John Wesley Powell, USGS 2nd Director, initiated streamflow measurements of Western streams in the late 1880s.

All of us are citizens of a watershed. And so it’s not uncommon to pass by a favorite nearby stream and wonder “How much water is flowing in the stream today?” Perhaps we casually wonder this as we contemplate the beauty of the stream, or perhaps we wonder about it with a goal in mind – a fishing or canoe trip, for example.

The uses of streamflow information touch every citizen’s life every day in countless ways. Reliable streamflow information is needed for many purposes: for flood warnings and forecasts; drinking water management; irrigation withdrawals; hydroelectric power production; wastewater discharges and reservoir releases; legal and treaty obligations on interstate and international waters; preservation of aquatic habitats; water quality standards; recreation; infrastructure designs for highways, bridges, culverts, dams, and levees; and for scientific investigations of streamflow history, ecosystem health, and climate change.

To provide reliable streamflow information across the country – information that’s available to every citizen for all these purposes – USGS works in partnership with more than 850 Federal, State, Tribal, and local agencies and collects streamflow information at more than 8,000 streamgages nationwide. Streamgages, like bridges and dams, are a vital part of the Nation’s water infrastructure. The latest streamflow information is increasingly at our fingertips – on our phones and computers in the “now” – as the U.S. Geological Survey (USGS) continues its mission to measure streamflow on thousands of rivers and streams.

How did the story of streamgages begin?                                                                            

USGS is the largest provider of water information in the world. It all began with the agency’s first streamgage in 1889 on the Rio Grande River in New Mexico. As U.S. populations began to expand westward into the drier regions of the country in the 1880s, John Wesley Powell, the second director of the USGS, requested monitoring of streamflow on the Rio Grande River, as well as within seven other major river basins in the West to determine potential water supplies for irrigation needed to support the new development and expansion.

Shortly afterward, USGS began to collect streamflow data at other western locations and two years later made the first streamflow measurements in the East on the Potomac River at Chain Bridge near Washington D.C. By 1895, streamflow was measured by the USGS in at least 27 states across the Nation.

In the 124 years since that first measurement was made on the Rio Grande, USGS and its partners have developed a robust national streamgaging network, which serves to help prevent loss of life and property from floods and to provide the critical scientific basis for using and managing our Nation’s streams and rivers.

Flood Warnings and Forecasting

Almost all USGS streamgages record and transmit streamflow information electronically so that information is available in real time (updated at intervals of 1 to 4 hours or less). The information covers the full range of streamflow conditions, which is critical to protect and minimize loss of life and property from water-related hazards, such as floods. The National Weather Service uses USGS information for forecasting rising stream levels and streamflow and issuing flood warnings to protect lives and property; the Corps of Engineers adjusts flood-control reservoir releases; the Coast Guard issues shipping directives and advisories, and states, tribes, and local communities prepare for floods based on USGS river measurements.

National Flood Safety Awareness Week, March 18-22

National Flood Safety Awareness Week is intended to highlight some of the many ways floods can occur, the hazards associated with floods, and what you can do to save life and property. Flooding is the number two weather killer in the United States, ahead of tornadoes and severe weather. It is the costliest weather-related disaster we face. While much of the focus remains on thunderstorms and tornadoes, flooding can often be an underrated killer.

This map compares current streamflow conditions to historic conditions over the last 30 years for this same day (here, Mar. 19) showing dry conditions in the Nation’s mid-section and wet in the Northeast and Northwest.

Consistent and broad records of streamflow increase knowledge

One of the highest priorities of the USGS is to maintain the long-term stability of streamgaging in recognition that consistent, systematically-collected information is paramount to track climate and land-use changes; improve flood forecasting models; observe flows across international, interstate, and tribal borders; and monitor flows into major river basins that serve heavily populated areas or that sustain vital aquatic communities in key estuaries, such as the Chesapeake Bay. The 8,000 streamgage network is relatively robust to cover the broad range of watersheds and streamflow conditions across the Nation. This robust network is also vital to support ongoing USGS science that provides critical streamflow estimates at ungaged locations, which is essential because it is not economically feasible to measure all rivers and streams at all the most important locations.

USGS places utmost value on the high quality and consistency of its streamflow measurements across the Nation to position the U.S. for a future that may hold unanticipated challenges. The USGS collects a full suite of measurements over the full range of streamflow conditions—extreme lows to extreme highs—with a high level of certainty at all 8,000 sites.

Such data become even more critical as our climate and land use changes and our populations grow, driving an even higher need to sustain water for competing priorities.

