Smart Bridge across the Mississippi River

The new, ten-lane I-35W St. Anthony Falls Bridge carries the highway across the Mississippi River, just east of  downtown Minneapolis, Minnesota. The bridge is modern, it’s state-of-the-art, and it’s billed as ‘smart’, and if you have time to do only one thing during your visit to the city, take a look at the bridge.

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Source: National Atlas of the US; US Dept. of Interior

If you’re not familiar with the area and you drive across the bridge, you probably won’t notice the bridge or the river. The bridge has no super structure above the deck and there’s little to differentiate the bridge deck from the highway. The transition from highway to bridge and back to highway is seamless. And whether you’re your heading north or south, you’ll be on a five lane highway and unlikely to get even a glimps of the river. To get a decent look at the structure, you must get off the highway, park your car, and walk.

Take any off-ramp leading to downtown Minneapolis. Your objective will be the West River Parkway. Several downtown cross streets connect to it. Once on the parkway, turn right and follow it to the riverside park called Bohemian Flats. There’s a pay-lot for cars within the park.

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Map shows I-35W Bridge in relation to West River Parkway and riverside parking lot.

The old eight-lane I-35W bridge collapsed suddenly on August 1, 2007 at 6:05 p.m. CDT, taking cars and trucks with it. Thirteen people were killed, many more injured.

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The 35W bridge in Minneapolis seen the day after it collapsed. Image by Mory Gash/AP

Nancy Daubenberger, bridge engineer for the state at the time (now Assistant Commissioner for Engineering Services), speaking on NPR’s ‘All Things Considered’ August 1, 2017, ten years after the collapse, said this: “The shock that came over me, that such a large bridge like that could collapse . . . it was devastating and tragic and shocking; a very, very sad situation.”

Considering the importance of the I-35W river crossing to the state economy, a new bridge was designed and built in jig time. It opened September 2008, a little more than one year after the collapse of the old bridge.

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Old I-35W Bridge. Undated image from en.wikipedia.org

To see the new bridge up close, follow the footpath beside the West River Parkway, first under the No. 9 bridge (a former railway bridge, now a bike path), then under the four-lane, 10th Ave. bridge which crosses the river within 50 yards of the new St. Anthony Falls bridge. Follow the footpath a bit further and you’ll be standing directly under the I-35W and behind the bridge’s four south piers. This is where you can see that the bridge is in fact two bridges, side by side but separated by a few feet of empty space.

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Under the I-35W St. Anthony Falls Bridge looking north. Image by innovata/Wikimedia Commons/ CC-BY-SA

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St. Anthony Falls Bridge at night. Image published by The Center for Transportation studies, U of MN.

Apart from its graceful lines and modernistic look, what makes this bridge a state-of-the-art ‘smart bridge’? Here’s an excerpt from The Catalyist, a publication of the Center for Transportation Studies, University of Minnesota.

During its construction, the [St. Anthony Falls] bridge was instrumented with more than 500 sensors that monitor strain, load distribution, vibrations, temperature, potential corrosion, and the overall movement of the bridge. Other sensors were installed to monitor the bridge’s security and control automatic anti-icing and lighting systems.

Although we can’t see any of these devices, we can imagine them constantly at work, transmitting information to the engineers responsible for the bridge’s wellbeing.

For side views of the New bridge, continue following the waterfront footpath to the Stone Arch Bridge, half a mile upstream. Built in 1883 as a railroad bridge and still standing firm after 135 years, the Stone Arch Bridge is now used only by pedestrians. The new I-35W bridge is designed to last 100 years.

 

Sea Level Rise and how you can track it in real time

Washington DC

On checking the weather, we see a day-old Coastal Flood Warning issued for the District of Columbia which says: “more than a third of Roosevelt Island will be covered by water and back water flooding of Rock Creek in Georgetown will begin.” An unusual occurrence? Not any more. Most low-lying coastal cities, including Washington DC, have begun to experience a new phenomena: High Tide Flooding during quiet weather days, the result of a gradual increase in sea level over the past one hundred and forty year.

Climate experts say that the the rate of sea level rise is speeding up and that the long-term effects could be dire. It’s a challenging subject and we’ve decided to find out more about it, starting today. Our first stop is Washington DC’s tide-gauge station on Pier 5 near the south end of Water Street, one of the many tide-gauge stations operated by NOAA, the National Oceanic and Atmospheric Administration.

