The Study Of Coastal Geomorphic Evolution At Laizhou Southern Bay Based On RS And GIS Over The Past Three Decades

The southern coast of Laizhou Bay lies in the binding site of Shandong Peninsula blue economic zone and the Yellow River Delta efficient ecological economic region, which is rich in natural resources, with high population density, and developed marine economy. With the rapid economic development especially in the last 30 years, the coastal landscape environment has gone through a significant change influenced by human activities.Based on the study of changes in coastal landform in the southern Laizhou bay, adopting four periods of remote sensing images,two periods of charts and other relevant data, this paper enhances and extracts the thematic information of coastal geomorphic through the establishment of remote sensing image interpretation signs and using the method of visual interpretation and computer interpretation combined. Moreover, supported by GIS, the paper will analysize the extracted coastal geomorphic information and establishes the geo-information of the southern Laizhou bay coastal geomorphic changes from 1979 to 2008. It further reveals the changing regularities of the landscape environment in the respect of time and space, and discusses the driving mechanism of the changes from the respective of nature and human activities. The major conclusions are listed below:(1)Changes of geomorphic types and structureThe main changes of geomorphic types in the southern Laizhou bay from 1979 to 1989 manifest in a way of decreases in natural geomorphic types, including seas, beaches, marine plains, alluvial plains, alluvial and marine plains, and increases in human landscapes of ponds, salt pans and buildings. Changes from 1989 to 2001 show the continuous decrease of beaches, marine plains, alluvial and marine plains, alluvial plains and increase of seas, building, salt pans and ponds. The variations from 2001 to 2008 behave a decrease of beaches, marine plains, alluvial plains, the alluvial and marine plains and ponds and an increase in seas, salt pans and buildings. As can be inferred from the above, the landscape of this area shows a rapid increase in human geomorphic types and a rapid decrease of natural geomorphic types.(2)Analysis of the geomorphic type transformationAs the main geomorphic types of human activities, ponds mainly transforms from marine plains, alluvial and marine plains and beaches, and salt pans converted from alluvial plains, marine plains and alluvial and marine plains, with ponds and salt pans are interchangeable. Besides, buildings are transformed from alluvial plains. Beaches, as a main natural geomorphic type, mainly convert into seas and secondly transformed to ponds, which correlates with tide level error. In addition, marine plains and alluvial and marine plains transform into ponds and salt pans, alluvial plain mainly transform to buildings.(3) Study on the Evolution of geomorphology erosion and depositionFrom 1979 to 1989, less affected by human activities, the southern Laizhou bay was shaped mainly by deposition, with its average net area increasing by 2.33 km~2 annually. While in the years from 1989 to 2001, the speed of deposition slowed down because of the intensity of human activities, with the average net area increasing by 0.99 km~2 annually. From 2001 to 2008, the increase of the erosion area exceeded that of the deposition area, with 84.85 km~2 in total, and the average 12.12 km~2 annually. It is suggested that the geomorphology erosion dominated in the southern Laizhou bay during 2001 to 2008, with a remarkable faster speed.(4) Information Analysis of Coastline ChangesAccording to the different types of coastline, extending to the sea or being steady or going backward, the studied coast can be divided into three categories. The both sides of Xiao Qing River and the right side of Bai Lang River goes to the same category, all first going backward then extending to the sea; The left side of Bai Lang River, the area between Yu River and Di River and the both sides of Wei River belong to the same category, going backward, turning steady and then going backward again; The right side of Jiao River is another distinct category, in the way of going backward, being steady and then extending to the sea. In accordance with its changes in length in different intervals, the coastline of the study area can be classified into three types. The left side of Xiao Qing River, the both sides of Bai Lang River, the area between Yu River and Di River and the left side of Wei River were of the same category, the length of whose coastlines decreased before increasing. Almost all the sections mentioned above reached to the minimum length in 1979, except the left side of Xiao Qing River in 2001, and the left side of We River in 1989. The right side of both Xiao Qing River and Jiao Lai River behave the same, the length of whose coastlines decreased, then increased, and at last decreased, reaching to the minimum in 1979. The right side of Wei River was a separate type, the coastline length of which changed frequently, decreased, then increased, then decreased and increased again.(5) Factors influencing the evolution of the landscapes Complicated factors are affecting the southern Laizhou bay, involving both natural elements as geological structures and marine dynamics, and human activities as coastal project, exploitment of salt pans, pools, and groud water resourcs.