关键词: 海平面上升, 危害性评估, 地理信息系统, 海岸带管理, 渤海海滨平原

Abstract: This paper deals in a quantitative way with the vulnerability assesment of the coastal plain west of Bohai Sea to sea level rise. The study area is covered by the Tianjin imigery sheet (Plate I). It includes mainly the Tianjin coastal plain, which makes up the most part of the Tianjin municipality, and part of the coastal plain in Hebei and Shandong provinces.The assesement is carried out according to the common methodology and guidelines developed by IPCC Coastal Zone Management Subgroup and mainly by using landsat imagery and geographical information system (GIS) The emphasis of the present research is put on compilation of an environmental-topographic map (Plate I). This kind of map is most useful for a low-lying coastal plain like the study area, because most of its landform have been intensely modified for a long time by human economic activities and the area has been developed for different types of land uses for the agricultural, acquacultural and industrial purposes. The conventional geomorphological and Quaternary maps are not enough to meet the requirements for the vulnerability assesment. They can only remain as supple mentary maps.The environmental-topographic map contains various landuse types and the information on coastal dynamics (erosion and deposition)identified by processing the recent Landsat TM data and by necessary field checking. It also involves contour lines with an interval of lm and sometimes the main trafic arteries. The function of this kind of map includes : 1. It can show the land area and the area of different landuse types not only in general. but also for the zones between the contour lines with 1m interval which can be used to estimate the area that will be lost (inundated or flooded) if is not protected by dykes during future sea level rise (Table 1). For example. the total area to be lost during 1 meter sea levei rise in the study area will amount to 11 821 km2. In case where the elevation boundry of the presumed sea level rise is not a round number it can be delineated on the map by computer-aided interpolation (Fig. 2).2. It can show the economic impact of sea level rise at different elevation in the study area by compiling a special kind of diagram based on the data from the map in case this area is not protected (Fig. 3) 3. If the study area is protected by newly built dykes. this inap can help to predict the adverse environmental impact behind the dykes, for example, to delineate the area of those landuse types such as puddy. irragated land, fresh water reservoir on the plain, which will be easily affected by salt water inland intrusion along coastal rivers or acquifers. Besides. it is necessary to delineate the city/town area where the foundations of infrastructures, industrial facilities and buildings will be decayed by the intruded salt water as well. For this purpose, some kinds of additional map at the same or smaller scales can be compiled to compare with or to overlay the environmental-topographic map to avoid the overload of the later. For example, the map of land subsidence caused by tectonic movements and especially by groundwater overpumping (Fig. 4) is a very important supplementary one. This map, while overlaid with the environmental-topographic map. can demonstrate the areas where the abovementioned adverse environmental impact is most likely to occur (Plate Ⅱ. Photo 1 and 2) . Furthermore, this map also can show the rate of regional relative land subsidence,which is actually the relative sea level rise on the background of global sea level rise. This is more essential than knowing only the rate of global sea level rise in the vulnerability assesment of coastal low-lying plain and in prediction of environmental impact of sea level rise. For example. on the Tianjin coastal plain the land settlement caused by exceeded groundwater extraction since 1950s has produced three"subsidence bowls"in the Tianjin downtown area, the harbor town Tanggu and the coastal industrial town Hangu with an average subsidence rate more than 50mm/a in the period 1983-1988. As a res 

Key words: sea level rise, vulnerability assesment, GIS, coastal zone management.Bohai Sea coastal plain