It is here that the adjacent River Kwai Noi – the southern tributary of the Kwai – afforded the Japanese a shortcut through to the next valley, which runs diagonally north all the way to Moulmein on the Indian Ocean coast of Burma. By following this river to its source high in the Tenneserim hills on its northern bank, the Japanese could minimise the number of large bridges it needed to build, and work on the relatively flat gradient in its floodplains. Nevertheless, as here, some points proved challenging as the river pushed up against the hills, as we will soon see.
In the 1980s, as part of its nation-building efforts, the Thai government decided to Dam the Kwai Noi river, creating a reservoir in the valley through which this railway ran, and destroying the possibility that the full railway would be restored and linked again to Burma’s rail network at Moulmein. The area around the reservoirs were designated as national parks by the King, and remain some of Thailand’s most untouched and biodiverse areas.