| The evolution tendency of Abandoned Yellow River Delta is one of the hot spots on the field of delta erosion and protection in China. The study of it’s evolution tendency, not only help us to protect the Abandoned Yellow River Delta, but also understand the evolution tendency of other delta region, especially for the Modern Yellow River Delta. The Abandoned Yellow River Delta has become one of the most serious coastal erosion areas since 1855. Based on the coastal erosion vulnerability map, the likely eroded area could be identified. The map is useful in protecting, developing and managing the resources in the study area.Based on the multi-temporal remote sensed satellite images, regional topographic maps, annual measurement data and historical recordation, the Abandoned Yellow River Delta coastal evolution tendency was studied by geographic information system technology and the digital shoreline analysis system. Shoreline change rate, depth contours change rate, coastal slope, subaqueous slope, sedimentary dynamic environment, suspended sediment concentration, mean high tidal height, utilization of coastal types and coastal development suitability have been used as the evaluation index to assess the coastal erosion hazard and vulnerability level. In addition, analytic hierarchy process (AHP) has been used to calculate the weights of each evaluation index. At last, the coastal vulnerability index (CVI) has been used to map the relative vulnerability along the study area.The results are:(1) The evolution of the Abandoned Yellow River Delta could be divided into five main stages:pro-development period, slow development period, fast development period, sandbars merging land adjustment period and decrease erosion period.(2) The erosion characteristics of the Abandoned Yellow River Delta are as follows: ① Shoreline erosion rate is decreasing year by year, from a few hundred meters per year to a few meters-tens of meters a year in the past 160 years; ② Current coastline has been basically stopped from retreating by coast protection engineering, but the submarine coast slope keeps eroding. The underwater delta has almost been eroded away;③Different area suffered different erosion rates because of the different topography. The Abandoned Yellow River estuary to Biandan port segment suffered the most serious erosion.(3) SB3 and SB4 section which are nearby the Abandoned Yellow River estuary suffered serious erosion. The submarine coast slope retreat fast. Section in the west of the Zhongshan River estuary fluctuated considerably, with deep scour channel. The change of the SB2 section, which is in the east of Zhongshan River estuary submarine coast, is not obvious. The SB2 section appears erosion characteristic in summer, and depositing in winter. Yet in the south, SB5 and SB6 appear deposition characteristic in shallow area, erosion in deep area.(4) A good method was put forward to predict the shoreline change based on the grey model GM(1,1). The result showed that the shoreline prediction based on the grey model GM(1,1) was reasonable and reliable when corrected by using the dam line. The prediction accuracy is poor in the place of Estuary and the area where have just suffered dam break disaster. The result also showed that about one third shoreline will be next to the dam line in Abandoned Yellow River Delta in 2025.(5) The coastal erosion vulnerability assessment results show the Abandoned Yellow River Delta appears a high vulnerability. The vicinity of the Abandoned Yellow River estuary, Zhendong River estuary to Biandan port and Zhongshan River estuary to Xinsheng port section appears very high vulnerability. High vulnerability was mainly caused by the absolute losing of sediment supply. The sea-level rise caused the coastal erosion be more serious. Human activities, such as tidal flat reclamation and revetment engineering, are becoming the more and more mainly factor for the Abandoned Yellow River Delta coastal erosion vulnerability distribution. |
PDF Full Text Request