It seems that you are talking about the cutoff wall design for a particular type of structure. The maximum static head, the length of the floor, and the safe exit gradient are some of the site- and structure-related factors that affect the depth of the cutoff wall (D/S cutoff wall).
Nevertheless, it's not clear from the information you've given how these parameters relate to the cutoff wall's design. Furthermore, it's unclear what is meant by "safe exit gradient" in this context.
Cutoff walls are frequently used in geotechnical and civil engineering to regulate seepage or stop the flow of water in a variety of structures, including dams, levees, and retaining walls. A cutoff wall's depth is determined by