The tide gauge at the end of the North Pier has been writing down the height of the sea every six minutes since 1941. For most of those years nobody looked at the numbers unless a storm was coming. This summer, three people did: a retired harbor pilot, a graduate student at the state university, and an engineer at the Public Works department who had been asked to explain why the seawall budget kept growing.
What they found is not a mystery, and it is not a catastrophe. It is a slow line that bends upward, and a set of days each winter when that line meets the wind. The city is now planning for the next forty years around those days. This is what the records show, what they do not, and what the people reading them think the city should do next.
The long line
The first thing anyone does with eighty years of tide data is average it. Take every six-minute reading from a year, add them up, divide, and you get that year's mean sea level. Plot eighty of those points and you get a line.
At North Pier the line rose about 17 centimeters between 1941 and last year. For the first forty years it climbed a little under 1.5 millimeters a year. Since about 1990 the rate has been closer to 3.4 millimeters, and the last decade has been steeper still.
"People hear 17 centimeters and think, that's the width of my hand, who cares," said Walt Brenner, who piloted ships into the harbor for thirty-one years before retiring in 2019. "But the sea doesn't come up evenly. It comes up on the worst day, on top of everything else."
Brenner started keeping his own notebook of high-water marks in 1994, after a February storm put two feet of water into the pilot station. He brought the notebook to a council hearing last spring. That is how the graduate student, Anika Sorensen, heard about the gauge.
Sorensen studies coastal flooding at the state university. She downloaded the full record from the federal archive, cleaned it — the gauge was moved eleven meters in 1968 and replaced twice since — and published her analysis in July. The rise itself was not news to her. What surprised her was how clearly it showed up in a place as small as Port Alden.
"A lot of small harbors have gaps in the record, or the gauge sits on a pier that is itself sinking," she said. "This one sits on bedrock and it almost never went dark. It is one of the cleanest records on this stretch of coast."
The days that matter
Average sea level is not what floods Front Street. What floods Front Street is a high tide, pushed higher by a storm surge, arriving at the same hour as a strong onshore wind. Tide scientists call the extra height on those days the "residual," the part of the water level that the tide tables did not predict.
Sorensen counted the hours each year when the water at North Pier stood more than 60 centimeters above the average high tide. That is roughly the level at which the lowest block of Front Street, near the fish market, starts to take water through the storm drains.
In the 1950s the harbor crossed that line on average about four hours a year. In the 2010s it was 31 hours a year. Last winter it was 58.
Most of that change is the long line. Storms have not become dramatically more frequent at Port Alden; the record shows no clear trend in the size of surges. But when the baseline sits 17 centimeters higher, a surge that once stopped at the curb now reaches the doorway.
"That was the part that made it click for me," said Hollis Carter, the Public Works engineer who was asked to review the seawall estimates. "I had been treating flooding as a storm problem. It is really a baseline problem with storms on top."
Carter now keeps a chart on his office wall that shows each winter's flood hours as a bar. He points to the bars from the last five years. "Every one of those is taller than any bar before 2000," he said. "Nobody on staff had seen that picture before this year."
What the pier remembers
The gauge itself is a steel pipe about the width of a coffee can, bolted to the pier's last piling. Inside is a float, a pulley and, since 2004, an acoustic sensor that bounces sound off the water's surface. A small solar panel keeps it running. The data goes by cellular modem to a federal server, which is why the record survived three changes of ownership at the pier.
Before 1968 the gauge sat in a wooden stilling well near the old ferry slip. Its paper charts, rolls of graph paper traced by a pen, are stored in the basement of the county records office. Sorensen spent two weeks there matching the charts against the digital record, which was transcribed in the 1970s by a federal contractor.
She found eleven days where the transcription was off by a full foot, almost certainly a misread line on the chart. None of them changed the long-term trend. Three of them were storm days that had been recorded as ordinary.
"It is a humbling thing to hold a piece of paper from 1952 where someone wrote 'wind NE, heavy' in the margin," she said. "They were paying attention. We should too."
The seawall math
The council approved a $48 million seawall reconstruction in the spring. The plan raises the wall by 60 centimeters along the most exposed stretch of Front Street and replaces the storm drains with ones that close when the tide is high.
