Tsunami Report(Page 21-40)

Subsequently a series of waves hit the coast at 10:45 hrs, 12:30 hrs, 15:10 hrs and17:10 hrs and the sea level returned to the original level around 18:30 hrs. At14:50 hrs water line receded by 150 m from the original shore (Fig.21). Theobservations revealed that the run-up height at Chennai is about 3 m. Thiscontradicts the estimated run-up height of 1.4 m at Chennai by Institute ofGeophysics and Planetary Physics, University of California (Fig.14) indicating thattheir model needs further calibration with regional data.HWLMWLLWLICMAM-PDFIG 21. Visuals of water level change during Tsunami at Besant Nagar beach,ChennaiScientists of ICMAM-PD making observations using RTK and DGPS.Elevation of beach/land and presence of sand dunes are controlling factors for waterexcretion and extent of damage caused by the waves. Marina beach, a fewcentimeter above mean sea level, experienced maximum inundation. About 1.8 km 2of coastal area between Adyar and Cooum rivers along Chennai coast is inundated.The sea water excursed up to 590 m at Foreshore estate (Adyar river side) and480 m at MGR memorial (Cooum river side) with a narrow excursion of 290 m atmid-stretch (Fig.22). The series of tsunami waves had a positive effect on Adyar andCooum rivers, which are sewage carriers, whose mouths closed for most part of theyear due to sand accretion, got opened, though temporarily, due to which theseheavily polluted waters with sludge were flushed out to a great extent (Fig.23) which31