---
title: a sudestada stacks the plata against the drains
canonical_url: https://ensurance.app/guide/what-a-sudestada-does-to-buenos-aires
markdown_url: https://ensurance.app/guide/what-a-sudestada-does-to-buenos-aires.md
subtitle: the wind is the flood. the residual risk sits over the riachuelo.
category: ecosystem-services
---

# a sudestada stacks the plata against the drains

*the wind is the flood. the residual risk sits over the riachuelo.*

A sudestada is a southeast wind on the Río de la Plata. It is a southeast wind, often over 35 km/h, with rain. The wind raises the estuary. Rivers and streams that cross Buenos Aires and end there lose drainage capacity. The plan says that can cause a coastal flood.

The city's climate plan, PAC 2050, is the English source for one figure, and only one. The level of the Plata at the city rose about 17 centimeters during the 20th century. That is a century, not one storm. The same pages are not a casualty count. No casualty count and no damage figure were sourced for this account.

## what a sudestada is

A **sudestada** is that wind holding the Río de la Plata up until the drains meet a higher outlet. The drains lose capacity when the estuary is stacked. The southern river does not make the wind.

Ciudad Autónoma de Buenos Aires is the door, read with the greater metro around it. The Province of Buenos Aires is a different geography, except where this basin crosses the line. The estuary is the living level in front of the city, and it is the tap. The **Matanza-Riachuelo** is the other living thing in the same weather: 64 kilometers, a plains river with little slope, southwest to northeast, discharging into the Plata. When the outlet stalls, this is the lowland the water already uses.

Buenos Aires depends on the estuary twice, and the jobs are not the same. AySA takes drinking water through intake towers and treats it at three surface plants. The company names General San Martín and Juan Manuel de Rosas. A third plant is in the count and was not named on the page used here. In the 2023 figures, average treated water was 6,219,234 m³ a day. Well water was 13 percent of production, not the main source. The concession area holds 15,103,199 people. Potable service reaches 11,351,535. Nothing sourced here makes a sudestada the day the tap stops. It is the day that same water sits higher against the drains.

## what the works already changed

In the first half of the 20th century, most natural streams in the city were rectified and piped. PAC 2050 says the natural drain network came apart and flood-prone area rose. Slope is slight. Natural evacuation is low. The ground is sealed. In that account, floods are the city's main natural risk. Eleven watersheds cross the city. The highest risk that remains is named for one of them.

The Hydraulic Management Master Plan, the Hydric Risk Management Plan, and the current Hydraulic Plan reduced floods and the number of flood-prone areas. That reduction is the margin. What remains is also written down: the highest hydraulic risk sits in the urban habitat over the Matanza-Riachuelo basin, in the south and the center. The remainder has an address.

About 17 centimeters of higher Plata sit under that address, a 20th-century rise, not a storm total. No casualty count and no damage figure belong in this account.

If you live over that basin, the next cool southeast wind is the level at the mouth and the rain on a former floodplain. The margin the works already bought is what gets spent if that remainder is treated as finished.

## who stands on the remainder

The basin holds 4,703,058 people, from the definitive 2022 census on ACUMAR's characteristics page, across about 2,047 km². Fourteen partidos of the Province, all of Comuna 8, and parts of Comunas 1, 3, 4, 5, 6, 7, 9, and 10. ACUMAR's documentary center still shows older lines, about 2,200 km² and about 6 million people. Those lines are still there. They are not the figures used here.

The census count is residency, not harm. The city depends on the estuary staying treatable and low enough for the drains. The basin depends on the Matanza-Riachuelo still carrying water when the Plata is slow to take it.

AySA operates the intakes and the Riachuelo wastewater works. ACUMAR does not run those works. Law 26.168 created ACUMAR as the authority of the Nation, the Province, and the City.

## the dirty river is not the wind

Contamination is a real hazard with another mechanism. In 2008 the Supreme Court, in *Mendoza*, ordered a cleanup. In October 2024 the Court ended its supervision. On 14 August 2025 it rejected appeals and reaffirmed that close. Execution stayed with ACUMAR. The court stepping back is not the river recovering, and it is not a sudestada.

