The Pacific Tsunami Museum Programs

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NZSEE

NZSEE reconnaissance mission to study the effects of the
26th December 2004 Asian Tsunami in Sri Lanka


Photography by Jeff Topping and Dr. James Goff

Dr. James. R. Goff (pictured above) of GeoEnvironmental Consultants teamed up with US and Sri Lankan researchers to study the East, South and West coasts of Sri Lanka. from January 7-17th. This preliminary report from Dr. Goff deals with data from the South and West coasts where he gathered geological information aimed at reducing tsunami risk in Sri Lanka. In addition, the team took survivor interviews to determine number and arrival times of waves, inundation and runup. Where possible, inundation and runup were also measured.

General findings:

	The first wave arrived at about 9.00am, with two subsequent waves arriving at 15-20 minute intervals. The positive part of the wave arrived first, and the second wave was the largest (max. runup = 11.0 m; av. = 4.0−5.0 m).
	There was a marked change in tsunami characteristics somewhere between Matara and Weligama on the SW coast. At Matara the wave pattern followed that described above, but at Weligama we start to see a consistent pattern for the rest of the West coast with small (c. 2.0 m) waves (1 or 2) starting around 9.20am, with a larger wave (5.0−7.0 m) arriving around Noon. Given the time delay and relatively shallow water depths, we believe this represents a wave reflected off the coast of India. Further work is being carried out to investigate this phenomenon.
	Nearshore and coastal topography/geomorphology were recognised as having a significant impact upon inundation and runup. Gaps in the shore platform and river mouths served to focus wave energy, artificially reduced dune heights and low-lying spits backed by lagoons (similar to PNG) allowed greater inundation and runup. Severe coastal erosion (the result of cyclonic activity and river/offshore sand mining) along the SW coast appears to have exacerbated tsunami damage by changing nearshore topography. Coastal protection features (riprap, etc..) have been severely compromised by tsunami erosion, and considerable amounts of remaining offshore and nearshore sand have been transported onto the land. We expect to see severe erosion and storm inundation in ensuing years unless remedial action is taken.
	We were able to collect a considerable amount of geological data that has already proved useful in determining wave behaviour on the land. It is hoped that this will be used in association with mathematic models to improve our understanding of how tsunami behave on land Two issues of concern were raised by our Sri Lankan counterparts−they wish to know whether the December 26 tsunami was the largest that could impact Sri Lanka, and how frequently has Sri Lanka been impacted by tsunamis in the past. New Zealand has good expertise in the area of palaeotsunami research and this may provide an opportunity to contribute further in the form of scientific aid.
	The coast road was reopened 3 days after the tsunami and, with the exception of one or two bridges, is in a moderate state of repair. The railway however has been ripped up and destroyed over many kms, with several bridges damaged or missing. The government has talked of having this operational within 3 weeks. 3 months is a more realistic figure.
	Most of the communication routes and lifelines run sub-parallel to the coast through densely populated settlements that form an almost continual urban sprawl from Colombo to the far south on what is often a narrow coastal platform. Most affected have been telecommunications, water supplies, and sewer pipes. Many wells have been contaminated by saltwater and debris but they are still the only source of water for many communities. The potential for disease is exacerbated by the dumping of debris in roadside wetlands.
	Buildings close to the shore were generally of poor construction (fishing communities and slums)−brick, some concrete with inadequate reinforcing, and wood. These were sandwiched between the road and/or railway line and the sea. Most were destroyed, or damaged beyond repair. On the landward side of the road/railway, buildings were more robust, generally constructed in brick or concrete. In many places however these were also partially or completely destroyed. The most resilient buildings were large hotels that appeared to be of better construction.
	Aid (international and central government) is patchy at best. We encountered our first aid vehicles on Jan. 12th. Aid centres have generally been set up adjacent to major centres, with good coverage of one or two areas, but with such a high population density, settlements even a few kms away are receiving nothing. In most cases we were the first people to be handing out any form of aid (clothing and toothbrushes).