What is the lowest point in a drainage facility where flows would typically pass?

The term that denotes the lowest point in a drainage facility where flows would typically pass is known as the invert. In drainage systems, the invert refers specifically to the lowest internal level of a pipe or channel. This is a critical measurement, as it determines the flow capacity of the system and impacts how efficiently water is conveyed away from a site. Understanding the concept of the invert is essential for engineers and inspectors, as it influences both the design of drainage systems and the management of stormwater runoff.

While the other terms mentioned may have related connotations, they do not serve the same specific purpose within the context of drainage facilities. The term "bottom" might refer to the lowest point in a general sense but lacks the precise application related to flow dynamics. "Perched water" refers to a condition where water is held above a water table due to an impermeable layer, and does not pertain to flow within the drainage facility. "Jam" typically describes a blockage or obstruction, which is counterproductive to the function of drainage and does not indicate a location for flow. Hence, the correct term here is the invert, as it accurately captures the essential characteristic of the drainage system's functionality.