The challenges of the Brazilian electric energy regulatory agency on mitigate effects from 2024 Rio Grande do Sul floods
Between April and May 1941, Rio Grande do Sul was hit by torrential rains that lasted more than four weeks. The rainfall was probably influenced by El Niño, although the phenomenon had not yet been identified.
As happened in 2024, the rains raised the water level of the river basins that flow into the Guaíba. The rainfall exceeded 1,000 millimeters in some regions of the state and reached 791 millimeters in Porto Alegre. Similarly, the strong wind coming from Lagoa dos Patos reduced the speed of the runoff, damming up the water in the Guaíba. The difference between the 1941 and 2024 events lies in the fact that this time they were more intense (22 days of rain on average in 1941 and now 6, less than a week, in 2024). When comparing the events of 1941 and 2024, the researchers[22,23]
indicate that in the first episode it took 22 days for the water level in Lake
Guaíba to reach 4.76m above normal levels. This year, however, the Guaíba exceeded 5m in just five days. Another condition to consider is that although both events occurred during an El Niño period, so did other cases listed by the authors over the last 124 years. However, the 1941 flood occurred at the height of an El Niño that lasted from 1939 to 1942; while the 2024 flood occurred during the end of the 2023 and 2024 episode. Figure 9 shows the years in which floods were recorded in the state. It can be seen that in every decade
there were at least three episodes. Even in the 1950s, considered the driest decade of the 20th century, there were still episodes of flooding.
Figure 9. Rainfall history in Rio Grande do Sul - Years with some record of flooding in Rio Grande do Sul (1900-2024)[23]
This brief analysis of vulnerability and exposure indicates that RS is likely to face more frequent and serious impacts related to flooding in the future. It should be noted that the variability of river flows does not always follow the behavior of rainfall, demonstrating that factors other than climate, such as those associated with water use, infrastructure operation, land use and occupation, among others, have a major impact on the events observed. In this context, there is a need to invest in hydrological studies, considering more robust analyses, including verification of the hypotheses of stationarity of series, risk analyses and scenarios of probable maximum floods.
5. Recorded Safety Accidents and Incidents and Their Implications The NDSP transfers to the supervisory body the power to determine the preparation of Emergency Action Plans (EAP) according to the risk category and potential damage associated with the dam and must always require this for dams classified as having HIGH potential damage. In this context, in addition to a monitoring policy based on risk classification, the Agency analyzes the Safety Level of the projects under its supervision through the reports it receives. The safety levels guide those involved in defining the degree of danger in emergency situations, helping with decision-making and
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