I do not view locked gates and out of use forest roads as an impediment but as an opportunity. Certainly it is nice to drive all the way there, I just go under a forest gate with my fat tired bike and pedal my way into remote areas where I know humans are not going very often. It the terrain is too steep to bike I hike or both on the same trip. Even at that I do not expect to encounter a BF sauntering down a forest road, Most such roads in this area, unless they are very old are covered with crushed basalt rock, often fist sized, and would be unpleasant walking for BF. Other than a suspicious pile of strange scat, I think that while BF may cross such roads, and I have seen footprint evidence of such crossings, I really do not think they use the roads just because of the road surface. One place I know there is a "game trail" that parallels a logging road for some distance. That "game trail" is marked by rock stacks on stumps. Careful examination of that trail, while it shows travel, because of wear down of vegetation, I have yet to find a hooved animal footprint on the thing. I do not know what is using the trail, but it is not deer and elk.
Georgerm; That area below Bonneville Dam while narrow the water is very swift. I have a hunch that frequent crossings are further down at about the mile marker 27 location. Three reasons, the water is not as swift, road crossing reports in that area, and sighting reports above that on the rim of the gorge. There is a small park on the gorge rim where a sighting was observed just above the mile 27 marker. A guy was just sitting there in the dark and a BF approached him. Visiting the location I could see where something could travel down into the gorge down a ravine. Many of the sighting reports, when I can determine the exact location, I have gone to the spot trying to figure out why the BF was there. There are also many locations in the gorge where the cliffs are too steep to scale down. That really limits where something can come out of the high country and get down to the river level. Once you get abeam Mt Hood at all, the elevations to the South increase tremendously with snow cover in place most of the year.