Flash Floods and DamsFlash Floods and Dams

Preview for JohnstownPreview for Johnstown

Flash FloodsFlash FloodsPerry, C.A. “Significant floods in the United states during the 20Perry, C.A. “Significant floods in the United states during the 20thth century – USGS century – USGS

measures a century of floods.” measures a century of floods.” USGS Fact Sheet 024-00USGS Fact Sheet 024-00. March 2000.. March 2000.

Several seconds to several hoursSeveral seconds to several hours Little warningLittle warning Rapid rises in water levelsRapid rises in water levels Devastating flow velocitiesDevastating flow velocities Deadly, quicklyDeadly, quickly

Factors in Flash FloodsFactors in Flash Floods Perry, C.A. “Significant floods in the United states during the 20Perry, C.A. “Significant floods in the United states during the 20thth century – USGS measures a century – USGS measures a

century of floods.” century of floods.” USGS Fact Sheet 024-00USGS Fact Sheet 024-00. March 2000.. March 2000.

Rainfall intensity and durationRainfall intensity and duration Rapid City, SD- 1972: 15 inches of rain in 5 hours Rapid City, SD- 1972: 15 inches of rain in 5 hours

from slow moving thunderstorms kills 237 peoplefrom slow moving thunderstorms kills 237 people Floodwaves more than 30 feet high occur many miles Floodwaves more than 30 feet high occur many miles

from rainfall area.from rainfall area.

Surface conditionsSurface conditions Topography of the areaTopography of the area

Slope of basin, mountainsSlope of basin, mountains UrbanizationUrbanization

Gravity Dam: ForcesGravity Dam: ForcesWater pushes against the gravity dam, but Water pushes against the gravity dam, but the heavy weight of the dam pushes down the heavy weight of the dam pushes down into the ground and prevents the structure into the ground and prevents the structure from falling over.from falling over.

“Building Big, Dam Basics”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

Gravity DamGravity DamGrand Coulee DamGrand Coulee Dam

Grand Coulee, WashingtonGrand Coulee, Washington

Photo, U.S. Bureau of Reclamation

Embankment Dam: ForcesEmbankment Dam: ForcesWater pushes against the embankment Water pushes against the embankment dam, but the heavy weight of the dam dam, but the heavy weight of the dam pushes down into the ground and prevents pushes down into the ground and prevents the structure from falling over.the structure from falling over.

“Building Big, Dam Basics”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

Embankment DamEmbankment DamNew Waddell DamNew Waddell Dam

Maricopa County, ArizonaMaricopa County, Arizona

Photo, U.S. Bureau of Reclamation

Buttress Dam: ForcesButtress Dam: ForcesWater pushes against the buttress dam, Water pushes against the buttress dam, but the buttresses push back and prevent but the buttresses push back and prevent the dam from toppling over. The weight of the dam from toppling over. The weight of the buttress dam also pushes down into the buttress dam also pushes down into the ground.the ground.

“Building Big, Dam Basics”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

Buttress DamButtress DamBartlett DamBartlett DamVerde River, Arizona Verde River, Arizona

Photo, U.S. Bureau of Reclamation

Arch Dam: ForcesArch Dam: ForcesThe arch squeezes together as the water The arch squeezes together as the water pushes against it. The weight of the dam pushes against it. The weight of the dam also pushes the structure down into the also pushes the structure down into the ground.ground.

“Building Big, Dam Basics”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

Arch DamArch DamEl Atazar DamEl Atazar DamMadrid, SpainMadrid, Spain

Courtesy Canal de Isabel II, Gabinete de Prensa e Imagen

Dam Challenge:Dam Challenge:“Building Big, Dam Challenge”. “Building Big, Dam Challenge”. PBS.org.PBS.org. 4/1/08 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html><http://www.pbs.org/wgbh/buildingbig/index.html>

Form groups of 2 or 3Form groups of 2 or 3 Decide on your course of actionDecide on your course of action Be ready to defend your choiceBe ready to defend your choice

Scenario:Scenario:

Dams don't last forever. Hot and cold weather makes them crack.Water erodes their foundations. They create environmental problems. Eventually, every dam must be repaired, removed, or replaced.

You are a consulting dam engineer, and today, four dams need yourattention. It is your job to advise the dam owners whether their dams must be repaired, taken down, or simply left alone. Listen to what the supporters and opponents of each dam have to say.

Like all dam engineers, you must weigh the pros and cons before you make your final decisions. Good luck!

“Building Big, Dam Challenge”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

Dam Challenge!Dam Challenge!

