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PBS&J Highlights Shoring Up Our Levees |
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Shoring Up Our Levees
The 28-foot storm surge that Hurricane Katrina generated as it swept up the central Gulf of Mexico in August 2005 was a brutal reminder that high winds are not the only danger from hurricanes. Forty-six overtoppings and four breaches in the levees of metro New Orleans were recorded as a result of that surge, leaving 80 percent of the city submerged.
The disaster was a wake-up call for the rest of the nation, where
levees are widely used to keep encroaching waters at bay. Today, state
and federal agencies are taking the important first steps in addressing
the condition of our nation's levee systems.
The profile of an earthen levee on the American landscape is a common sight. Across the nation, there are thousands of miles of these structures, which are often the only line of defense against flooding for communities during high-water events.
The Federal Emergency Management Agency (FEMA) identified levees as an important consideration in flood risk reduction when it announced its Map Modernization Program with the passage of the 1994 National Flood Insurance Reform Act. In fact, FEMA noted that many levees had not been assessed since they were originally accredited by the original National Flood Insurance Program, introduced in 1968.
"Certainly, we've known for a
long time that many levees had
not been kept up for one reason or
another," states Donald W. McEvoy, PE,
senior manager of PBS&J's flood hazard
management division. "Also, over
time, a lot of development occurred,
and the level of protection that many
of the levees were originally designed
for is less than it now needs to be."
Even as Katrina was still organizing itself into a hurricane, FEMA issued its Procedure Memorandum No. 34, intended to help the agency's mapping partners (communities, levee owners, and others) properly handle levee mapping issues. But it was when the images of New Orleans' levee breaches hit the national media a week later that the public took note, and government officials put the condition of our levees as a national priority.
Assessing the Situation
The ability to accurately assess flood risk and the integrity of levees and floodwalls starts with data— volumes of data, actually, about elevations, cross-sections, and features like pump stations, gravity drains, sand boils, and encroachment points. It's a monumental task, and the U.S. Army Corps of Engineers (USACE) is hard at work creating a new National Levee Database (NLD) that will give access to this critical information.
Today, a pilot program is under way to capture data for approximately 2,800 miles of levees in five USACE districts under the authority of the federal government. As part of this effort, the USACE is creating the foundation for a national geographical information system (GIS)-based database that will serve multiple federal users, including the USACE districts, the National Levee Safety Program, the Inspection of Completed Works (ICW) Program, and FEMA's Map Modernization and Levee Certification programs.
"But data collection can't be done effectively without an understanding of what is needed. So the USACE is also developing the standards for levee field data collection, information research, and geodatabase development," explains PBS&J Project Manager Thomas J. Schweitzer, PE, CFM. The collected data is entered into the USACE's Spatial Data Standard for Facilities, Infrastructure, and Environment-compliant database model to test and refine the data model.
The levee inventory is the first of
three components that will comprise
the National Levee Safety Program.
Because it ultimately will include
recorded inspection ratings, the
database will be used to support the
National Flood Insurance Program.
Accountability for levee maintenance
will be most apparent here,
when levees that are unable to be
certified result in homeowners and
businesses behind the levees having
to purchase federally underwritten
flood insurance.
California Forges Ahead
In California, the state's Department of Water Resources (DWR) is making headway on its own levee system inventory. Prompted by an urgency identified formally in a January 2005 DWR report—and made all too real months later in the wake of Hurricane Katrina—the California Levee Database project is the first step in defusing what has been called "a ticking bomb."
"California alone has approximately 10,000 miles of river levees," states Don McEvoy. "The Central Valley, which drains into the Sacramento-San Joaquin Delta, is considered to be a particularly highrisk area. It has more than 2,600 miles of levees built for flood protection, and many are quite old."
Certainly, a severe flood would have major consequences. According to DWR's Flood Warnings: Responding to California's Flood Crisis report, many of the levees were constructed adjacent to channels that were used to clean out silt accumulation from Gold Rush mining operations. Now these channels run cleaner, and high-water flow has weakened the peat soils of the old levees. If the area were hit by a major flood, hundreds of thousands of Central Valley residents could be forced out of their homes. Residential and agricultural water supplies to two-thirds of the state could be disrupted, and more than 4.5 million acres of the Central Valley could be under water. And with some of the world's richest farmland contained within the valley, the impacts of a massive flood would resound not only in California, but around the globe.
