This study investigated the influence of the presence/absence of linear structures such as roads on inundation propagation through numerical experiments using the 2015 Kanto/Tohoku heavy rainfall disaster as a case study. The numerical experiments revealed that the propagation speed of inundation flow differs by up to half depending on the presence/absence of linear structures such as roads. Specifically, the maximum speed of inundation flow without roads was 0.49 m/s, while that with roads was 0.27 m/s. Since the estimated walking speed for people with walking difficulties or physical disabilities is 0.5 m/s, it was suggested that the presence/absence of linear structures such as roads plays an important role in ensuring that evacuees have a sufficient distance to travel before the inundation flow reach them.