South Jersey bays and tidal creeks will see unusually high tides today and Thursday. An unusual alignment of the sun and moon and their proximity to the Earth will cause these highest water levels of the year.

But this so-called “king tide” is also prompting an area environmental group to ask residents and visitors along the Barnegat Bay’s shoreline to take photographs at high tide to illustrate what a normal high tide may be like in several decades as the sea level continues to rise.

“The main objective is to try to document the extra tide level as a kind of a preview of what tide levels will look like in the future,” said Karen Walzer, spokeswoman for the Barnegat Bay Partnership, based in Toms River. The partnership hopes volunteers from throughout the bay area, particularly in places that already flood easily, will participate.

Once the information has been collected — participants need to take a photograph at high tide on Thursday and then another photograph at an average tide another day — the partnership will make the photographs available publicly.

“We’re hoping that planners, engineers and people who are making decisions about the future will take a look at it and take it into consideration, that this could be the future (average high) tide level and prepare for it,” Walzer said.

Locations vulnerable to tidal flooding will likely be under water at times until possibly Saturday, even if there is no wind or rain, according to forecasted tide levels and an analysis of National Weather Service tidal impact tables.

Among the areas that likely will see problems at high tide Thursday morning are the Black Horse Pike in the West Atlantic City section of Egg Harbor Township and areas near the Route 47 bridge into Wildwood, based on tide charts. A coastal-flood advisory is in effect this morning, for high tides along the oceanfront occurring just after 7 a.m., according to the National Weather Service.

Thursday’s tide will be the highest of 2011, but will not be at a historic level, said Stew Farrell, director of the Coastal Research Center at the Richard Stockton College of New Jersey in Galloway Township.

“This just happens to be the biggest one of the year and probably a couple of years, but the difference we’re talking is tenths of a foot,” he said.

According to the National Oceanic and Atmospheric Association, high tide Thursday in Atlantic City will be 8:06 a.m. It will be 8:39 a.m. in Cape May harbor.

The king tide, also called a perigean spring tide, is caused by the sun and the moon aligning at just the right time such that the moon is closest to the Earth and the Earth is closest to the sun. A spring tide occurs during new and full moons and refers to the “springing” of the tides as the lunar gravity makes high tides higher and low tides lower.

While the forecasted tide height is predicted to be 5.83 feet in Atlantic City on Thursday morning, the exact height in the back bays will depend on terrain, wind and rain. A westerly wind will blow the water out of the back bays and cause lower-than-expected low tides, but will keep the predicted high-tide levels down. But if the wind is blowing from the east, the high tide could be higher than predicted, Farrell said.

National Weather Service forecasters are calling for a potential storm system that may bring heavy rain and some wind to the region, but another storm may also come this weekend, bringing the potential for moderate coastal flooding.

The average sea level in South Jersey has risen about 1.2 inches in the past decade and predictions estimate that the sea will continue to rise about one foot per century. However, if the ice sheets in the Arctic continue to melt at a rapid pace, Farrell said, the rise could be even faster.

That could mean that areas such as Ventnor Heights, parts of Ocean City and Long Beach Island or Stafford Township that flood every time the high tide rises above about five-and-a-half feet would have tidal flooding as a daily norm rather than an occasional occurrence, Farrell said.

Walzer said the Barnegat Bay photography initiative was set for Oct. 27 simply because organizers knew that the tide would be extremely high regardless of the weather.

Other estuary-advocacy groups in the region as well as nationwide also are taking Thursday’s tide as a day to do similar efforts, including groups along Puget Sound and San Francisco Bay.

The Delaware Estuary Partnership, based in Wilmington, Del., is encouraging people who live along the bay to take similar pictures and post to its Facebook account, spokesman Shaun Bailey said.

“We’re hoping that (people) will realize that they live in an area influenced by the tide, and we hope that they will realize that sea levels are slowly rising over time,” he said.

The partnership recently published an electronic booklet on its website that discusses climate change, sea level rise, population increases and stressors on water systems.

And the prediction of rising seas is why keeping an eye on what an extreme tide brings to the region today is smart planning, Farrell said.

“It’s a good idea because today’s storm level is tomorrow’s high tide in terms of what’s happening,” he said.

Contact Sarah Watson:

609-272-7216