A location-determining receiver collects terrain data within a work area. The terrain data comprises elevation data and corresponding location data. A path planning module or data processor defines a planned path for a drainage channel. The planned path comprises a starting point with first coordinates and a termination point with second coordinates within the work area. The drainage channel extends from the starting point to the end point such that the starting point has a higher elevation than the termination point. A user interface establishes constraint data comprising a minimum cut parameter, a maximum cut parameter, a minimum slope parameter and a maximum slope parameter. A data processor determines a validated path for the planned path or a digging plan based on compliance with the constraint data.