•  Start with Science to Address Vulnerable Coastal Communities
• Hurricane Sandy Coastal Change Hazards
• Predicted Likelihood of Coastal Change Impacts from Hurricane Sandy
• Hurricane Sandy Storm Tide Data and Mapper
• Water-Quality Sampling Immediately After Hurricane Sandy
• Real-Time Monitoring: Rapid deployment storm tide sensors and streamgages, and permanent streamgages in Sandy impact area
• USGS Issues Landslide Alert for Hurricane Sandy
• WaterWatch: View streamflow during Hurricane Sandy (Oct 29 and subsequent days)

• Coastal Change Hazards: Hurricanes and Extreme Storms
• Coastal Elevation Data: Access National Elevation Dataset and other coastal elevation information
• Sustainable Estuaries, Coastal, Urban, and River Enviroments
• Ready.gov

More than 160 USGS scientists, technicians, and specialists are responding to Hurricane Sandy’s aftermath, from Virginia to Massachusetts. Crews from USGS are working hard to retrieve data for emergency managers.

Hurricane Sandy’s impacts have been significant. Many USGS tidal sensors recorded peaks of record and several were completely overtopped. In addition, high-water marks flagged by USGS crews show sizeable storm surge, including 18.98 feet at Long Branch, NJ; 12.93 feet at the Verazzano Narrows Bridge between Brooklyn and Staten Island, NY; and 7.43 feet at Lindenhurst on Long Island, NY.

USGS scientist recovers storm surge sensor in Annapolis, MD.

Storm-Surge Sensors

USGS crews are currently out retrieving the more than 150 storm-surge sensors that were deployed prior to Sandy’s landfall. These sensors extended from the mouth of the Chesapeake Bay in Virginia to the coast of Maine.

The data from these sensors will be used to create models of the precise time the storm-tide arrived, how ocean and inland water levels changed during the storm, the depth of the storm-tide throughout the event, and how long it took for the water to recede.

This information gathered is being used to assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future coastal change.

All data collected by these sensors and the existing USGS streamgage network are available on the USGS Storm-Tide Mapper.

High-Water Marks

In addition, at the request of FEMA, USGS scientists are marking high-water marks. Crews in New York currently have 150 sites they are checking, many established in the 1992 Noreaster that struck the Long Island area. New Jersey crews have an additional 100 sites they are checking along the Atlantic shoreline as conditions are safe to do so. USGS scientists from Maryland, Delaware, Connecticut, and Rhode Island are also be looking for high-water marks in their areas.

USGS scientist Kerry Caslow using RTN GPS surveying to establish an elevation for a storm-tide sensor in New Jersey. Photo credit: Chris Smith, USGS.

High-water marks serve a very important function in assessing damage. USGS crews look for sustained high-water marks, meaning indications of the highest level the water stayed for a time. Because water-levels change often due to wave action, sustained high-water marks allow USGS scientists to determine the levels the water stayed at long enough to cause significant impacts.

High-water marks are useful in determining the amount of damage sustained due to flooding and storm surge. Impact models use high-water marks to determine likely levels of damage to a building’s structural integrity, as well as potential scour damage. Scour damage is the abrasive erosion caused by dissolved solids in water rubbing against buildings or other structures that can wear away the surface, eventually leading to instability.

In addition, FEMA uses high-water marks to determine what damage comes from wind and what damage comes from water when formulating their own impact models.

Coastal Change

In addition, USGS crews have returned to coastal New Jersey and Long Island to do lidar surveys for before and after studies of coastal change, using the pre-storm lidar surveys taken October 26^th and 27^th.

Also, USGS crews will conduct aerial surveys from Cape Hatteras, North Carolina, to Montauk, New York. These surveys will include oblique aerial photography and lidar topography. The photographs will be compared to pre-storm photography for a qualitative look at coastal erosion, while the lidar data will be compared to pre-storm beach elevations to quantify actual changes in the beach, such as dune erosion and overwash.