An August 2025 World Bank paper says the Riachuelo system — collector, outfall, and treatment plant — was in testing, and that testing already reduces overflows. It does not say the outfall is finished. The World Bank has called the tannery sector a major industrial source. The paper says the industrial treatment plant still required those tanneries to relocate, and that the relocation would take years. A load, not a villain.

| | the wind | the contamination |
|---|---|---|
| what it is | a southeast wind over 35 km/h, with rain, raising the Plata | sewage, the tannery load, the *Mendoza* cleanup |
| what it does | cuts drainage where the city's rivers meet the estuary | leaves a burden in the river the basin still uses |
| where the remainder sits | highest hydraulic risk over the Matanza-Riachuelo, south and center | execution of the cleanup, with ACUMAR since 2024 |
| what the record will not support | a storm height of 17 cm, a casualty count, a damage bill | a cause for the wind, or a claim the water is clean |

The wind does not come from a tannery. A judgment does not lower the Plata. The river does not cause the wind. A collector in testing is not a clean river.

:::johnson
**the wind holds the plata up. what cannot drain still sits over the riachuelo.**

The hydraulic risk that remains is the southern river. Regional flood mitigation funds the living margin beside the plan already running. It does not take that plan over.

[see regional flood mitigation →](/solutions/governments?from=guide&topic=matanza-riachuelo)
:::

## what is already working

The work has names. PAC 2050 names the wind, the century of level, and the basin where hydraulic risk remains. The hydraulic plans have already reduced flood-prone area. Gray works are meant to be joined by green and blue infrastructure that holds water back: sustainable urban drainage, and listed actions that include opening sections of piped streams and improving river mouths. ACUMAR still carries the cleanup the Court returned, through the Plan Integral de Saneamiento Ambiental. AySA is testing the system that moves sewage out of the southern river.

Basin wetlands, in ACUMAR's account, still retain rain and river rises and slow a flood. A CONICET agreement to map them has been in force since January 2022. The city occupies the floodplain whose streams were piped, so less of that storage is open. The pipes do not set the level of the Plata.

## beside the plan, not a second city hall

**Regional flood mitigation** is the government service for the remainder. A city or a basin government uses it to fund the floodplain storage that still slows a rise, beside hydraulic works that already exist. The funding layer is *ensurance*. It coordinates. It does not operate the Hydraulic Plan, it does not write a city decree, and it does not bill ACUMAR for a statute the authority already holds.

The estuary, the towers that take its water, and the Matanza-Riachuelo are there whether or not anyone holds a certificate. Ensurance funds the living estuary and the living river. It is not the river.

The line for the river is `matanza riachuelo`, in ideation under the live parent [`parana-river.basin`](/parana-river.basin?from=guide). The Paraná is the outlet this water reaches. It is not the subject of the wind. [Co-create the line](/specific/create?mode=suggest&agent=parana-river.basin&name=matanza%20riachuelo&from=guide): a person reviews it, and the parent agent receives it. The line is a layer people can hold beside the collector in testing. It does not replace the collector.

If you run the plants and the wastewater works, the door is [source watershed investment and sewer overflow restoration](/solutions/utilities?from=guide&topic=matanza-riachuelo): the living shore and the living river, next to pipes you already operate. If you are the city, or a government on the basin, start with [regional flood mitigation](/solutions/governments?from=guide&topic=matanza-riachuelo). If you want a person in the room, [talk to someone who can help](/contact?from=guide&topic=matanza-riachuelo).

## frequently asked questions

### what is a sudestada?

A sudestada is a southeast wind over the Río de la Plata, often over 35 km/h, with rain. It raises the water and reduces the drainage of rivers and streams that end in the estuary. The wind can flood the coast. The risk that remains after the city's hydraulic work sits over the southern river.

### what does a sudestada do to the drains?

It holds the Plata up, so the drains meet a higher outlet. After the hydraulic works, the highest remaining hydraulic risk is the urban habitat over the Matanza-Riachuelo, in the south and the center. That is a drainage fact. No casualty count belongs to it.

### is 17 centimeters the height of the flood?

No. PAC 2050 says the Plata at the city rose about 17 centimeters during the 20th century, and that this rise intensifies a sudestada. That 17 centimeters is a century of level, not a street depth and not a damage bill.

### does the riachuelo cause the sudestada?

No. The wind comes off the estuary from the southeast. The Matanza-Riachuelo is the lowland river that ends in the Plata, which is why the residual hydraulic risk sits over it. Sewage, the tannery load, and *Mendoza* are a separate hazard. Works in testing are not a finished outfall, and the wind does not mean the water is clean.

