Arroyo Maldonado relief tunnels & Buenos Aires's storm alert network
Two bored tunnels — 9.8 km and 4.6 km, both 6 m across — have carried the culverted Maldonado's overflow since mid-2012, financed by a World Bank loan and sized for a 1-in-10-year storm. Water enters them hydraulically; no sensor sits in that loop. The measuring layer is separate: rain, wind, flow and level sensors feed a control desk, and a Sistema de Alerta de Tormentas with automatic stations and a Doppler radar followed in October 2016, its data converging at the city's Centro Único de Coordinación y Control. Readings raise alerts and send crews — no source describes a pump or gate starting on a threshold. The Bank's own evaluation arm rated the loan Moderately Unsatisfactory: the tunnels got built, but only two of six secondary-network groups were under way at closing and the monitoring network was never finished.
World Bank ICR: the works were designed to prevent flooding in the city's Maldonado basin in a 10-year storm, with about 342,968 direct beneficiaries in the basin's critical zone. The Bank's Independent Evaluation Group nonetheless rated the project's outcome Moderately Unsatisfactory, with the secondary drainage network under way in only 2 of 6 planned areas at closing.
🎓 Lesson
Bundling concrete and instruments in one budget rewards the concrete. IEG's own lesson from this loan is that structural and non-structural components need separate implementation arrangements — here the tunnels were finished and the monitoring network was not.
Evidence📊 Independent
Scale🏙️ City-wide
Cost≈US$193M actual (appraisal US$189M)
FundingWorld Bank IBRD loan of US$134.01M plus City of Buenos Aires counterpart funds
Sources
↗ World Bank — IEG ICR Review, Urban Flood Prevention and Drainage (P088220)Independent review. Gives the Moderately Unsatisfactory outcome rating, appraisal cost US$189M against actual US$193.01M, an IBRD loan of US$134.01M (originally EUR 98M), board approval 5 April 2005 and closing 31 August 2012 after extension from 31 December 2010; states the secondary drainage works were 'underway in 2 of the 6 proposed areas, with the remainder expected to be completed with City funds', and draws the lesson that combining structural and non-structural components in one project is challenging. The PDF at the same document ID returned unparseable binary to our fetcher; this identical .txt rendition was read instead.
↗ World Bank — Implementation Completion and Results Report, ICR2686Source for the tunnel dimensions (9.8 km and 4.6 km, 6 m inner diameter, both in operation from mid-2012), the design standard ('designed to avoid flooding in the area of the City within the Maldonado Basin during rain events of 10 year intervals'), the figure of roughly 342,968 direct beneficiaries, and the statement that 'shortage of funding meant that the Project could not achieve the development of a complete hydrological monitoring network for the City'. PDF unparseable; .txt rendition read.
↗ Gobierno de la Ciudad de Buenos Aires — Sistema de Alerta de TormentasOperator page. Dates the system to October 2016, describes a network of 34 automatic meteorological stations 'of which 10 are already transmitting data', a dual-polarisation Doppler radar then still being installed at Merlo, and data converging at the Centro Único de Coordinación y Control, 'currently operated by the Ministry of Justice and Security'. The page reads as an undated snapshot close to launch — we did not find a current count of stations actually transmitting, so the entry claims none. Nothing on the page describes automatic actuation of pumps or gates.
↗ Gobierno de la Ciudad de Buenos Aires — Red hidrométricaConfirms the sensing layer: 'Los sensores monitorean en forma constante la lluvia, la temperatura, el viento, el caudal y el nivel del agua', feeding 'un tablero de control donde se visualizan en mapas y gráficos con la finalidad de detectar variaciones en los caudales y anticipar posibles inconvenientes'. No sensor count, no public data feed and no automatic response described — the basis for this entry's placement as warning-only.
↗ Infobae — inside the Maldonado conduits, 2 July 2024Describes maintenance rather than control: constant inspection because 'en esos conductos pluviales una obstrucción puede generar un problema muy grande', robots in the smaller pipes, cleaning of some 900 km of conduits and 30,000 sumideros by Espacio Público e Higiene Urbana, and a 6 m conduit that routes inflow from the Province to the Riachuelo via the Cildañez. Also cites rainfall up about 11% over two decades. No sensor-driven control is mentioned anywhere in the piece.
↗ La Nación — flooding in the city, 8 February 2024Counterweight: flooded streets and businesses and three subway lines out of service, a decade after the tunnels opened. Surfaced via search with headline and date; the article page itself was not fetched.
↗ Infobae — storm across the AMBA, 25 October 2025Second dated counterweight: close to 118 mm across the AMBA, with 155 mm in Villa Devoto and 114 mm in Villa Santa Rita, flooded neighbourhoods and cut streets. Surfaced via search; page not fetched.
↗ Infobae — eight dead in the city, 2 April 2013Contemporaneous reporting put the toll inside the Autonomous City at six to eight, in Saavedra, Colegiales, Villa Luro, Villa Ortúzar and Villa Urquiza — neighbourhoods largely in the Vega basin, not the Maldonado. Surfaced via search; page not fetched, and the exact final city figure varies between outlets, so the entry gives no number.
↗ La Nación — courts ratify 89 deaths in La PlataCited only to keep the tolls apart: the 89 judicially confirmed deaths of 2-3 April 2013 belong to La Plata, a different city roughly 60 km away, and are routinely merged with Buenos Aires figures in coverage. They are not attributed to this entry.
📎 Cite this project
1001 Smart Cities (2026). “Arroyo Maldonado relief tunnels & Buenos Aires's storm alert network” — Buenos Aires, Argentina. The Smart City Atlas. https://1001smartcities.org/projects/buenos-aires-flood-management/ (last verified 2026-07-26). Data: CC BY 4.0.
The underlying data is free to reuse with attribution — see the open data page.
