Responding to Hurricanes, Floods and Droughts in North Carolina

[Music]

Kara Capelli: Hello and welcome to USGS CoreCast. I'm your host, Kara Capelli.

After being hit by Hurricane Irene, North Carolina is facing floods and water quality issues in the East. Meanwhile, areas of the western part of the state are suffering from drought. On this episode of CoreCast, we'll hear from Holly Weyers, the director of the USGS North Carolina Water Science Center, who addresses these extreme water events.

Holly Weyers: Well, regrettably this is not a unique situation for North Carolina, especially in regard to hurricanes. We've had a long hurricane history here and a great deal of hurricane science is focused on our state. In fact, about 3% of all Atlantic tropical cyclones make windfall in North Carolina. So, it's really sort of a very diverse, mixed bag of relationships here with regard to where we get rain and where we don't.

Prior to Irene in North Carolina, we've had reduced rainfall amounts. The typical summer thunderstorms have been less frequent and until Irene, we haven't had any major tropical systems producing significant rainfall, and as a result, we have a lower than average water table in many portions of the state.

01:10 So, it's not unusual for one portion of the state to be impacted by floods, by events such as hurricanes, while experiencing drought in other areas, especially when you consider how large the state is and how geographically diverse that it is.

Kara Capelli: Hurricane Irene, which struck in August of 2011, was a major event for the state. The rain, wind and storm surge brought not just flooding but also impacts to water quality.

Holly Weyers: When the public typically thinks of the impact of hurricanes, they think of coastal and rain and wind-driven riverine flooding. We are just now, along with our state and other federal partners, beginning to understand the full impact of Irene in some of these areas.

However, some impacts from hurricanes are more subtle and not as publicly visible, at least not immediately. For example, not only can hurricanes produce the excessive coastal and riverine flooding, but on occasion there can be significant water quality issues related to these tropical cyclones.

02:08 As Irene moved onshore tracking northward, dumping rain and causing extreme surge events in many river basins, resulting flooding led to a steep decline in dissolved oxygen in the lower portions of the Roanoke River Basin. These low dissolved oxygen levels are of immediate concern to state and federal officials because they can lead to fish kills.

It should be noted however that this is a natural phenomenon; the lower Roanoke River corridors supports extensive wetlands that are rich in organic matter and the counterclockwise winds from Irene pushed water from Albemarle Sound up into the mouth of the Roanoke River and other tributaries, causing water to rise into the surrounding flood plains and marshes with their large stores of organic matter.

The effect of flooding in these areas is like steeping a tea bag, but on a really large scale. The water soaks up the organic material and then drains back into the river after the hurricane passes and the bacteria in the water break down the organic material, consuming large quantities of oxygen in the process. The result of this process is lower oxygen levels in the river, which can be harmful to fish populations inhabiting these regions.

Kara Capelli: The wet conditions in the east have kept Holly and her staff of hydrologists busy. Crews have been out in the field, measuring the hurricane waters and floods.

Holly Weyers: The U.S. Geological Survey has developed a program to deploy storm surge sensors at locations that may be impacted by tropical systems. Once a hurricane prediction forecast indicates a significant probability of impact, USGS scientists spring into action in an effort to collect critical storm surge data.

Many of our crews work from sunup to sundown or later, both in advance of the storm, deploying these storm surge sensors in coastal counties, and even a rapid deployment real time gage in Newburn on the Neuse River. After the passage of Irene, made stream flow measurements, retrieved sensors, found and flagged and documented high water marks, and monitored the water quality conditions.

These data are not only important from an emergency response perspective, but the scientific data related to the storm surge and flooding will be used to estimate when, where and to what degree storm surge flooding will occur in the future and to calibrate and verify storm surge models resulting in better understanding of the dynamics of storm surge.

Kara Capelli: It's not just the high waters that are keeping them busy; drought is causing a separate set of issues in the western part of the state.

Holly Weyers: Drought, really, is defined as the period which a region has a deficit in its water supply and is a normal feature of climate which happens in all climate zones from time to time, but was often never looked is that drought is one of the most severe among all natural disasters.

Here in North Carolina Water Science Center, we monitor drought by checking extreme flow, as well as lake reservoir and aquifer levels and compare those measures to historical data to determine the impacts of precipitation shortfalls. So just like measuring flooding, measuring drought is a big part of what we do.

05:06 So, in addition to the 280 real-time streamgages we operate across the state, we have 53 real-time ground water sites where we measure aquifer levels, and a 162 precipitation gages. Data from all these sites allow us to continually monitor water levels across the state and assist our partners with not only determining when and to what degree drought conditions are present, but to provide unbiased scientific data when water resources may be in limited supply.

Kara Capelli: Holly's message is clear: science is crucial in addressing water issues like floods and droughts. The North Carolina Water Science Center is now looking ahead and preparing to continue to address these issues in the future.

Holly Weyers: We are near the climatological peak of the hurricane season, which runs from June through November so we really need to be prepared for anything and respond accordingly if we are impacted. We can also count on our partners and other USGS Water Science Centers and at the national level to assist if needed and we were fortunate this time with Irene to have our partners from South Carolina and the Georgia Water Science Centers helping with this event.

06:13 Kara Capelli: For more information on USGS Water related work in North Carolina, visit www.nc.water.usgs.gov/.

[Music]

And don't forget to follow the USGS on Twitter at www.twitter.com/usgs/ or visit our other social media channels at www.usgs.gov/socialmedia/.

I'm Kara Capelli and CoreCast is a product of the U.S. Geological Survey, Department of the Interior.

