| 其他摘要 | Coastline is the ocean-land indicator and contains abundant environmental information. Its changes directly influences the environment and resource of tideland, which could cause many types of alternation of coastal resource and eco-processes. Since the beginning of 21st century, a new round of rapid development of Bohai Rim further bears pressure on local marine environment. Thus, it is of urgent importance to be acquainted with the current status and change of the coastline of Bohai Rim as a whole, to establish the key technical system of monitoring the change of coastline base on ecosystem, to achieve effective supervison and evaluation of areas experiencing dramatic change and to provide suggestion for coastline exploitation and protection. Base on extraction of the coastline of Bohai Rim of 2000, 2005, 2010 and 2012 by means of RS and GIS, this paper systematcally analyzes the spatial and temporal change of coastline of Bohai Rim. The main research work includes:(1) Defining the classification system of Bohai Rim coastline according to coast material composition, coast function zoing and development model. Indicators for each coastline type and rules for visual interpretation are established based on landsat-7 ETM+ and HJ CCD imageries;(2) In the light of the difficulties during extraction of natural coastline with satellite data, proposing a new method based on Airborne LiDAR Data and Tidal Estimation. By employing this method, instantaneous water edge is firstly extracted from ortho-rectified images acquired by airborne LiDAR system. Coastline of study area is estimated through tidal data, by utilizing inter-conversion model of elevation system and DEM retrieved by airborne LiDAR system. Compared with “908 coastline”, the RMSE of 3 types of natural coastline (sandy coastline, rocky coastline and silty coastline) extracted in this paper is 1.7m, 5.2m and 32.5m, individually. Results show that the method established in this paper is efficient and capable of extracting sandy coastline and rocky coastline, without the need of field mapping; Based on the estimated coastline, the interpreted Bohai Rim coastline is verified and the average RMSE of rocky coastline and sandy coastline is within one pixel width of satellite image. However, the accuracy of silty coastline is 70.5m, which is relatively unsatisfactory;(3) Systematically analyzing the spatial-temporal distribution of Bohai Rim coastline of 2000, 2005, 2010 and 2012. From long to short, the length of coastline of 3 coastal provinces and 1 city is Liaoning province, Shandong province, Hebei province and Tianjin City; Among the three bays, Liaodong Bay’s coastline is the longest, followed by Bohai Bay and Laizhou Bay. As to all the coastline types, the breeding coastline is always the longest during the whole period and estuary coastline is the shortest. Liaoning Province possesses most Rocky coastline and sandy coastline. Silty coastline distributed mainly in Liaoning Province in 2000 and 2005, but in 2010 and 2012 it is mainly occupied by Shandong Province; Liaoning Province possesses most of saline coastline and the percentage is keeping increasing. Breeding coastline spreads mainly in Liaoning and Shandong Province, while harbor coastline distribute mainly in Hebei Province and Tianjin City; (4) Counting the change of Bohai Rim coastline and analyzing the change regulation based on its distribution. Bohai Rim coastline kept lengthening in 12 years from 3128.8km in 2000 to 3627.5km in 2012, with average speed of 41.6km/a. In each time scale, the speed of increase is highest during 2010 to 2012, with average speed of 108.3km/a. Natural coastline kept shortening and to the contrary, anthropogenic coastline is lengthening during 12 years. Bohai Rim coastline is entirely advancing towards the sea and significant withdrawing happens in Yellow River Estuary. Net accretion of Bohai Rim coastal land area caused by change of coastline is 2126.83 km2，with average speed of 177.24 km2/a. Changes of coastline types include transformations from natural coastline to anthropogenic coastline and from breeding and saline coastline to harbor and construction coastline. (5) Based on systematical analysis of the change status of Bohai RIM coastline since 21st century，summarizing change reasons from the aspect of natural and anthropogenic factors. Thereinto, natural factors include change of river course, water and sediment variation, waves, tides and storm surges; anthropogenic factors consists of construction and extension of aquaculture ponds, saline, port, habor and Urbanization. Finally, pointing at the causes mentioned above, this paper provides relevant suggestions and strategies for Bohai Rim coastline management. |
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