I am using SewerGEMs (10.03.01.08 - Connect Edition Update 3) to analyse the hydraulic behavior of a small urban catchment in EPS mode (24h analysis) under both dry and wet weather conditions.
1) I am creating two different scenarios, one with sanitary loading at the area's manholes and a zero depth storm event under the Rainfall-Runoff alternative and another with a two-hours duration storm event of a return period equal to 100 years in the Rainfall-Runoff alternative and the sanitary loading. Is this the correct way to model both dry and wet conditions? I noticed that I could not run the model without defining a storm event. Or do I have to define in Active Topology alternative that all catchments, gutters and catch basins are inactive for the dry conditions scenario?
2) For the wet conditions scenario, I defined a storm event of 2-hours duration using Storm Data - Time depth in Components menu. To set the 2-hours event at the beginning of the simulation interval (first two hours of the 24h simulation period), I distributed the storm event using alternating block model (Time-Depth) in the first 2 hours and prolonged the event up to the end of the 24h interval (daily simulation) setting the cumulative storm event depth to 0 mm. And then in the Rainfall-Runoff alternative I defined a Global Rainfall event of 100 years return period represented by the aforementioned event. Is this correct? Or am I missing something? How can I treat a two-hours storm event starting lets say 6 hours after the begging of the simulation? Is there a simple way to define this i.e. in Options field?
3) When I run the model I get a User Notification that (20284) Element 78 "Link has adverse slope" (I am attaching the model in Secure File Upload - Small Urban catchment.rar). However, for this conduit this seems not to be true. What is happening there? Results, especially for Depth/Rise (%) for all conduits at manhole 25181 seem wrong.
Thank you in advance,
Panagiota Galiatsatou said:I am creating two different scenarios, one with sanitary loading at the area's manholes and a zero depth storm event under the Rainfall-Runoff alternative and another with a two-hours duration storm event of a return period equal to 100 years in the Rainfall-Runoff alternative and the sanitary loading. Is this the correct way to model both dry and wet conditions?
What you did will work, but an easier way would have been, like you said, to use Active Topology to turn the catch basins "inactive" so that they are not included in the hydraulic calculation for your "Dry" scenario.
2 & 3)
You have defined the storm event as "Cumulative" but you haven't defined the "Depth" as "Cumulative". You should carry out the highest "Depth" through the end of the storm definition. And as for the start time of the storm, you can simply begin adding your Depth values starting at the Time value of 2.00 (2 Hours)
As for the error
Panagiota Galiatsatou said:"Link has adverse slope"
We saw by using the Network Connectivity Reviewer, that flow in the identified conduit is away from the Wet Well. We reversed 363722 and 363731 so that they now flow toward the Wet Well. Here is a Wiki article that explains the Network Connectivity Reviewer and this Wiki article gives more information about the error.
Please reply if you have other questions.
Answer Verified By: Sushma Choure
Thank you so much for your helpful answers.
Regarding my previous question 3, namely the error that the "Link has adverse slope", I should note that the link from node 25181 to 13078 serves as a weir to manhole 25181 in case of heavy rainfall, so that this conduit does not flow towards the wet well. However, even if I am defining an invert elevation in 25181 higher than that of 13078, the message keeps appearing and the conduit receives zero flow. What is going wrong? Am I defining something the wrong way?
This Wiki article has more information on the User Notification you are getting. Please check the nodes around the one being called out in the error and make sure their elevations are right.