Report on Asian tsunami ascending the river,and its associated bank erosion and bridge failure in Sri Lanka

Hiroyasu YASUDA*, Yasuharu WATABABE*, Kazuyoshi HASEGAWA#,Hiroshi MITAMURA*, and NMNS Bandara Nawarathna$

* CERI, Civil Engineering Reaserch Institute of Hokkaido # Factory of Engineering, Hokkaido University $ Technology Center, Taisei Corporation,

INTRODUCTION

When a extremely destructive earthquake occurred off Sumatra at the end of December 2004, many regions were struck by a colossal tsunami. At west coast area of Sumatra the tsunami heights reached 30 m or more. The tsunami attacked along coastlines and ascended river channels in countries on the Indian Ocean, killing more people than any other tsunami disaster in history and devastating houses, river structures, roads, bridges and other infrastructure.

Major rivers and elevations in coastal areas of Sri Lanka (major cities, and the surveyed rivers )

This report presents the results of an onsite investigation on the mechanism of tsunami runup in the river, which has not been elucidated, and damage to river structures such as bridges and embankments. The damage was only from the tsunami and no other forces. The area covered in this research includes two rivers whose estuaries are on Sri Lanka's east coast.

• SURVEY ON TSUNAMI RUNUP IN THE RIVER
  1) Yan Oya
  2) Mahaweli Ganga
  3) Comparison with the tsunami runup in the river in Japan
• DRAINAGE OF WATER INTO SMALL CHANNELS
• DAMAGE TO BRIDGES, AND NEARBY TSUNAMI TRACES