A King Tide is the colloquial term used to describe the highest predicted high tides of the year. This natural, regularly occurring phenomenon results in the greatest vertical reach of the ocean along the coast. King Tides are significant for coastal communities, including those along the Oregon Coast, because they offer a glimpse into the potential effects of future sea-level rise.
The Astronomical Causes of King Tides
King Tides result from a specific alignment of celestial bodies that enhances the usual gravitational forces driving the ocean’s tides. The rhythmic rise and fall of ocean water is primarily caused by the gravitational pull exerted by the Moon and, to a lesser extent, the Sun. The greatest tidal range, known as a spring tide, occurs when the Earth, Moon, and Sun align during the full and new moon phases.
The King Tide event requires a further intensification of this alignment, known as a perigean spring tide. The Moon’s orbit around Earth is elliptical, meaning its distance from our planet constantly changes. When the Moon is at its closest point to Earth (perigee), its gravitational influence is strongest. A King Tide occurs when the Sun and Moon are aligned, and the Moon is simultaneously at perigee.
The Earth’s orbit around the Sun is also elliptical, and its closest point (perihelion) occurs in early January. When the perigean spring tide aligns with perihelion, the gravitational forces combine to produce the highest astronomical tides possible. These are predictable astronomical events, distinct from temporary, weather-driven increases in water level like storm surges.
Seasonal Timing and Manifestation on the Oregon Coast
King Tides on the Oregon Coast typically manifest multiple times each year during the winter months, spanning from late fall through early spring. This seasonal timing is partly because the Earth is closest to the Sun during the Northern Hemisphere’s winter, which amplifies the gravitational pull. The exact dates vary annually, dictated by the lunar cycle and the precise alignment of the Sun, Moon, and Earth.
The extreme high water levels are most visible in low-lying coastal areas, estuaries, and river mouths, pushing ocean water farther inland than usual. Locations like Siletz Bay often show increased flooding of marshlands and mudflats. Coastal towns built near the water, such as Depoe Bay, frequently see the effects of the tide pushing into harbor areas.
These elevated water levels are particularly significant in Oregon because they serve as a valuable benchmark for sea-level rise monitoring. By documenting how high King Tides reach today, scientists and coastal planners can project what “normal” daily high tides might look like in the future as global sea levels continue to rise. Researchers encourage the public to submit photos to help visualize and track these future water levels.
Coastal Impacts and Essential Safety Precautions
The practical effects of King Tides include the temporary inundation of infrastructure and increased erosion. Low-lying coastal roads, parking lots, and beach access points can become flooded or impassable during the peak high tide. The combination of elevated water level and powerful winter wave action dramatically increases the rate of beach and cliff erosion.
In harbor areas, such as Depoe Bay, the exceptionally high water can disrupt normal operations, making boat navigation difficult. The force of the water can also impact marine life habitats, temporarily covering tide pools and altering foraging areas. When a King Tide coincides with a winter storm, the resulting conditions can be violent and unpredictable, with massive waves crashing against sea stacks and headlands.
Observing King Tides requires strict adherence to safety guidelines. The public should always view the spectacle from a safe, elevated area well away from the beach, such as a bluff-side viewpoint. It is important to avoid walking on the beach or jetties during the peak high tide, as the immense power of the waves can be life-threatening.
A major hazard during these events is the risk of “sneaker waves,” which are unexpectedly large waves that surge much farther up the beach than others. Never turn your back to the ocean, and stay clear of driftwood logs, which can be heavy and roll without warning when struck by a wave. Checking local tide charts is an important step to know when the high-water periods will occur.