Water body delineation using index composition and HIS transformation

The use of satellite data for mapping water bodies is important for environmental management. Previous approaches exhibit limited applicability in southeastern China, given its complex and heterogeneous landscapes as well as the difficulty to obtain cloud-free images. To overcome these problems, we proposed an approach using index composition and HIS (hue, intensity and saturation) transformation. First, a colour image was generated using three indices: the Normalized Difference Built-up Index (NDBI), the Normalized Difference Vegetation Index (NDVI) and the Modified Normalized Difference Water Index (MNDWI). Then, HIS transformation was employed to extract water bodies and remove hill shadows. Another colour image, composed by Landsat TM (Thematic Mapper) 4, NDVI, TM1 and HIS transformation, was further applied to separate water bodies from residual shadows. This approach was tested and verified with Landsat TM images in the Tiaoxi watershed, southeastern China. The results indicated the high accuracy and promising applicability of this new approach for fragmented landscapes, given its insensitivity to seasonal and subjective factors.