Trends and variability of storm surges in Buenos Aires

SANTAMARIA-AGUILAR S.; SCHUERCH M.; CARRETERO S.; VAFEIDIS A.

Conferencia; EVAN; 2017

Buenos Aires is located inthe inner part of the Rio de la Plata estuary, which is one of the largest andmost densely populated of South America. Due to the shallowness of the estuary,storm surges can rise up to 3.5 meters above mean sea level (MSL). Extensiveparts of the city are located in low-lying areas, prone to coastal and riverineflooding and thus can be heavily affected by extreme water levels (EWL). Theseevents also affect navigation in the Rio de la Plata and the operability of theport of Buenos Aires, which is the largest port of Argentina and one of the 10largest of South America; and impact the morphological development of thewidespread estuarine marshes. Basedon the tide-gauge records of Buenos Aires over the last century (1906-2013) weassess secular changes in the main factors contributing to EWL, namelyastronomical tide and storm surge. Although previous studies have assumedindependence between the storm surge and the astronomical tidal levels, we observethat the peaks of the non-tidal residual tend to coincide with low tidal levels.For this reason, we use the skew-surge parameter in order to account for themeteorological contribution. Preliminary analysis shows that the majority ofthe EWL (defined as those exceeding the 99.5% level) do not arise from springtidal levels, but from extreme skew surges. Tidal levels show significantdecadal changes resulting in a significant long-term decrease of the mean tidalrange. However, both EWL and skew surges show no significant linear trends exceptfrom a MSL trend over the last century. EWL can occur at any time of the year,but they are less frequent, albeit more intense, during winter months. During theother seasons, EWL are produced by the occurrence of moderate skew surges incombination with high and spring tidal levels. This introduces differences inthe interannual variability of EWL compared to the variability of extreme skewsurges. Further to this analysis we also look at changes in the seasonality andinterannual variability over the last century and explore potential links to riverdischarge and climate systems, such as the El Niño Southern Oscillation, inorder to assess different hazard scenarios for the region of Buenos Aires.