GIS-based Evaluation On Suitability Of Constructive Land In The New Urban Area Of Pukou, Nanjing

With the rapid development of urbanization, many cities are faced with such problems as urban spread and the reconstruction of old city. The former urban planning does not place enough importance on the natural attributes in the suitability evaluation of constructive land, which leads to some security accidents of constructions and also causes a great many heavy losses of people's life and the property. Meanwhile, there has not formed a integrity theory and method system to direct the suitability evaluation of constructive land; the primarily evaluation method is also qualitative evaluation, the quantitative evaluation is just in the starts stage; The union of appraisal process and the GIS is not close ,and the database construction is still imperfect.Integrating the experimental project of Evaluation on Suitability of Constructive Land in the New Urban Area of Pukou, Nanjing, this article comprehensively analyzes the achievements and main problems in the theories,methods,practice of the domestic and foreign suitability evaluation of constructive land; studies its appraisal method system, the selection of influence factors, the quota standard, establish the spatial database and the attribute database under MAPGIS, carry on DTM and the spatial analysis, determine the influencing factors'weight with the Analytic Hierarchy Process, calculates the suitability value with the space weighted-stack method. This research could enrich the theory and the method system of the suitability evaluation of constructive land, and also provide the advantageous model and the reference for the similar construction land.The conclusions of this study are as follows:1. This article try to evaluate the suitability of constructive land in the new urban area of Pukou, Nanjing based on GIS. In fact this process is a multi-disciplinary research which integrate Geology, Landform, Hydrology and some other disciplines and is helpful in the information expression. Simultaneously it is also a mutually affect and feedback process of the qualitative and the quota analysis. The qualitative and the quota analysis can not only complete different kinds of geographical environment analysis, instruct the urban construction, but also provide more auxiliary decision information for the city.2. This article uses the construction suitable levels—construction limits to evaluate. According to an appraisal result, the construction land can be divided into four levels: the suitable construction land, the possible construction land, unsuitable construction land, impossible construction land. There isn't impossible construction land in the evaluation area—under the nowadays technology and the current economic condition it can be used for urban construction when changing the limiting factors. The area of the suitable construction land is the smallest one, moreover even if the suitable construction land, it also has some own limits at the engineering construction. This indicates that with the urban city expansion and certain limits, the construction land whose natural condition is good and limiting factors are few remains not so much. But the area of possible construction land is quite large, this kind of land may carry on the construction through the reasonable measures and the improvements.3. The suitable construction land is mainly located at the west of Yanshan Road, around the Puwu Road, in low mountain and topography districts. These districts do not have earthquake liquefies, and have the convenience traffic conditions, could not be affected by flood, also the ground foundation is good, the supporting capacity is high, the terrain slope is suitable. The possible construction land is located at the west of Puzhu Road and within the radius of influence scope of secondary road. Being influenced by terrain slope and underground water, the evaluation value of this type is lower. But it can be utilized after slight renovation. Unsuitable construction land lies on the east of Puzhu Road. Such disadvantage factors as low ground supporting capacity,the existence of earthquake liquefies,likely being submerged by the flood make the value of this kind low.4. The suitability of constructive land is influenced by a good many factors. It is necessary to collect as many factors as we can to choose the main factors for determining comprehensive effect.5. For being systematic, logic, usable and succinct, the applications of Analytic Hierarchy Process are widespread, particularly in deciding the factors'weight. Analytic Hierarchy Process can also be used to make the scientific decision of quite complex, the fuzzy question.6. This article applies space-weighted-stack method of vector data to evaluate the suitability of construction land. Compared with the grid data model, there is not so many data to deal with for vector data model. Moreover, it has avoided the division of evaluation region; it can also show the terrain units, the roads, the boundary of rivers and so on. As a whole, the vector data model can reflect the natural characteristic of evaluation region more accurately.7. MAPGIS, as a widespread used GIS platform, has a good many advantages in the construction of spatial database,attribute database and the inquiry of data. Simultaneously its spatial analysis function is quite perfect. It can also provide DTM analysis module,Buffer analysis module to create the drawing of the ground gradient, gradient direction,the influence scope of roads .