Sam Mabry, Director of Land and Water Resources at Mississippi’s Department of Environmental Quality, states, “Historical and long-term [more than 30 years] data are valuable for identifying the kinds of changes that occur with stream flows as a result of climate variation or changes in land and water use. We simply can’t use information that we gather during any one year as intelligently as we could otherwise without continuous historical data to compare it with.” (Environmental Science and Technology, v. 39, issue 3, pp 57-58)

Endangered streamgages

Unfortunately, funding challenges continue to erode the national network. Since 1990, more than 600 USGS streamgages with records of more than 30 years have been discontinued. More than 300 stations are currently threatened or endangered for discontinuation. Confronted by this challenge, USGS and its many partners are committed to continually seek new avenues of support and innovation that promotes more cost-effective monitoring of our Nation’s rivers.

Due to recent budget cuts as a result of sequestration, USGS will discontinue operation of up to 375 streamgages nationwide. Additional streamgages may be affected if partners reduce their funding to support USGS streamgages. Even though the operation of most streamgages is now highly automated, the gages still require periodic maintenance to ensure physical stability and for instrument calibration, communication adjustments, and battery replacement. The USGS is working to identify which streamgages will be impacted and will post this information as it becomes available.

Learn More

National Water Information System (NWIS)

USGS WaterWatch

USGS WaterNow

DOI WaterSMART

An eye on rising waters

The USGS provides practical, unbiased information about the Nation’s rivers and streams that is crucial in mitigating hazards associated with floods. Flooding costs the Nation billions each year.

Dr. Thomas Graziano, Chief of the Hydrologic Services Division, National Weather Service (NOAA-NWS), has said, “USGS streamgage observations serve as the foundation for National Weather Service river forecasts and warnings. We work closely with USGS on a daily basis and during all flood events. The USGS is usually the first to respond and go out in the midst of floods to acquire the observations necessary for the NWS to get the forecast right and provide timely and accurate warnings. The USGS’s high resolution and real-time and historical high quality data, collected over the full range of conditions, are necessary to run and improve our operational forecasting models. NOAA-NWS values our partnership and the USGS’ long history of responsiveness and professionalism.”

A USGS hydrologist measures flow on the Black River at Black Rock, AR during Spring 2011 flooding on the Mississippi River. Waters reached 16 feet above floodstage. When flooding happens, USGS field crews are among the first to respond.

Major General Michael Walsh of the Corps, former Commander of the Mississippi Valley Division, Vicksburg, Mississippi and currently serving as the Deputy Commanding General of Civil and Emergency Operations, reported on the value of USGS monitoring inside the Birds Point-New Madrid floodway during the historic Mississippi River Flood of 2011, stating, “The science we got from the USGS was exactly what I needed to make the decision I had to make [regarding breaching of the Madrid levee to alleviate upstream flooding in Cairo, Illinois and other areas along the Mississippi River].”

Emergency managers with localities and States and the general public use the real-time information and dynamic flood inundation maps to see the expected extent of a flood on a street-by-street basis, hours or even days before it occurs, reducing the possible devastating toll of floods on communities.

The USGS provides practical, unbiased information about the Nation’s rivers and streams that is crucial in mitigating hazards associated with floods.

A citizen from Pennsylvania commented on the USGS National Water Information System online service during a 2006 flood: “It is now 2:26am. We are a community with water around us. This [USGS real-time] service has been very beneficial in watching the water levels. I am a member of the local fire company and live along the Susquehanna River in Lycoming County, Pa. Thanks for the hard work and keeping the site updated.”

Helping Federal, regional, State, and Tribal partners manage water

States, regional commissions, Tribes, localities, and Federal water resource agencies — such as the National Park Service, U.S. Army Corps of Engineers, and Bureau of Reclamation — operate water supply systems on a day-to-day and seasonal basis. These organizations are often charged with developing operating strategies to maintain the ecological function of rivers while also serving multiple water needs for recreation, cities, farms, energy production, navigation, and industries. With such diverse requirements, stream gage measurements are fundamental to (1) manage reservoir releases for water supply, irrigation, hydropower, environmental and navigation uses; (2) protect stream ecology and other instream uses; and (3) plan for a sustainable water future.

Gage house for the streamgage on the Souris River above Minot, North Dakota.

USGS collaborates with the U.S. Army Corps of Engineers (Corps) and Bureau of Reclamation (BOR) on an ongoing basis to assist their daily operational decisions. These data-assisted decisions can include managing daily and hourly flows through gates and hydropower penstocks, pumping water into diversion systems, or managing hydroelectric reservoirs. Thousands of streamgages operated by USGS are used by the Corps, BOR, and others to operate flood control, navigation, and water-supply reservoirs across the country.

USGS and the National Park Service jointly operate more than 600 streamgages within or near national parks. In some places, for example, at Happy Isles along the Merced River in Yosemite National Park, we have partnered for more than 95 years to measure streamflow.

