When melting ice combines with a high tide, you get some wildly rushing rivers and waters reaching up past the bottom steps of coastal walkways.

Standing on the bridge between Topsham and Brunswick last week, you could hardly hear as the water rushed over the rocks. Just a few weeks ago, there were ice shacks on its crusty surface. Now, all that extra volume has been added to the river. When last Thursday’s full moon produced a high tide that was nearly eleven feet, these effects combined to cause the coast to look quite a bit different. Usual rocky outcroppings were covered and typically punctuated places looked almost lake-like under the still waters of a high slack tide.

April 18’s high tide, which was the highest of the month, was a large high tide. Typically, high tides in Casco Bay range from 8-10 feet. Spring tides from March through May are unusually high. But, the highest tides of all result from an unusual alignment of the sun, moon and earth. This is called the moon’s perigee – when it is closest to the Earth. The combined effect of their gravitational pull on the oceans tugs all that water much further up the shore than we are used to. These occurrences happen a few times a year and are dubbed King Tides. The most recent King Tide in Casco Bay was on Feb. 20 and measured 11.6 feet. 

During King Tides, it isn’t unusual to see people out with their cameras documenting this strange phenomenon. This got several organizations working on coastal issues thinking that these rare events could provide a real-world visualization of what our coast might look like as a result of sea level rise. In order to encourage people to document what the coast looks like under extra high water conditions, the states and Canadian provinces around the Gulf of Maine created the Gulf of Maine King Tides Photo Project. The Gulf of Maine group is actually part of a larger international initiative that includes communities around the world. According to the Gulf of Maine Project, “It is possible that by 2060 we could experience tides of the magnitude of king tide events every month due to sea-level rise induced by climate change.” The Project encourages people to take photos along the coast that include recognizable landmarks as well as coastal structures like bridges piers and breakwaters and to record the exact time and location of the photograph. They hold an annual contest that has generated some amazing images (gulfofmaine.kingtides.net).

Several years ago, a group of students from the University of Southern Maine created another King Tide visualization as a part of the Envisioning Change project. They installed a temporary “King Tides Trail” in downtown Portland using red markers and solar lights to mark a 3-foot sea level rise along the Bayside to Old Port trail. The trail was in December of 2014, but you can still view images from it online at media.usm.maine.edu/~slc/map.html. There are additional modeling tools that have been developed and are accessible under the “For Educators” tab of the Gulf of Maine King Tides website including video simulations of sea level rise and slide shows of coastal predictions.

Tools like these not only help people to understand the potential changes along the coast, but also help planners to make preparations for responding to these changes. For example, which streets will be most vulnerable to flooding? Or, which beaches will experience the most erosion? And what can be done to buffer these impacts. Many local organizations around the Gulf of Maine are working together to educate people about the potential impacts of sea level rise and to give planners useful tools.

If you’re interested in tracking the tides, you can look up a tide chart for your local harbor on US Harbor’s website, usharbors.com. May’s highest tide will be on the 17th and will be yet another of the large Spring tides.

As we approach the Summer Solstice on June 21, we’ll also have large tides due to the proximity of the sun to the Earth’s equator. Stay tuned for some high water events and help prepare the coast by documenting your observations.

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