# Analysis of Coastal Zone Data of Northern Yantai Collected by Remote Sensing from 1990 to 2018
## 4 Discussion  
The northern coastal area of Yantai is the key development area of the Blue Economic Zone in the Shandong Peninsula. The sensible development and utilization of coastal areas and marine  
Figure 10: The relationship between the coastline length of different terrain types and artificial boundary lines. (**a**) The relationship between the length of the coastline bounded by structures and the length of the artificial boundary. (**b**) The relationship between the length of the coastline bounded by manually excavated land and the length of the artificial boundary. (**c**) The relationship between the length of the coastline bounded by roads and the length of the artificial boundary. resources is of great significance to the economic development of this area [35]. In the past 30 years, the economic development of Yantai City has been very fast, especially in the northern coastal areas. Due to the impact of human activities on the coastal zone, the coastal zone of the study area has undergone significant changes, which can be confirmed by the interpretation and analysis of remote sensing images. Coastal zone information was extracted every 10 years between 1990 and 2018. The analysis shows that the increase range of coastline length changed in the following order: 1990-2000 \(<\) 2000-2010 \(<\) 2010-2018. Among them, in the period of 2010-2018, the coastline length experienced the greatest change. With the development of the economy, the exploitation and utilization of the coastal zone have been intensified, and the coastline has shown a rapidly increasing trend. However, the analysis results show that the length of the coastline has not been increasing rapidly during this period. During the period from 2015 to 2018, the growth rate of the coastline decreased significantly. Since 2015, in view of a series of problems in coastal areas, relevant departments have begun to take measures to rectify and repair damaged islands and coastal zones, and the over-exploitation of coastal zones has been alleviated to a certain extent [36]. According to Figures 4 and 8, the change of the fractal dimension of the coastline in the study area is consistent with that of its length, first showing a trend of rapid increase and then slowly increasing. There are two main reasons for this trend. One is because of the low resolution of remote sensing images from 1990 to 2010 and the rough coastal information extracted, the coastline length and fractal dimension values are smaller. The resolution of remote sensing images in 2015 and beyond is higher, which can extract coastal information in more detail, and the length and fractal dimension of the extracted coastline are more accurate. The second reason is that with the rapid development of the social economy, especially the economic development of the coastal zone, people's utilization of the ocean has been strengthened. The construction of reclamation, artificial islands and port wharfs have increased the length of the coastline and made it more tortuous, and the fractal dimension value of coastline increases with the length. Since 2015, the coastline has changed slightly, which is because various departments began to attach importance to the development of coastal areas and actively take measures to control the development and utilization of coastal areas and effectively protect marine resources. This awareness of coastlines being adversely impacted by multiple driving forces has accelerated our efforts to assess, monitor and mitigate coastal stressors [37]. The coastal environmental quality has been greatly improved. In recent years, the artificial exploitation of the coastal zone has been increasing, the carrying capacity of coastal area has become fragile, and the environment on which human beings depend has been challenged. Local government should attach importance to the development of coastal areas and actively take measures to control the development and utilization of coastal areas and effectively protect marine resources.