I am not sure that I can help you with this but administrative boundaries are provided typically by the government through open data sharing agreements and uploaded to OpenStreetMap (OSM). Similarly for rivers. Creeks are likely mapped from satellite photography, as it appears in this case. Satellite photos are good to a few metres and for this creeks matches up nicely. The error appears to be with the administrative boundary. Creeks and river beds move over time. Perhaps this is the cause. I would presume when the government data source is updated, so will OSM.