Kailua, Oahu
In another study on Oahu, the effects of a 1 meter (3.3 feet) sea level rise were studied on shoreline migration and groundwater for the town of Kailua (population 43,780) located on the eastern coast of Oahu. The study anticipates that a 1 meter (3.3 feet) rise in sea level will not have a detrimental impact on Kailua’s freshwater lens, although Kailua does not obtain drinking water from this source. Even if sea level rise would not be a detriment to local groundwater resources, it would cause the water table to rise and result in an increased opportunity for coastal flooding. Oahu’s freshwater lens rides on top of underlying, denser saltwater. As sea level rises, as it may around Oahu and the globe (Figure 37), so will the level of the underlying saltwater. This would result in bringing the freshwater lens, or height of the water table, closer to the land surface. With the freshwater lens closer to the land surface, this would promote flooding during heavy rain events because there would be less ground to soak up excess rain (see below). Furthermore, tidal action can exacerbate the baseline rise in sea level over short time periods by elevating an already raised sea level due to global warming and climate change.
Figure 37. Sea level change measured by tide gauges.
