Impact-based forecasting to cope with riverine floods in a Peruvian Andes-Amazon basin

Impact-based forecasting (IBF) enhances natural disaster risk management by focusing on the vulnerabilities, livelihoods and assets. Here we introduce the methodology of PANDORA, a system designed to provide impact-based forecasts for Huallaga River Basin in the Andean-Amazon region of Peru. PANDORA integrates a large-scale hydrological model with precipitation forecasts resampled from historical meteorological data to produce 5-day probabilistic streamflow forecasts. These forecasts are compared against flood thresholds for 2, 5 and 10-year return periods, and are subsequently linked with five key flood-exposed elements. The system performance was evaluated in terms of the ability to represent flood events and their impacts during December 2023. Results show that flood events were primarily forecasted between 27 and 30 December, while the IBFs indicated extreme severity for the exposed elements mainly on 27, 30 and 31 December. These findings align with reports from the Information System for Response and Rehabilitation of Peru.