For hundreds of years, thousands of people have connected with the Mississippi River. Today, we sometimes forget that the Mississippi is always flowing through our fair cities, at least until it floods.
In this moment, the river can be an extraordinarily humanizing resource. When we stand together on the Science Museum's plaza, peek over the rails on Kellogg Blvd.'s parkland, or sit near the steps on Harriet Island, all gazing at the flooding river, we are not accountants, scientists, or novelists but everyday people witnessing an event that still produces the same awe, fear, romance, or dread that thousands of people for hundreds of years before us have experienced when they too watched or experienced a flood.
In future posts, my colleagues and I will chat about the impact of flooding on the Mississippi's landscape and try providing some historical perspectives on river floods.
If you'd like to learn more about our National Park Service unit, the Mississippi National River and Recreation Area, please visit us at www.nps.gov/miss.
-Ranger Brian
Check out our full feature on the 2010 Mississippi River flooding.
Tags : High and fast
in Earth and Space Science, Math, The Water Cycle, Weather and Climate, and Forces of Nature
Look out the window or walk down the street to nearly any river or stream in Minnesota right now and you are likely to observe two things about the river:
- it is getting deeper (or “rising” in relation to the banks); and
- it appears to be moving faster.
You can, of course, confirm these observations by investigating reports from gauging stations along these rivers, maintained by the U.S. Geological Survey. (See data for the gauging station serving downtown St. Paul.) But what is really happening?
It may be high and fast...: ...but (as of today) the Mississippi at St. Paul is still in a bankfull state.
Courtesy Liza Pryor
Until a river flows over its banks, it is considered to be in a “bankfull” state. In this state, the water flowing through the river is confined to a relatively fixed channel area. Simply put, floods occur because more water is being introduced into this channel from upstream, due to snowmelt, heavy rains, or a dam breach. As this added volume of water moves through a fixed area, it both increases in velocity and in depth until it overflows the banks, at which point some, but not necessarily a lot, of the volume and velocity moving through the channel are reduced.
Scientists call the rate of flow through a channel “discharge." Discharge is defined as the volume of water passing through a given cross-section of the river channel within a specified period of time.A simple equation for determining discharge is
Q = D x W x V
where Q = discharge, D = channel depth, W = channel width and V = velocity.
Looking at this equation, it is easy to see that if discharge becomes greater and channel width is fixed, then an increase in both volume and depth (or height relative to the banks) is likely to be the cause. Discharge can be measured in cubic feet per second or cubic meters per second, for example.
But is the river flowing at the same rate at the surface as it does along its banks and beds? Understanding this requires investigating some more detailed equations, as the banks and bed introduce friction, which affects the rate of flow.
To learn more about rivers and how they flow, you may want to check out the works of Luna Leopold, and M. Gordon Wolman. In particular:
- Leopold, Luna B. (2006, reprint). A View of the River. Harvard University Press; and
- Leopold, Luna B.; Wolman, M. Gordon; and Miller, John P. (1995). Fluvial Processes in Geomorphology. Dover Publications, both classics for understanding how rivers work.
Also, check out our full feature on the 2010 Mississippi River flooding.
As of 11:19am, the US Geological Survey is forecasting that the Mississippi River will crest here in downtown St. Paul at 18 feet.
New flood crest prediction, 3/17
Courtesy USGS
That would put Water Street and the lower section of Lilydale Regional Park underwater (at 14'), require secondary flood walls at the St. Paul Downtown Airport (17'), submerge much of Harriet Island (17.5'), and make Warner Road impassable due to high water.
An 18-foot crest would also make this year's flood #9, historically speaking, bumping the flood of 1986 (16.10') off the top-10 list.
Also, check out our full feature on the 2010 Mississippi River flooding.
Minnesota Public Radio featured the new Saint Paul condo developments, down by the Mississippi River, this morning. The Mississippi is predicted to reach flood stage by Friday, and these folks are going to have a pretty good view of the rising water. Check out our full feature on the rising Mississip', with a time-lapse of the river's rise.
Watching the river, 3/16/10
in Earth and Space Science, Physical Science, The Water Cycle, Weather and Climate, and Forces of Nature
All day, up in the Mississippi River Gallery, people have been stopping to look out the window and watch the river.
Here's how the US Geological Survey sees it:
Mississippi River, actual vs. forecast, 3/16/10, 1pm
Courtesy USGS
The river's rising, but not as fast as yesterday. And yesterday's rise outpaced predictions by almost a foot, but today the rise matches the predicted curve almost exactly.
So what are folks seeing out the window? Take a look.
Also check out our full feature on the 2010 Mississippi River flooding.
Watch the steps: They're a good benchmark.
Courtesy Liza Pryor
Raspberry Island: Still high and dry
Courtesy Liza Pryor
Looking upstream: You're still looking at Harriet Island. But low-lying areas of Lilydale (upstream, south side of the river) get inundated when the river reaches 14 feet or so. Right now, that's predicted to happen sometime after 7pm on Sunday, 3/21.
