Proposta de classificação quanto ao dano potencial associado para barragens em cascata

Abstract

The failure of dams represents one of the highest-risk scenarios associated with hydraulic infrastructure, particularly when these structures are arranged in cascade along the same watercourse. Despite the relevance of this topic, the criteria currently adopted in Brazil for classification regarding potential associated damage (DPA), established within the framework of the National Dam Safety Policy (PNSB), consider dams individually, without explicitly addressing the cumulative effects and hydrodynamic interactions between interconnected structures. In this context, this study aims to evaluate the hydrodynamic behavior of flood waves resulting from the hypothetical failure of dams arranged in cascade, as well as to propose new classification criteria for DPA under such scenarios. To this end, nine sets of earthfill dams for water storage were analyzed, representing different combinations of upstream and downstream dam sizes. The failure simulations were carried out using two-dimensional hydrodynamic modeling in the HEC-RAS software, considering four hydrological scenarios: no precipitation and precipitation events associated with return periods of 500, 1,000, and 10,000 years. The results were analyzed based on maximum depth, velocity, and hydrodynamic hazard maps of the floodplain, and the methodology proposed by Smith et al. (2014) was also considered. The results showed that, in several scenarios, small upstream dams had their impacts attenuated by downstream dams, whereas certain volume combinations led to a significant intensification of hydrodynamic risk, highlighting the importance of integrated assessment. The findings indicate that analyzing dams individually may underestimate or overestimate the associated potential damage, reinforcing the need for specific criteria for cascade dam systems. Thus, this study contributes to the improvement of risk assessment practices and dam classification, providing technical support for a more representative approach to the impacts associated with cascade systems.