OBSERVATION OF RIPARIAN VEGETATION IN WESTERN NAMIBIA BY USING NDVI AND NDWI DERIVED FROM SPOT-VEGETATION

Abstract

Ephemeral rivers in western Namibia are unique entities that support both natural vegetation and human activities. This paper presents an approach for observing riparian vegetation along them synoptically using remotely sensed datasets, derived from a satellite borne sensor named SPOT-VEGETATION. The most commonly used vegetation index, the Normalized Difference Vegetation Index (NDVI), certainly delineates the overall distribution of vegetation, but not without errors. A vegetation index that was designed as a supplement for NDVI, the Normalized Difference Water Index (NDWI), showed some inter- esting features, but again, with faults. By synthesizing the two indices, the scarce and sparse vegetation in coastal deserts and the relatively dense vegetation in inland highlands could be effi ciently observed. Furthermore, by introducing a fl ow accumulation model produced from a digital elevation model (DEM), it became possible to observe such riparian vegetation quantitatively and systematically.