And there's another reason for urgency, adds Schweitzer. In 2003, a California court found the state liable for $500 million in damages following a levee break in Yuba County in 1986. The levee was operated, but not owned, by the state.
Hoping to preempt a catastrophic flood event, the state initiated its levee inventory project in early 2005 to identify the most pressing needs for levee maintenance, repair, and rehabilitation. The project is being coordinated closely with the USACE and FEMA through PBS&J to complement the USACE national database efforts and to support FEMA's Map Modernization Program. Data is being shared between the USACE, DWR, and FEMA efforts. The state hopes that a comprehensive levee catalog will also help them to analyze risk, educate the public, and conduct emergency management activities.
Learning From California's Experience
For any entity faced with levee maintenance responsibilities, California is an example from which to learn. The state's efforts have revealed the complexity involved in cataloging our neglected levee systems. For example, while some information exists in transferable digital formats, much of the information requires reformatting, and still more is available as paper documentation only and must be converted to digital maps that can be referenced and maintained more easily.
Using a GIS platform for these digital maps allows for quick visual reference. The California levee database represents a state-of-the-art application of GIS, explains Gary Yagade, PE, assistant project manager for the California DWR Levee Database project. "It's built on the latest geodatabase design technologies, able to be accessed without expensive software. You don't need special training, and it will be accessible via the Internet. Best of all, it is compatible with other local, state, and federal resources, including FEMA's flood insurance rate maps."
This will be a particular advantage in California, where like many other locations across the nation, jurisdiction is divided among multiple entities. For the California Levee Database project, data sources required to cover the state included the U.S. Geological Service, U.S. Bureau of Reclamation, State Reclamation Board, and California Office of Emergency Services. Then there are 48 counties, more than 100 public and private levee districts, and several hundred cities and towns.
According to Ricardo Pineda, PE, CFM, chief of the Floodplain Management Branch of DWR, the database will be a repository for information that is critical to determining whether existing levees will meet many of the factors that are required to receive certification of meeting FEMA standards. "The ultimate plan," he adds, "is for the database program to provide the detailed framework for levee inventories from all related state and federal agencies, including USACE and FEMA."
The 28-foot storm surge that Hurricane Katrina generated as it swept up the central Gulf of Mexico in August 2005 was a brutal reminder that high winds are not the only danger from hurricanes. Forty-six overtoppings and four breaches in the levees of metro New Orleans were recorded as a result of that surge, leaving 80 percent of the city submerged.
The disaster was a wake-up call for the rest of the nation, where
levees are widely used to keep encroaching waters at bay. Today, state
and federal agencies are taking the important first steps in addressing
the condition of our nation's levee systems. The profile of an earthen levee on the American landscape is a common sight. Across the nation, there are thousands of miles of these structures, which are often the only line of defense against flooding for communities during high-water events.
The Federal Emergency Management Agency (FEMA) identified levees as an important consideration in flood risk reduction when it announced its Map Modernization Program with the passage of the 1994 National Flood Insurance Reform Act. In fact, FEMA noted that many levees had not been assessed since they were originally accredited by the original National Flood Insurance Program, introduced in 1968.
"Certainly, we've known for a
long time that many levees had
not been kept up for one reason or
another," states Donald W. McEvoy, PE,
senior manager of PBS&J's flood hazard
management division. "Also, over
time, a lot of development occurred,
and the level of protection that many
of the levees were originally designed
for is less than it now needs to be."Even as Katrina was still organizing itself into a hurricane, FEMA issued its Procedure Memorandum No. 34, intended to help the agency's mapping partners (communities, levee owners, and others) properly handle levee mapping issues. But it was when the images of New Orleans' levee breaches hit the national media a week later that the public took note, and government officials put the condition of our levees as a national priority.
Assessing the SituationThe ability to accurately assess flood risk and the integrity of levees and floodwalls starts with data— volumes of data, actually, about elevations, cross-sections, and features like pump stations, gravity drains, sand boils, and encroachment points. It's a monumental task, and the U.S. Army Corps of Engineers (USACE) is hard at work creating a new National Levee Database (NLD) that will give access to this critical information.
