| Taiwan Island is the largest island of China, it is the center of the western Pacific waterways, and it is also an important transportation hub and important strategic area in the sea links between China and other countries of the Asia-Pacific region. In recent years, to meet the needs of achieving social and economic development in Taiwan, the human activities of the Taiwan coast is frequent. A lot of large-scale and intense development activities of the coastal areas caused a dramatic change to the coastline morphogenesis, the change of the coastline will cause the corresponding change to the coastal ecological environment, thus affecting the coordinated development of the coastal economic and the survival residents along the coast. Therefore, to carry out the related research about the analysis of the Taiwan island coastline evolution characteristics is urgently needed.In this paper, we take a series of Landsat images in the year of 1981?1991?2001 and 2013 and the GF-1 satellite data in 2015 as the main source of data, and take the topographic map, sea chart, historical data and the SPOT-5 satellite images in 2005 for the secondary data to establish the classification system of Taiwan island coastline. And put forward four computer methods for extracting the coastline based on the image processing; Extract 4 coastlines of the Taiwan island from 1981 to 2015; Carry out the coastline evolution characteristics and driving force analysis based on the coastline information extraction results. The main work and achievements in this paper are as follows:1. Based on literature data and situation in Taiwan, this paper established a classification system for the shoreline of the two sides of Taiwan Strait. The classification system includes two categories which are natural shoreline and artificial shoreline. The natural shoreline have 5 kinds shoreline which include rocky shore line, sandy shoreline, muddy coastline, estuary shoreline and biological shoreline. Artificial shoreline has 4 types of shoreline. These are anthropogenic shoreline, saline shoreline, harbor and construction shoreline. Based on the classification system and the characteristics of shoreline in remote sensing image which including features adjacency relationship such as location, color and texture. this paper build up the Taiwan Island coastline remote sensing interpretation symbol.2. This paper proposed the method of computer extract bedrock shoreline, sandy shoreline, muddy shoreline, biological shoreline and artificial coastline. It was based on image processing. The accuracy is verified by experiment. The results show that the extraction method of 4 shoreline precision is better than 1 pixels. Bedrock shoreline offset distance is 17m, and its RMSE is 23m. Muddy shoreline offset distance is 19m, and its REMS is 10m. Biological shoreline offset distance is 19m, and its REMS is 23m. Artificial shoreline offset distance is 21m, and its REMS is 30m.3. Systematically analyzing changes of the past 35 years Taiwan Island coastline from the coastal line type, length, distribution characteristics and change of erosion and deposition area, the results show that:For 35 years, Taiwan island coastline length in 2001 as the time node show the overall trend of first increase and then decrease, of which 1981 Taiwan island coastline with a total length of 1370.84 km, total length of the coastline of 1569.08 km by 2O15.There is a net growth in total length of 198.24km of the coastline of the Taiwan island for 35 years, the annual growth rate of 5.66km/a, of which natural coastline reduce 262.77km and the reduction rate of 7.51 km/a, artificial coastline increase 461.02km and the growth rate of 13.17km/a; as far as the natural coastline, muddy coastline change is most dramatic, for a total reduction of 171.53km, the annual rate of change for the 4.9km/a.As far as Taiwan island coastal 17 cities (counties), the longest and shortest coastline distribute in Taitung County and Keelung City,respectively.The other coastline of Taiwan Island mainly concentrated in Hualien County, Pingtung County and Taipei County. It is Yunlin County which coastline changes is most violent in Taiwan Island for 35 years.The coast of the island was sustained expansion trend during 1981 to 2015, The island coast net expansion area is 15876.77hm for 35 years, with coastal erosion area of 1741.71 hm2 and coast expansion area of 17618.48 hm2. The average annual rate of coastal erosion and dilation of the island were 49.76hm2/a and 503.39hm2/a for 35 years, with net expansion rate of 453.62 hm2/a. In the three time periods of 1981 to 1991,1991 to 2001 and 2001 to 2015,the silt and erosion of island coast mainly occurred in the West Bank of Taiwan, the change in the Coastal Erosion silting situation is most intense especially in Tainan County, Yunlin County, Taichung County, Changhua County and Taichung County for 35 years.4. Coastline length of Taiwan Strait overall showed a rising trend in 1981 to 2013, The total length of the coastline increased 65.48 km from 1981 to 2013, with the average speed of 1.98 km/a;and the shorelines of Fu Jian reduced 109.27km, the west part of Tai Wan's shoreline incresased 174.74km sheerly;Strait coastal area overall upward trend in 33 years, the land area expended 512.77 hm2 during 1981 to 2013 and with annual expand rate of 15.54 hm2/a; The tremendous change of Taiwan Strait coastline was caused by human activities, however, at the same period the factors of coastline transformation are different.5. Coastline of Taiwan Island was affected by natural and anthropogenic factors, thereinto, natural factors include Sea-level change, river sediment into the sea, storm surge, the terrain changes, waves and tides etc; anthropogenic factors consists of sand mining, coastal barrier, port and pier, construction and extension of aquaculture ponds and saline, the urban construction, urbanization. |
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