arcgis desktop - Python Script to Identify and Flip Lines Digitized in the Wrong Direction?

I have a river dataset that was digitized both in the direction of flow and opposite the direction of flow. I need to find an automated method to determine which lines were digitized from downstream to upstream and flip them automatically. I do not have spatial, 3D or network analyst. I am looking for a python code. These lines were created in MicroStation using a bare earth LiDAR dataset. They were hand digitized and it is not a stream centerline but a line following the edges of the river.