The bridge to nowhere on an islet in the commune of Billy-Berclau, France

Bridges are very important engineering works that have served to span rivers and geographical features for millennia.

Norddalsbrua, a bridge that resisted being blown up during World War II
The tunnel and the bridge of Cerro Salomón: some formidable ruins of the Riotinto Railroad

However, in the north of France, in the commune of Billy-Berclau, there is a port that seems absolutely useless. It is a beautiful tensioned arch bridge located on a small islet, l'Îlot aux Saules, which is in the middle of the Canal d'Aire, a section of the Dunkerque-Escaut Canal between the Neufossé and Deûle canals. The bridge is on the western part of the islet and leads nowhere. Six years ago, the YouTube channel Canna-jo showed it in this video:

As we see in the video, on the southern part of the island is the Bauvin Bridge, which connects Berclau with Les Baraques and serves the few homes located on the islet. The rest of this small island is a landscaped park that is now used for walking. Today, the channel LostintimeNL has published a video traveling across the bridge to nowhere on the western side of the island. As we can see, its northern end abruptly ends in some fences, to the right of which there is a pedestrian access:

What is the purpose of this bridge and why is it there? It appears to be wide enough to allow a vehicle to pass. The website velo-ravel.net says the following about this bridge:

A bridge lost in the middle of an island, it was abandoned when the Aire Canal was widened. Bridge located on the islet of Haute-Deûle or Willow Island.

An old French website explains that the situation of this bridge is due to works to widen the Canal d'Aire in the early 1970s:

Initially, the Canal d'Aire from Dunkirk and the Canal du Deûle, connecting Douai to Lille, were perpendicular; the radius of curvature was very small and did not allow the passage of 3,000-ton barges. The construction of a diversion then became essential. The triangular shape of the island was determined by creating a symmetrical diversion and filling in the central axis, leaving the bridge that once crossed the Canal d'Aire on land. This architectural vestige of the "bowstring" type, commonly called the broken bridge, now offers a fabulous observation point.

Judging from the video by LostintimeNL, the bridge barely needs any maintenance. The southern section is overgrown, and the bridge's columns are covered in graffiti. You can see some screenshots from that video here. This is the southern section of the bridge, overgrown.

The northern section of the bridge ends like this. The video shows the view from the top of that fence. The northern section of the bridge was demolished when the Canal d'Aire was forked.

The bridge seen from its western side. Surely before the works completed in the early 1970s, the canal passed under the bridge.