InfoWorks ICM 9.0 Help provides a description for the dimension field of the Subcatchment Data Fields as:

"This field is required by the Large Catchment runoff model and the Desbordes runoff model (representing catchment length) and the SWMM runoff model (representing catchment width). It is not used by the standard Wallingford Procedure runoff model or the SPRINT runoff model.

Calculated as the radius of a circle with area = Contributing Area."

  1. What is the theory behind the default calculation?
  2. Should I be replacing the default value with the value I get following the guidance for subcatchment width in “Storm Water Management Model Reference Manual Volume 1 – Hydrology" if I'm using the SWMM runoff model?

Thanks in advance!