The landforms would be the islands in the River Thames, its meanders, the floodplains that are mostly located on the islands, The Thames Valley, the Thames Estuary, and the Thames Gateway. Though these might not be the landforms you have in mind, these are all called river landforms.
They were all formed by the natural process of erosion, transportation, and deposition. Most of the formations are formed by this together with the movement of the river and the changing of its course over the period of time.
