A control system for an irrigation system is disclosed that is configured to prevent a substantial positional change of the irrigation system while the system is traversing a substantially non-flat terrain, or surface. In an implementation, an irrigation system includes multiple interconnected spans that are supported by multiple tower structures. Each tower structure includes a drive unit for driving a tower structure at a selected speed. The irrigation system also includes a position-determining module configured to determine an actual position of the main section assembly. The irrigation system also includes a control device configured to determine an actual position of the main section assembly, compare the actual position with a desired position of the main section assembly, and to determine that the main section assembly is traversing a substantially non-flat surface.