Ecological interactions of natural processes and new urban form : a landscape ecological analysis fo the change of urban and natural patterns in eastern-Taipei metropolitan fringes

Abstract

The ecological effect of urban form has been an important issue in 20" century planning history. The inadequate relationships between development patterns of modern cities and their natural surroundings had been discussed in Geddes's Cities in Evolution, McHarg's Design with Nature, Lynch's Good City Form, Forman's "ecologically optimum spatial form" in Land Mosaics, and Mitchell's "fine-grain urban pattern" in City of Bits and Etopia (Geddes, 1915; Lynch, 1961, 1981; McHarg, 1969; Forman, 1995; Mitchell, 1995, 1999). However, these normative theories have almost never been tested by empirical studies and quantitative analysis. The thesis is about ecological effects of a twenty-year period urbanization in the fringe area of eastern Taipei metropolis. Using the technology of GIS and the principles of landscape ecology, some quantitative and spatial analyses are applied here to verify the complicated non-linear relationship between city form, forest patch shape and hydrological effects in the case study of eastern Taipei. Some landscape ecological indices like forest patch numbers, corridor connectivity, compactness of city form, landscape fragmentation and landscape heterogeneity are measured across different spatial scales and over twenty years period. Some correlations between the landscape indices and the hydrological change are verified. The following are the main findings of the study: 1. The empirical study provides an operational approach to large-scale metropolitan spatial analysis. The integration of GIS technologies and landscape ecological analysis shows the potential for the future development of a GIS based ecological design and planning tool. 2. A holistic framework is proposed for the purpose of integrating consideration of urban development, landscape change and hydrological processes. The evidence shows that there exist some correlations among the three processes. 3. Some landscape ecological indices are highly correlated with hydrological effects, including the number of 10 hectare or larger forest patches, the compactness index K and the fractal dimension D of city form, and the evenness index E of the landscape heterogeneity. 4. The data show a 10 year "time lag" phenomenon between urban development and hydrological effect in eastern Taipei. The differences of the runoff effect between 1980s and 1990s support the hypothesis that there exists a threshold point or limitation of the natural system. When the magnitude of urban development goes beyond that limitation, the original hydrological system became "irreversible" or "less reversible". 5. The evidence of the threshold point indicates that the strategic timing point and spatial points could become the basis for design and planning intervention. Using scenarios planning procedure, a sustainable urban environment could be achieved gradually by applying landscape ecological principles.