The Cascade approach is a procedure for setting objectives in which the objectives are set from the top level of management to down.
Suppose, some managers report to a director and some individual contributors report to those managers. These individual contributors are the targets of any change i.e. the changes will impact them. Assume, a change is needed to be announced.
The cascade approach states that the director i.e. the change sponsor first introduces the change to her/his managers (as targets). S/he teaches them how to deal with the change and expresses that they have to sponsor this change in their respective departments or offices, instructing them to repeat the session they have just been in with their individual contributors.
Then the managers as the sponsors for their own organizations or departments, cascade this communication to their individual contributors in their departments or offices. Generally, the cascade approach works quite well because individuals need to do what their immediate supervisor or boss instructs them to do. Everybody gets aware of the change in a quite sequential and consistent manner from their immediate boss.