This definition is from the Code of Iowa:
"Navigable stream" means all streams which can support a vessel capable of carrying one or more persons during a total of a six-month period in one out of every ten years.
and
"Meandered stream" means a lake or stream which at the time of the original government survey was so surveyed as to mark, plat and compute acreage of adjacent fractional sections.
dblmainbeam- Let me know what county you are curious about and I will post all meandered, navigable, and trout streams for that county.
Also, as far as snowmobiles:
321G.13 Unlawful operation.
1. A person shall not drive or operate a snowmobile: g. In any park, wildlife area, preserve, refuge, game management area, or any portion of a meandered stream , or any portion of the bed of a nonmeandered stream which has been identified as a navigable stream or river by rule adopted by the department and which is covered by water, except on designated snowmobile trails.
This paragraph does not prohibit the use of ford crossings of public or private roads or any other ford crossing when used for agricultural purposes; the operation of construction vehicles engaged in lawful construction, repair, or maintenance in a streambed; or the operation of snowmobiles on ice.