partially to what shadetree said..only,,id get TWO 40 foot flatdecks........id buildsome sort of support,parellel to the creek,right in the center. you have enough drop to the creek,,that if you had one flatdeck on each side of a support pillar,,the decks of the trailers hooked together,,would be almost flat across the creek..and should be high enough,,for a lot of water to cross underneath..with some sort of anchor,at both ends,,to hold the decks if the water level got crazy,,and anchors on the center support also..no matter what the flat deck tops are,,id throw some sand all across all the surface,,as with rain,,,steel,alum, or wood,,will be slippery....