Possible exit on the north side
A ramp or steps (as shown in the image below) could be built to the west of the viaduct down onto the river bank, that area of river bank being owned by the Environment Agency.
This arrangement would not impede the flow of the river in time of flood as it is downstream of the viaduct and would butt up against the viaduct itself. The Cumbrian Coastal Way path passes along the river bank through the kissing gate (arrowed) on the image.