Water Quality

USGS crews have also performed water quality sampling at various locations, including the Delaware River near Trenton, New Jersey; from the Potomac River and the Eastern Shore in Maryland; various sites in Washington, DC, and sites throughout Northern Virginia.

Oblique aerial photographs of Fire Island, New York, at Pelican Island before and after Hurricane Sandy impacts shows coastal change on an undeveloped coastline.

Oblique aerial photographs of Seaside Heights, New Jersey, before and after Hurricane Sandy impacts shows coastal change on a developed coastline.

• Hurricane Sandy Storm Tide Mapper (accessible version and web services)
• Water-Quality Sampling After Hurricane Sandy
• USGS Issues Landslide Alert for Hurricane Sandy
• Real-Time Monitoring Sites
• Coastal Elevation Data and Research
• Coastal Change Hazards: Hurricanes and Extreme Storms
• Flood Information
• WaterWatch
• Ready.gov

***Updated: coastal change section edited from original, based on an updated assessment from October 29, 2012***

As millions of northeast residents bought water, batteries and food this weekend in preparation for Hurricane Sandy, USGS scientists, engineers, and technicians worked up and down the Atlantic Coast, deploying storm-surge sensors and maintaining real-time streamgages in preparation for Hurricane Sandy’s arrival.

Storm-Surge and Real-Time Sensors

USGS Storm-Tide Mapper, showing all data collected by the storm-surge sensors and the USGS streamgage network.

Much of the work involved installing more than 150 storm-surge sensors along the Atlantic coast, from the mouth of the Chesapeake Bay to Massachusetts. These sensors, which measure water elevation every 30 seconds, augment an already robust network of coastal and inland streamgages in place to monitor water levels throughout the storm.

A USGS scientist installs a storm-surge sensor for Hurricane Rita in 2005, the first storm in which these sensors were deployed.

In addition, eight of the recently deployed sensors are Rapid Deployment Gages, which provide real-time information to help forecast floods and coordinate flood-response activities in affected areas. These real-time gages will complement the many near real-time streamgages already installed along rivers and streams.

All data collected by these sensors and the existing USGS streamgage network are available on the USGS Storm-Tide Mapper.

Working with various partner agencies such as NOAA, FEMA, and the U.S. Army Corps of Engineers, the USGS strapped the storm-surge sensors – typically about 1 ½ inches wide and a foot long – to piers, docks or other structures in the water expected to withstand the storm.

They record the precise time the storm-tide arrived, how ocean and inland water levels changed during the storm, the depth of the storm-tide throughout the event, and how long it took for the water to recede.

This information gathered will be used to assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future coastal change.

Anticipated Coastal Change

Probabilities of collision, overwash, and inundation for Sandy for the Atlantic coast of Delmarva.

Elevated water levels and waves during tropical storms can lead to dramatic coastal change of beaches and dunes. The USGS has completed an assessment of likely coastal-change impacts from Hurricane Sandy.

Nearly 91 percent of the coast along the Delmarva Peninsula is very likely to experience beach and dune erosion from the storm, while overwash is expected to affected more than  half of the shoreline, and 22 percent of the beaches are expected to experience inundation by waves and storm surge   In these areas, waves and storm surge transport large amounts of sand across coastal environments, depositing sand both inland and offshore, causing significant changes to the landscape.

Overwash, the landward movement of large volumes of sand from overtopped dunes, is forecasted for portions of the east coast with the projected landfall of the storm. The severity of overwash depends on the strength of the storm, the height of the dunes, and how direct a hit the coast takes.

Probabilities of collision, overwash, and inundation for Sandy for the Atlantic coast of New Jersey

The models show that along the New Jersey shore, 98 percent of the coast is very likely to experience beach and dune erosion, while 54 percent is very likely to experience overwash, and 9 percent to experience inundation.

