You can read about the EA Thames Area assets. From the document: ‘In the Thames area we have a wide range of assets, including locks, weirs, flood defences, boat moorings and monitoring stations for air and water quality. Flood defences can include embankments, walls, flood gates and flood diversion channels. Our assets help to protect people, property, and the environment from flooding, drought and pollution’.
Further interesting reading from source document here
IMPORTANT QUOTE FROM THE DOCUMENT:
Responsibility for maintaining main rivers ultimately remains with the riparian land owner.