; and (BB) reverted to a wetland. (bb) Abandonment For purposes of subitem (AA) of item (aa), an area described in that item is considered abandoned when the area is not used for, or in support of, agricultural purposes at least once in the 5-year period immediately preceding a determination described in that item. (cc) Final authority Notwithstanding a determination by the Secretary of whether an area described in subclause (I) has been abandoned, the Administrator shall have final authority to make that determination. (xi) Secretary The term Secretary means the Secretary of the Army, acting through the Chief of Engineers. (xii) Snowpack The term snowpack means 1 or more layers of snow that have accumulated over an extended period of time in certain geographic regions or at high elevations, such as in northern climes or in mountainous regions. (xiii) Tributary (I) In general The term tributary means a river, stream, or similar naturally occurring surface water channel that contributes perennial or intermittent surface water flow to a body of water described in clause (i) or (ii) of subparagraph (A) in a typical year through— (aa) direct means; or (bb) 1 or more bodies of water described in clause (iii), (iv), or (v) of that subparagraph. (II) Inclusion (aa) Alteration or relocation The alteration or relocation of a channel described in subclause (I) does not otherwise modify the status of the channel under this paragraph if the channel continues to meet the requirements of subclause (I) after that alteration or relocation. (bb) Effect of flow through certain features A channel described in subclause (I) shall be considered a tributary for purposes of this clause if the channel contributes surface water flow in a typical year through— (AA) a channelized surface water feature that is not otherwise described in subparagraph (A); (BB) a subterranean river; (CC) a culvert, dam, tunnel, or similar artificial feature