A systematic review on rainfall thresholds for landslides occurrence.

The study of rainfall thresholds is vital in understanding the factors that trigger landslides, being one of the criteria applied to landslide early warning systems that aim to mitigate their consequences. These thresholds enable the prediction of landslide occurrences as a function of rainfall measurements. This work presents an overview of the parameters involved in defining rainfall thresholds based on scientific articles published between 2008 and 2021 that discuss the subject through statistical or physical methods. These articles provided data such as publication information, threshold types, details on the data used in the works, methodology, and application of the threshold in early warning systems. There was a significant increase in research papers on this theme during this period, possibly due to the strategies advocated by the Sendai Framework. However, some regions of the world severely affected by landslides are barely mentioned in these studies. The results indicate specific trends, such as those found in the methods used to define rainfall thresholds and the parameters relating to the database when a statistical approach was used. Certain deficiencies were found, such as those concerning geological-geotechnical conditions for categorizing thresholds, the time scales of rainfall data, rain gauge density, and the criteria to define the accumulated rainfall period to be considered.

Payment for environmental services for flood control analysis and method of economic viability.

Disorganized urban growth, deforestation, and the occupation of floodplains and riverside areas significantly alter land-use patterns and social and environmental wellbeing. This work aims to present the analysis of the feasibility of the proposal for the implementation of a Payment for Environmental Services (PES) project for flood control. It is related to the recovery and conservation of areas of environmental interest in a hydrographic basin and considering the river channel as a reference and its buffer areas. For the implementation of a PES project aiming at the reduction of floods downstream through the recovery of riparian forests, including their subsequent maintenance, this work proposes a flowchart of the applicable steps, develops a formulation for the definition of payment for the service, and defines a set of measures necessary for its management. Through a case study, it was possible to simulate different scenarios for different recurrence time (RT) in the study area, and thus assess the damage caused by these different events. The innovation of this work comes from the use of PES for the control of floods, with the use of an integral formula to calculate the costs of PES and to evaluate the expected damages. The application of the Poisson distribution was used to estimate the losses for different RT events expected in 50 years, estimating the losses overtime for the scenario with the implementation of the PES project and without it. The damage when reduced or avoided becomes a useful resource for the establishment of other public policies.