Arch DamArch Dam Embankment DamEmbankment Dam Gravity DamGravity Dam Buttress DamButtress Dam

“Building Big, Dam Challenge”. PBS.org. 4/1/08 <http://www.pbs.org/wgbh/buildingbig/index.html>

South Fork DamSouth Fork Dam

Embankment damEmbankment dam Poorly maintainedPoorly maintained Major mistakes were madeMajor mistakes were made

Change in the structureChange in the structure Change in the materials usedChange in the materials used

Original DesignOriginal DesignSmoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic Smoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic

Johnstown Flood of 1889.” Johnstown Flood of 1889.” Civil EngineeringCivil Engineering. May 1988, 63-66.. May 1988, 63-66.

http://smoter.com/flooddam/images/culvert.jpg

ReconstructionReconstructionSmoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic Smoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic

Johnstown Flood of 1889.” Johnstown Flood of 1889.” Civil EngineeringCivil Engineering. May 1988, 63-66.. May 1988, 63-66.

http://smoter.com/flooddam/images/culvert.jpg

South Fork DamSouth Fork Dam

http://www.nps.gov/archive/jofl/image3.gifNational Parks Service

http://www.jaha.org/FloodMuseum/Dam.jpg

http://www.shadedrelief.com/birds_eye/more_images/townsend/johnstown3.jpg

South Fork Dam and club house. c1889Courtesy Library of Congress

Residents of Johnstown find refuge on rooftops after Johnstown Flood, Residents of Johnstown find refuge on rooftops after Johnstown Flood, South Fork Dam disaster, Johnstown, Pennsylvania, 1889South Fork Dam disaster, Johnstown, Pennsylvania, 1889

Johnstown Area Heritage Association Archives, Johnstown, Pennsylvania

Looking west on Main Street. c1889Courtesy Library of Congress

Cambria Company's store looking towards Kernville. c1889Courtesy Library of Congress

General view of Johnstown looking towards Kernville. c1889Courtesy Library of Congress

Close up of previous view. c1889Courtesy Library of Congress

Club House Press looking south. c1889Courtesy Library of Congress

Club House and Morrell Institute. c1889Courtesy Library of Congress

View showing relief camps. Wood, Morrell & Co.'s store and office from Prospect Hill. c1889

Courtesy Library of Congress

Close up of relief camps from previous photo. c1889Courtesy Library of Congress

Problem Solve:Problem Solve:

Scenario:Scenario:

You are living in Walnut Bottom, where the creek floods frequently. The You are living in Walnut Bottom, where the creek floods frequently. The National Weather Service is calling for a flash flood watch, and you need to National Weather Service is calling for a flash flood watch, and you need to make preparations.make preparations.

Decide what you will do about the following:Decide what you will do about the following: Figure out your plan for: (1) riding out the storm in your home and (2) going Figure out your plan for: (1) riding out the storm in your home and (2) going

to a shelter to ride out the storm. to a shelter to ride out the storm. Pets (most shelters do not allow you to bring pets)Pets (most shelters do not allow you to bring pets) Food & water for yourself (how much should you have on hand?)Food & water for yourself (how much should you have on hand?) Medical needs (what medical supplies should you have on hand?)Medical needs (what medical supplies should you have on hand?) KeepsakesKeepsakes Grandparents or other extended family (how will you reach them, or let them Grandparents or other extended family (how will you reach them, or let them

know where you are?)know where you are?) What will you do about sanitation?What will you do about sanitation?

SourcesSources

“Building Big, Dam Basics”. PBS.org. 4/1/08 http://www.pbs.org/wgbh/buildingbig/index.html

Heritage Johnstown Area Association Archives, Johnstown, Pennsylvania

McCullough, David. 1968. The Johnstown Flood. New York, NY: Simon & Schuster.

Perry, C.A. “Significant floods in the United states during the 20th century – USGS Perry, C.A. “Significant floods in the United states during the 20th century – USGS measures a century of floods.” measures a century of floods.” USGS Fact Sheet 024-00USGS Fact Sheet 024-00. March 2000.. March 2000.

Smoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic Smoter-Frank, Walter. “The Cause of the Johnstown Flood: A new look at the Historic Johnstown Flood of 1889.” Johnstown Flood of 1889.” Civil EngineeringCivil Engineering. May 1988, 63-66.. May 1988, 63-66.

Photo CreditsPhoto Creditshttp://www.jaha.org/FloodMuseum/Dam.jpg

http://www.nps.gov/archive/jofl/image3.gif National Parks Service

http://www.shadedrelief.com/birds_eye/more_images/townsend/johnstown3.jpg