I have always determined floodway in Wisconsin by using method 4 and limiting rise in base flood to 0.01' or less.
I was informed by FEMA that the floodway must be modeled "using ineffective areas rather than encroachments". I inquired WisDNR as to how to go about this. Their answer is: "There is not black and white solution to this. The ineffective flow limits need to be based on your engineering judgement at pinch points. Make sure to take into account the contraction/expansion through these pinch points. They need to make sense (roughly 1:1 contraction & 2:1 expansion)".
Does this mean I go RS by RS and approximate Ineffective flow areas and compute and then adjust and then recompute to get less than 0.01'?