Increases in typhoon intensity and sea level rise could pose significant challenges to coastal defences around Tokyo Bay. In order to analyse the extent of future problems the authors determined the increase storm surge that could result from an increase in typhoon intensity and sea level rise to this area around the turn of the 21st century. Results show how the various settlements around Tokyo Bay are at considerable risk of storm surges and sea level rise in the future. If defences are breached the potential direct economic consequences could be significant, potentially in excess of 100 trillion yen, with the indirect costs likely to be even greater. As a result it is likely that sea defences will have to be strengthened around Tokyo Bay in the future, which could cost in the order of 370bn yen to defend against a 1 in 100 year storm by the year 2100. Alternatively, a storm surge barrier could be built, which would be more expensive (possibly in the range of 700-800bn yen), though it could increase the protection level and would be able to cope with 1 in 200 or 500 year events, amongst other benefits.