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.
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.