Today, a pilot program is under way to capture data for approximately 2,800 miles of levees in five USACE districts under the authority of the federal government. As part of this effort, the USACE is creating the foundation for a national geographical information system (GIS)-based database that will serve multiple federal users, including the USACE districts, the National Levee Safety Program, the Inspection of Completed Works (ICW) Program, and FEMA's Map Modernization and Levee Certification programs.
"But data collection can't be done effectively without an understanding of what is needed. So the USACE is also developing the standards for levee field data collection, information research, and geodatabase development," explains PBS&J Project Manager Thomas J. Schweitzer, PE, CFM. The collected data is entered into the USACE's Spatial Data Standard for Facilities, Infrastructure, and Environment-compliant database model to test and refine the data model.
The levee inventory is the first of
three components that will comprise
the National Levee Safety Program.
Because it ultimately will include
recorded inspection ratings, the
database will be used to support the
National Flood Insurance Program.
Accountability for levee maintenance
will be most apparent here,
when levees that are unable to be
certified result in homeowners and
businesses behind the levees having
to purchase federally underwritten
flood insurance.
California Forges Ahead
In California, the state's Department of Water Resources (DWR) is making headway on its own levee system inventory. Prompted by an urgency identified formally in a January 2005 DWR report—and made all too real months later in the wake of Hurricane Katrina—the California Levee Database project is the first step in defusing what has been called "a ticking bomb."
"California alone has approximately 10,000 miles of river levees," states Don McEvoy. "The Central Valley, which drains into the Sacramento-San Joaquin Delta, is considered to be a particularly highrisk area. It has more than 2,600 miles of levees built for flood protection, and many are quite old."
Certainly, a severe flood would have major consequences. According to DWR's Flood Warnings: Responding to California's Flood Crisis report, many of the levees were constructed adjacent to channels that were used to clean out silt accumulation from Gold Rush mining operations. Now these channels run cleaner, and high-water flow has weakened the peat soils of the old levees. If the area were hit by a major flood, hundreds of thousands of Central Valley residents could be forced out of their homes. Residential and agricultural water supplies to two-thirds of the state could be disrupted, and more than 4.5 million acres of the Central Valley could be under water. And with some of the world's richest farmland contained within the valley, the impacts of a massive flood would resound not only in California, but around the globe.
And there's another reason for urgency, adds Schweitzer. In 2003, a California court found the state liable for $500 million in damages following a levee break in Yuba County in 1986. The levee was operated, but not owned, by the state.
Hoping to preempt a catastrophic flood event, the state initiated its levee inventory project in early 2005 to identify the most pressing needs for levee maintenance, repair, and rehabilitation. The project is being coordinated closely with the USACE and FEMA through PBS&J to complement the USACE national database efforts and to support FEMA's Map Modernization Program. Data is being shared between the USACE, DWR, and FEMA efforts. The state hopes that a comprehensive levee catalog will also help them to analyze risk, educate the public, and conduct emergency management activities.
Learning From California's Experience
For any entity faced with levee maintenance responsibilities, California is an example from which to learn. The state's efforts have revealed the complexity involved in cataloging our neglected levee systems. For example, while some information exists in transferable digital formats, much of the information requires reformatting, and still more is available as paper documentation only and must be converted to digital maps that can be referenced and maintained more easily.
Using a GIS platform for these digital maps allows for quick visual reference. The California levee database represents a state-of-the-art application of GIS, explains Gary Yagade, PE, assistant project manager for the California DWR Levee Database project. "It's built on the latest geodatabase design technologies, able to be accessed without expensive software. You don't need special training, and it will be accessible via the Internet. Best of all, it is compatible with other local, state, and federal resources, including FEMA's flood insurance rate maps."
This will be a particular advantage in California, where like many other locations across the nation, jurisdiction is divided among multiple entities. For the California Levee Database project, data sources required to cover the state included the U.S. Geological Service, U.S. Bureau of Reclamation, State Reclamation Board, and California Office of Emergency Services. Then there are 48 counties, more than 100 public and private levee districts, and several hundred cities and towns.
According to Ricardo Pineda, PE, CFM, chief of the Floodplain Management Branch of DWR, the database will be a repository for information that is critical to determining whether existing levees will meet many of the factors that are required to receive certification of meeting FEMA standards. "The ultimate plan," he adds, "is for the database program to provide the detailed framework for levee inventories from all related state and federal agencies, including USACE and FEMA."