Courtesy Liza Pryor
Strike-slip fault
Courtesy USGSLast weekend’s massive magnitude 8.8 earthquake off the coast of Chile released 500 times the energy generated by the magnitude 7 earthquake that hit in Haiti the month before. Damage is extensive in both countries but so far Haiti seems to have taken a worse hit than Chile, despite suffering a less-powerful quake. In fact, there's news today that the death toll in Chile has been lowered, which is unusual with earthquake tolls. They're usual revised upward. So why the discrepancy between the two quakes? There are several reasons but a big one is the types of earthquakes involved.
The Haiti tremblor occurred along a strike-slip fault where stress is created as two tectonic plates (in Haiti’s case, the Caribbean plate and North American plate) scrape and grind past each other in opposite directions, like two cars trying to squeeze past each other on a single lane bridge. Tension builds as the plates catch and grind and energy is released in fits and starts in the form of tremors. California’s San Andreas fault is a classic strike-slip boundary. There the Pacific plate is moving in a northwesterly direction beside the North American plate.
Subduction zone: Megathrust earthquakes occur near subductions zones.
Courtesy USGSWith a subduction zone megathrust quake – like that which occurred in Chile - it’s more like a head-on collision, where a lighter oceanic crust slams into a heavier continental crust and pushes (or is pulled) beneath it. This creates tremendous tension which eventually gets released, and when it is does, megathrust earthquakes can sometimes occur. They don’t occur all the time, in fact, megathrust earthquakes are rare – only fourteen have been recorded in history – but they only happen in subduction zones, like the one along the coast of Chile where the oceanic Nazca plate is subducting beneath the continental South American plate. Chile’s Andes mountain range rose up as a result of this subduction.
To give an idea of the incredibly huge amount of energy involved with the Chilean quake, it’s been estimated the jolt shifted Earth’s axis 3 inches, caused the planet’s entire mass to contract, become denser, and it’s rotation to speed up, thereby shortening the length of a day by 1.26 milliseconds! (see story)
The nearness and depth of an earthquake’s epicenter is another factor in the amount of perceived intensity and actual damage (measured using the modified Mercalli Intensity Scale), and this figures in the Haiti-Chile comparison. Haiti’s tremblor occurred six miles below the surface, and within ten miles of the severely over-populated capital of Port-au-Prince. That’s a fairly shallow earthquake, so the intensity level was high. Chile’s earthquake was centered 22 miles underground and five miles offshore, more than 70 miles from the nearest large population center (Concepcion).
Haiti’s capital is also built on loose soil that’s been eroded and carried down from the hillsides, and since earthquakes are rare in the region, the poor island nation is ill-prepared and under-equipped to deal with them. Building construction is flimsy, and collapsed easily when shaken, even by many less intense after-shocks. Chile, however, is on solid bedrock, both geologically and in regards to their central government. The country has a long history of dealing with the many quakes that occur there (the normal-sized ones anyway), and has had building codes in place since the 1920s.
MORE EARTHQUAKE INFO
More earthquake information
USGS earthquake page
While much of the Pacific Rim area was on a tsunami alert this weekend in the wake of the earthquake in Chile, the harbor of Long Beach experienced something much different on Saturday. The harbor had a huge tidal drop occur in just a matter of minutes, grounding many sailboats and yachts and closing the harbor to large sea vessels for a while. Here's a complete video report:
The other amazing thing, nothing anywhere near this drastic happened in any other California harbors the same day.
It's been a very snowy winter so it should come as no surprise that the flood risks in Minnesota are going to be high as well. There's a 60-percent chance that the Mississippi River will be creeping up close to our backdoor here at the museum in the latest forecast announced today. Start packing the sandbags right now in Moorhead and Fargo. There's a 98-percent chance that the Red River will flood this spring.
Strong magnitude 6.1 aftershock hits Haiti
Haiti aftershock earthquake
Courtesy American Red Cross
A strong aftershock rocked Haiti on Wednesday morning just as much-needed medical aid was set to reach the earthquake-ravaged nation.
The 6.1-magnitude aftershock was about 6.2 miles deep, with an epicenter about 35 miles (60 kilometers) west-southwest of the capital of Port-au-Prince, the U.S. Geological Survey said. CNN
Learn more about Haiti earthquake news
- CNN has a comprehensive page about the Haiti earthquake here.
- For CNN's up to the minute Haiti earthquake developments click here.
Earthquake and hurricane proof
Haiti housing resource
Courtesy jasonpearce Housing for Haitians may already be on hand. Sturdy, earthquake and hurricane proof, shipping containers often sit empty in port yards because exporting empty containers is not cost effective.
Pernille Christensen, at Clemson’s School of Architecture, along with Martha Skinner and Doug Hecker, have been working to develop a method to convert the shipping containers into homes.
“Because of the shipping container’s ‘unibody’ construction they are also very good in seismic zones and exceed structural code in the United States and any country in the world,” associate professor Hecker said.
“You get people back in their communities and it strengthens those communities,” Christensen said. “They work on their home, not a temporary shelter, and then they work with their neighbors to rebuild the neighborhood. It leads to a healthier and safer community. And these are places often in dire need of better housing.”
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Learn more about shipping container housing
- Clemson University media release
- WYFF4 News video
- Project Green Cube (Clemson University)
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