The department shall establish and publish minimum criteria for assessing a river’s eligibility and classification under the State Scenic Rivers Program. To qualify as eligible, the river or river segment must possess unique or outstanding scenic, recreational, geological, botanical, fish, wildlife, historic or cultural values. The level of pollution of a river’s waters must be considered in determining eligibility for qualification as a scenic river. A river with relatively polluted waters may qualify as eligible as a scenic river if other values are considered outstanding. The river or river segment must be managed permanently for the preservation or enhancement of its values.