Greetings,
As I am aware, SewerGEMS includes the feature of embedding a surface TIN or terrain models along with a stormwater hydraulic model, such that catchment areas can be automatically generated and allocated to their respective nodes/ catchment basins.
Since this is the case, I presume that the maximum distances/ overland lengths within each catchment area accounting for the land slopes, can also be automatically determined using the terrain model.
If this was correct, then at least some of the methods used for determining the Tc values for these catchment areas (Carter, Wallingford(UK), Bransby-Williams methods, etc), would have their input parameters known and the Tc values could be automatically calculated rather than manually inputted in the model. Other methods (such as the Length and Velocity and FAA methods), would require some additional input but a large effort would have been saved by availing the overland lengths and slope values.
Could you please advise on how such a procedure for automating the input of the Tc values could be implemented, in order to avoid or minimize manual input, especially for large numbers of catchment areas?
Thanks and best regards,
Amine Salameh
Hello Amine,
There is a feature request in place for this. The downstream trace feature will not display the length or slope of the trace line. Enhancement 677454 was filed for the ability to do this in a future release. In the meantime if you need to see the length and slope for purposes of determining the time of concentration (Tc), you can trace over the line with a pipe, holding down the CTRL key to add bends, then look at the scaled length of that pipe. Elevations could be added to the end nodes to check the pipe's slope.
Using Downstream Trace and Digital Terrain Models
Apart from this you can use Modelbuilder to import Tc data externally for automating the process for large models. See link below.
Assigning Catchment Outflow Node and Tc Automatically (in bulk)
Regards,
Sushma Choure
Bentley Technical Suppport