When acting for a purchaser, a conveyancing lawyer will carry out an environmental search, which will identify if the property is on a known floodplain.
Whether the house or flat is in one of these locations or not doesn't necessarily mean that it has flooded in the past, or will be flooded in the future, because the basic environmental search only assesses the general risk. Furthermore, the information returned in the search cannot factor in the existence and effectiveness of flood defences, such as the Thames Barrier.
If a potential risk is identified and is deemed significant, your conveyancing lawyer may recommend a further, more detailed search (from a specialist company such as Searches UK or Landmark), which will be charged as a third-party fee. Please speak to your solicitor if you have any concerns about the flood risk with respect to your property.
See a sample Homecheck Flood Report.