Montpellier

Montpellier's rivers rise fast, and its flood system stops deliberately short of acting by itself. The métropole's flood-management service runs about fifty water-level and rain sensors plus cameras and piezometers into a platform called Ville en Alerte, built between 2016 and 2021 and renewed at the end of that period; when a gauge crosses a threshold a message goes to the duty service, which sends agents to look before relaying anything to mayors, the prefecture and the fire service. Nothing is actuated automatically, and the reason is in the geology: a karst catchment produces false rises, so piezometers had to be added at two sites just to tell when the underground network is saturated. In the week to 23 December 2025 the territory took about 450 millimetres of rain, more than half its annual total, with 163 in 24 hours at one station; the duty room opened at eight that morning, low points were closed and evacuations advised. The oldest part of the network is the most revealing about why cities instrument anything: the first two gauges went in for the 1998 World Cup, because the stadium had been built in a flood zone.

The city's data platform was rebuilt after an early failure and is now complete on licensing and mid-table on permissiveness. A first platform deployed from 2010 with a technology company's local research centre was stopped, in the métropole's own account, because the tool had not given satisfaction; what replaced it was assembled in pieces — a catalogue for all 31 communes from November 2016, and a context broker exposed publicly as an interface serving live and historic data from January 2023, starting with bike availability, cycle counts and car-park occupancy. Of 943 listed datasets, 939 resolve and every one of those names a licence — but 863 of them carry a share-alike database licence that obliges reusers to publish enriched derivatives back under the same terms. That is an open licence with a string attached, and it is a different choice from the plain attribution licences elsewhere in this atlas.

The entry that will be argued about is the fare policy, and its most interesting property is what it did to measurement. The métropole phased out fares for its own residents — weekends from September 2020, under-18s and over-65s from September 2021, every resident of the 31 communes from December 2023 — but free travel is not open: residents apply with identification, a photograph and proof of address, and must renew every year or risk a fine, while visitors still buy tickets. Abolishing validations also removed the operator's own ridership meter, so passengers are now counted by cells fitted in every vehicle instead. The métropole reports ridership up more than a third after the first full year; the national audit court, reviewing the scheme in November 2025, put the net rise at about 20 per cent and found 39 per cent of the additional trips had switched from walking, cycling or scooters and 33 per cent from cars, leaving 28 per cent genuinely new. The same review recorded fare revenue falling from roughly a third of operating costs to six per cent. Separately, the utility taken back in-house in 2016 has been fitting transmitter heads to water meters on a published commune-by-commune calendar running to 2027, reporting twice a day — enough to catch a continuous leak, too coarse to reconstruct when a household showers.