The Waterborne Toxic Event

satellite image of the Rio de la Plata; the large amounts of freshwater pouring from the Parana and Uruguay Rivers mean that the water contains almost no salt at Buenos Aires; strong, sustained winds out of the south east over the atlantic ocean can push a wall of water up the estuary, backing up the flow of the Parana and Uruguay- flooding the delta- and backing up smaller rivers such as the Riachuelo, resulting in floods in the low-lying areas of Buenos Aires

Sudestada events are meteorological phenomena particular to the Rio de la Plata estuary.  They occur when sustained winds out of the southeast push ocean water up the estuary.  When combined with high tide these events can raise water levels in the estuary 13 feet or more.  These events can cause flooding in low-lying urban areas, especially the densely populated zones around the Riachuelo, and when combined with heavy rains they effects can be devastating as the stormwater has no outlet.  When these floods occur inhabitants are in danger from the overtopping of bulkheads and levees by the disgusting and highly contaminated waters of the Riachuelo, as well as sewers backing up into the streets and basements of homes.  Personal damage to property and long-term health effects are proving devastating to residents.

A 2004 report in the Journal of Climatology classifies a sudestada as an event that raises the water level 8.25 feet or more for longer than 24 hours.  In the fifty year study period from 1950-2000, these occurred an average of six times per year, with a slight uptick in recent years.  At 10.25 feet the protective bulkheads and levees along the canal are overtopped in some vulnerable places in the lower portion of the Riachuelo basin.  These events occurred on average more than once per year during the study period and seem likely to increase given effects of possible sea level rise on the estuary in the future.

To combat the most serious flooding issues- caused by a sudestada combined with overland rain- ACUMAR is developing a macro/micro drainage strategic plan.  This plan calls for the creation of 10 large reservoirs in the upper basin of the Riachuelo (macro-drainage) and for new urbanization patterns to focus on minimizing damage to property, health, and habitat in the urban areas.  This is opposed to the historic strategy of simply trying to flush the water away as quickly as possible, which often causes issues downstream, especially when the water cannot go further downstream because of a 10 foot wall of water being pushed up the Rio de la Plata.  Under this strategy stormwater in urban areas (micro-drainage) should be retained and allowed to percolate into the soil or small-scale surface or subterranean reservoirs where possible.

a map showing ACUMARs macro-drainage strategy for the Riachuelo watershed; the metropolis of Buenos Aires is in grey, the watershed of the Riachuelo the irregular red line, the macro-drainage reservoirs are in blue positioned outside of the city; this strategy will reduce flooding pressures on the Tierra Plastica site near the mouth of the Riachuelo during events when a sudestada combines with overland rain

Objective

Given the frequency and severity of these events the design strategies for Tierra Plastica must be aimed toward the objective of retention and percolation.  In addition, while the bulkheads and levees in the lower basin prevent all but the most severe flooding, and there is a tradition of private adaptation (building the first floor higher) in the neighborhood of La Boca, the long term strategy of Tierra Plastica must take in to account more severe and frequent sudestada events as indicated by the trends of the last 30 years, as well as the effects of possible sea level rise on the estuary.  Lastly, while damage to health and property must be limited, the phenomenon of flooding itself is an important cyclical aspect of the hybrid ecology of the Riachuelo.  The salt water intrusion and elevated water levels bring seeds, sediments, salt, and organisms to the ecosystems as necessary nutrients and provide a sort of inadvertent locomotion for certain residues and organisms in the landscape.  These annual cyclical events should be leveraged as power- as work- for their instrumental effects, a moment when humans retreat inside from the weather, and a new world is created.

sections through the Tierra Plastica portion of the Riachuelo; the text on the left side of the channel in the sections indicates the historical depths of the channel and the white layer is newly accumulated sediment since dredging ceased; on the right side of the channel in the sections are the water levels along the floodwall of during specific events such as daily tidal fluctuations, an average sudestada, a major sudestada, and the highest ever recorded

About these ads
2 comments
  1. Daniella Gitlin said:

    Hello!
    I’m looking for a map of Buenos Aires and I love the one you’ve got here that shows the trajectory of the pushed ocean water. I’m wondering if you can share that map with me, or have any suggestions of how to create one myself. Thank you very much!

    • Hi Daniella-
      I just produced that using gis info from streetsmap.org and integrating it with the .kml files available from ACUMAR. You are welcome to use the jpg of the image there on my site.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 29 other followers

%d bloggers like this: