At present it is not possible to apply climate change rainfall uplifts directly within the ReFH2 software. However, this additional functionality will be available within the next release of ReFH2. ReFH2.3 will be released this summer.
As a work around, the increase in rainfall could be modelled by determining the corresponding return period event for the required increase in rainfall and add this in as a design event. However, given the large uplifts within current regulatory guidance it may not be possible as the uplifted rainfall value may exceed the 1 in 1000 year event; the current maximum return period within ReFH2.