Rights in respect to the crossing of navigable waterways granted pursuant to the provisions of this subchapter shall be perpetual and shall inure to the benefit of the river crossing proprietor, its successors, mortgagees, and assigns. However, this subchapter shall not destroy, impair, repeal, or amend any right of eminent domain or reversion inuring either to the state or the river crossing proprietor under the laws of the State of Arkansas or of the United States.