How is drainage invert elevation determined in pipe drainage design?

How is drainage invert elevation determined in pipe drainage design?

• A. It is the highest interior pipe elevation used to ensure proper slope and flow; derived from design elevations, slope, and pipe diameter.
• B. It is the lowest interior pipe elevation used to ensure proper slope and flow; derived from design elevations, slope, and pipe diameter.
• C. It is the top of the trench
• D. It is the surface grade

Answer: (B)

Drainage invert elevation is the elevation of the bottom inside surface of the pipe—the lowest interior point where flow occurs along the pipe run. It’s set so that the pipe’s slope from upstream to downstream delivers the designed grade and proper flow characteristics. In practice, you establish the upstream invert at the required design elevation, apply the specified slope over the pipe length, and confirm the downstream invert aligns with the design. Pipe diameter can influence how deep the flow is and the resulting velocity, which affects performance, but the fundamental concept is the bottom interior elevation, not the top of the trench or the surface grade.

Drainage invert elevation is the elevation of the bottom inside surface of the pipe—the lowest interior point where flow occurs along the pipe run. It’s set so that the pipe’s slope from upstream to downstream delivers the designed grade and proper flow characteristics. In practice, you establish the upstream invert at the required design elevation, apply the specified slope over the pipe length, and confirm the downstream invert aligns with the design. Pipe diameter can influence how deep the flow is and the resulting velocity, which affects performance, but the fundamental concept is the bottom interior elevation, not the top of the trench or the surface grade.