Correlations between liquefaction induced damage and former river channels in Kaiapoi

The town of Kaiapoi, 17 km north of the city of Christchurch, suffered significant liquefaction induced damage during the Canterbury earthquake sequence. Severe lateral spreading and large volumes of ejecta were present throughout the town and surrounding region after multiple earthquakes in this sequence. This region has also seen significant changes to the paths of rivers since European settlement in the 1850’s, and as a result there are many areas within the town and surrounding area that were, until recently, channels of the Waimakariri River. Using historical data, the reclaimed channels were identified, which were shown to have a strong correlation with the areas of severe liquefaction damage following these earthquakes. Examples of damage in these areas are presented and related to the relatively recent changes to the river channels in the region. The significant damage to the infrastructure in these old channels highlights the importance of having a clear understanding of the historical changes to river paths in seismically active regions.