Floating bridge

What about something like this?

https://twitter.com/i/status/1507969313549930504

 

@Engineerium, you are in the PNW. Are the regulations and restrictions you are citing, state or federal?
Oregon, for example, has permitting through the use of mitigation. A way of paying reparations by helping to develop wetlands to replace the wetlands you want to build on.
Department of State Lands : Aquatic Resources Mitigation Framework : Waterways & Wetlands : State of Oregon https://www.oregon.gov/dsl/WW/pages/aquatic-resources-mitigation-framework.aspx

Where are the codes located for the bridge restrictions you have outlined? There seem to be plenty of examples of small bridges, such as hiking trail board walks, that don't meet those requirements. What is meant by "disturbing the stream bed"? For Florida waterway construction, they are interested in allowing enough flow to keep the water clear so the bottom is visible to sunlight. The goal is to encourage plant growth. I'm assuming the stream bottom, in your case, is meant to maintain flow for unaltered drainage of the upstream and down stream bodies of water.

Are you allowed to ford the river in a vehicle? Would that disturb the stream bed or, because it isn't a permanent structure, be allowed? Something like a swamp buggy with a modified stock trailer might be a less expensive solution.

It also sounds like your parcel is land locked by the railroad tracks and neighboring lands. You may have legal recourse for right-of-ways across neighboring land.

 

If you are being washed down river rowing, just think what the side pressure will be on a floating bridge. You tie downs either end would have to be huge and heavy
.

What you need is Rowing boat fitted with wheels, small outboard when the rivers flowing.

 

Swamp Buggy For Sale | Wetland Equipment https://wetlandequipment.com/swamp-buggy

15s Model Amphibious Carrier | Wetland Equipment https://wetlandequipment.com/products/amphibious-carriers/15s-model-amphibious-carrier

Here's a company that builds wetland equipment, including carriers

-Will

 

Imagine how a pig or sheep would react to riding out those waves!

Though maybe you wouldn't see waves that large.

I think an unrollable floating bridge a la US3258800A - Continuously extensible and roll-up structure - Google Patents https://patents.google.com/patent/US3258800 would be kind of cool. Since it isn't a permanent structure over the water, maybe it would be OK - because it unrolls, it isn't a permanent structure while over the water, so MAYBE a some of the rules don't apply.

But not in fast water. A fast flow might rip it apart. Even if it went across at a diagonal, pointing somewhat downstream.

Fast deep water could also be a problem for an amphibious vehicle.

Does fast water last very long? Could you afford to wait for it to slow down?

A floating bridge has to support much less weight than a suspension bridge, because buoyancy supports the weight. But in some ways, a floating bridge in a current is like a horizontal suspension bridge, because you structure needs to support the integrated horizontal forces from the intercepted current and debris. Does that make any sense to you? (On top of that, sometimes water flow creates standing waves that sweep back and forth across a river, rather than a stable form.)

BTW, a floating bridge is also a "strainer" - something that can sometimes trap a boater or swimmer underneath it, and they drown, maybe creating legal liability. And I can easily imagine a few paddlers sneaking in some dark night with saws, and cutting your bridge apart, to get rid of that strainer.

Something I read said the U.S. Navigable Rivers act has sometimes been interpreted to cover anything you could take a canoe through. Some canoes are pretty shallow draft, and can paddle in pretty shallow water. You can't own anything it covers - except that some states, like Virginia, have claimed priority or U.S. law, because of British crown grants prior to the establishment of the United States - but I'm not sure if anything in the Pacific Northwest would qualify that way. I'm not a lawyer, or an expert on these matters. It might be worth talking to someone in a local paddling club who specializes in river access, even though they are on the other side of the issue from you. Sometimes the most knowledgeable people about a anything are the people who fight it, not the people who support it. (On the other hand, if you gave paddlers access to the river across your land, and they don't have access elsewhere nearby, they might decide they were on your side. River access is often a huge deal for paddlers.)