What is the term used for the distance from the inside of one wall to the inside of the other wall in a culvert?

The correct term for the distance from the inside of one wall to the inside of the other wall in a culvert is referred to as the span. The span specifically indicates the horizontal distance across the structure, allowing for the measurement of the effective opening that water and other materials can pass through. Understanding the span is crucial for engineers and planners when designing water flow systems, as it ensures adequate capacity and structural integrity.

In contrast, other terms do not accurately describe this measurement. Width can refer broadly to the extent of a structure, but in the context of a culvert, it does not imply the internal measurement between the walls. Gap generally signifies a space or break, which does not apply here. Clearance typically refers to the vertical distance between the highest point in a structure and the ground or other structure, which is not relevant to the specific measurement of distance between culvert walls.