Abstract
Abstract. Flood-inundation hazard maps are generally made based on the anticipated flood patterns under the configurations such as current topography and land use/land cover situations. These maps have not taken into account the possible significance of land subsidence and surface environmental changes. The Kujukuri Plain, Japan, the site of this research, has experienced severe land subsidence due to 2011 Tohoku earthquake. This paper aims to quantify the effects of local land subsidence on flood hazards under heavy rainfalls in the Kujukuri Plain. The high-resolution LiDAR data at two different periods (before and after the Tohoku earthquake) were obtained and used as the input data for the physically-based hydrological model. Through the comparison of simulated inundation areas of the scenarios with the same precipitation pattern but different topographies, the effect of land subsidence was discussed. The maps estimating the inundation areas by only considering rainfalls, i.e., without taking into account the effect of land subsidence, underestimated the inundation areas by around 10 % compared with the ones that accounted for the local land subsidence. The results of this study highlight the importance of taking into account the temporal changes of elevations and other parameters in flood hazard assessments.
Highlights
Flood hazard, which means intensity and severity of floods, affects human society and its economic development (Willner et al, 2018; Winsemius et al, 2013)
Around 98 % of the surveyed flooded area can be reproduced by the calculated inundation areas with T13W case, which further gained the confidence of the developed dynamic flood model
The inundation areas of both case T13W and T04W (Fig. 4) showed that the coastal areas, urban areas, and the places along the rivers were most vulnerable to floods
Summary
Flood hazard, which means intensity and severity of floods, affects human society and its economic development (Willner et al, 2018; Winsemius et al, 2013). The low latitude regions in Asia and Africa, show severe inundation hazards with the warmer climate (Hirabayashi et al, 2013; Moss et al, 2010). Earthquake is another natural hazard, which causes significant negative repercussions including soil liquefaction, infrastructure collapse, landslides, tsunamis and land subsidence. The tectonic movement due to 2011 Tohoku earthquake has caused severe land subsidence in this area. Ozawa et al (2011) reported that almost all the land in the study area showed more than 0.1 m settlements. The main objective of the contribution is to examine the effects of the local land subsidence on the inundation hazards in the coastal basins
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