Urban catch basin modeling - techniques and calculations: Or how I learned to stop worrying and love the flow-by

Kyle Burton


This presentation will cover best practices for modeling catch basins in both ponding and continuous grade (flow-by) capture conditions. If time allows, it will also cover how the catch basin capture curve calculations for Calgary are made.

Part 1: Catch Basin Modeling Best Practices

  • The three elements making up a catch basin in modeling, and what they represent.
    • Using storages to represent storage capture conditions
    • Setting outlet curve for representing a combination of the catch basin type, barrel depth, lead size, and inlet control device.
    • How to model a ponding catch basin while avoiding “ghost-storage.”
    • Depth vs. Head
  • How to model an interconnected catch basin that combines a ponding and a flow-by condition.
  • Use of Grated Top Manholes.

Part 2: Calculating Catch Basin Capture Ratings.

  • Review of the factors that determine the calculated capture curve.
    • Surface Capture Condition
    • CB geometry
    • Barrel Depth
    • Lead capacity
    • Inlet Control Device 
  • Discussion of the Flow-By capture curves, what makes them different and their origins, with regards to Calgary.
    • Empirical values vs. Theoretical calculations.
    • Adapting empirical values for use in modeling. 
  • Use of Riveted Grated Top Manholes.
  • Importance of Documentation for catch basin curves.

 Click here to download a static PDF version of the presentation.

 Click here to watch recorded presentation on YouTube.

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