The role that radar forecasting and hydrodynamic modelling may play in predicting flooding in coastal areas

Flooding is one of the most common and destructive natural disasters in coastal areas, involving considerable deaths, losses, and other severe consequences in many low-lying regions across the globe. Because of their highly developed economies and dense populations, coastal cities are especially vulnerable to flooding. In recent years and beyond, climate change is anticipated to considerably increase the flood risk in coastal areas. Consequently, it is of ultimate importance to develop efficient flood risk mitigating measures based on numerical models that properly capture the dynamic processes of coastal flooding based on reliable rainfall measurements and forecasts.

Radar rainfall measurements have been viewed as potential model input for flood modelling as it is able to provide better representative of rainfall patterns with their variations at high spatial and temporal resolution. Radar forecasts at short lead times are also found to be the most skilled method for producing QPE (Quantitative Precipitation Estimation) and QPF (Quantitative Precipitation Forecast) at high spatiotemporal resolutions. For urbanized catchments in coastal areas, hydrodynamic models driven by high resolution rainfall data provided by radar observation and forecasting may present efficient tool for simulating and predicting the rainfall–runoff responses.

This study, therefore, aims to develop a robust way to assess the impact of spatial and temporal variability of floods using radar rainfall data against rain gauge ones over Guangzhou, a typical city in the Pearl River Delta of the Greater Bay Area in the southern China, which is frequently suffered from pluvial flooding. A 2D High-Performance Integrated hydrodynamic Modelling System (HiPIMS) was employed to support the flood modelling, especially for simulating highly transient flooding process in intensely urbanized part of Guangzhou. With the objective of exploring the spatial and temporal heterogeneity of flooding in coastal areas induced by complex rainfall patterns, comparisons were made between the simulations driven by rain gauge measurements and radar QPE and QPF, in terms of maximum inundation conditions and spatiotemporal evolutions. Results of this study may potentially help improve the accuracy of coastal flood forecasts and thus provide information for developing more reliable flood mitigation measures.