File:Louisiana tmo 2018063.jpg
Louisiana_tmo_2018063.jpg (720 × 480 pixels, file size: 210 KB, MIME type: image/jpeg)
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English: In late February 2018, a series of rainstorms pounded the central United States, causing damaging flooding along the Ohio River and parts of the Mississippi. Weeks after the storms, the effects were still being felt as far away as Louisiana. That pulse of flood water traveled down the Mississippi River and, by early March, reached the Gulf of Mexico.
On March 8, the U.S. Army Corps of Engineers opened the Bonnet Carré Spillway, which diverts excess water from the Mississippi River and relieves pressure on levees downriver in New Orleans. It marks the 12th time that the spillway has been opened since the structure was completed in the early 1930s. “This was a big event, but on the scale of big events, it’s a small one,” said Alex Kolker, an associate professor with the Louisiana Universities Marine Consortium. Still, the flood was substantial enough to color coastal waters brown with suspended sediments. On March 4, 2018, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this image of the sediment plume spilling into the Gulf of Mexico. According to Nan Walker, director of Earth Scan Laboratory at Louisiana State University, sediment plumes are visible almost every spring. “The biggest floods of the Mississippi River occur on average in March or April,” she said, “depending upon the weather over the drainage basin.” When sediment-laden floodwaters reach the mouth of the Mississippi, they can contribute to land building. That’s important because the wetlands in the lower part of the Mississippi River delta, particularly around a sub-delta known as Bird’s Foot, are some of the most rapidly sinking wetlands in the country. “In order to keep pace with subsidence, you need floods like this one to bring sediment to the mouth of the Mississippi,” Kolker said. “Many restoration plans revolve around diverting the flow of the Mississippi River in order to recreate systems like Bird’s Foot higher up in the river system. But you need a lot of data to make these decisions when dealing with such a large, complicated hydrological issue.” Satellite data helps scientists understand the movement of sediment and freshwater into the Gulf. According to Kolker, MODIS is good at telling scientists how a plume gets redirected by winds and currents. It also improves the understanding of plume dynamics—that is, where fresh water, nutrients, and sediments end up. When this image was acquired, winds were blowing out of the southeast, pushing the plume of sediment and freshwater to the northwest almost to Grand Isle. “This is the time of year when shrimp are spawning in that bay,” Kolker said. “Events like this one can impact their life cycle.”Deutsch: Ende Februar 2018 traf eine Serie von Regenstürmen die Zentralstaaten der Vereinigten Staaten und führten zu einem schädigenden Hochwasser entlang des Ohio River und Teilen des Mississippi. Wochen nach den Unwettern waren die Auswirkungen davon noch bis nach Louisiana zu spüren. Die Hochwasserwelle wanderte den Mississippi River flußabwärts und erreichte Anfang März den Golf von Mexiko.
Am 8. März 2018 öffnete das U.S. Army Corps of Engineers den Bonnet Carré Spillway, der überschüssiges Wasser vom Mississippi River ableitet und so den Druck auf die Deiche flußabwärts in New Orleans verringert. Es ist das 12. Mal, daß der Flutkanal seit seiner Fertigstellung zu Beginn der 1930er Jahre geöffnet wurde. “Es handelte sich um ein großes Ereignis, aber auf der Skala der großen Ereignisse, war es ein kleines”, sagte Alex Kolker, ein Assistenzprofessor am Louisiana Universities Marine Consortium. Dennoch war die Flut stark genug, um die Küstengewässer mit Schwebesedimenten braun zu färben. Am 4. März 2018 fertigte das Moderate Resolution Imaging Spectroradiometer (MODIS) auf dem Terra-Satelliten der NASA dieses Bild der Sedimentwolke an, die der Fluß in den Golf von Mexiko entläßt. Nan Walker, die Direktorin des Earth Scan Laboratory an der Louisiana State University, zufolge sind solche Sedimentwolken fast in jedem Frühjahr sichtbar. “Die größten Fluten am Mississippi River treten im Schnitt im März oder April auf,” sagte sie, “abhängig vom Wetter im Einzugsgebiet”. Wenn das mit Sedimenten geladene Hochwasser die Mündung des Mississippi erreicht, dann kann es dies zur Landbildung beitragen. Das ist wichtig, weil die Sumpfgebiete im unteren Teil des Mississippi River Delta, speziell in der Umgebung um das Teildelta, das als Bird’s Foot (Vogelfußdelta) bekannt ist, eines der am stärksten absinkenden Sumpfgebiete des Landes ist. “Um mit diesem Absinken standzuhalten, braucht es Fluten wie diese, die Sedimente zur Mündung des Mississippi bringen”, sagte Kolker. “Viele Erneuerungspläne drehen sich darum, den Fluß des Mississippi River so umzuleiten, das Systeme wie Bird’s Foot weiter oben im Mündungsgebiet entstehen. Aber man braucht eine Menge von Daten, um diese Entscheidungen zu treffen, wenn man es mit einem so großen, komplizierten hydrologischen Problem zu tun hat.” Satellitendaten helfen den Wissenschaftlern, die Bewegung von Schwebesedimenten und Süßwasser in den Golf zu verstehen. Nach Kolker verrät MODIS den Wissenschaftlern gut, wie eine Sedimentwolke von Wind und Strömungen umgeleitet wird. Es verbessert auch die Dynamik der Wolke, das heißt wohin Süßwasser, Nährstoffe und Sediment gelangen. Als diese Aufnahme angefertigt wurde, wehte der Wind aus Südosten und drückte die Sedimentwolke nach Nordwesten fast bis Grand Isle. “Dies ist die Zeit es Jahres, wenn Krabben in dieser Bucht laichen”, sagte Kolker. “Ereignisse wie diese können deren Lebenszyklus beeinträchtigen.” |
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| Source | https://earthobservatory.nasa.gov/IOTD/view.php?id=91822&src=iotdrss |
| Author | NASA Earth Observatory image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Kathryn Hansen with image interpretation by Nan Walker (Louisiana State University) and Alex Kolker (Louisiana Universities Marine Consortium). |
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References
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- LSU Earth Scan Laboratory (2018, March 4) MODIS Louisiana Coast Truecolor. Accessed March 9, 2018.
- NASA Earth Observatory (2018, February 28) Flooding in the Central and Southern U.S.
- The Times-Picayune (2018, March 8) Bonnet Carre Spillway opens, releasing water to lower the Mississippi River. Accessed March 9, 2018.
- The Times-Picayune (2018, March 6) Cool satellite image shows rising Mississippi River pouring sediment into the Gulf of Mexico. Accessed March 9, 2018.
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This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.) |  |
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| current | 06:07, 10 March 2018 | | 720 × 480 (210 KB) | Matthiasb (talk | contribs) | {{Information |description ={{en|1=In late February 2018, a series of rainstorms pounded the central United States, causing damaging flooding along the Ohio River and parts of the Mississippi. Weeks after the storms, the effects were still being felt as far away as Louisiana. That pulse of flood water traveled down the Mississippi River and, by early March, reached the Gulf of Mexico. On March 8, the U.S. Army Corps of Engineers opened the Bonnet Carré Spillway, which diverts excess water from the Mississippi River and relieves pressure on levees downriver in New Orleans. It marks the 12th time that the spillway has been opened since the structure was completed in the early 1930s. “This was a big event, but on the scale of big events, it’s a small one,” said Alex Kolker, an associate professor with the Louisiana Universities Marine Consortium. Still, the flood was substantial enough to color coastal waters brown with suspended sediments. On March 4, 2018, the Moderate Resolution... |
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