@2024 Afarand., IRAN

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ISSN: 2538-4384    Geographical Researches 2020;35(2):177-187

Background
Monitoring the coastline changes influenced by permanent erosion has been one of the fundamental studies in recent years.
Previous Studies
Urmia Lake coastline was monitored in 2004 using Landsat images and TOPEX data that showed the depth of the lake had changed by almost 3m [Allesheikh et al., 2004]. Asaluyeh coastline changes in Bushehr province were monitored using remote sensing and GIS. The results show that sedimentation has increased twice as much as erosion during the study period (16 years), and human activity was mentioned as the main cause [Naemi et al., 2010]. The results of Karnataka coastline changes monitoring show 70% of this region is in an unstable situation, and the remaining 30% is influenced by erosion [Chethnamilselvan et al., 2013]. The research results in Haiti islands show there had been 6474 ha erosion in the studied area [Kumar & Ghosh, 2012]. According to other studies in this field, remote sensing is one of the best and more reliable devices for monitoring and managing environmental resources. A better understanding of the coastline helps better manage the coastlines, more accurate designs, more suitable coastal facilities, and determination of safe margins [Razmi et al., 2017].
Aim(s)
This study aimed to monitor Bushehr coastline changes and erosion and sedimentation processes from 1976 to 2018.
Research type
This is an empirical case study.
Research society, place and time
The current research is carried out in almost 130km of Bushehr coastline using the data from 1976 to 2018.
Sampling method and number
There is no sampling method mentioned.
Used devices&materials
This research uses quantitative methods and spatial analysis to gather information and ARC GIS and ENVI5.3 to analyze them.
Findings by Text
Geomorphological landforms were detected through field study and the analysis of satellite images. These landforms are Helleh river estuary, firths, sand beaches, delta, muddy surfaces, flood plains, badland areas, and alluvial valleys that undergone transformation during the study period (42 years). The areas with backward and forward changes, i.e., the areas prone to erosion and sedimentation, were detected by analyzing coastline changes in 42 years. The longest coastline was recorded in 2018 with 200 km, and the shortest one was recorded in 1976 with 122km, which are shown in Figure 4.The maximum transformed area during this period is 555〖km〗^2 in 2001 and the minimum transformed area is recorded in 1976 with 515 〖km〗^2 which shows significant changes in coastline and beaches in the studied area (Figure 5).The images were compared two by two after classification. The results show that most of the changes were backward in the first period (1976-1986), but they were not the same all along the coastline. For example, the Bandar Ganave coastline had forward changes while moving toward the south; the coastline had a slight backward movement (Figure 7). The coastline moved forward during the second period (1986-2001), shown in Figure 6. Bushehr coastline curvature coefficient from 1976 to 2017 There were backward changes all over the studied area during the third period (2001-2018), which are more significant in the southern parts (Figure 7). In general, the coastline changes during the study period (42 years) were backward. The coastline length was 122, 177, 189, and 200km in 1976, 1986, 2001, and 2018, respectively. According to the studies, the changes were more severe in recent years. The rivers' and the beaches' features should be measured as measurable quantitative geometric parameters and indicators for the classification to identify the hydraulic and hydrophysical properties. The curvature coefficient is one of the most important parameters for this purpose, used for the quantitative analysis of the coastline changes. Table 2 shows the changes in the curves' number and their curvature coefficient of the Bushehr coastline in four studied periods. Considerably, the number of curves has decreased in the first and last classes (CC<1 & CC>2), while they have increased in the second class (1<CC<1.5). It might be the consequence of an imbalance in the region because of the beach's enormous constructions and expansion of the residential zone to the sandy areas.
Main comparison to the similar studies
The use of image classifications in the current research is similar to the methods Negahban et al. (2017), Tamassoki (2016), and Negahban et al. (2018) used in their research. This is an accurate method to monitor and detect coastline changes.
Suggestions
Sedimentation in this region has led to the expansion of the land. Hence, it is suggested to benefit from this potential and efficiently manage the sedimentation to avoid the consequences. The rise in seawater level might be threatening in this region because of the low slope. Then there are some suggestions, including 1) the sea riparian zone should be considered as a vulnerable zone by governmental entities 2) the riparian zone should be considered in all human activities. It could be determined again to make some of the infrastructures move out of the zone. 3) An environmental management project is needed in this region due to the oil, gas, and nuclear infrastructure.
Limitations
There is no limitation reported.
Conclusions
Bushehr coastline monitoring from 1976 to 2018 shows that Bushehr beaches have undergone various transformations that are not the same along the coastline. Although a regular and clear trend of the coastline changes cannot be seen, Bushehr's coastal areas can be classified into three main groups: A) Stable beaches with no significant changes. B) The beaches with severe erosion, such as Halileh beaches near the nuclear power plant or Shif island beaches in the northern part of Bushehr. C) Sedimented beaches with backward changes. The analysis of the Bushehr coastline curvature coefficient shows an imbalance in the studied area, which is the result of human activities as well as natural processes. The imbalance between erosion and sedimentation in Bushehr coastal areas has changed the coastal landforms too.
Acknowledgments
None.
Conflict of interest
None.
Ethical Permissions
None.
Funding Sources
None.

TABLES and CHARTS

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