Ed Harvey, Director of the National Park Service Water Resources Division, states, “USGS streamflow information is required to manage our National Parks and assure public safety and property protection, support threatened and endangered species, and accurately assess long-term changes in relatively pristine watersheds resulting from climate change.”

River Basin Commissions by their nature employ a whole basin planning, development, and management approach to identify “win-win” solutions that cut across functional and jurisdictional boundaries. Bob Tudor, with the Delaware River Basin Commission, has said, “USGS streamgage measurements are the single most important sound science tool in the State/Regional/Federal toolbox to leverage the talent and resources of multiple jurisdictions in common ground strategies to assure community flood resilience and long-term water supply needs.”

Peter Evans, Executive Director of the Interstate Council for Water Policy, the national organization of State and regional water resource management agencies, states, “Streamgages are like our stethoscope on America’s rivers and water supplies. Without reliable, long-term measurement of our water resources, we can’t possible understand, protect or assure sustainable supplies in our future.”

Streamflow monitoring is critical to many Tribes in the United States, not only for its importance in flood warning predictions and water supply management, but for tribal sustenance and sovereignty as well. Ms. Sharri Venno, Environmental Planner with the Houlton Band Maliseet Indians in Houlton Maine, says, “Our Tribe relies on USGS streamflow gaging activities to maintain aquatic habitat and the seasonal harvesting of a variety of native medicinal flora of importance to our tribal lifestyle and long-standing tribal ceremonies. In addition, USGS stream gages, such as on the Meduxnekeag River in Eastern Maine, provide us valuable real-time information on river flow and water-quality that is critical to native fish habitat, including for spawning Atlantic Salmon, a native species the Tribe hopes to restore back to its once healthy populations.”

USGS streamgaging on the Meduxnekeag River in eastern Maine helps the Houlton Band Maliseet Indians manage and restore native fish habitats, such as for spawning Atlantic Salmon.

Recreation

American Whitewater is a membership organization with over 5000 individual members and more than 100 local paddling club affiliates collectively representing a broad diversity of individual whitewater enthusiasts and river conservationists. The organization connects the interests of human-powered recreational river users with ecological and science-based data to conserve and restore America’s whitewater resources and to enhance opportunities to enjoy them safely.

Canoeists enjoying the Shenandoah River in western Virginia.

Thomas O’Keefe, American Whitewater’s Pacific Northwest Stewardship Director, reports, “Whitewater boaters use USGS streamflow data on a daily basis to assess the safety of river conditions and plan boating trips across the country. In addition, USGS long-term data records represent an important resource for those who manage our Nation’s rivers. We are active participants in management forums with river managers, irrigators, and hydropower operators and we all depend on the reliable and accurate long-term records collected and archived by USGS for the critical scientific guidance they provide to quantitatively evaluate various river management scenarios.”

Specialized uses

Learn more about these and other more specialized uses of USGS water resources research and data — such as designing highways and bridges; protecting water quality; managing water rights and transboundary issues; fulfilling legal obligations related to treaties, compacts, and decrees; advancing education and research — in a 2006 report by the National Hydrologic Warning Council and USGS Circular 1123

Streamflow information for the Nation

The USGS remains dedicated to providing its stakeholders and the public with continuous, consistent, unbiased, well- documented, and well-archived streamflow data to meet a wide spectrum of current and future needs.

People in Sacramento navigate K Street in rowboats during the California flood of 1861-62, which historians say obliterated up to 25 percent of the assessed property value in the state. Photograph by Charles L. Weed.

While popular culture often portrays California as sunny, California residents are familiar with the rains that often batter their state in winter and spring. Measured in total rainfall over a three-day period, these West Coast storms are as big and as frequent as any in the United States, according to USGS research hydrologist Mike Dettinger, who studies the giant atmospheric rivers of water vapor flowing from west to east over the Pacific Ocean that trigger the biggest West Coast storms.

Because West and East coast storms have different characteristics and causes, they are difficult to compare using existing metrics, such as the Safir-Simpson scale used to classify hurricanes. Dettinger is co-leading the development of a simple classification system with Marty Ralph of the National Oceanic and Atmospheric Administration (NOAA) to help scientists and public officials compare East and West Coast storms, and to provide accurate and easily grasped warnings to West Coast residents when a big storm is headed their way.

Dettinger, a research hydrologist with the USGS National Research Program, studies the giant atmospheric rivers — found in the lowest 2 kilometers above Earth’s surface and stretching 400km wide on average, each carrying the equivalent of 10 to 20 Mississippi Rivers of water in the form of vapor — that are responsible for the biggest West Coast storms. When these atmospheric rivers encounter high mountains such as California’s Sierra Nevada, they are forced upward, cooling as they go, and their vapor condenses and falls as rain or snow. Precipitation from atmospheric rivers is double-edged for Californians, says Dettinger: It can manifest in destructive storms, but it also provides much of California’s water supply.