It also indicates that on the south shore of Long Island, N.Y., including Fire Island National Seashore, 93 percent of the coast is very likely to experience beach and dune erosion, 12 percent to experience overwash, and 4 percent to experience inundation; the lower percentages of overwash and inundation in these areas is because of the relatively high dune elevations.

The impact of previous storms on sandy beaches along the mid-Atlantic Coast has made them increasingly vulnerable to significant impacts such as erosion.

Beaches and dunes often serve as the first line of defense for coastal communities against flooding and other hazards associated with extreme storms.

Probabilities of collision, overwash, and inundation for Sandy for the southern coast of Long Island

Any compromise to these features means that storm-related hazards are more likely to threaten coastal property, infrastructure, and public safety during a future extreme storm event.

USGS hydrographer deploying a storm-surge sensor prior to Hurricane Rita

In response to Hurricane Sandy, USGS has deployed several hundred storm surge sensors to collect information about the effects of Sandy on the Atlantic Coast. Here are some frequently asked questions about these important sensors:

1.  What is this program?  The USGS has developed a mobile network of rapidly, deployable experimental instruments with which to observe and document hurricane-induced storm-surge domes as they make landfall and interact with coastal features.

2. Why are we undertaking this work?  The work will enable us to compile data so that we can quantify storm-surge dynamics (wave heights, forces, speeds, and extent) for various storm conditions, topographies, ecologies, built environments, and landuses.  This information will lead to better storm-surge models, more accurate flood forecasts, more effective flood-protection infrastructure, and wiser landuse policies.

3. What is the nature of the work?  About 40 to 70 storm-surge sensors (non-vented pressure transducers) are strapped to bridge piers (picture A), power and light poles, and other structures along and inland of the coast about 50 miles left and 100 miles right of the projected path of hurricane landfall.   The effort involves 6 to 10 2-person teams that deploy the instruments 24 to 48 hours prior to landfall.

Typical storm surge sensor housing

4. What type of data do the sensors collect?  Water-level (hence storm surge levels) and barometric pressure are recorded every 30 seconds for most sites.  Sensors located on beaches record wave height every 2 seconds.  The recording period lasts for 1 to 3 days depending on the magnitude of the storm and post-storm access to the sensor sites.

5.  What do these sensors look like?  They are 1-1/2” aluminum or steel pipes strapped to a piling or other stable structure.  The top will have a metal or PVC cap and the bottom will be open for the water to enter.  The sensor housing protects a water-level sensor inside.  A unique USGS visual ID sticker will be on the outside (shown below).  They may be yellow or aluminum in color.  Please call the phone number on the sticker before doing anything.

6. What are we going to do with the data?  Data are uploaded to the web as stage and pressure time series.  We generate various graphics to create 3-D water-surface images, and depth (picture B) and duration maps.  Together they enable us to study surge flooding, including wave height, and moment by moment, visualize its interaction with the coastal features such as beaches, islands, estuaries, and streams.  By tying these data together and with local topography, we can determine the rates at which flood waters transverse various water bodies and landforms, the major paths of penetration, their duration, and the height and frequency of waves that strike dunes and built infrastructure.

Data of this nature is quite rare and very valuable for determination of flood insurance maps, building codes, and for calibration of the hurricane inundation models.  Accurate model forecasts are critical for community preparation of storm response and evacuation plans.

An example of a label placed on all USGS storm surge sensors

7. Are the surge data reported in real-time?  The surge data are not reported in real time but are logged on-site and are not available until they are processed and calibrated for barometric pressure, water density, and elevation datums.  We are experimenting with downward-looking radar devices for directly sensing surge elevation in real-time.  Three such devices were deployed during Hurricane Ernesto.

8. What other kinds of data are needed?  There are several kinds of data that would compliment this work and for which we seek collaborators.  These include offshore water-level and wave-height data, wind speed and direction, inland water salinity, post-storm ecological assessments, and geological evaluations of beach and landform behavior, and engineering evaluations.

