; and (II) indicated by physical characteristics such as— (aa) a clear, natural line impressed on the bank; (bb) shelving; (cc) changes in the character of the soil; (dd) destruction of terrestrial vegetation; (ee) the presence of litter and debris; and (ff) other appropriate means that consider the characteristics of the surrounding areas. (ix) Perennial The term perennial means surface water that flows continuously throughout the year. (x) Prior converted cropland (I) In general The term prior converted cropland means an area that, prior to December 23, 1985, was drained or otherwise manipulated for the purpose, or having the effect, of making production of an agricultural product possible. (II) Designation by Secretary of Agriculture For purposes of this clause— (aa) the Secretary of Agriculture may designate an area as prior converted cropland; and (bb) except as provided in subclause (III), the Administrator and the Secretary shall recognize a designation by the Secretary of Agriculture under item (aa) for purposes of this Act. (III) Exclusion (aa) In general The term prior converted cropland does not include an area described in subclause (I) that has, as determined by the Secretary, in coordination with the heads of other relevant Federal agencies, as appropriate— (AA) subject to items (bb) and (cc), been abandoned