Historical sites’ accessibility to water
As mentioned above, precise georeferencing makes it possible to conduct a thorough analysis of the spatial dynamics in the region.
Other types of information can be obtained through statistical calculations. These calculations are derived from a specific spatial analysis technique. The field data are combined together to allow for a comparative analysis of water accessibility from the ancient times until today. This provides new insight into complex phenomena, such as lifestyles and exchange systems.
A statistical analysis of the water accessibility of the ancient Cham sites yields a median value of approximately 400 meters; this implies that a distinction should be made between two functions of the Cham sites, a distinction based on a distance to water of more or less than 400 meters.
The Cham sites located less than 400 meters from a river are primarily the citadels, which were all built directly on a river. We know of five Cham citadels in the region, three in the Quảng Trị province and two in the Thừa Thiên – Huế province. In the north, the northern access was guarded by the citadel of Co Luy (Thanh Co Luy) on the banks of the river Hien Luong, which probably dates back to the tenth century. The central plain, situated on the winding Thach Han River, was guarded by the citadels of Thuan Chau (Thanh Thuan Châu, also called Ve Nghia, after thr name of the modern village closest to it) and of Co Thanh. In the South, Thanh Loi guarded the south bank of the Perfume River; and Hoa Chau guarded what was probably an opening to the sea, possibly situated near the channel of Thai Duong Ha.
The function of each ancient Cham citadel seems to have been structured around the role of water. The Thanh Loi Citadel in the Thừa Thiên – Huế province dates back to the 8th century. It was built on the banks of the Perfume River, and its role seems to have been to protect the local population. In the tenth century, the purpose of the Cham citadels seems to have been to safeguard the access to the sea. Thus, in the Quảng Trị province,
the Co Luy Citadel stands along the Hien Luong river (also called the Hoi / Luong Minh / Ben Hai river) which runs into the sea at the Viet river mouth ((cua viet));
the Thuan Chau Citadel is situated on a secondary network of the Thach Han River (also called Cai river or Quảng Trị river ) which flows into the sea at the Tung river mouth (cua Tung);
the Co Thanh Citadel, which was destroyed as a result of changes in the course of Thach Han River, seems to have had the role of guarding the river leading to the Thừa Thiên – Huế province.
Unlike the Nguyễn citadels, none of the Cham citadels seems to have been built to safeguard the access to the highlands.