20110906_166_hurricanefloodsdrought ________________________________________

[Music]

Kara Capelli: Hello and welcome to USGS CoreCast. I'm your host, Kara Capelli.

After being hit by Hurricane Irene, North Carolina is facing floods and water quality issues in the East. Meanwhile, areas of the western part of the state are suffering from drought. On this episode of CoreCast, we'll hear from Holly Weyers, the director of the USGS North Carolina Water Science Center, who addresses these extreme water events.

Holly Weyers: Well, regrettably this is not a unique situation for North Carolina, especially in regard to hurricanes. We've had a long hurricane history here and a great deal of hurricane science is focused on our state. In fact, about 3% of all Atlantic tropical cyclones make windfall in North Carolina. So, it's really sort of a very diverse, mixed bag of relationships here with regard to where we get rain and where we don't.

Prior to Irene in North Carolina, we've had reduced rainfall amounts. The typical summer thunderstorms have been less frequent and until Irene, we haven't had any major tropical systems producing significant rainfall, and as a result, we have a lower than average water table in many portions of the state.

01:10 So, it's not unusual for one portion of the state to be impacted by floods, by events such as hurricanes, while experiencing drought in other areas, especially when you consider how large the state is and how geographically diverse that it is.

Kara Capelli: Hurricane Irene, which struck in August of 2011, was a major event for the state. The rain, wind and storm surge brought not just flooding but also impacts to water quality.

Holly Weyers: When the public typically thinks of the impact of hurricanes, they think of coastal and rain and wind-driven riverine flooding. We are just now, along with our state and other federal partners, beginning to understand the full impact of Irene in some of these areas.

However, some impacts from hurricanes are more subtle and not as publicly visible, at least not immediately. For example, not only can hurricanes produce the excessive coastal and riverine flooding, but on occasion there can be significant water quality issues related to these tropical cyclones.

02:08 As Irene moved onshore tracking northward, dumping rain and causing extreme surge events in many river basins, resulting flooding led to a steep decline in dissolved oxygen in the lower portions of the Roanoke River Basin. These low dissolved oxygen levels are of immediate concern to state and federal officials because they can lead to fish kills.

It should be noted however that this is a natural phenomenon; the lower Roanoke River corridors supports extensive wetlands that are rich in organic matter and the counterclockwise winds from Irene pushed water from Albemarle Sound up into the mouth of the Roanoke River and other tributaries, causing water to rise into the surrounding flood plains and marshes with their large stores of organic matter.

The effect of flooding in these areas is like steeping a tea bag, but on a really large scale. The water soaks up the organic material and then drains back into the river after the hurricane passes and the bacteria in the water break down the organic material, consuming large quantities of oxygen in the process. The result of this process is lower oxygen levels in the river, which can be harmful to fish populations inhabiting these regions.

Kara Capelli: The wet conditions in the east have kept Holly and her staff of hydrologists busy. Crews have been out in the field, measuring the hurricane waters and floods.

Holly Weyers: The U.S. Geological Survey has developed a program to deploy storm surge sensors at locations that may be impacted by tropical systems. Once a hurricane prediction forecast indicates a significant probability of impact, USGS scientists spring into action in an effort to collect critical storm surge data.

Many of our crews work from sunup to sundown or later, both in advance of the storm, deploying these storm surge sensors in coastal counties, and even a rapid deployment real time gage in Newburn on the Neuse River. After the passage of Irene, made stream flow measurements, retrieved sensors, found and flagged and documented high water marks, and monitored the water quality conditions.

These data are not only important from an emergency response perspective, but the scientific data related to the storm surge and flooding will be used to estimate when, where and to what degree storm surge flooding will occur in the future and to calibrate and verify storm surge models resulting in better understanding of the dynamics of storm surge.

Kara Capelli: It's not just the high waters that are keeping them busy; drought is causing a separate set of issues in the western part of the state.

Holly Weyers: Drought, really, is defined as the period which a region has a deficit in its water supply and is a normal feature of climate which happens in all climate zones from time to time, but was often never looked is that drought is one of the most severe among all natural disasters.

Here in North Carolina Water Science Center, we monitor drought by checking extreme flow, as well as lake reservoir and aquifer levels and compare those measures to historical data to determine the impacts of precipitation shortfalls. So just like measuring flooding, measuring drought is a big part of what we do.

05:06 So, in addition to the 280 real-time streamgages we operate across the state, we have 53 real-time ground water sites where we measure aquifer levels, and a 162 precipitation gages. Data from all these sites allow us to continually monitor water levels across the state and assist our partners with not only determining when and to what degree drought conditions are present, but to provide unbiased scientific data when water resources may be in limited supply.

Kara Capelli: Holly's message is clear: science is crucial in addressing water issues like floods and droughts. The North Carolina Water Science Center is now looking ahead and preparing to continue to address these issues in the future.

Holly Weyers: We are near the climatological peak of the hurricane season, which runs from June through November so we really need to be prepared for anything and respond accordingly if we are impacted. We can also count on our partners and other USGS Water Science Centers and at the national level to assist if needed and we were fortunate this time with Irene to have our partners from South Carolina and the Georgia Water Science Centers helping with this event.

06:13 Kara Capelli: For more information on USGS Water related work in North Carolina, visit www.nc.water.usgs.gov/.

[Music]

And don't forget to follow the USGS on Twitter at www.twitter.com/usgs/ or visit our other social media channels at www.usgs.gov/socialmedia/.

I'm Kara Capelli and CoreCast is a product of the U.S. Geological Survey, Department of the Interior.