Mapping Changes of Surface Topography under Urbanization Process in Ho Chi Minh City, Vietnam, Using Satellite Imagery

Urbanization is indispensable for the development of humanity. The changes from the urbanization process have a significant impact on other components of natural systems in Ho Chi Minh City. The problem of filling low-lying swamps, ponds, lakes as well as canal encroachment has made ​​significant changes to the shape of the surface topography of the city and particularly affected the current flood situation around the city. The objective of the study was to map changes in surface topography in relation to urbanization process in central part of Ho Chi Minh city during the period 1989- 2011. Band ratio method and Maximum Likelihood classification were implemented to separate the objects of urban and low-lying swamp from 3 satellite images in 1989, 2003 and 2011. The change detection has been done by post-classification method combined with GIS and field data to detect changes in the disappearance of low-lying swamps as well as the existence of urban areas on it. Classification process has resulted in an overall accuracy greater than 89% with urban area increased to a half of the entire area within 22 years. Meanwhile the area of ​​low-lying swamps reduced almost 5 times compared to the existing area in ​​the early stage. Research has built spatial maps of the current status and changing as well as carried out the analysis and evaluation to affect flooding in the city. This is a proof of the lack of scientific methods in the urban management and the positive transformation to reduce flooding today is needed.