A Hybrid Machine Learning Framework for Improved Short-Term Peak-Flow Forecasting

Reliable river flow forecasting is an essential component of flood risk management and early warning systems. It enables improved emergency response coordination and is critical for protecting infrastructure, communities, and ecosystems from extreme hydrological events. Process-based hydrological models and purely data-driven approaches often underperform during extreme events, particularly in forecasting peak flows. To address this limitation, this study introduces a hybrid forecasting framework that couples Extreme Gradient Boosting (XGBoost) and Random Forest (RF). XGBoost is employed for continuous streamflow forecasting, while RF is specifically trained for peak-flow prediction, and the two outputs are combined into an enhanced forecast. The approach is implemented across 857 catchments of the LamaH-CE dataset, using rainfall and discharge observations at 6-hour resolution. Results demonstrate consistently high skill, with 71% of catchments achieving a Kling-Gupta Efficiency (KGE) greater than 0.90. Peak-flow detection reaches 87%, with a false-alarm rate of 13%. Compared to the European Flood Awareness System (EFAS), the framework achieves lower peak-magnitude errors, fewer false alarms, and improved streamflow and peak-flow forecasting accuracy. The proposed framework is computationally lightweight, scalable, and easily transferable across watersheds, with training times of only seconds on standard CPUs. These findings highlight the potential of integrating hydrological understanding with efficient machine learning to improve the accuracy and reliability of operational flood forecasting, and outline future directions for hybrid hydrological-machine learning model development.