We proposed an evacuation route search method that takes into account the depth of inundation caused by river flooding. From a map of the Kuma River basin in Hitoyoshi City, Kumamoto Prefecture, which was inundated by river flooding in July 2020, we created a graph that takes into account intersections, the length of roads connecting them, the depth of flooding, and the burden on walking due to flooding. The proposed method using these graphs shows the possibility of finding safer evacuation routes that are more realistic and take into account the depth of flooding, rather than simply assuming the shortest route to an evacuation site or that the flooding is a dead end. The graphical representation of the map and the load on the walker provides a basis for future research on evacuation routes that take into account congestion avoidance, using complex network analysis methods.