Just found this on an Iowa Paddlers club's site... interesting... sounds like in Iowa, the "high water mark" law only applies to the lower portions of river where they become much larger...



"In Iowa, on those rivers designated as meandered (see list below), the state owns the stream bed up to the normal high water mark. On those designated as non-meandered, the state owns the water only, and the adjacent land owners own the stream bed.

It's often said that if you step out of your boat on a non-meandered river, technically you are trespassing. This may not be so, as this could be considered a part of "navigating" (see below). But it's never been tested in court.

There are (portions of) 13 interior rivers classified as meandered:

Cedar, lower 157 miles beginning near Cedar Falls
Des Moines, 278 miles, mouth to confluence of east & west forks
East Fork DM, mouth to north edge of Algona, 39 miles
West Fork DM, mouth to Emmetsburg, 44 miles
Iowa, lower 123 miles beginning west of Marengo
Maqouketa, lower 26 miles beginning near Maquoketa
Little Maquoketa, lower 2 miles
Nishnabotna, lower 6 miles
Raccoon, mouth to Dallas-Polk County line, 13 miles
Skunk, lower 61 miles (none of the South Skunk)
Turkey River, lower 58 miles beginning near Clermont
Upper Iowa River, lower 6 miles
Wapsipinicon, lower 98 miles beginning near Central City

"Meandered" is a surveyor's term going back to when the state was first surveyed.

The Iowa DNR has this to say about public waters: "Water occurring in any river, stream or creek having definite banks and bed with visible eveidence of the flow of water is declared to be public waters of the state of Iowa and subject to use by the public for navigation purposes in accordance with law".

Iowa further defines "navigable waters" as "all lakes, rivers and streams, which can support a vessel capable of carrying one or more persons during a total of six months period in one out of every ten years". The US Supreme Court has ruled that a stream may be navigable even if it contains some obstructions.

Where a public road crosses a stream, the road right-of-way extends across the stream and it's banks. You may encounter and cross a fence in the right-of-way, but, as with those encountered in a stream, do not damage it."