DRAINS Hydraulic Models
The following table sets out the differences between the two hydraulic models used in DRAINS:
These differences have developed due to the way that DRAINS developed. Initially, flow depths and characteristics were calculated by a combination of hydraulic grade line projections and full pipe system modelling. This, now superseded basic model operated as a series of steady states, creating a quasi-unsteady result. When the Lite and Full Unsteady hydraulic models were developed, these were provided for pipes and open channels in the Lite hydraulic model, but unsteady flow modelling of overflow routes and other features were made available when utilising the Full unsteady hydraulic model.
These differences have developed due to the way that DRAINS developed. Initially, flow depths and characteristics were calculated by a combination of hydraulic grade line projections and full pipe system modelling. This, now superseded basic model operated as a series of steady states, creating a quasi-unsteady result. When the Lite and Full Unsteady hydraulic models were developed, these were provided for pipes and open channels in the Lite hydraulic model, but unsteady flow modelling of overflow routes and other features were made available when utilising the Full unsteady hydraulic model.
In the Full unsteady hydraulic model, all conduits (pipes, channels and overflow routes), are modelled using the same procedure, so there is more consistency in modelling, and results are more accurate. There will often be lower peak flowrates due to the modelling of storage effects along overflow routes and at sag pits.