Radiation levels in Hiroshima today are comparable to those in any other city. Levels of residual radiation declined quickly after the bombing as a result of radioactive decay as well as a devastating natural event. On September 17, 1945, the Makurazaki Typhoon struck the region, killing hundreds of bombing survivors. However, the extensive flooding caused by the storm also washed away the fallout-contaminated layer of topsoil. Subsequent measurements of residual radiation reflected a significant drop, suggesting that the Makurazaki Typhoon (as well as second typhoon that hit Hiroshima in October 1945) had effectively functioned as a large-scale decontaminator.