Factor: Depth of penetration

A tsunami's depth of penetration depends on the wave height and the topography on the coast and inland. This loss inspection revealed that, in most cases, the water on the west coast of Thailand only penetrated 200—300 m inland. Only in Khao Lak did the tsunami go as far as 1.5 km inland.

Damage

It was generally observed that the buildings with the most severe damage were those built directly on the shore. Nearly all total collapses occurred in the row of bungalows nearest the sea, whereas the only damage in the second and third rows involved non-structural elements like partition walls that had caved in.

It was also found that, regardless of the depth of penetration, the water flowing back into the sea caused much the same degree of damage as the inrushing water.

There was considerable soil erosion, particularly in areas near the shore. Weak spots like the mouths of small streams or inlets were particularly badly affected. As the flood waters apparently had a higher rate of flow in these areas, their destruction potential was also greater. In many instances, the foundations were eroded by the water, numerous bungalows collapsed, and palm trees and even reinforced concrete pillars simply toppled over.