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

• Published in: Journal of hydrology. Regional studies 2022-12, Vol.44, p.101261, Article 101261
• Main Authors: Ouyang, Mao, Kotsuki, Shunji, Ito, Yuka, Tokunaga, Tomochika
• Format: Article
• Language: English
• Subjects: Hydraulic model; Input river water level; Land use/land cover; Social media data; Soil infiltration; Urban flood
• ISSN: 2214-5818; 2214-5818
• DOI: 10.1016/j.ejrh.2022.101261

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 levels. New 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. •Hydraulic model and social media data were integrated for flood simulation.•Permeability change caused by land use/land cover change affected flood extents.•Land subsidence exacerbated both flood extents and depths in urban cities.•Intensive rainfall-induced high river water level was a dominant factor to flood hazard.•Nonlinear relationship between floods and parameters was needed to account for flood assessment.