Question: I am receiving different opinions about the flow transfer rate regarding flow from the 2D terrain to a 1D subsurface element. Group 1 says that flow is transferred from 2D terrain to 1D catch pit using the weir equation. Group 2 says that the user can enter the capture rate using a depth (m) to hydraulic capture (m^3/s) chart. All flow will be tranferred from the 2D terrain to the 1D catch pit according to the parameters of the chart. Which of these two groups is correct? How does TUFLOW transfer flow from 2D to 1D? Answer: In TUFLOW a pit channel is designed to convey water to/from a 2D overland domain to a 1D pipe network. There are multiple options available for calculating flows, these are: Depth-discharge curve ("Q" type pit)Weir flow ("W" type pit)Rectangular culvert ("R" type pit)Circular culvert ("C" type pit, this one is rarely used)For more information on setting these up please see the Chapter in the TUFLOW manual on Pits and Pit Channels. Regards TUFLOW Support Team