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Washington DC showing location of NOAA Tide Gauge Station

It’s a cloudy, not-too-hot September day. From Independence Avenue we walk ten blocks south on 4th Street to where it ends at P Street, then west by a short footpath to the Washington Channel shoreline. The Titanic Memorial (a large granite statue of a man with arms outstretched as if in flight) stands at that point. Pier 5 lies a few hundred yards to the north. We approach it by the waterfront footpath. We can see the tide gauge from the shore but cannot inspect it closely. The DC Police Harbor Patrol have their headquarters on the pier and they refuse to allow unauthorized access. No matter; we’ll look into how tide gauges work later.

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Image from NOAA website

Knowledge about sea level is based on information generated by a global network of about 2000 tide-level stations. A British organization called the Permanent Service for Mean Sea Level (PSMSL) is responsible for the collection and publication of the data produced by the network.

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From: PSMSL website (psmsl.org > data coverage)

There are two trends that give climateologists nightmares: global warming and sea level rise, the second the result of the first. The trend line for the rise in sea level is based on the data generated by the global tide gauge network since 1880. Here’s an example, one of many available on the web.

From: EPA website published 2016

The graph shows that since 1880, sea level has risen by about 9 inches, an average of about 1/16th of an inch per year. However, since 1993, the rate of rise has speeded up to about 1/8th of an inch per year, twice the rate of the long term average. What do the experts say will happen next? Many suggest 1.5 to 3 feet higher by the year 2100. Others, pointing to increasing global warming and the potential for rapid melting of the polar ice sheets, talk about six feet and up by the year 2100, enough to put southern Florida under water and swamp most of the world’s major cities.

Predictions that imply 2100 is the year the rubber hits the road, are not useful. Why? Two reasons: (1) predictions that are safe from being proved wrong within the lifetime of the predictors, are not impressive and easily ignored; (2) the year 2100 is eighty years in the future, much too long a time frame to be of practical use to most people. We need predictions that focus on the near term. We also need a way to keep track of the situation in real time and without having to depend directly on experts for information on which to base personal decisions, such as where to live, for example.

Help is at hand in the form of a paper titled ‘Sea level rise drives increased tidal flooding frequency . . . ‘ published Feb. 3, 2017 in the ‘open access’ journal PLOS ONE. Here’s an excerpt:

“. . . because the general public often perceives climate change as a temporally distant threat, we have chosen to focus on two time frames (15 and 30 years into the future) that are easily comprehensible within a human lifetime.”

In the paper, the authors have predicted the severity of tidal flooding at 52 locations along the U.S. east and gulf coasts by the years 2030 and 2045. They did this by first establishing a correlation between tide-gauge measurements and Coastal Flood Advisories (CFAs) issued by the U.S. National Weather Service. They then show that the number and frequency of CFAs for any  given location can substitute for tide-gauge measurnts as a predictor of future flooding severity.

This is great. We, or anyone else with access to the web, can easily keep track of the number and frequency of CFAs affecting coastal property. A daily check on the Coastal Flood Advisory section of the National Weather Service takes little effort. After two or three years we can crunch our numbers and decide for ourselves whether or not sea level rise is a threat to take seriously. We won’t have to depend on media reports about climate change to be in the know.

Here’s an example from the PLOS ONE paper. By 2015, the number of tidal flood events affecting the shore area of Annapolis, Maryland, had risen to about 35 per year. Based on the CFA record for Annapolis, the authors predict that that number will rise to 145 by the year 2030 (only 11 years from now) and to 180 by the year 2045. If those predictions become fact, who is going to put up with streets and shop fronts that get swamped by sea water every second or third day of the year? The report paints a similar near-term future for the waterfront areas of Washington DC and other cities.

Since we intend to keep track of the Coastal Flood Advisories issued for Annapolis, we decide to visit the city to see for ourselves how tidal flooding has affected it so far. Annapolis lies about 30 miles from DC on a different branch of Chesapeake Bay. We retrieve our car from its parking spot and head east out of Washington, aiming to connect with Route 50.