To quantify West Coast storms, Dettinger and Ralph propose a simple ranking called R-Cats, or Rainfall Categories. An “R-Cat-1” storm brings between 200 and 300 millimeters (approximately 8-12 inches) of rain in a three-day period. The scale rises in 100mm intervals to an R-Cat-4 storm, which unleashes more than 500mm (just under 20 inches) of rain in a three-day period. The R-Cat system is meant to be simple enough to facilitate communication in public and technical arenas. As a communication and research tool, it is meant to provide a clear, objective perspective on the severity of precipitation in West Coast storms, and potentially of storms elsewhere.

R-Cats is just part of USGS’ ongoing work to inform the public and management officials about the potential of extreme storms. In 2011, USGS and partners unveiled the ARkStorm Scenario, a hypothetical storm similar in magnitude to the intense West Coast winter storms of 1861 and 1862 that destroyed up to a quarter of California’s taxable property and rendered the state’s 480-kilometer- (300-mile) long Central Valley impassible. Today, the economic loss from such an event would total billions. To help emergency managers, universities, businesses, public agencies and others in planning for such natural disasters, ARkStorm (for “Atmospheric River 1,000 Storm”) modeled a storm that the West Coast might expect, on average, once every 500 to 1,000 years.

One implication recognized by ARkStorm’s creators was the need to develop consistent and easily understandable terms to communicate the risk and magnitude of West Coast storms to the public. Dettinger and Ralph, who were part of the more than 120 scientists on the ARkStorm team, and co-led the development of the meteorological part of the scenario, see the R-Cats system as a response to that need.

The Russian River at Guerneville, Calif., on Jan. 20, 2010, in the midst of a series of storms. Photograph by Stumptown Brewery.

The idea for a scaling system came to Dettinger and Ralph as part of their collaboration exploring the causes and impacts of extreme precipitation on the U.S. West Coast.  They were bad, locals asserted, but how bad were they in comparison, for example, to storms in Texas? They compared 30 years of daily precipitation reports from more then 5,800 weather stations across the United States and grouped them into R-Cat levels.  They found that nearly all the R-Cat-3 and -4 events occurred in California, Texas or the Southeastern states. Seventeen storms west of the 115^th parallel during the 30-year reporting period were R-Cat-2 or higher – that is, they dropped more than 300mm (11.81 inches) of rain in three days – and all were associated with atmospheric rivers. Further, only in California did any stations report multiple R-Cat-3 or -4 episodes during those 30 years.

“Three-day precipitation extremes associated with landfalling ARs on the U.S. West Coast are heavier than extreme storms anywhere else in the country outside the southeast United States (including those related to landfalling tropical storms and hurricanes). Also, they yield comparable precipitation totals with the southeastern storms, and occur station-by station just as frequently as the extreme precipitation episodes elsewhere,” Dettinger and Ralph concluded in their paper in a recent Bulletin of the American Meteorological Society that explains the R-Cats system.

Today, atmospheric rivers are tracked from space using passive microwave sensors onboard polar orbiting satellites. In 2010, Dettinger said, forecasters were well prepared for the storms because of their improved understanding of the role of atmospheric rivers. Current research adds to the mix ground-based sensing of water vapor and soil moisture, among other factors, with the goal of giving federal, state and local forecasters and water managers a much more precise understanding of the West Coast’s water situation and the potential for floods.

“Knowing about the role of atmospheric rivers has already made a difference,” Dettinger said. “Not so long ago, it was the rare storm you’d hear about a week ahead of time. Now it’s not uncommon for weather forecasters to see storms forming near Japan a week ahead of time. In large part, that’s because they now know a little better what to look for: atmospheric rivers.”

“We’re not trying to replace older methods, just to add on our simple R-Cats categories, which offer a simple way of comparing the size of storms from place to place,” Dettinger said. Our goal was specifically to ask, How big are the biggest historical storms at places all over the country’ in ways that were simple and logical and that still allowed us to compare the absolute sizes of those largest storms. In doing so, as much a surprise to us as to everyone else we’ve ever shown this to, we found that California’s biggest storms are absolutely as big as the storms made by landfalling hurricanes in the American southeast. This is an amazing finding that had been lost in the return-interval and percentile reporting that has been the norm.”

• Haitian woman carrying supplies amid the destruction from the January 2010 Haiti earthquake.

September is National Preparedness Month, a time to highlight the threats posed by natural hazards and the importance for individuals and communities to be prepared.