9. Who uses this information?  Our data is used by the National Ocean and Atmospheric Administration (NOAA) National Weather Service (NWS) and National Hurricane Center (NHC) and the U.S. Army Engineer Research and Development Center (ERDC), as well as state responders and emergency management officials.

10. Where can I lean more?  Reports on previous USGS storm surge documentation efforts are available online.

The Arkansas River at Great Bend, Kansas, on July 13, 2012. Lying west of Isaac’s rain reach, the river was drier still on September 10.

More than three quarters of the contiguous United States still faces abnormally dry conditions in spite of scattered relief from rains generated by tropical storm system Isaac.  As seen on the U.S. Drought Monitor, exceptional drought — the worst category — persists in the very center of the nation from Nebraska south to Texas, east through Missouri and Arkansas to the Mississippi Valley. Much of Georgia is also in exceptional drought.

Drought: the slow but costly disaster

Drought is the nation’s most costly natural disaster, far exceeding earthquakes, tornados, hurricanes and floods. FEMA has estimated that the annual average cost of drought in the United States ranges from $6 to $8 billion. (By comparison, the annual costs of flooding are in the $2 to $4 billion range.) Unlike flooding, drought does not come and go in a single episode. Rather, it often takes a long time for drought to begin to impact an area, and it can fester for months or even years.

In order to reduce the impacts of drought, governments and managers rely on objective and unbiased scientific information about trends in streamflow, precipitation, and other factors that contribute to drought, so that they can understand where drought is occurring, how long it is likely to impact an area, and where drought is likely to strike next.

What about Isaac’s effects on the current drought?

The obvious question comes from both expert and casual observers: What difference did tropical system Isaac make in drought-stricken areas?

NOAA records show that Hurricane Isaac made landfall in southern Louisiana the evening of August 28 and then tracked north-northwest, losing its tropical character over Missouri on September 1 and then merging with another frontal zone to move on into the Ohio Valley. This NASA graphic of rainfall based on satellite measurements shows that Isaac’s rainfall was concentrated to the east of its tropical storm center. (100 mm is about 4 in. of rain.)

One week after Isaac officially dissipated (9/1), this real-time map of national stream flow from USGS WaterWatch  (below normal 7-day average streamflow compared to historical streamflow, updated 9/8) shows that streamflows have returned to normal or higher levels in the middle and lower Mississippi Valleys and the Ohio Valley where much of Isaac’s related precipitation fell.

However, while real-time streamflow levels from USGS WaterWatch are an essential aspect of measuring drought, stream and river conditions are not the only drought indicator.

Drought is a bigger concept than streamflow can show

The national Drought Monitor is the official report detailing drought conditions. This complex map service paints a fuller picture of drought than just stream flow information. In addition to relying heavily on USGS streamgage data, this map also incorporates soil moisture, agricultural information, satellite data, and precipitation.

The map — a joint product of NOAA, the U.S. Department of Agriculture, and the National Drought Mitigation Center — is prepared in consultation with scientists from several agencies, including the USGS. It portrays a comprehensive geographic assessment of areas experiencing drought, as well as the severity of drought.  This map has important economic significance because it is used by many states as the basis for declaring a drought emergency and requesting federal funding.

You can see that, according to the U.S. Drought Monitor (updated 9/4), extreme or severe levels of drought persist in parts of Arkansas, Missouri, Tennessee, Kentucky, Illinois, Indiana, and Ohio — states to which Isaac’s rains did come in varied amounts.

The next obvious question might be: Why didn’t Isaac make more of a difference in the drought?

That’s a complex inquiry that involves lots of issues like precipitation rates and volumes, water runoff, groundwater levels, and soil moisture. Let’s look for a broader answer in a story about accumulated precipitation deficit that’s no less true for its simplicity.

