Shepperton has a long boundary with the River Thames in its southernmost salient, which almost surrounds Spelthorne. Old Shepperton is almost surrounded by the extreme southern meander within this. Prehistoric glacial retreat north of this has made the north bank almost flat for a considerable distance and as such, elevation never exceeds 14 m above mean sea level (on the border of Laleham). The river never exceeds 11.5 m, (beside Dumsey Meadow and under Chertsey Bridge). The lowest elevation is 9 m in flood meadows at the confluence of the Ash with the Thames. The Ash is the border with Littleton and Sunbury-on-Thames (mostly, to the northeast, with its technical hamlet, Upper Halliford).