Lessons learnt

The design rainfall under future climate change may impact the current river planning by highlighting the need for revisions and adaptation. A further lesson learnt is expected to be that assessing how the present and future climate situation will change is extremely important for adaptation planning. It is also expected that we can estimate the design rainfall for future climates using the global data.

Importance and relevance of adaptation

It is important to evaluate the climate adaptability of current flood control measures by understanding the changes in the frequency of heavy rain in the future and the worsening of the river water level and river flooding accompanying it. We will continue to discuss with clients about the importance of climate adaptation on measures to control floods in small and medium rivers.

Pros and cons or cost-benefit analysis of climate adaptation

It is difficult to describe the Pros and Cons analysis of climate adaptation.
In the Measures against flood control of medium and small rivers conducted by the Tokyo Metropolitan Government, the level of 50 mm has been attained at last in recent years. It is estimated that future maintenance period is 30 years for 75 mm correspondence. On the premise of future heavy rain events due to climate change, we will promote measures to ensure the safety of life in particular.
In this case study, we will provide materials to decide adaptation measures by concretely showing changes in rain intensity, trends in frequency until reaching danger level, etc. using climate change future prediction information.

Policy aspects 

The basic countermeasure for heavy rainfall currently underway by the Tokyo metropolitan government does not consider the impact of climate change. It is necessary to take measures other than river improvement in order to deal with the increase in risk of flooding associated with future climate change, and it is important to promote countermeasures against rainwater outflow together with municipalities.

Department of Civil and Environmental Engineering, Tokyo Metropolitan University (TMU)


Civil Engineering Support and Training CenterBureau of Construction of Tokyo Metropolitan Government

Poster displayed at the Kick–Off meeting, 7/8 September 2017, Norrköping, Sweden

Distribution of times for hourly rainfall of 50 mm