The ground
Chalk · Head · river gravels
Henley is mapped on chalk overlain by Head — a poorly sorted mix of clay, silt, sand and gravel that crept downslope. Towards the Thames, river gravels and alluvium are mapped within half a kilometre.
So the ground can vary from stony and free-draining to heavier and clay-rich, sometimes within one garden. Soil can change markedly over a short distance, which is worth knowing before a new lawn, patio or fence.
Planning
Henley main · St Marks Road · Reading Road
The town centre is in Henley’s main conservation area, and the St Marks Road and Reading Road conservation areas are within 700 metres. Inside any of them, you need to tell the council six weeks before tree work (trees under 75 mm across, measured 1.5 m up, are exempt), removing an old fence, wall or gate can need consent, and a shed or garden room at the side of the house needs planning permission.
The town is just outside the Chilterns National Landscape — about 0.6 km from the centre — but about 30% of the parish is inside it. At those addresses, buildings, enclosures and pools more than 20 metres from the house can total no more than 10 square metres under permitted development.