A Story of Drought: The Water Bank

USGS WaterWatch map of monthly-average streamflow for August 2012. Note how rain from Isaac accelerated the monthly average east of New Orleans.

It can be useful to think of drought as a water bank account held by Mother Nature. When it rains, Mother Nature makes a deposit into Earth’s water bank account. When it stops raining, Mother Nature is obliged to withdraw water from the soil and from vegetation for “payment” to the atmosphere; this is done through evapotranspiration. The longer she goes without making water deposits, the greater the amount of water that gets withdrawn from the soil, as well as from other storage accounts like lakes and reservoirs, and the greater her water deposits (i.e., precipitation) will have to be to bring the account back up to what it was before the drought started.

That’s essentially what’s going on when one huge storm system with its sudden rains seems to make little immediate difference in a drought. Mother Nature may have hit the million-dollar lottery with Isaac and is making big deposits into her terrestrial account. But she needs to make two or three more deposits like this to get back to the starting point of local average conditions of water deposits and withdrawals.

Looking ahead on drought

In addition to the U.S. Drought Monitor, which tracks current and historic drought conditions, every month the National Weather Service produces a Drought Outlook, with bi-weekly updates based primarily on precipitation forecasts.

The latest long-range report, released on September 6 and looking ahead to November 30, indicates that drought is likely to develop, persist, or intensify across much of the Great Plains (including Texas but not the Dakotas) and all or parts of the Rocky Mountain and Western states (excluding Arizona and Washington).

U.S. Seasonal Drought Outlook, Sept. 6 – Nov. 30. NOAA forecast.

Drought conditions are likely to improve in Louisiana, Alabama, the Dakotas, the upper Mississippi Valley, and the Ohio Valley. Arkansas, western Tennessee, and Georgia will see lesser degrees of improvement.

Links and resources

USGS WaterWatch

National Drought Monitor

NOAA Drought Outlook

Droughts of the Past

For local details and impacts related to drought, please contact your State Climatologist or Regional Climate Center.

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.

Update (8/28/2012): There’s an update to the latest information on Hurricane Isaac.

The U.S. Geological Survey is keeping careful watch as Tropical Storm Isaac continues to track northwest toward the west coast of Florida and the Gulf of Mexico.  Along with federal partners, the agency is taking actions to help minimize potential risks to lives and property.

Before, during and after any hurricane or tropical storm affecting the United States, the USGS is involved in measuring the height and intensity of the storm surge, and monitoring water levels of inland rivers and streams, providing critical information used to forecast floods.  Using state-of-the-art modeling, the USGS is also involved in forecasting coastal change caused by storm surge, assessing the likelihood of beach erosion, overwash or inundation.

USGS Streamgaging Network at the Ready

The USGS, in cooperation with local, state and federal agencies, operates long-term sensor networks on inland rivers and streams throughout the nation. These networks provide real-time data important to the National Weather Service, FEMA, the U.S. Army Corps of Engineers, and other USGS partners involved in issuing flood and evacuation warnings, coordinating emergency responses to communities, and operating flood-control reservoirs.

Data from the USGS Streamgaging Network are routinely used for water supply and management, monitoring floods and droughts, bridge and road design, determination of flood risk, and for many recreational activities. However, during a storm’s landfall, this network helps capture the depth and duration of storm-surge, as well as the forecasted time of its arrival and retreat.  Understanding storm surge allows for more accurate modeling and prediction capabilities and for improved structure designs and response for public safety. Inland streamgages also are used to track the rainfall and flooding caused by the remnants of the storm.

Storm tide sensor bracket mounted on a fishing pier at the Fairhope Municipal Pier and Park in Fairhope, AL.

USGS crews are on alert.  Immediately after the worst of the storm has passed, USGS hydrologists will deploy to measure high-water marks at rivers and streams and to verify high river flows and peak stages. The crews will also calibrate and repair streamgages damaged by the storm to ensure they continued to transmit information in real time to users working to protect lives and property.

