Employment of hydraulic model and social media data for flood hazard assessment in an urban city

Study region An urban city in the coastal region of East Japan.Study focus This study implemented the hydraulic model to investigate the flood events in Mobara city, Japan. The model was calibrated by the flood on July 1, 1970, and then validated against the flood on October 25, 2019. Simulated flood extent and temporal changes of water depths agreed well with the observations from social media data, suggesting that the hydraulic model could reproduce floods in the study area. Comparison of the two flood events indicated that the areal extent of flood increased by a factor of 5.5 over the 50-year period, caused by the changes of land use/land covers, topographies, and input river water levelsNew hydrological insights for the region Intensive rainfall-induced fluvial floods have caused catastrophic repercussions in urban areas. One of the major challenges in urban flood simulations is lack of field observations to evaluate the performance of numerical models. Our study highlights the possibility of employing hydraulic model and social media data to reduce the uncertainty in flood simulation, and the necessity of considering the temporal changes of land use/land covers, topographies, and input river water levels for flood mapping in urban cities.

Automated summary

This study implemented a hydraulic model to investigate flood events in Mobara city, Japan. The model accurately reproduced the floods in the study area, and it was found that the extent of flooding had increased by a factor of 5.5 over a 50-year period. Therefore, it is important to consider changes in land use/land covers, topographies, and input river water levels in urban flood mapping.