The Tawai Association is restricted to the Tawai Plateau, which occurs at about 420 m on the Tawai Range south of Telupid. The plateau is bordered to the south and west by low minor peaks of the Tawai Range and on the northeast by the major peaks and ridges. It is level to gently sloping and apart form the perimeter, much of it is swampy. Its surface is formed of ironstone and alluvium derived from ultrabasic rocks.
Minor streams which drain the swamps have carved trench-like valleys with narrow terraces. The Meliau River drains the northern part and descends by a spectacular waterfall over the sheer northern edge. The major part, however, is drained in an easterly direction by the Tangkulap River.
There are severe limitations of soil depth, stoniness and drainage in the Tawai Association so that the land is of no agricultural value.