Carter's job was to check whether 60 centimeters was enough. The original design, drawn up in 2016, used a sea-level estimate that assumed the pre-1990 rate would continue. Using the current rate, the new wall would still hold back the worst surge on record through about 2060. Using the steeper projections in the state's guidance, it holds until the mid-2050s.
"The honest answer is that the wall buys us thirty to forty years," Carter said. "That is a good deal for $48 million. It is not forever, and nobody should say it is."
The design includes footings strong enough to add another 40 centimeters later without rebuilding the base. That added about $3 million to the cost, and it was the part of the plan that drew the most questions at the hearings.
Council member Ellen Marsh, who cast the only vote against the plan, said she supported the wall but not the harbor fee that pays for a quarter of it. "The people on Front Street did not raise the ocean," she said. "I don't think they should carry a quarter of the bill for it."
What the city does not know
The gauge measures the sea. It does not measure the land, and on this part of the coast the land is moving too.
A GPS station on the roof of the county courthouse shows the ground under downtown Port Alden sinking about half a millimeter a year, slow enough to ignore for most purposes. But the fill along the harbor, laid in the 1920s over what used to be tidal flats, may be settling faster. Nobody has measured it.
Carter has asked for $40,000 in next year's budget to survey the elevation of every storm drain inlet along Front Street and repeat the survey in five years. Without it, he said, the city is planning around the water and guessing about the ground.
The other gap is groundwater. When the sea rises, the water table under low-lying streets rises with it, which can push water up through basements and drains even on dry days. Two businesses on Chestnut Street reported that kind of flooding last winter. The city has no wells to track it.
Up and down the coast
Port Alden is not the only harbor reading its gauge more closely. Three towns within a day's drive have gauges with records longer than forty years, and all three show the same bend in the line around 1990.
In Kessick Bay, forty miles north, the town raised its harbor road by a meter in 2018 after the flood-hour count passed 50 in two winters running. The work cost $11 million and closed the road for a summer. The town manager, Lorna Pike, said the count was what persuaded the budget committee. "We had been arguing about whether it was getting worse," she said. "The count ended the argument."
Farther south, Wexley took the opposite approach. Instead of raising the harbor front, the town bought out eleven waterfront properties over six years and turned the land into a park that is allowed to flood. The buyouts were voluntary and slow, and two owners are still in court over the price. But the park took on water four times last winter and nobody had to pump out a basement.
Sorensen said neither choice is right for every place. "Kessick has a road it can't move. Wexley had houses on a marsh. Port Alden has a downtown that people want to keep," she said. "What they share is that they decided based on their own record, not a national average."
The state coastal office keeps a list of gauges with usable records. There are nine on this coast. Only four towns have published an analysis like Sorensen's. The office has offered a small grant for towns that want to do one, and so far two have applied.
What people on Front Street are doing now
The seawall will not be finished until 2029. In the meantime, the businesses closest to the water have been making their own arrangements.
The fish market on Dock Street installed flood barriers at its loading doors in 2021, aluminum panels that slot into steel frames when a storm is forecast. The owner, Sam Okoye, said the barriers have been up nine times in three winters. "The first time we used them we were proud of ourselves," he said. "Now it is a chore, like taking the trash out."
Three doors down, the hardware store moved its electrical panel from the basement to the first floor. The bookshop on the corner raised its lowest shelves by a foot.
The city offers a matching grant of up to $5,000 for flood-proofing work on Front Street and Chestnut Street. Fourteen businesses have used it since it opened in 2022. The program has $60,000 left for this year.
Residents who want to follow the gauge can see the live reading on the federal tide website, which updates every six minutes. Brenner checks it every morning. "It is the first thing I look at, before the weather," he said. "The weather tells you what might happen. The gauge tells you what did."
Reading the next forty years
Sorensen's report ends with a recommendation that is easy to make and hard to follow: look at the record every year. Count the flood hours, compare them with the projections, and adjust the plans when the bars start to run ahead of the line.
"The mistake is to do a big study once, build something, and then stop looking," she said. "The gauge will tell you if you got it wrong. You just have to read it."
Public Works has agreed to publish the flood-hour count each spring alongside the seawall construction report. The first one is due in April.
Brenner, for his part, still writes down the high-water mark after every storm. His notebook is on its fourth volume. On the inside cover of the first one, in pencil, is the date of the 1994 storm and a note: "Two feet in the station. Won't be the last."
"I wasn't trying to predict anything," he said. "I just thought somebody ought to write it down."
