ReFH can be used to produce net rain values that can be used as input to 2D hydraulic models to produce surface water runoff grids.
However, it should be noted that the net rain (rural and urban) values in the result tables are ‘scaled’ based on the equivalent rural and urban areas within a catchment. This ensures that they sum up to the total net rain. However, it does mean that when viewing or exporting the urbanised results, the net rainfall values do not represent the runoff that would occur over a completely rural or urban surface, which is typically required for input into a 2D hydraulic model.
To obtain rural net rain, the proportion of rural land use needs to be 100%. This is already the case with the rural or total net values listed in the rural results table (upper table). To obtain urban net rain, the proportion of urban land use needs to be 100%. To achieve this, first adjust the urban area (km2) in the Urbanisation tab such it matches the total catchment area. Then view the urban or total net rain in the urban results table (lower table). These values now represent the net rain over a completely urban surface and can be used as input into a 2D hydraulic model.