Evolution of the openings to the sea

The first stage of this process consisted in studying  the map of Hong Duc, dated 1490. Although the representation of the local landscape is schematic, the handwritten information on the map indicates the name of the regional districts, and shows that five rivers used to wind through the region, and that no lagoon could be found in the region of what is today known as Huế.  This first map raises the question of the evolution of the landscape over time ;  Indeed, the coastal lagoons, which are now a characteristic feature  of the Thừa Thiên – Huế province do not seem to have existed in the remote past, which raises the question of the historical dimension of the coastal lagoons.

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The research can be refined by comparing the maps with the Annals and other Chinese-Vietnamese texts, which, for example, report changes in the locations of the accesses to the sea. For example, the mouth of the Huế river, or Perfume river, is to be found in different locations over the centuries (to Hoà Duân, or Hoà Quan, later called Thuận An, and to Thai Duong Ha).

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An examination of historical records written in Chinese-Vietnamese enables us to gain a better understanding of the evolution of each channel. Thus, the so called “Thuan An” channel opened in 1404, closed in 1467 and re-opened in 1504 … closed again … and finally reopened in 1740, before being permanently closed in the wake of a tsunami in 1897. There is some confusion as to the names given to those channels. Indeed, the channel that opened in 1897 – which still exists today- bears the same name as that of the Thuan An estuary, even though it is formally located in the village of Thai Duong Ha. And the Thai Duong Ha channel opened in 1467, closed in 1504, eventually reopened, qo that it has become the main opening onto the sea since 1897.

The maps make it possible to see how the landscape has changed, as well as to understand how swift the shift in the openings to the sea could occur, causing significant changes in the communication channels.

For example, a French map dated 1883 shows all the fortifications that protected the Thuan An channel (opened between 1740 and 1897). In 1882, Emperor Tự Đức reinforced the Thuận An forts – which defended the entrance to the Huế river. Aerial photographs taken in 1952 indicate that this channel was closed off and that two channels were opened further north.

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