What role does a cutoff wall typically play in drainage systems?

A cutoff wall is specifically designed to control the flow of water to help manage drainage systems effectively. Its primary function is to prevent scouring at the base of structures, such as outlets or spillways. By acting as a barrier, a cutoff wall helps to maintain the stability of the surrounding soil, safeguarding the structural integrity of the outlet and preventing erosion that could compromise the system.

The other options, while important aspects of drainage and erosion control, do not accurately describe the primary function of a cutoff wall. For instance, enhancing water infiltration pertains to features that allow water to seep into the ground, which is not a role served by a cutoff wall. Similarly, reducing sediment buildup typically involves structures like sediment basins or traps, not cutoff walls. An emergency spillway serves a different purpose, specifically designed to handle excess water during overflow events, rather than directly preventing scouring.