For more than a decade the multinational (Australian, French, Cambodian) Greater Angkor Project has been investigating the rise and fall of medieval urbanism at Angkor, in Cambodia, using a diverse range of techniques, including extensive use of remotely sensed imagery to find, map and analyse elements of urban form. The research activities have focussed on the role of Angkor’s elaborate water management system in the demise of the urban complex, and has recently been expanded to include nearby ‘secondary’ settlement complexes such as provincial centres and ephemeral capitals. In such a research agenda, it is crucial to gain a full understanding of the original hydrological layout of the Angkor basin, in order to provide essential insights into human modifications to the natural hydrology and topography. To this end, a number of multispectral satellite images (including QuickBird and ASTER) were processed and analysed to identify palaeo-environmental traces and anthropogenic features relevant to the identification of remnants of the original fluvial system. Vegetation indices (VI), Vegetation suppression and Principal Component Analysis (PCA) were adopted as the primary procedures in order to detect relevant traces over differing environments such as perennially forested zones, scrubland and barren terrain. The outcome of this work has been to add significant chronological resolution to the current map of Greater Angkor.