Hurricane Isaac recently swept through the Gulf Coast, wildfires continue to ravage the west, and drought grips more than three quarters of the contiguous United States facing abnormally dry conditions. Natural hazards like these threaten lives and cause billions of dollars in damage every year throughout the nation. Sound science is essential for preparedness to natural hazards, guiding the best decisions to minimize their impacts.

USGS: Start with Science

The U.S. Geological Survey works with many partners to monitor, assess and conduct research on a wide range of natural hazards, providing policymakers and the public a needed understanding to enhance preparedness, response and resilience. USGS research includes earthquakes, volcanoes, landslides, wildfires, floods, droughts and extreme storms.

Earthquakes

Earthquakes pose a risk to more than 165 million people in 37 states. The USGS has created and provides information tools to support earthquake loss reduction, including hazard assessments, scenarios, comprehensive real-time earthquake monitoring and public preparedness handbooks.

Imagine if doctors had time to stop delicate procedures before an earthquake. And if emergency responders had a few extra moments to gear-up, airplane landings could be postponed, trains slowed, and people could move to safer locations. The USGS and its partners are helping to provide critical seconds of notification by developing a prototype Earthquake Early Warning System in the United States.

You can sign up to receive earthquake notices through the USGS Earthquake Notification System as well as USGS social media channels. Tips and suggestions for earthquake preparedness can be found on the Earthquake Country Alliance website and the USGS Prepare website. When you feel an earthquake, you can report your experience on the USGS “Did You Feel It?” website.

The Next Earthquake: Are You Ready?

Numerous states and countries will be participating in the next ShakeOut earthquake drill on Oct. 18, 2012. At 10:18 a.m., participants will “drop, cover and hold on.” This event offers citizens a chance to learn how to get better prepared and practice what to do when an earthquake happens in their community.

Shishaldin Volcano on Unimak Island, part of Izembek National Wildlife Refuge in Alaska.

This is the first year an official drill is being coordinated in the Southeast United States, and you can see a full list of participating locations at the ShakeOut website. Mark your calendar and sign up your family, school, business, or organization to join as well.

Volcanoes

When the violent energy of a volcano is unleashed, the results can be catastrophic. Lava flows, debris avalanches and explosive blasts have devastated communities. Noxious volcanic gas emissions have caused widespread lung problems. Airborne ash clouds from explosive eruptions have caused millions of dollars of aircraft damage and nearly brought down passenger flights.

Fortunately, volcanoes show signs of unrest hours, weeks and months before they erupt, and the USGS National Volcano Early Warning System is designed to detect these precursors. The USGS issues warnings and alerts of potential volcanic hazards – including ash fall forecasts – to responsible emergency-management authorities and those potentially affected. See current alerts and status for volcanoes in the United States.

Preparedness is increasingly important for the growing number of people that live, work, play and travel in volcanic regions. Learn more by visiting the USGS Volcano Hazards Program website and watching a video on USGS volcano science.

Landslides

Landslides occur in all 50 states and pose a risk to every citizen. Falling rocks, mudslides and debris flows can be deadly hazards, and we are still learning more about them. To protect communities from landslide hazards, USGS science is helping answer questions such as where, when and how often landslides occur, and how fast and far they might move.

For example, USGS scientists produce maps of areas susceptible to landslides and identify what sort of rainfall conditions will lead to such events. The USGS is working with the National Weather Service on a Debris Flow Warning System to help provide forecasts and warnings to inform community and emergency managers about what areas are at imminent risk of having a debris flow or mudslide.

For more information, watch a video about USGS landslide science, and visit the USGS Landslide Hazards Program website. Scientists at the USGS are also asking the public to help them track landslides and collect a more complete catalog of events. Report your landslide experiences and sightings at the new USGS “Did You See It?” website.

Wildfires

This landslide occurred in 2005 in La Conchita, California.

The USGS plays an integral role in preparing for and responding to wildfires. The USGS provides tools and information before, during and after fire disasters to identify wildfire risks and reduce subsequent hazards, while providing real-time geospatial support for firefighters during the events. For example, the USGS provides fire managers with up-to-the minute maps and satellite imagery about current wildfire extent and behavior throughout the nation.

The wildfire itself is a hazard, but once the smoke clears, the danger is not over. Secondary effects of wildfires, including erosion, landslides, invasive species and changes in water quality, are often more disastrous than the fire itself. As fires are contained, USGS scientists help to assess their aftermath to guide the re-building of more resilient communities and restoration of ecosystems.

Flooding, Storms and Drought

The USGS conducts real-time monitoring of the nation’s rivers and streams, providing officials with critical information for flood warnings and drought mitigation. If you want to know whether river levels are higher or lower than normal, visit USGS WaterWatch. You can also use USGS WaterAlert to receive texts or emails when water levels at a specific streamgage exceed certain thresholds.

