Theme: Floods

 

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Text, Viewspace. The show will continue in 15 seconds. Coming up: Observe flooding with NASA satellites. 

 

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The text appears on a background of stars which move slowly towards and past us. 

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A satellite view of the US with a white box over a section of the Pacific Northwest.

 

Text, 19,000 Years Ago, Northwestern United States. About 19,000 years ago an ice dam in the Clark Fork River Valley trapped water melting from the Cordilleran Ice Sheet.

 

An enormous glacial lake formed over what are now valleys west of the Rocky Mountains in Montana.

 

Glacial Lake Missoula reached a depth of about 2000 feet, nearly double the average maximum depth of the Great Lakes.

 

It held more water than Lake Ontario and Lake Erie combined.

 

A red dot marks the location of the dam. Text, When the ice dam gave way, Glacial Lake Missoula sent a torrent of water rushing across the landscape.

 

The towering wall of water and ice equal to 10 times the combined flow of all the rivers of the world shook and scoured the landscape.

 

Waterways spread on a map. A red dot marks Dry Falls. Text, As the deluge thundered toward the Pacific Ocean, it stripped away thick soils and cut deep canyons some 600 feet and 20 miles wide.

 

A red dot marks the location of Palouse Hills. Text, It roared across what is now eastern Washington at speeds approaching 65 miles per hour, carving what we know today as the Channeled Scablands.

 

Glacial Lake Missoula drained its 500 cubic miles of water in as little as 48 hours.

 

This cataclysmic event happened again and again before the ice finally retreated north.

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An animation of Earth in a star-filled sky. Text, at-a-GLANCE, Floods

 

There are three main types of floods; coastal, seasonal, and flash floods.

 

Coastal Floods, Southern Gulf Coast, Mexico, Flash Floods, Brazil, South America, Seasonal Floods, Mozambique, Africa

 

Coastal floods occur when ocean water surges onto the land.

 

Before and After satellite images, Coastal Floods, Southern Gulf Coast, Mexico. Hurricanes are the most common cause of coastal flooding.

 

Hurricane Karl flooded land along the coastline of Veracruz, Mexico, in September 2010.

 

Mozambique, Africa. Seasonal floods happen regularly.

 

They may be the result of snow melt, spring rain, or summer monsoon rains.

 

Before and After satellite images, Seasonal Floods, Mozambique, Africa. The rainy season begins in October and runs through March in southern Africa.

 

The Pungue River in Africa and its surrounding wetlands are saturated and will offer life-giving water during the dry season.

 

Brazil, South America. Flash floods are rapid floods that can occur after a heavy rainstorm, hurricane, tsunami, or collapse of a dam.

 

Flash floods often occur in desert regions, where sudden heavy rains fill dry canyons, riverbeds, and lakebeds.

 

Before and After satellite images, Flash Floods, Brazil, South America. landslides. Nearly 10 inches, a month's worth of rain, fell on the Serra do Mar mountain region in Brazil on January 12, 2011.

 

The downpours provoked flash floods and sent rivers of mud flowing down steep hillsides, killing 860 people and leaving at least 8,700 homeless.

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An aerial view of Missouri River flooding near Hamburg Iowa in natural color.(SPEECH)

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Text, Myth vs. Reality

 

Flooded rivers and streams always deposit nutrient-rich mud on the land, enriching it for farmers.

 

In many cases, floodwaters are dirty. Floodwaters carry trash and other debris, raw sewage, and chemical pollutants. The muddy sludge they leave behind can be toxic. It may take years for flooded farmland soils to recover and be healthy again.

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An aerial features the Yazoo River, Vicksburg, Mississippi River. Text, Lingering Floodwaters near Vicksburg, Mississippi. The Mississippi River is the longest continuous waterway in the United States.

 

It wanders more than 2,300 miles from Lake Itasca, Minnesota, to the Gulf of Mexico.

 

Old bends or meanders in the river from oxbow lakes as the Mississippi changes its flow pattern.

 

On May 19, 2011, the Mississippi River reached a historic 57.1-foot crest.

 

This satellite image was captured on June 11, 2011, when water levels around Vicksburg had already begun receding but we're still above normal.

 

Standing water is most apparent in the floodplain between the Yazoo and Mississippi Rivers north of Vicksburg.

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The Mississippi River on a terrain map.

 

Text, Mississippi Rising.

 

Planet Earth zooms in on an area of Eastern Missouri and Arkansas. The state lines bolden.

 

In the spring of 2011, the Mississippi River Drainage Basin began to fill as heavy spring rains quickly melted record amounts of snowfall from the previous winter.

 

An icon of a cloud with snowfall.

 

February 1, 2011.

 

Raindrops fall from the cloud.

 

March 1, 2011.

 

Image of a satellite with a large panel.

 

Text, NASA's Terra satellite tracked the resulting flood.

 

Surrounding rivers are labeled on a map, the White, Wabash, and Ohio Rivers.

 

On March 1, waters on the Mississippi River remained largely confined to braided river channels.

 

A cover of clouds appear.

 

By March 20, water had risen substantially, especially south of the Ohio-Mississippi confluence.

 

Water levels were also substantially higher on the Wabash, Ohio, and White Rivers.

 

Several map markers appear as exclamation points in a red circle.

 

On April 28, 2011, measurements along the Mississippi River basin showed major to minor flooding at 404 locations.

 

The Black River to the west is labeled.

 

Text, In this satellite image, high water levels are visible along the Wabash, Ohio, Black, and Mississippi Rivers.

 

An area on the map is circled and magnified. Map marker lands on Cairo, Illinois. Just south, an area is labeled "floodway."

 

Text, To protect Cairo, Illinois from rising floodwaters, the U.S. Army Corps of Engineers blew a hole in the Birds Point Levee near the confluence of the Ohio and Mississippi Rivers just after 10 PM on May 2, 2011.

 

Satellite image transforms and an overcast of clouds appear above a much wider river which expands into the floodway.

 

The two-mile hole flooded 200 square miles of farmland and damaged or destroyed about 100 homes in the Birds Point New Madrid Floodway.

 

On a separate satellite image, a map marker lands on Memphis.

 

Text, As floodwaters continued to move south, the Mississippi River reaches nearly 48 feet in Memphis Tennessee on May 10, 2011.

 

A line scans over Memphis and the date changes from April 21 to May 10. The Mississippi River's brown water floods into West Memphis.

 

Text, It was the highest water level for Memphis since 1937, when the river reached a record 48.7 feet.

 

Floodwaters span the distance between Memphis and West Memphis, about 6 miles.

 

Map shows the Mississippi River down to New Orleans.

 

Text, By mid-May, the U.S. Army Corps of Engineers feared that weeks of pressure on the Mississippi's levees would cause them to fail, swamping New Orleans under as much as 20 feet of water.

 

An area on the map is circled and magnified. Near the Mississippi River, a spillway is labeled near a levee.

 

Morganza Spillway, Pointe Coupee Parish, Louisiana. May 15, 2011. Text, To release some of that pressure, they opened the 10-ton floodgates of the Morganza Spillway on May 13, 2011 -- the first time in 38 years.

 

A map key with four color-coded areas, Clear water, Sediment-Laden water, Vegetation, and Cleared Farm Fields. Much of the area on one side of the spillway is vegetation, with sediment-laden water on the other side.

 

Text, Five days later, water had spread 15 to 20 miles southward across the Louisiana landscape.

 

A total of 17 bays on the spillway had been opened, with roughly 114,000 cubic feet per second flowing out of the Mississippi River and into the floodway.

 

Water rushes from the concrete bays of the spillway toward patches of trees.

 

Text, This action covered roughly 3,000 square miles with as much as 25 feet of water.

 

A massive area of trees flooded with brown water.

 

Text, By the time Mississippi floodwaters reached New Orleans, they were heavily burdened with the debris of modern life.

 

As floodwaters scour the land, they pick up sediment, chemical pollutants, raw sewage, trash, and other debris.

 

A bird perched on a stick on the bank of floodwaters. Debris floats nearby.

 

An image shows a clear distinction where sediment-filled water meets the dark waters of the Gulf of Mexico.

 

Text, Northern Gulf of Mexico, 2009. These pollutants travel with the river to the ocean, where they dump their toxic soup into the bays and estuaries along the continental margins.

 

Sewage and fertilizers in floodwater cause tiny aquatic plants to multiply very quickly.

 

Bright green algae stands out in brown waters.

 

Text, As these plants die, they sink to the ocean floor where bacteria use oxygen in the water to decay the plants.

 

Fish lie sideways on sand as waves hit the shore.

 

Text, Without oxygen, sea life can't breathe and they die, creating a dead zone.

 

Northern Gulf of Mexico, May 17, 2011. Swollen rivers dumped thousands of tons of pollutants into the Gulf of Mexico and Lake Pontchartrain in 2011.

 

Heat map of North America surrounded by dark blue ocean water. Orange and red colors come from the New Orleans area into the Gulf of Mexico.

 

Text, Floods are the most chronic and costly natural hazard in the world.

 

On the map, several cities are highlighted which lie on the Mississippi River.

 

In the United States, about 100 people die in floods each year.

 

Between the years 2000 and 2010, floods caused an average of 9.5 billion dollars per year in damages.

 

Yet nearly 4,000 towns and cities, each with more than 2,500 inhabitants, continue to cope with life on the floodplains of the United States.

 

Muddy water covers a farm, reaching halfway up a silo.

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A banner is outlined in blue for the title, Myth vs Reality and it is split into two sections. An illustration with sea serpents surrounding a ship is above Myth. A row of trees standing in a flooded area is above reality. A dark, rotating planet floats in the background at the bottom. The Myth side is highlighted. Text, Levees and spillways always reduce damage from flooding.

 

The reality side is highlighted. Text, Constraining a river's natural flow pattern with levees will make a swollen river flow faster. The high, fast-moving water can eat away at levees, causing a breach. Floodwaters that break through a levee travel faster and with more force than a slowly rising river in its natural channel.

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Text, An ever-changing river, the Mississippi River. An illustration of the river's various positions over the years shown in different colors and appearing as overlapping winding ribbons. 

Text, The Mississippi River is in constant flux, but the shifting paths it has carved across the landscape are still discernible. The Army Corps of Engineers has recorded this history of change by mapping the landscape in and around the Mississippi River. This 1944 map reveals the river's modern course as superimposed on channels from 1880 (green), 1820 (red), and 1765 (blue). Bends in the river that were cut off from the main channel form crescent-shaped oxbow lakes.

 

A satellite image of the river, a stripe of brown curving through green and brown land. A curved brown oxbow lake sits to one side of a curve. Text, A 1999 satellite image reveals the current course of the river and old oxbow lakes. Despite our levees and spillways, the river still slowly changes as it fights against its manmade restraints.

 

Text, in mid-June 2011, the Missouri River spilled over its banks along the Nebraska-Iowa border, not far from Hamburg, Iowa.

 

On June 14, the Landsat 5 satellite captured natural- and representative-color images of the flood.

 

The aerial view in false color. Water covers the area between the Missouri River and Hamburg. Text, water is navy blue and clouds are white in this representative-color image.

 

The flooding here lingered for weeks.