vol. 2, no. 1

79--87

Studying the trends in shoreline erosion and accretion is essential for a wide range of investigations conducted by coastal scientists, and coastal managers. Shoreline erosion and accretion occur as a result of both natural and human influences. Some areas along shoreline in Sam Son are eroded and deposed by natural coastal processes and human actions, such as storm, wave, tourism activities. Purpose of this work is to study the erosion and deposition in Sam Son over 33 years (1989–2022). Coastlines were extracted using multi-temporal Landsat images, and the shoreline change rate was determined using Digital Shoreline Analysis Systems (DSAS). The results of this paper inlustrated that the shoreline change in Sam Son undergoes significant and varied fluctuations across different areas. At the Hoi estuary, erosion rates vary from -2.22 m/year to -40.32 m/year. The construction of FLC Sam Son is one of the factors contributing to sedimentation loss in the northern part of Sam Son City, which is situated adjacent to the East Sea and next to the Ma River. Furthermore, the accretion rate has strongly increased, reaching 9.7 m/year in the Do River estuary. The phenomenon of sediment deposition serves as the basic for constructing hotels to cater to tourism in Sam Son.

Badanie trendów erozji i akrecji linii brzegowej jest istotne dla szerokiego zakresu badań prowadzonych przez naukowców nadmorskich i menedżerów wybrzeża. Erozja i akrecja linii brzegowej występują zarówno w wyniku procesów naturalnych, jak i wpływu człowieka. Pewne obszary wzdłuż linii brzegowej w Sam Son ulegają erozji i akrecji w wyniku naturalnych procesów przybrzeżnych i działań ludz-kich, takich jak burze, fale, działalność turystyczna... Celem tej pracy jest zbadanie erozji i akrecji w Sam Son na przestrzeni 33 lat (1989–2022). Linie brzegowe zostały wyodrębnione z wykorzystaniem wieloczasowych obrazów satelitarnych Landsat, a wskaźnik zmian linii brzegowej został określony przy użyciu systemów cyfrowej analizy linii brzegowej (DSAS). Wyniki tej pracy ilustrują, że zmiany linii brze-gowej w Sam Son podlegają znacznym i zróżnicowanym fluktuacjom w różnych obszarach. W ujściu rzeki Hoi wskaźniki erozji wahają się od -2,22 m/rok do -40,32 m/rok. Budowa FLC Sam Son jest jednym z czynników przyczyniających się do utraty osadów w północnej części miasta Sam Son, która sąsiaduje z Morzem Wschodnim i rzeką Ma. Ponadto, wskaźnik akrecji znacząco wzrósł, osiągając 9,7 m/rok w ujściu rzeki Do. Zjawisko osadzania się osadów służy jako podstawa do budowy hoteli obsługujących turystykę w Sam Son

Detection of Shoreline Changes due to Abrasion and Accretion Using Landsat Imagery – A Case Study in the Coastal Areas of Supiori Regency, Indonesia

85%

Rumahorbo B. T. , Warpur M. , Hamuna B.

tom Vol. 24, iss. 7

161--171

Shoreline changes have become a serious problem in all coastal areas worldwide. This study aimed to detect shoreline changes and analyze the shoreline change rate caused by abrasion and accretion in the coastal area of Supiori Regency, Indonesia. Landsat 8/9 imagery was used to determine the position of the coastline in 2013 and 2023. The shoreline movement (Net Shoreline Movement) and the shoreline change rate (End Point Rate) were analyzed using the Digital Shoreline Analysis System installed on ArcMap software. The results of this study indicate that there has been abrasion and accretion where there are several very significant locations. The maximum distance of the shoreline movements due to abrasion and accretion occurred in the Supiori Selatan District as far as -67.15 and 92.86 m, respectively. The average shoreline movement caused by abrasion ranges from -11.37 to -13.59 m and from 9.75 to 15.64 m in the case of accretion. From the comparison of abrasion and accretion, only the Kepulauan Aruri District has a positive value (dominant accretion), while the other four districts have a negative value (dominant abrasion). The shoreline changes rates in the study area caused by abrasion and accretion ranged from -1.22 to -1.46 m/yr and 1.05 to 1.68 m/yr, respectively. Abrasion and accretion in the study area are predominantly caused by natural factors such as waves, currents, and river flows, as well as caused by non-natural factors mainly due to human activities. Information on shoreline changes in the study area is an important aid for stakeholders involved in coastal area management. Therefore, planning, strategies, and mitigation efforts are urgently needed to anticipate increased coastal erosion and possible negative impacts.

Periodical Morphodynamic Changes of Sand Movements at El Jadida Beach

85%

Bourhili A. , El Khalidi K. , Minoubi A. , Maanan M. , Zourarah B.

Ecological Engineering & Environmental Technology

2023

tom Vol. 24, iss. 4

15--26

El Jadida Beach (X: -8.5007116; Y: 33.2316326) is a sandy beach of low altitude that constitutes a kind of enclave located between the port of El Jadida and rocky outcrops. It is influenced by natural and anthropic factors, as well as the impact of tourism, particularly during the summer, when sand is used for amusement activities (Beach Ball competition). In order to follow the morphodynamic changes of this beach, we carried out a study on two different time scales: a fifty-five years (1963 – 2018) shoreline evolution study using aerial photos and satellite images based on GIS tools using the Digital Shoreline Analysis System (DSAS) and a two-years (2017–2019) morphological beach study using a Differential Global Positioning System (DGPS). According to the results obtained by the diachronic study, the beach studied showed erosion in its middle and an accumulation at these bulges. This result is due to the presence of the harbor breakwater to the NW and the rocky outcrops to the SE; acting as a barrier preventing the movement of sediments and the erosion in the middle can be explained by the reduction of the sediment supply from the Oued Oum Erabia and by the exposure of this part to the dominant swells and also the human activities like used the beach for amusement activities (Beach Ball competition and other). Beach profile observations results show accumulation in the subaerial beach and erosion in the lower part of the foreshore. The study on two different time scales adopted in this paper, allowed us to understand longshore and cross-shore sedimentary mobility.