During floods, USGS scientists measure water levels, river velocities and high water marks. The USGS and the National Weather Service work together to make flood inundation maps that show you exactly where the water will be – what yards, roads and buildings will be covered – and when a river or stream reaches a certain water level.

The USGS also studies coastal vulnerability and change from hurricanes and extreme storms, helping inform flood forecasts and evacuation warnings. Before, during and after major hurricanes or tropical storms affecting the United States, the USGS assesses the likelihood of beach erosion, overwash or inundation. Scientists also measure storm surge and monitor water levels of inland rivers and streams.

Unlike flooding, droughts often take a long time to begin to impact an area, sometimes festering for months or even years. USGS science contributes to the national Drought Monitor, which is the official report detailing drought conditions, as well as the National Weather Service’s Drought Outlook, which forecasts future drought.

More Information

Flooding hit record highs in in North Dakota and many other areas of the U.S. in 2011. For more on the floods of 2011: http://gallery.usgs.gov/videos/439

To learn more about National Preparedness Month, visit www.fema.gov/ or www.ready.gov.

Isaac’s floodwaters and impacts were measured using a variety of tools before, during and after the storm, including terrestrial and airborne lidar, acoustic Doppler and aerial photography

Mapping in 3-D: Terrestrial lidar and acoustic Doppler

USGS scientists mapped the Tangipahoa Dam using terrestrial lidar (video at right), or T-lidar and acoustic Doppler technology to capture multiple scans of different areas near the dam, showing the above and underwater topography. The dam was damaged during heavy rainfall in Hurricane Isaac and caused thousands of people downstream to be evacuated late last week.

These scans captured a clear view of two landslides on the dam’s downstream side. The larger of the two landslides occurred mostly underwater. While T-lidar provides a clear view of above ground features, scientists used acoustic Doppler techniques to conduct underwater measurements.

A 3-D terrestrial LiDAR scan of the Percy Quin Mississippi State Park Dam in McComb, Mississippi, taken Monday, September 3, 2012. The U.S. Geological Survey is using this new technology in select areas of Louisiana, Mississippi and Alabama to map impacts by Hurricane Isaac.

The first T-lidar scans took place Saturday, with more completed on Monday to assess whether additional movement of the landslides had occurred.  Monday’s scan showed little movement. This information and other data has been provided to the U.S. Army Corps of Engineers as they continue to address the dam’s structural risk and public safety.

T-lidar allows scientists to quickly generate 3-D maps of buildings, dams, levees and other structures, and can show areas of storm damage as well.  In a four-to-five minute scan, the instrument collects millions of topographic data points in a full 360-degree view to quickly produce highly accurate topographic information and can map areas up to two-thirds of a mile away.

Acoustic Doppler instruments are frequently used to measure stream or lake geometry and water velocity. An acoustic signal is bounced off the river or lake bottom and the amount of time required for the signal to return to the sensor provides a measurement of the distance to the bottom. In the Tangipahoa Lake application an acoustic Doppler instrument was used to map the underwater portion of the landslide area, and to determine the force of the water on the dam structure.

Isaac is the first storm in which USGS has used its terrestrial lidar capabilities to map urban flooding.

The view from above: aerial flight surveys and lidar showing coastal change

After the worst of the storm passed, USGS scientists began conducting aerial photography and elevation surveys of post-storm beach conditions along the Gulf Coast to document the impacts of hurricane surge, waves, and currents on beaches. Information obtained from these surveys allows scientists to measure changes to coastal environments.

Oblique aerial photography was collected this week from Isle Dernieres in Louisiana to Dauphin Island in Alabama.  Scientists compared these images with pre- storm images of the same location to illustrate the coastal changes and damage from Hurricane Isaac. Photo pairs of several locations are available online.

Photos from Dauphin Island indicated beach erosion and island overwash, furthering the erosion the island has seen during repeated storm events — Ivan, Katrina, Gustav and Isaac — that have led to the island’s increased vulnerability to future storms. This photo shows the effects that repeat hurricane waves and surge have had on Dauphin Island from 2004 -2008.

Some areas of the Chandeleur Islands in Louisiana experienced such extreme erosion from Isaac that only underwater shoals, or submerged shallow areas, remain. This erosion resulted in the disappearance of an oil-protection berm constructed following the BP oil spill.  Due to cumulative damage from previous storms like Hurricane Katrina, it remains in question whether this beach system will ever be able to fully recover from storm impacts.

Scientists are also conducting an airborne lidar survey of beach elevations to gather additional information in the most heavily impacted areas and to measure the amount of erosion.

