Spatial Configurations of Water Management at an Early Angkorian Capital – Combining GPR and TerraSAR‐X Data to Complement an Archaeological Map

Abstract

Hariharalaya was a medieval political centre of the eighth-ninth century CE, located on the northern shore of Lake Tonle Sap in Cambodia. Mapped in detail in the 1990s by means of aerial photographs and ground surveys, more recently ground-penetrating radar (GPR) and high-resolution satellite synthetic aperture radar (SAR) were applied to further interpret this complex archaeological landscape. In combination with remote sensing imagery, the two radiofrequencybased imaging techniques were used to complement the existing archaeological maps. The area housed an extensive low-density urban complex of earthen mounds and ponds, approximately 5 × 5 km square and centring on the Bakong, an early Angkorian state temple, crossed and encircled by a mostly disconnected water-management network of embankments and canals. Extensive GPR surveys, conducted predominantly on the existing small roads and paths criss-crossing the landscape, appraise the visible archaeological features with subsurface information. The analysis verifies the existence of channels and embankments, complementing the information with depth and width. The identification of additional, now desiccated, canals and river channels assisted in connecting a number of already mapped archaeological features, and helped to distinguish possible later additions, thereby untangling the water-management network. Spotlight TerrSAR-X satellite data together with satellite images of the visual spectrum complemented the analysis, by providing information about water saturation in areas inaccessible to ground surveys, marking out palaeochannels and providing clues about the landscape before development took place. This three-dimensional interpretation informs on the functioning of this particular early Angkorian hydraulic system, adding to the understanding of water management in medieval Southeast Asia.

Using ground penetrating radar to understand the failure of the Koh Ker Reservoir, Northern Cambodia

“…Similarly, geophysics has largely been used in Cambodian archaeology to directly detect archaeological material (Sonnemann & Chhay, ; Sonnemann et al, 2015). Where GPR has been previously used in studies of water management features (Sonnemann, ) it has not been used to understand the engineering aspects of design. Given the centrality of water management to Angkorian archaeology (i.e., Fletcher, Pottier, Evans, & Kummu, ), we expect the use of geophysical methods to understand detailed aspects of the design of such features to have considerable application in the future.…”

“…Geophysical survey has rarely been used for archaeological investigations in Cambodia, with the principal focus of published studies being the mapping of large‐scale monumental structures (Sonnemann, ; Sonnemann, O'Reilly, Chhay, Pottier, & Fletcher, ) or pottery kilns (Sonnemann & Chhay, ). Nonetheless, this approach has great potential to contribute to archaeological studies in the region because of its ability to provide rapid, noninvasive assessments of the subsurface over large areas (e.g., Donati et al, ).…”

Mapping Indigenous Settlement Topography in the Caribbean Using Drones

“…Drone photogrammetry can fill the void for mapping surveys in a local perspective. The tradition to utilize aerial imagery in archaeology is nearly as old as the first flight trials, and satellite and aerial platforms with active and passive sensors that reach into frequencies outside the visible electromagnetic spectrum have also been embraced in archaeology (e.g., hyperspectral [37], or SAR (synthetic aperture radar) [38,39]). While here, using only the visible spectrum, the particular advantages of drones in archaeology are their simple operability [40]: flights can be set up anytime and anywhere, can be frequently repeated, and image resolution is only dependent on flight height or distance to the target [41].…”

An opinion on issues for future investigation of the water management of Greater Angkor

“…The construction of Angkor Thom drastically altered the operation of the West Baray by closing off its eastern exit channel. The eastern exit of the East Baray was blocked by a substantial barrier wall (Fletcher, Pottier, & Johnson, 2008, p. 234) and the east exit of the Indratataka is filled in (Sonnemann, 2015, p. 7), when we do not, as yet, know. In addition, the Jayatataka does not now have a visible eastern exit canal, which was a feature of the three previous baray , but instead has an outlet toward the western end of its south bank.…”