Information on streamflow and water levels may be especially important in Florida, where the water levels of many rivers are still high from Tropical Storm Debby’s heavy rainfall in June.

USGS Deploys Additional Storm Surge Sensors on Northern Gulf Coast

Storm surges are increases in ocean water levels generated at sea by extreme storms and can have devastating coastal impacts.  Prior to extreme weather events, the USGS may also deploy storm surge sensors at key coastal locations just a few days – or sometimes hours — before a Hurricane or Tropical Storm’s anticipated landfall. These storm surge sensors, housed in vented steel pipes a few inches wide and about a foot long, are installed on bridges, piers and other structures that have a good chance of surviving a storm surge during a hurricane. The number of sensors installed and their locations depend on the strength of the storm as well as what gages may already be in place.

In preparation for Tropical Storm Isaac, the USGS is already installing a small number of additional sensors in the northern Gulf coast area.  If the storm reaches these sensors, they will record water level and barometric pressure every 30 seconds to document storm-surge crests – or waves of water – as they make landfall.  Data will be uploaded to the USGS Hurricane Storm Tide Sensor Map if significant storm-tide is recorded.   Following the storm, USGS crews will retrieve these sensors and begin to analyze the data.

Together, the USGS Streamgaging Network and the mobile USGS storm surge sensors provide critical data to the National Weather Service, FEMA and other USGS partners involved in issuing flood and evacuation warnings and in coordinating emergency responses to communities. In the event of a large tropical storm event, storm surge information will also help public officials assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future floods.

Screenshot of interactive map which illustrates areas vulnerable to erosion during a Category 1 hurricane landfall.

Monitoring Coastal Change

Sand overwash, which occurs when waves and storm surge overtop dunes and transport sand landward, is a likely impact of hurricanes and tropical storms. The severity of erosion and overwash depends on the strength of the storm, beach elevation, and how direct a hit the coast takes.

While it’s difficult to tell where exactly the storm is headed or what its impacts may be, USGS scientists are using state-of-the art models to give emergency managers and local residents an accurate picture of what coastal changes are likely to occur if the tropical storm makes landfall along the Gulf Coast of the United States.

A new USGS report determines the probabilities of dune erosion, overwash and inundation during direct hurricane landfall for sandy beaches along the entire U.S. Gulf Coast shoreline. This report includes a publicly available interactive map which anyone can use to focus on different parts of Gulf Coast shoreline and view how the likelihood of erosion changes depending on hurricane intensity.

This model shows that during the landfall of a Category1 storm, where winds are between 75 and 94 miles per hour, overwash is very likely for 70 percent of Gulf Coast beaches. Overwash is likely at these locations because of increased water levels at the shoreline. During Category1 hurricane events on the Gulf Coast, wave height and storm surge combine to increase water levels at the shoreline by 14 and a half feet higher than their normal levels.

A hotel in Orange Beach, Alabama, was toppled during Hurricane Ivan in 2004. USGS science aims to reduce such damage by informing the public about which parts of the coasts face the most danger to buildings, infrastructure, and danger in the face of an oncoming storm.

Because Tropical Storm Isaac’s current path is forecasted to affectthe entire Florida Gulf Coast, USGS scientists are using data on coastal features –like dune height and beach slope – and models of hurricane waves and surge to predict the likely impact of storms on gulf coast beaches.  Learn more about the initial assessment of potential coastal-change impacts in Florida.

Tracking River Levels in Real Time

All information from USGS Nationwide Streamgaging network can be accessed at the USGS WaterWatch website. In a storm, this information can be particularly useful to local residents who want to know how increased rainfall from tropical storm Isaac will impact the rivers and stream in their areas. This site displays maps, graphs and tables that describe current and past streamflow conditions for the United States. The real-time streamflow data are generally updated on an hourly basis.

