Shoreline Change Analysis Of Guangxi Mainland Based On Remote Sensing From1973to2013

There are many types of coast along Guangxi mainland, such as delta-coast,drowned-valley-coast, mountainous-coast, platform-coast, etc. The shoreline typesare varied, such as rocky shoreline, muddy shoreline, biological shoreline and so on.Guangxi is an international transport channel which is beneficial to China andASEAN. It occupies an important position in economic exchanges between Chinaand Southeast Asia. Therefore, it is important to strengthen supervision andprotection of the shoreline and to conduct a long-term monitoring and analysis ofshoreline changes.In this study, images of Landsat TM, ETM+, HJ-1A CCD and two charts ofBeihai city were collected. Based on GIS (Geographic Information System) and RS(Remote Sensing) technology, we extracted shorelines in1973,1978,1990,2000and2013of Guangxi mainland. Later, the position, length, distribution of five shorelinesand the coastal area changing were analyzed. In addition, four typical coastalsegments sandy shoreline of Beihai city, biological shoreline in Pearl Bay, artificialshoreline of Fangcheng Harbor and muddy shoreline in Qinzhou Bay were chosento have a further study. Shoreline changes were analyzed from different angles for itsfeatures. The main work and results are as follows:1. This paper classified the shoreline into rocky shoreline, sandy shoreline,muddy shoreline, biological shoreline and artificial shoreline. Combined with fieldsurvey data, we made a layerstack of near-infrared, red and green band to get falsecolor images. In terms of color, texture and the adjacency relations, we establishedinterpretation signs as well as principles of5types of shoreline in Guangxi. Based onCA (Cellular Automata) model, automatic extraction of the boundary between landand water was implemented. Finally, we got the shoreline by modifying the boundary,combining principles and interpretation signs.2. A statistic of the distribution of shoreline in different time was made in termsof the length, type and land area. The study area was divided into3units: the Beihaicity, the Qinzhou city and the Fangcheng harbor city, where the shoreline changes and types changing were analyzed. The results showed that the length of shoreline inGuangxi decreased before1990and increased after1990. From1973to1990, thetrend was decreasing, it reduced19.35km with an average speed of1.14km/a. From1990to2013, it increased21.52km with an average speed of0.94km/a. After1973,the main shoreline type of the study area was muddy, as long as757.49km, which is55.03%of the total length. While in2013, it is mainly dominated by artificialshoreline with the length of919.88km,66.72%of total. Changes brought an additionto the coastal land area for about13112hm2with an average speed of327.8hm2/a. Inthe entire study period, the most dramatic changes appeared in Fangcheng harbor city,followed by Qinzhou, while Beihai was relatively the most stable. In the40years,shoreline types had a severe transformation, of which the muddy shoreline reducedthe most, and the artificial shoreline increased the most. There was a trend that naturalshoreline turned into artificial.3. Based on the final results of the analysis, the reasons of shoreline changeswere discussed from natural and human factors aspects of Guangxi, combined withrelevant information. The results showed that Guangxi mainland shoreline wasaffected by both natural factors and human factors, of which natural factors includeriver sediment into the sea, sea-level change, tectonic movement, storm surges,climate change, waves, tides and so on, and human factors including coastal miningprojects, construction of seawalls, ponds and salt ponds construction, land reclamation,etc.4. This paper took four shorelines as the research objects including sandyshoreline of Beihai city, biological shoreline in Pearl Bay, artificial shoreline ofFangcheng Harbour and muddy shoreline in Qinzhou Bay. Features and reasons ofshoreline changing in the study area were analyzed and discussed. The results showedthat: in40years, the shorelines of Beihai city presented a trend that it accretedseaward first and eroded landward later. The trend of Isobath extracted from twocharts in1986and2005is consistent with the shoreline change, with a biggestadvance about701.29m to the sea, and underwater slope steepened gradually. Due todeforestation before1990, mangrove of Pearl Harbor had continued to decline with the dwindling of biological shoreline of10.42km. But human have realized theimportance of mangrove to coastal ecological environment gradually since then. Andthe original mangrove forests were protected that both area and length of biologicalshoreline has a significant rebound. After40years of continuous expansion, artificialshoreline of Fangcheng Port has reached338.11km as large reclamation for harbor,which makes it assume absolute superiority. Fractal dimension of Qinzhou Baydropped from1.0142to1.0123for constant construction of artificial breedingfacilities, that is, the degree of shoreline complexity reduced gradually.