July 19, 1924 Tsunami: Chatham I., New Zealand

On July 21, 1924, the steamship "Tease" encountered a tidal wave while proceeding to Chatham Island; the impact of the wave resulted in a cracked high-pressure cylinder head. This tidal wave hit the islands during the same night the steampship was damaged and caused exntensive losses there too (according to the Record of Unusual events at Sea, compiled by an English Steamship Company, and reproduced by the Nautical Branch of the Meteorological Service of England). (reference #415)

On 19 July 1924 starting at about 19:15 NZMT (possibly Chatham island time CIT (18:30 NZMT)), a series of waves variously said to be 3-6 m high or reaching up to 6 m above HWM, locally called a tidal wave, affected a number of locations on the Chatham Islands over a period of just over three hours. Those locations most affected were the settlements of Wharekauri, Kaingaroa and Owenga on north and eastern side of Chatham Island, and the settlement on Pitt Island. At Kaingaroa, the waves swept over 100 m inland, sweeping away a dam supplying fresh water, one trawler was smashed and another lost. Near Wharekauri, a bridge was badly damaged, fences washed away, and the water washed over Te Awanui island. Several boats were damaged at Owenga, a small hut was washed away and some machinery at the shell-crushing plant damaged. On Pitt Island, the wharf disappeared, two small boats swept up a stream, and beaches eroded of shells. Mangere Island was also affected and a large landslide occurred. There were no deaths or injuries, although one person was washed from his horse near Owenga, and deaths may have been prevented by people at Kaingaroa and Owenga hearing the roaring approach of the first wave and running inland. According to contemporary reports locations on the west coast were not affected. However, recollections written some 70 years later (Holmes, 1993; see transcriptions), which accurately record effects at Wharekauri, also record higher than expected water levels in the creek at Waitangi during the time locations on the east side of the island were affected. However, the account incorrectly attributes the source to South America.

Several accounts also relate the near-capsizing of the ship Tees en route to the Chatham Islands from Christchurch to the tsunami on the Chathams. However the damage to the Tees occurred two days after the tsunami, and was storm related.

Tide charts for Lyttelton on July 19 (held at National Archives, Christchurch) have been checked, but no disturbance is visible on the poor quality records.

The newspaper and other reports of this event give a very credible account of a tsunami affecting the Chatham Islands only. The sea level disturbances had a sudden onset with the arrival of the first wave heralded by roaring, effects over eastern and western coasts of the islands within a short time, the occurrence of a series of large waves followed by smaller waves and duration of several hours. The occurrence of a storm is not mentioned, and while the tide was high at the start of the waves and it was a spring tide (both of which are about correct, HW at 1920 CIT, acc. to NIWA Tide Forecaster (www.niwa.co.nz/services/free/tides)), a recollection (Holmes, 1993; see transcriptions) specifically states that the high level at Waitangi, 2 hours after high tide, was odd as the weather was fine at the time. (reference #5324)