WaterAlert also allows users to receive updates about groundwater levels, water temperatures, rainfall and water quality at sites where USGS collects real-time water information.

For information on the latest storm track, listen to NOAA radio.  For information on preparing for the storm, go to Ready.gov or Listo.gov.

Additional Links/ related areas of USGS study:

Coastal Elevation Data and Research

Coastal Change Hazards: Hurricanes and Extreme Storms

Aerial map of the storm tide gauge locations in Baldwin County, AL.

On August 1, USGS scientist Robert Holmes will give a lecture about the anatomy of floods in relation to the 2011 Hurricane Irene and Tropical Storm Lee landfalls.

Flooding costs the United States more than $7 billion per year and claims over 90 lives annually. During the Spring and Summer of 2011, flooding associated with snowmelt and rain devastated the Central U.S. while Hurricane Irene followed by Tropical Storm Lee caused severe and unrelenting flooding in the East and Northeastern U.S. Join us on August 1 to learn more about the anatomy of flooding: What are the different causes of these extreme events, and how is USGS science helping prepare residents for future foods.
FREE and Open to the Public
Follow this event LIVE! @USGSLive

Date: Wednesday, August 1, 2011, 7:00-8:00 PM
Location: 12201 Sunrise Valley Drive Reston, VA 20192
Phone:  703-648-4748
Visit our website!
About the Lecture Series
The USGS Science in Action public lecture series in Reston, VA is a monthly event. These evening events are free to the public and intended for a general audience to familiarize them with science issues that are meaningful to our daily lives.
The USGS speakers are selected for their ability and enthusiasm to share their expertise with an audience that may be unfamiliar with the topic.
The USGS lecture series provides the public an opportunity to interact with scientists and ask questions about recent developments in biology, geography, geology, water resources, climate change, energy and more. Ultimately, the goal is to create a better understanding of the importance and value of USGS Science in Action.
Contact: Melanie Gade

Map of real-time streamflow

Rivers and streams are reaching record levels as a result of Hurricane Irene’s rainfall, with more than 80 USGS streamgages measuring record peaks. USGS scientists are measuring streamflow and river levels, and repairing and installing streamgages.

Crews continue to collect and analyze storm surge data from Hurricane Irene and document coastal erosion impacts. Other crews are out sampling water for pesticides, E. coli, nutrients, and sediment to document water quality impacts in areas affected by the hurricane.

John Erbland, Hydrologic Technician with the USGS South Carolina Water Science Center, holds a white board with information on the Hurricane Irene storm surge sensor deployment on a pier by the U.S. Coast Guard Station in the town of Wrightsville Beach.

John Byrnes of the USGS office in Troy, NY collecting a Hurricane Irene sample at the Mohawk River at Cohoes on August 29, 2010. As Hurricane Irene left her mark along the East Coast, USGS crews sampled water for pesticides, E. coli, nutrients, and sediment to document water quality in areas affected by the hurricane.

Links to flooding, storm surge, coastal erosion, and water quality information are available at:

• USGS Hurricane Irene Response

News Releases:

• Aerial Photos of Outer Banks Show Coastal Damage from Hurricane Irene
• Smart Phones Know When Rivers Rise…with USGS WaterAlert
• River Levels Set Records in 10 States
• Media Advisory: USGS Crews to Retrieve Storm Surge Sensors
• USGS In the Surge Sampling for Nutrients, Sediment, E. coli, and Pesticides
• USGS Responds to Hurricane Irene and Prepares for Aftermath
• Stormproofing Water Data from Hurricane Irene
• USGS Installs Sensors along Atlantic prior to Hurricane Irene’s Arrival
• Extensive Erosion Likely along North Carolina Beaches during Irene

Video:

• 2011: Interior Thanks USGS for Flood Efforts

Other Agencies:

• NWS Flood Page
• NOAA Hurricane Center
• Federal Emergency Management Agency (FEMA)
• U.S. Environmental Protection Agency (EPA)