The 2010 Chilean tsunami was generated by a magnitude 8.8 earthquake off the coast of Chile on 27 February. The tsunami waves arrived in the Chatham Islands after 11.5 hours, and along the Canterbury coast after approximately 14 hours, on the morning of Sunday 28 February. The tsunami waves arrived as a series of surges that continued for the entire day, and sea levels continued to fluctuate for several days.
The last tsunami to significantly affect the Canterbury coastline was the 1960 Chilean tsunami in May 1960. This tsunami was generated by a magnitude 9.5 earthquake off the Chilean coast a little further north than the 2010 earthquake. This earthquake was the largest ever scientifically recorded earthquake and the surges in Canterbury were larger than the 28 February tsunami.
The recorded effects of the tsunami in Canterbury are summarised below. We'd like to know about your stories - send them, photos or footage to firstname.lastname@example.org.
Kaikoura District Council staff observed approximately 0.5 metre shifts in water level at Kaikoura, and "sideways" currents along the esplanade and South Bay. Police had evacuated freedom campers along the Kaikoura coast and alerted camping grounds.
No reports from beach settlements on the Hurunui coast or Pegasus Bay.
The Environment Canterbury ranger reported a surge less than 0.2 metres high that came up the river at approximately 12.30pm and filled the whole area of the river mouth around Kairaki. It apparently travelled up as far as the Kaiapoi River mouth.
A further surge came in at about 3.30pm, before high tide, which was almost up to the top of the rock riprap at Kairaki (see photo). The Environment Canterbury ranger thought that if there had been another surge at high tide it would have overtopped the riprap and potentially inundated the camping ground. The current generated during this surge eroded away 2-3 metres of land, including about a dozen trees, from the end of Brooklands Lagoon spit (on the south side of the river mouth).
People fishing in the area around the Old Highway Bridge saw a surge come up the river "later in the afternoon", which was likely to be this same surge. They reported hearing water running over the pebbles, and the whole river filled up in the area.
A surge entered the Avon Heathcote Estuary (Ihutai) in the late afternoon. While this surge was relatively small in height, it occurred just after high tide and came close to overtopping the estuary in places. Footage shot by a Southshore resident on the estuary shows the force behind a seemingly small surge, and how waves in an enclosed water body can reflect off different parts of the shore and then build up on eachother to make larger waves.
The initial tsunami surge was recorded at the Port of Lyttelton at 9.40am. One ship had been sailed from the port at 2am, and ships due to come into port during the day were kept out to sea.
Water levels at the port were strong affected by the seiche set up within the harbour. A seiche is a "sloshing" of water back and forward in an enclosed water body, such as a lake, estuary or harbour, that is started by a distubance such as a tsunami entering the water body.
The graph below from the Port of Lyttelton shows the forecast water level and what was actually recorded as a result of the tsunami.
The negative wave around 11am occurred just after low tide and cause water to recede from bays in the harbour to well below normal low tide level, exposing the sediment of the harbour floor in many places. Small boats in port and the marina were touching the bottom of the harbour during this time.
Strong currents were generated when the next incoming surge arrived around 12-12.30pm. A current of almost 5 knots was felt alongside the wharf at Lyttelton, and there were reports of the sea "flowing like a river" at the harbour entrance.
A further surge entering the harbour around 4pm almost coincided with high tide and overtopped the fisherman's wharf at the port and the Governors Bay jetty. This surge also flooded part of the Wheatsheaf Tavern car park at Teddington, and some low lying areas of Teddington and Charteris Bay.
Normal shipping resumed at the port at 8pm. The main surges had decreased, but water levels continued to fluctuate in the harbour for several days.
Surges were noted during the day in Port Levy, and the water was discoloured. There was no major inundation of land, but the water level got up to around half a metre above the bottom of the boat shed doors.
At Pigeon Bay regular surges were noted approximately every 30 minutes. The surges didn't appear to affect the western or southern areas of the bay as much as the eastern part - the water appeared to "sweep around" anti-clockwise within the head of the bay. The camping ground was inundated during the surge around high tide in the late afternoon, and the wooden flooring of several caravans were damaged. There also appeared to be damage to a boat shed door near the wharf, with the roller door stove in. The wharf was underwater and three of the wharf pylons were loosen. The tsunami current was strong enough to drag one of the yacht moorings in the bay towards the wharf.
In Little Akaloa the tsunami surges appeared from mid-morning as a rapid series of very high and very low tides, with periods of up to about half an hour. At about 4pm, coinciding with high tide, a surge came up onto the road and also partially inundated a paddock beside the bridge. Witnesses said that the surges came in relatively slowly and quietly compared to the 1960 tsunami, when the surges were rapid and the sea "roared".
At Okains Bay the camping ground was evacuated early in the morning. The sea receded around 50 metres, to the extreme low tide mark, at about 9am and then came back in again, right up to the edge marram grass on the dunes. The surges continued like this in cycles of 15-20 minutes. The tsunami surges created a very strong current at the western end of the beach and the estuary of Opawa Stream, which scoured out sand and mud in a deep channel. The photo below of the Opawa esturay was taken by Derek Cox of the Department of Conservation from Chorlton Road.
People in Barry's Bay noticed surges around 10.30am and 1pm that came up to the normal high tide level. At Duvauchelles the first surge was noticed at around 9am. By lunchtime the sea was up to normal high tide level, at the bottom of the sea wall. By 4pm the water level was up to the top of the seawall with overtopping in some places, and flow up through the stormwater drain, which continued until about 6pm.
In Akaroa, the sea drew out from Childrens Bay at about 9.45am, and then "sloshed around" at 20-30 minute periods. During the afternoon the operators of the Black Cat cruises noticed strong swirling currents around the wharf, which shuddered with the surges, particularly the outgoing ones. The maximum water level got to above the king tide mark on the wharf, not far from the bottom of the offices on the wharf. The Black Cat staff commented that they were lucky the day was calm, because if there had been a chop or swell on top of the surge in the late afternoon their offices would certainly have been flooded.
Surges continued for several days in Akaroa and there was a lot of debris floating in the water and washed up on the beach, which was unusual for the calm weather conditions.
In Timaru surges were noticeable along Caroline Bay in the late afternoon. At its peak the water reached up to the plantings at the foot of the dunes. Anecdotal observations are that surges were occurring in 40 minute cycles. The photos here were taken from Benvenue Cliffs by Timaru photographer Geoff Cloake and show the currents created by the surges.
No surges were noticed at Rangitata Huts on the south side of the Rangitata River mouth during the morning, but fishermen at the Rangitata River mouth noticed two strong surges around the high tide in the late afternoon.
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