### who already handles the flood and the river?

The city runs the hydraulic plans and PAC 2050. AySA runs the plants and the Riachuelo wastewater works, in testing in an August 2025 World Bank paper. ACUMAR, under Law 26.168, holds the basin, and since October 2024 the Court has left the cleanup's execution there. Regional flood mitigation funds the living margin beside those works.

## what the next wind meets

The next sudestada will not ask whether a certificate exists. The wind will raise the estuary, the drains will meet it, and the water that cannot leave will look for the Matanza-Riachuelo, the lowland the plan already named. Wetland and bank are the storage the pipes do not replace. If that remainder is your office, your intake, or your side of the river, there is a door.

[regional flood mitigation →](/solutions/governments?from=guide&topic=matanza-riachuelo)

[the utility already on the water →](/solutions/utilities?from=guide&topic=matanza-riachuelo)

[talk to someone who can help →](/contact?from=guide&topic=matanza-riachuelo)

## sources

[PAC 2050, English text](https://static.buenosaires.gob.ar/sites/default/files/2023-02/pac_2050_buenos_aires_eng.pdf) — Climate Action Plan of the City of Buenos Aires. Sudestada: a southeast wind, often over 35 km/h, with rain, that stacks the Plata and blocks the drains. The figure to keep is the century of rise, not a storm total. The Plata at the city rose about 17 cm during the 20th century, and that rise intensifies a sudestada. The city's hydraulic work has reduced flood-prone area. Highest remaining hydraulic risk: the urban habitat over the Matanza-Riachuelo, south and center. The highest remaining hydraulic risk sits over the Matanza-Riachuelo. Most natural streams were rectified and intubated in the first half of the 20th century. Green and blue complements include sustainable urban drainage, opening sections of piped streams, and improving river mouths.

[ACUMAR, características de la cuenca](https://www.acumar.gob.ar/institucional/que-es-acumar/caracteristicas-de-la-cuenca2/) — main stem 64 km; basin about 2,047 km²; 4,703,058 people in the definitive 2022 census; fourteen partidos and the comunas named above; a plains river with little slope; wetlands that hold rain and high water. The CONICET agreement has been in force since January 2022.

[ACUMAR, qué es ACUMAR](https://www.acumar.gob.ar/institucional/que-es-acumar/) — the basin authority brings together the Nation, the Province of Buenos Aires, and the City.

[ACUMAR, informe al Congreso 2023](https://www.acumar.gob.ar/wp-content/uploads/2025/11/Informe-al-congreso_2023_Final.pdf) — Law 26.168 created the authority in 2006.

[ACUMAR documentary center, la cuenca](https://centrodocumental.acumar.gob.ar/la-cuenca) — older lines still on the page: about 2,200 km² and about 6 million people. Not the figures used here.

[AySA, nuestros números](https://www.aysa.com.ar/Quienes-Somos/nuestros-numeros) — 2023 sustainability figures: average treated water 6,219,234 m³/day; well water 13 percent of production; concession area 15,103,199 people; 11,351,535 on potable service. AySA names the plants General San Martín and Juan Manuel de Rosas. The third plant in the count of three was not named.

[World Bank, August 2025, P105680](https://documents1.worldbank.org/curated/en/099082025172028148/pdf/P105680-60a8b946-e924-4105-8690-a2f3d85c639a.pdf) — the Riachuelo system in testing, and overflows the paper says testing already reduces. The tannery sector as a major industrial source, and a relocation that would take years. The outfall is not described as finished.

[Infobae, 14 August 2025](https://www.infobae.com/judiciales/2025/08/14/la-corte-ratifico-el-cierre-de-la-causa-riachuelo-y-dio-por-concluida-su-supervision-del-saneamiento/) — the Court rejected appeals and reaffirmed the close of its supervision in the Mendoza case. Used only for that close.

## the series

The Matanza-Riachuelo, with Buenos Aires as the door. The estuary is the level and the tap. The southern river is where the remaining hydraulic risk sits.

- [what buenos aires depends on](/guide/what-buenos-aires-depends-on?from=guide)
- [who depends on the matanza-riachuelo](/guide/who-depends-on-the-matanza-riachuelo?from=guide)
- [the plata is an estuary, not a tap](/guide/the-plata-is-an-estuary-not-a-tap?from=guide)
- [a sudestada stacks the plata against the drains](/guide/what-a-sudestada-does-to-buenos-aires?from=guide)
- [who already pays for the riachuelo](/guide/who-already-pays-for-the-riachuelo?from=guide)