MECHANISM OF LATE RECOVERY OF RIVER MOUTH MORPHOLOGY AFTER THE 2011 TOHOKU TSUNAMI

Abstract

 The 2011 Great East Japan Earthquake and Tsunami induced such intense devastation on many coastal regions and among them, the Naruse and Kitakami River mouths are the areas where their sandspits had not been recovered for a long period. This study, by analyzing aerial photos, has learned that the sandspit were vanished after being hit by the tsunami. Subsequently, waves were able to propagate further into the river mouth and sediment deposition was observed at the areas roughly hundred meters to 1 km upstream from the river mouth. Afterwards, the recovery of the sandspits has reflected similar process which sediment advances seawards. This phenomenon is observed in either the Abukuma River mouth in which the area was also damaged by the tsunami or the Mogami and Koyoshi River mouths where the jetties were constructed. Based on this study, the expected time for these areas to recover is evaluated as well.