Towards improved flood prediction: a review of deterministic hydrologic-hydraulic model coupling

This review article examines how deterministic hydrologic and hydraulic models have been coupled to improve flood prediction and forecasting. Based on a scoping review of 94 peer-reviewed studies published between 1994 and 2024, it traces the evolution of model coupling approaches, identifies the most frequently used model combinations, and discusses how these methods support flood early warning, especially in places where data are limited. The paper pays particular attention to the practicality of deterministic coupling in data-scarce contexts, where highly data-driven methods are often difficult to implement.

The findings show that the most widely used coupling is HEC-HMS + HEC-RAS, which appears most often in the literature and consistently shows strong predictive performance, including high coefficients of determination and good inundation mapping accuracy. It also highlights a strong global imbalance in research, with most studies concentrated in high-income regions, while Africa remains underrepresented despite severe flood impacts. The authors conclude that deterministic hydrologic-hydraulic coupling remains a realistic and effective pathway for improving flood forecasting and early warning systems in resource-constrained regions, provided that calibration, validation, and local constraints are carefully addressed.