In 2016, the Centre of Ecology and Hydrology (CEH) and Wallingford HydroSolutions (WHS) released another version of the revitalised rainfall-runoff model (ReFH2) which allows users to generate flood peak flows and hydrographs from given rainfall events for both catchment and development sites. For a full description of the approaches, the reader is referred to their document which can be freely accessed at:-
http://files.hydrosolutions.co.uk/refh2/ReFH2_Technical_Report.pdf
There are 2 components to the ReFH 2 model. The first is a new runoff volume and routing model, ReFH2, which was added to InfoWorks ICM in version 6.5. The second component is the FEH 2013 generated design rainfall which was added in version 7.5. This blog post will go on to describe the implementation of both components within InfoWorks ICM/ICMLive and how users can use these to generate rainfall events and runoff within these software packages.
The first point to note, is that the equations used to generate FEH2013 rainfall and ReFH2 runoff are proprietary and have not been published publicly. Therefore, unlike the previous FEH and ReFH approaches, it has not been possible to code these equations directly into the InfoWorks ICM/ICMLive simulation engines. The user therefore requires a copy of the ReFH2 software with a licence obtained from Wallingford HydroSolutions (WHS). The ReFH2 software must be available when the FEH2013 rainfall is generated and the relevant calculations are undertaken for determining the parameters for the subcatchments ReFH2 runoff. However, once the rainfall and runoff parameters have been determined, InfoWorks ICM/ICMLive simulations do not need access to the ReFH2 software and runs can be distributed onto other machines/servers as is desired.
FEH2013 Rainfall
Like all rainfall the FEH2013 generated rainfall is created by using a Rainfall Event Editor. In the list of available rainfall models the appropriate FEH2013 Rainfall generator should be selected.
Fast forward to today and there is still too much use of the Rational method and design storms. Perhaps they have their place in sizing a culvert based on conveyance or some onsite detention in the case of a design storm. However, there is simply too much misuse since these methods ignore the physical processes that are occurring. It is simply not appropriate to use such a method to design stormwater systems when storage is a significant component of the system or when there is sensitive downstream receiving waters to name just a couple cases. The rational method produces a peak flow and using that flow value in design ignores the natural attenuation that would occur to storage effects in the system and can even result in under design. 
and select AV Characteristics Curve Generator