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Annapolis MD showing the tourist area affected by intermittent tidal flooding

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Washington DC and Annapolis, Maryland in relation to Chesapeake Bay

 

The Geographic Center of the 48 States – why moving it could help

One hundred years ago, someone employed by the U.S. Coast and Geodetic Survey cut the shape of the contiguous 48 States out of a cardboard sheet and determined its center of gravity by balancing it on a point. The balance point on that cardboard map was said to represent the geographic center of the country.

Map of USA (lower 48 States) showing location of geographic center

Lower 48 States with star marking geographic center

Humans are attracted to centers no matter how they are determined. People flock to city centers, cultural centers, shopping centers, garden centers, sometimes even to detention centers. No one speaks of ‘places’ of excellence. In physics, the center of attraction is the point to which bodies tend by gravity. We, on planning a trip across the Great Plains, pick the route that passes through the center of the land.

From St. Joseph, Missouri, we head west on U.S. Route 36, cross the Missouri River, and enter Kansas. It’s early morning so the rising September sun is directly behind us. The expressway narrows to a two-lane highway and soon the country opens up. We see fewer trees and broader vistas. Before us lie the Great Plains, a vast sweep of land stretching east from the Rocky Mountains and from the Rio Grand in Texas to Alberta and Saskatchewan in the north, half a million square miles of relatively flat land, once the home of prairie grasses and bison, now largely given over to crops and cattle.

Some say there’s nothing to see on the plains except endless fields of wheat. In her novel Death Comes for the Archbishop, Willa Cather says:

“. . . there was so much sky, more than at sea, more than anywhere else in the world. The plain was there, under ones feet, but what one saw when one looked about was that brilliant blue world of stinging air and moving cloud.”

Lebanon, Kansas, is a small agricultural community situated a few miles north of Route 36 in an unremarkable area of the plains. The city has suffered from rural flight and shows it: empty lots, closed schools, deadly quiet streets. Its population, once above 800 in the 1920s, is down to a couple of hundred. Its only claim to fame is its proximity to a set of map coordinates that have no cartographical or scientific relevance.

The cardboard cutout method used by the Geodetic Survey in 1918, determined the country’s geographic center to be at 39″50’N 98″35’W. Since that position lies fairly close to Lebanon, the Lebanon Hub Club, anticipating a sizeable tourist flow, arranged in 1940 for a monument to mark the spot. However, due to the spot being on private property, an alternate location on which to plant the monument had to be found. The result of the search was a piece of land two and a half miles northwest of the center of Lebanon, accessible by a turn-off from Route 281.

Map of City of Lebanon, Kansas, showing location of geographic center. Man by Kansas Dept. of Transportation (KDOT)

City of Lebanon, Kansas in relation to geographic center (upper left). KDOT map.

There’s a mystery here. Why wasn’t the monument planted in the center of Lebanon instead of out in the middle of nowhere? After all, the cardboard cutout method used to determine the center of the country was only accurate to within ten miles at best. To put it another way, any point within a ten-mile radius of the calculated coordinates, including any point within the city of Lebanon, could have been chosen to represent the geographic center.

While the chosen site is pleasant and well maintained (the tiny chapel is a nice touch),  it has never attracted more than a trickle of visitors. A motel built to accommodate the anticipated flood of tourists closed down long ago. A monument within the city would not only give tourists a reason to visit the town, it would also enable Lebanon to advertise itself as the geographic center of the country, not just a place that happens to be near such a center. There seems to be no shortage of potential sites on which to plant a center monument within city boundaries. There are empty lots in the very center of the town. The land fronting the city’s water tower on Main Street might suit nicely.

Who would object to such a move? Certainly not the U.S. Geodetic Survey. That department is no longer interested in geographic centers. Oscar S. Adams, Senior Mathematician at the department, in his article titled Geographic Centers, says this:

“As a matter of fact, the conclusion is forced upon us that there is no such thing as the geographical center of any state, country or continent. The point determined will depend entirely upon the definition given by the one making the computation.”

After inspecting the existing center monument and then returning to Lebanon to walk about the streets, we are hungry and thirsty but find no place to eat. We head back to Route 36 and continue our journey westward. A twenty minute drive takes us to a restaurant called Paul’s Cafe and Dining Room in the city of Smith Center.

Kansas Dept. of transportation (KDOT) of Smith County Kansas showing location of City of Lebanon

Smith County, Kansas. Image from KDOT.