Total Surcharge Time vs Total Time Above Rim Elevation in InfoSWMM

Subject: Total Time Above Rim Elevation at a Node

1. Total Surcharge Time is the total time above the crown of the highest connecting pipe to a node.

2. Total Time Above Rim Elevation – this is the flooding time of the node and it includes flood time as well as ponding time. You can find this in the Junction Summary Report of InfoSWMM under the column Total Flood Time. The Total Flood Time should be less than the Total Surcharge Time as the depth in the Node is higher.

  1. A node is flooded if the node depth equals the node rim elevation – the flooded time is the total time excess flow is coming out the top of the manhole,
  2. A node is flooded if the node depth is above the rim elevation and you are using the Surface Ponding Option – the flooded time is the ponding time
  3. A node is flooded if the node depth equals the node surchage elevation – the flooded time is the total time excess flow coming out the top of the surcharged manhole.