Topography and geology Much of the town is built on gravel "islands" that rise above the low-lying floodplains of the Thames and Colne. These gravel deposits have a typical maximum elevation of above ordnance datum (AOD) and are as little as above the surrounding floodplain. Staines High Street, oriented northeast to southwest, runs across one of these islands to the site of the medieval bridge and was the nucleus of the Roman town. St Mary's Church, on "Binbury island" to the northwest of the centre, is thought to have been the focus of settlement activity in the late-Saxon period. Elevations below AOD were liable to flooding until the early 19th century and many areas of gravel are covered by muddy silts and sands. There are brickearth deposits to the east of the town, along the A30, and outcrops of alluvium to the north and south.
Topography and geology Muc,h of the town is built on gravel "islands" that rise above the low-lying floodplains of the Thames and Colne. These gravel deposits have a typical maximum elevation of above ordnance datum (AOD) and are as little as above the surrounding floodplain Staines High Street oriented northeast to southwest runs across one of these islands to the site of the me,dieval bridge and was the nucleus of the Roman town. St Mary's Church, on "Binbury island" to the northwest of the centre, is thought to have been the focus of settlement activity in the late-Saxon period. Elevations below AOD were liable to flooding until the early 19th century and many areas of gravel are covered by muddy silts and sands. There are brickearth deposits to the east of the town, along the A30, and outcrops of .alluvium to the north and south.