Nanda- if the stream is navigable (you'd be going up not down) around the giant talus slope below the cliff you would reach the terminus of the old portage which is a dry relative highway to Kahsh.

I went through there last year. There was not enough water to paddle on the other side of the hump, at least not for any distance. The portage was a faint path through the marsh close to it's edge on the right (along the edge of the steep rock bank climbing into the woods). The trail went up the bank briefly before descending into the long corduroy-being-consumed-by-mud section that eventually ties into the old trail.