Lidar, light detection and ranging, is an aircraft-based, remote-sensing technique that uses laser pulses to collect highly detailed ground elevation data. The photography and lidar data, as well as the coastal change analyses of these data, should be useful in mitigation and restoration efforts along the Gulf Coast shoreline. Data acquired will also be used to improve predictive models of future coastal impacts from severe storms and to identify areas vulnerable to extreme coastal change.

Flyover Shows Storm Damage and Marsh Dieback:

Another set of USGS aerial flight surveys flown this week used similar techniques to document vegetation and habitat change, and other ecological impacts and along coast and barrier islands post Isaac.

These flights examined areas from Wax Lake Delta, Louisiana, to Ship Island, Mississippi., and preliminary assessments suggest that Hurricane Isaac damaged coastal wetlands in a manner that is substantial, but not unprecedented. Damage to coastal wetland areas was evident throughout much of southeast Louisiana. The intensity of hurricane effects was most abundant in areas of upper Breton Sound, an area just to the south of the community of Braithwaite, which experienced devastating flooding.

The most prevalent effects of Hurricane Isaac observed were expansive wrack fields. Wrack is accumulated organic debris and trash that are transported and deposited by a hurricane’s surge. Wrack deposits from Hurricane Isaac were observed throughout southeast Louisiana, burying existing marsh areas and obstructing infrastructure, such as canals and railroads.

Large areas of marsh dieback, termed “brown marsh” or “sudden marsh dieback,” were observed in the Terrebonne and Barataria basins in Louisiana. Previous reports of sudden marsh dieback in the spring and summer of 2012, before Hurricane Isaac, indicate that the dieback in this area has been increasing over time and may be the result of a combination of other stressors. Evidence of vegetation stress, such as widespread discoloration, was also observed in areas that were directly impacted further to the east by hurricane storm surge. The browning and destruction in the marshes east of the Mississippi River in coastal Louisiana appear to be recent, indicating a more direct link to salinity and flooding stress associated with the Hurricane Isaac’s storm surge. The USGS will further investigate the recent history of sudden marsh dieback events in coastal Louisiana. Subsequent aerial surveys will be conducted to quantify the extent of brown marsh and to potentially separate the phenomenon of sudden dieback and the storm surge impacts.

Louisiana currently experiences more wetland loss then all other states in the U.S. combined. Coastal Louisiana has lost a wetland area the size of Delaware, equaling 1,883 square miles, over the past 78 years, according to a 2011 USGS National Wetlands Research Center study. For more information about NWRC’s hurricane research, visit http://www.nwrc.usgs.gov/hurricane/index.html. To view images collected during post-Hurricane Isaac reconnaissance flights, click on the Hurricane Isaac link. To learn more about marsh dieback or brown marsh, visit http://www.nwrc.usgs.gov/about/capabilities/brwnmrsh.htm.

Seeing the Surge: Collecting Sensors and Gathering High Water Marks

USGS field crews responded to the storm deploying 170 storm surge sensors and rapid deployment gauges along the Gulf coast between Mobile Bay in Alabama and Venice, Louisiana. Now those sensors are being collected and the data are being analyzed.

Surge elevations ranged from more than five feet in eastern Mississippi to nearly 11 feet west of Bay St. Louis.  Along the North Shore of Lake Pontchartrain, surge elevation ranged from six feet to over seven and a half feet near Madisonville, Louisiana.  The LaPlace area southwest of Lake Pontchartrain experienced over five feet of surge elevation, but the worst hit was the Plaquemines Parish area, where flooding continues to impede access to USGS sensors.  All data (provisional and subject to change upon review) are available via interactive mapper.

In addition to in measuring storm-tide, more than 75 independent high-water marks have been recorded to provide additional points between the sensors to document the extent and magnitude of storm surge from Isaac. Rains from Hurricane Isaac cause record flows on Mississippi streams. Inland flooding was recorded in Mississippi on the Wolf River, Black Creek and Wiggins. Three stations in southeastern Louisiana had the second highest peak stage of record ever recorded at these sites.  Bogue Chitto River near Bush, La. peaked at 19.82 feet on September 2^nd; Bogue Chitto River at Franklinton, La. also peaked on September 2^nd with a high-water mark of 22.13 feet; Tangipahoa River at Robert, La. peaked on September 1 with high water mark of 24.02 feet.

Over the next few days, USGS will send crews into the field to assess flooding, gather high water marks, and begin to collect and analyze data from storm surge sensors deployed prior to Hurricane Isaac’s landfall. USGS will also conduct aerial surveys along the Gulf’s coastline to photograph coastal change from the storm’s waves and currents.

USGS Flood Monitoring Network:

USGS boat launched during 2011 flood waters in Louisiana.

