Exploring the Connection Between Sea Level Rise, Groundwater Level, and Liquefaction in Hawke’s Bay, New Zealand

open_access
Open Access
Author:
Louw, Gabriel
Area of Honors:
Civil Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Kaleigh Yost, Thesis Supervisor
Jay Regan, Thesis Honors Advisor
Keywords:
Climate Change
Sea Level Rise
Liquefaction
Earthquake
Civil Engineering
Environmental Engineering
Geotechnical Engineering
Saltwater Intrusion
Groundwater Modeling
FEFLOW
DPCH
Abstract:
Hawke’s Bay is a coastal, seismically active region located on the East side of the North Island of New Zealand. The region’s largest earthquake in recent history occurred in 1931 and resulted in multiple documented manifestations of liquefaction (loss of soil strength during earthquake shaking) in populated areas. Sea level rise is expected to impact this coastal region and exacerbate liquefaction hazard by causing shallower groundwater tables, increasing the soil’s liquefaction susceptibility. Understanding the risk of liquefaction of this area under future groundwater conditions is important for preserving public safety and building resilient infrastructure. Predicting liquefaction hazard accurately requires knowledge of groundwater table depth and depth to fully saturated soil, in addition to information about soil stiffness and earthquake parameters; the former two being the focus of this thesis. This thesis presents the results of a 2023 field investigation conducted at several sites near historical liquefaction manifestations, which show how a typical assumption that full soil saturation occurs at the location where the groundwater table is measured is not true in every case. This thesis also presents a numerical groundwater model of an area of the region created in FEFLOW that sea level rise causes coastal groundwater levels to rise. This serves as a proof-of-concept that numerical groundwater models can be used to model groundwater rise with climate change, with the intention to one day employ this type of modeling to show a direct connection between sea level rise and future liquefaction hazard. Future work on this subject will need to incorporate the findings of the field study to develop a way to model partial saturation below the groundwater table together with the findings of the groundwater model to simulate the change in groundwater levels with sea level rise.