King Tides Provide a Glimpse into the Future

Jen Kalt, Humboldt Baykeeper Director

Kayakers take a break on the earthen dike that normally separates Jackson Ranch Road from Liscom Slough in the Arcata Bottoms. Photo by Aldaron Laird, Dec. 23.

It’s that time of year again, when the highest tides of the year often coincide with storms to cause flooding and erosion in coastal areas. Known as King Tides, they tend to be about a foot higher than typical high tides, providing a glimpse into the future. With one foot of sea level rise, these high water levels will become more and more common. 

The former Sierra Pacific Industries lumber mill in Manila is one of dozens of low-lying contaminated sites around the bay. Although the site has been partially cleaned up, contaminated groundwater beneath the buildings could move off-site as groundwater rises, impacting Mad River Slough and the bay. Photo by Jen Kalt, Dec. 24.

The December 23 King Tide was even higher than predicted by about half a foot, peaking at 9.28’ at the North Spit tide gage. According to meteorologist Troy Nicolini at the National Weather Service in Eureka, this was due to storm surge and southerly winds pushing more water toward the coast, a phenomenon known as Ekman Transport. 

The Humboldt Bay area is experiencing the fastest rate of sea level rise on the West Coast. That’s because plate tectonics are causing the ground beneath us to sink at the same rate as sea level is rising, doubling the relative rate of sea level rise.

Erosion along New Navy Base Road dislodged a PG&E utility vault near the County boat launch in Samoa. Photo by Jen Kalt, Dec. 24.

To document King Tides, Baykeeper volunteers photograph high water levels relative to bridges, roads, seawalls, and other man-made structures. To add your photos to our collection, you can email them to Or you can upload them to the Coastal Commission’s California King Tide Project at