A without development model scenario is created by starting with a current conditions model scenario and switching off as much development in the model as possible. Typically this means removing all water users such as irrigation and towns along with infrastructure such as dams and weirs.
A without development scenario is useful in understanding the extent to which human uses of the river have altered flows.
This type of model scenario is sometimes known and a “natural case” but this terminology has fallen out of favour over time as a true natural condition scenario would attempt to reflect catchment conditions such as land use, vegetation cover and so on that existed prior to human interventions.