Steel posts and handrails worth £200,000 have been stolen from the Thames Gateway Regeneration project.
The thieves struck twice within a week at the Rochester Riverside development, forcing the closure of the walkway and cycle path five weeks after it opened.
Early on Monday, 82 posts and 200 handrails were unbolted and driven away after security gates were forced open.
A week earlier on 8 July, 100 posts and 148 handrails awaiting installation were stolen from a nearby site.
Workmen have since welded in place all the nuts on the bases of the remaining posts on the mile-long walkway in an effort to prevent any further thefts.
Security has also been stepped up.