Nature's Sudden Slosh: How to Prepare for a Seiche Before It's Too Late
- Hannah M
- Jul 29
- 2 min read
We often hear about challenging weather at sea—but what about the conditions on a lake?
Ever heard of a seiche? It’s a fascinating natural phenomenon (from the French word meaning “to sway”) where a standing wave forms in a large body of water, like a lake, causing it to oscillate back and forth.
Even when the surface looks calm, a seiche can lead to sudden and significant changes in water level—much like water sloshing in a bathtub after it’s been disturbed. It’s an invisible force that can catch even seasoned operators off guard.
Read on to learn more about what causes a seiche and why it’s important to understand its impact.
What Causes a Seiche?
Seiches are typically caused by meteorological events. The most common triggers are:
Rapid changes in atmospheric pressure across a body of water.
Strong, sustained winds that push water to one end of a lake.
When the atmospheric disturbance passes, the piled-up water rushes back to the other side, creating an oscillation that can continue for hours or even days, posing a recurring threat.
Who is Most at Risk?
These events can occur on any large lake, but some areas are more vulnerable. The Great Lakes, for instance, have a well-documented history of seiches.
Vessels on shallow lakes, like Lake Erie, are particularly susceptible due to the lake’s shape and orientation to prevailing storms.
Mariners and port operators who may not be tracking subtle environmental shifts can be caught completely unaware.
Any vessel moored or navigating in areas prone to rapid water level changes of several feet (a metre or more).
Understanding this risk is the first step toward mitigating it, as a seiche can happen on any of the five Great Lakes.
Why Is a Seiche So Dangerous?
Unlike a storm you can see approaching, a seiche’s danger is deceptive. The primary risks include:
Sudden water level changes that can exceed $3$ feet ($~0.9$ metres) in mere minutes.
Unexpected groundings as water rapidly recedes from a shore or harbor.
Damage to moored vessels and port infrastructure from the powerful surge.
“The 1954 Chicago seiche, which produced a 10-foot wave, serves as a tragic reminder that lake conditions can change with deadly speed. Diligent observation is key.” – Inspired by National Weather Service historical reports
How SeaLogs Helps Mariners Prepare for a Seiche
Preparing for an unpredictable event like a seiche means turning routine observations into actionable intelligence. SeaLogs helps by:
Digitally tracking key environmental data like barometric pressure, wind shifts, and unexpected water level changes in real-time.
Creating a verifiable audit trail of conditions, allowing you to see patterns as they develop.
Storing all necessary logs and observations in one accessible place, ensuring your crew can act on information quickly.
With SeaLogs, you can transform your digital logbook from a simple record into a powerful tool for situational awareness, ensuring your crew is ready for whatever the lake throws at them. Keen to learn more? Book a demo today.
