HR: 15:00h
AN: OS43A-05    [Abstracts]
TI: Coastal Sedimentation And Risks Of Tsunami Associated With 26Th December 2004 In The Kanyakumari Coast Tamil Nadu, India
AU: * Chandrasekar, N
EM: ncsmarine@yahoo.co.in
AF: Manonmaniam Sundaranar University Manonmaniam Sundaranar University , Centre for GeoTechnology Abhisekhapatti, Tirunelveli, TN 627 012, India
AB: The Tsunami signatures were formulated from the field evidence from 26th December 2004 tsunami surge in the Kanyakumari coast. The impact of Tsunami can be identified form the preservation of geomorphic signatures and sedimentary deposits. The more common signature of Tsunami in the deposition of sand with thickness of 20cm towards landward and are sandwiched between finer material and debris on flat coastal plains. Black sands were transported by the strong Tsunami wave flow across the coastal vegetation and could be seen as deposits discontinuous pencil thin lenses in the landward. Thicker units were characterized by a series of lighter minerals fining upwards stacked one upon each other. Each unit indicates the single wave in the Tsunami wave train. Further the relative size of sediment in each site gives and indication of the magnitude of each Tsunami wave. Coarse marine sand mixed with pebbles in landward. tapering sheets was noticed. The Tsunami characteristics were heavily dependent upon the configuration of the coastline. Run up heights In the many locations were three times greater than the initial height of the wave at shore. The damage of concrete roof and Manakudi Bridge indicates the flow velocities and force of tsunami. The Tsunami deposited 15 to 20 can thick sand splays behind sand dunes of chothavilai, pallam and Azhikal coast were seen. The dump deposits were observed around obstacles and road erosion also occurred with formation of turbulent vortices around obstacles and in channelised backwash. Flow velocities were interpreted form these sediment features with those of structural and building damages. A careful observation in the fields indicate that the coast of Kanyakamari is more susceptible to tsunami run up, flooding and inundation. The type of offshore bathymetry and coastal setting are prone to tsunami. The tsunami flood across river inlet and offshore bathymetry is steep. The river mouth surfaces lying only a few metters above sea level have allowed tsunami to penetrate long distances inland. Tsunami wave approached the shore rapidly and with most of their energy intact in manakudi and colachel. The wave at shallow depth of river inlet / creek has traveled less whereas the deep area experienced the more flood. The residents living along the river banks were affected by the tsunami. The risk is very high. Tsunami has an affinity for head lands. They are not blocked by cliffs. The wave energy is concentrated here by wave refraction. Amplitude of wave on headlands is two to three folds relative to an adjacent embayed beach.
DE: 0468 Natural hazards
DE: 1861 Sedimentation (4863)
DE: 1862 Sediment transport (4558)
DE: 4217 Coastal processes
DE: 7914 Engineering for hazard mitigation
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly