We present an overview of the unprecedent hydrological event that occurred in Rio Grande do Sul state in late April and early May 2024, causing floods and landslides in a scale that was not seen before in Brazil. The rainfall that caused the disaster is incomparable to any recent event in Brazil at large spatial and temporal scale. The intense and long-lasting precipitation led to record floods from small rivers with drainage areas below 1000 km² to the Patos Lagoon, which drains more than 180,000 km². The rainfall also led to landslides that rank first in Brazil in terms of spatial scale and number of occurrences. Mountain rivers experienced flash floods with extreme water levels, while in the lowlands the large rivers and the Patos Lagoon experienced long duration flooding, with stage remaining high for about 30 days. The flood event is probably ranked first in terms of displaced people and damage to property and infrastructure in Brazil. Almost 200 fatalities occurred due to the disaster and protection structure failures. The April-May hydrological event show a glimpse of what can be expected along the coming decades due to climate change in a region that covers South Brazil, and parts of the neighboring countries.

In Brazil, little is known about climate change impacts on extreme events at local scale. Here, we explored ways of communicating it, in the form of intensity-duration-frequency (IDF) curves, using the nonstationary equidistant quantile matching (EQM_NS) method. EQM_NS was applied in two urbanized areas of Brazil: São Paulo and Porto Alegre. This research was conducted using recorded and modeled precipitation data, the latter using the Regional Climate Model Eta. Results indicated an increase in rainfall intensity for rare events, which were intensified under nonstationarity. The use of stationarity misrepresented the trends related to precipitation, being able to mask the direction of change in future conditions. Future IDFs with Eta’s 3-hourly resolution appeared to be intensified when compared with those from daily resolution. The increase in rainfall intensity was more significant for short durations than for daily ones, bringing concerns about associated hazards and their impacts on society and urban infrastructure.

The degradation of urban rivers is a phenomenon caused by virtually all cities intersected by rivers. Currently, there is a substantial number of revitalization projects in progress. Nonetheless, their execution demands significant investments, particularly for water quality enhancement. Moreover, apart from the cost factor, the scarcity of space along their banks constrains the implementation of improvement systems. This study introduces a simplified methodology aimed at evaluating the technical feasibility of revitalization interventions within urban river segments, with a focus on enhancing water quality and user experience. The method follows a structured framework encompassing four sequential phases: execution of hydraulic, hydrological, and sanitary analyses concerning the watershed; development of foundational principles and intervention strategies pertaining to the riverbed; appraisal of the congruence between proposed interventions and the intrinsic attributes of the river channel; comprehensive assessment of the overall viability of the revitalization initiative. The method's validation was conducted through a case study involving the Dilúvio Stream in Porto Alegre, RS, showcasing its coherent application and adaptability within the predetermined premises. Thus, the methodology emerges as a preliminary decision-making support tool for projects related to the urban river requalification domain, facilitating the identification of met prerequisites and provision of informed guidance.

Este artigo apresenta uma nova t