4. ReFH2 Analysis

We want to perform ReFH2 analysis with our amended (version 2) catchment descriptors to estimate flood hydrographs for a range of return periods. We notice that, as these are specified as our preferred version, starting a new ReFH2 analysis pulls them through automatically.

The user manual is provided on right-hand-side so we can confirm the technical details at any point. 

Moving to the design rainfall, we are also interested in the 500-year and 10,000-year return periods, so add both of these events. Initially, we leave the storm duration unaltered from the default value of 52 hours. We also ensure the latest research has been accounted for by using the FEH22 model.

We review the results within ReFH2, considering both the rural and urbanised hydrographs. We notice we can apply adjustments as needed to the model parameters, and can further account for urbanisation by supplying a sewer capacity, for instance. We save this initial analysis ensuring we provide a meaningful name and description. 

A secondary analysis, using a longer storm duration of 63 hours, is also required. We note that the storm duration divided by the timestep interval must be an odd integer, and therefore adjust the timestep to 3 hours for this analysis. Again, we save this with a meaningful name and description and return to Flood Modeller.  

User Steps. Perform an initial ReFH2 analysis. Add the 500-year and 10,000-year return periods, leaving other parameters at their default values. Perform a second analysis with a storm duration of 63 hours and timestep of 3 hours (hint - you may want to review the initial analysis, make the amendments, and then save as a second analysis - this way you will not need to repeat the addition of the extra return periods).