For more than 125 years, the USGS has monitored flow in selected streams and rivers across the U.S. through an extensive streamgaging network. More than 7500 streamgages throughout the U.S. provide real-time information of river and stream flow which is routinely used for water supply and management, monitoring floods and droughts, bridge and road design, determination of flood risk, and for many recreational activities.

Rising Floodwaters from Isaac:

Several southern states have experienced significant flooding as a result of rains from Hurricane Isaac.

Multiple USGS field crews from several states are recording high-water marks, collecting discharge measurements and obtaining water quality data in coastal and inland Alabama, Mississippi and Louisiana. This information is important because it is used by the National Weather Service to issue flood warnings, and the data is also used by emergency responders and planners to mitigate current and future flood hazards. These crews are being augmented by USGS staff from the Georgia Water Science Center. As the storm continues to move, crews from Illinois, Indiana, Kentucky, Missouri and Arkansas remain ready to address flooding along the storm’s track.

USGS field crews have also begun retrieving the 170 storm surge sensors and 17 temporary real-time gages that were deployed in response to Hurricane Isaac in locations where the storm has passed. Data from these sensors networks will be uploaded to the USGS Hurricane Storm Tide Sensor Map.  The sensors provide critical data for more accurate modeling and prediction capabilities and allows for improved structure designs and response for public safety.

Three dimensional (3D) topographic and bathymetric model of Yellowleaf Creek, AL.

New 3-D Mapping Technology to Measure Isaac’s Flooding

A new technology is being used by the USGS to map flooding in certain urban areas caused by the hurricane. Called terrestrial lidar, or T-lidar, this new capability is being deployed by scientists from the USGS to collect highly-detailed information in select population areas where the storm had the greatest impact in Louisiana, Alabama and Mississippi. The USGS has not previously used T-lidar for flood work.

Drought Persists in other parts of the U.S.

Although Isaac has brought significant precipitation in its wake, much of the country continues to be plagued by severe drought conditions. The U.S. Drought Monitor has provided the latest drought impacts for the states listed below. Real-time updates on the Nation’s drought conditions are available on the USGS drought homepage:

Dry, cracked streambed as a result of drought.

All of Wyoming is experiencing moderate drought, with 37 percent of the state comprising parts of the Cheyenne, North Platte, and Green River basins in extreme drought conditions.  More than 74 percent of Arkansas continues to be in extreme or exceptional drought conditions.  Colorado, Nebraska and Missouri all have 100 percent of the state in severe drought. Indiana is experiencing 97 percent of the state in severe drought. Moderate to below normal drought conditions cover the vast majority of the state of Georgia. Only the upper Tennessee basins and the Suwannee, Alapaha, and Ochlockonee River basins are in the normal range. In Kansas there are 56 USGS streamgages measuring zero water flow and in Oklahoma there are 22 gages currently measuring zero flow.

Access current flood and drought conditions across the country by visiting the USGS WaterWatch website.

Receive instant, customized updates about water conditions in your area via text message or email by signing up for USGS WaterAlert.

USGS has installed more than 120 storm surge sensors in advance of Hurricane Isaac’s landfall. Click the image above to see the locations of each USGS sensor.

Note: This was originally posted on 8/28/2012. View the most updated information on this event.

USGS has posted all information regarding our efforts to respond to Hurricane Isaac on this page and in the links at the bottom.

USGS scientists, engineers, and technicians are working along the Gulf Coast in response to Hurricane Isaac, deploying storm-surge sensors and maintaining real-time streamgages in anticipation of Isaac’s arrival. The USGS, in concert with our partners, is providing scientific assessments of the challenges wrought by Isaac.

Storm-Surge and Real-Time Sensors

The USGS has deployed more than 120 storm-surge sensors along the northern Gulf of Mexico in Florida, Alabama, Mississippi, and Louisiana. Of those sensors, 12 are reporting data in real-time, while the other sensors will be collected post-landfall.

The instruments will be removed as soon as possible, following the departure of the storm.

These sensors are typically about 1 1/2 inches wide and a foot long, and will be strapped to piers, docks or other structures in the water expected to withstand the storm to collect data on storm surge, and in some cases, transmit water levels in real time.  They are typically installed on the coast or just inland of the coast about 50 miles west and 100 miles east of the projected landfall area.  Learn more about our storm surge sensors and what to do if you see one.

Coastal Change Impacts

Elevated water levels and waves during tropical storms can lead to dramatic coastal change through erosion of beaches and dunes. USGS has developed a storm-impact scale that predicts the likelihood of coastal change by comparing modeled elevations of storm-induced water levels to known elevations of coastal topography in order to define three coastal change regimes. USGS has completed an assessment of potential coastal-change impacts from Tropical Storm Isaac.