Mapping And Indexing The Urban Estuaries

Muddy estuaries have always been reclaimed to construct ports. Their morphology shows obvious urbanized characteristics which have not been studied substantially and deeply in urban morphological studies. The lack of guidance has led reclamation planning to blind and arbitrary. This paper chose 20 reclaimed muddy estuarine ports at northern hemisphere in temperate and subtropical climate zone as research objects. Google Earth image data sources with 1.42m and 2m resolution were selected for constructive and unconstructive areas respectively. According to the stability thresholds of base indices, 100-300km2 research extents and 6m×6m minimum mapping unit (MMU) were used in process of mapping urban estuaries with CAD and ArcGIS conversion tools. The characteristic morphology indices about sinuousness, broadening shape, reclamation pattern and intertidal zone were calculated and classified. The results show that intertidal zones are experiencing serious recession and civil defenses have to face the erosion of tides and the increasing risk of natural disasters in most research estuaries. The Asian urban estuaries are characterized by larger mean area and smaller number of reclaimed patches, single reclamation pattern with high recognition, fuzzy limit of reclaimed areas, as well as poor morphology stability and ecological condition on the premise of intertidal indices as ecological effect evaluation elements. The correlation analyses of indices indicate that reclamation with a single patch brings greater damage to intertidal zones than with more dispersed patches in the same scale of reclamation. While Tianjin Nanjiang Port reclamation project in Duliujian Estuary, which the single patch area is almost 6 times to the mean patch area of the other research estuaries, can be predicted to bring a hidden danger to estuarine habitats and reclaimed land inside the dikes. In order to ensure accuracy of analyses, the paper takes characteristic elements of urban estuarine morphology as standard in defining mapping resolution and extents which may become references for similar studies. The characteristic indices reflect different aspects of morphological information, among of which the reclamation pattern and intertidal zone indices may be important to express reclamation characteristics. Their correlation analyses also show preliminary confirmation of links between morphology and ecology that will be instructive to guide and assess the reclamation planning.