Improving Landslide Forecast in Real Time Using the Integration between Weather Radar and Rain Gages: Case Study; Megacity São Paulo

This paper aims to show how the integration between weather radar and rain gages is used to improve landslide forecast in the megacity of São Paulo. The city of São Paulo is one of the biggest city in the world. However, this megacity has a chronic landslide problem that occurs every year, especially during the summer. Structural measures for landslide control are extremely expensive and not possible to be built in short term. In this scenario, non-structural measures such as a warning system is an alternative measure. This system aims to provide real-time occurrence and forecast of landslide that may cause impacts in several areas of the city. The city of São Paulo has more than 400 areas with high and very high landslide susceptibility. The accuracy of landslide forecast in real time is extremely important for a good result. Precipitation is the main forcing in this process and must be estimated properly. Rain gauge networks can represent rainfall locally but has a bad spatial representativeness. Weather radars provide very high spatial resolution but not so good accuracy for rainfall intensity. The integration of radar estimations with rain gauge network is capable to minimize errors of both. The goal of this work is to present a methodology to merge weather radar estimates with rain gauge network to calculate the rainfall accumulation over the risk areas. For the integration, it was used São Paulo weather radar and the rain gauge network from São Paulo Flood Warning System.