Tide gauges: Predicting the future

From everyday to exciting

Every six minutes, sensors like these collect a water level reading in sites around the city of Norfolk.
The data collected by those sensors is straightforward: time stamp, water level at a tide gauge, location.
"What makes it exciting is what we do with it," said Kyle Spencer, Deputy Resilience Officer for the city.

Coastal survival

Spencer works in the Resilience Office, the city division responsible for strategies "to survive, adapt and grow in the face of stress and shocks and even transform when conditions require it."
First on the priorities list: coastal resilience, and a plan to mitigate the effects of increasing sea level rise and flood risk.
The team is also charged with creating economic opportunity and growing existing and new industry, as well as connecting communities, strengthening neighborhoods and deconcentrating poverty.
These priorities are connected to and dependent on each other. 
Coastal resilience tops Norfolk's priorities because water defines this area: Norfolk sits on the Chesapeake Bay and is crossed by the Elizabeth and Lafayette rivers that flow into it.
The city's history also explains today's efforts to mitigate the effects of water in neighborhoods.
"We flood where we filled," Spencer said. These maps illustrate his point. The map on the left -- from 1736 -- depicts the city's historic shoreline. The map on the right shows that historic shoreline over today's existing shoreline. And the blue shows the inundation in those areas. Approximately 8 percent of Norfolk's developed land is reclaimed.  
Because businesses and neighborhoods occupy the filled areas, water puts homes and other property at risk. And in an area that is just barely above sea level, all kinds of things can be affected when water rises.
"We’re constantly fighting sea level rise, storm surge, and precipitation," Spencer said. In Norfolk, as in other coastal areas, high water events are becoming more frequent and more severe. For an idea of how much all that flooding costs, check out the FEMA National Flood Insurance data and its accompanying story, also here in Norfolk Open Data.
The tide gauge at Sewells Point, which has been in its location for about 100 years, showed a significant and worrisome pattern.
"It’s getting way worse," Spencer said. "We are seeing these events happen every year, sometimes multiple times in a year." 
This chart illustrates Spencer's concern. Since 2000, the gauge at Sewell's Point has experienced more significant high water events than it did from 1933 to 1999 -- a time span of more than 60 years.
When the gauge reads four feet or above, the city begins to shut down because of water intrusion. "So we will close roads – Lexan Avenue and Hampton Boulevard. The roads around The Hague. The intersection of Boush Street and Olney Road. Llewellyn Avenue near Lafayette Bridge," Spencer said. "The city may close offices."
Here's where the sensors come in. The city installed sensors in several locations beginning in 2008, and started collecting data from them shortly thereafter. "These gauges are filling in the gaps," Spencer said. 
The interactive chart above, created by pulling the tide sensor data into data analysis software PowerBI, shows the locations of the sensors around the city, and the marked differences in the measurements at each tide gauge.
Data from the sensors is crucial to help city planners understand where and when flooding occurs, as well as what to do about it.
"This is the why," Spencer said. "Why it’s important. We can understand our problem better."

Higher at Ohio Creek

For example, Spencer said, the tide gauge now in place near Ohio Creek consistently measures 1/2 a foot higher than the one at Sewells Point. 
"If you built a flood wall at eight feet at Chesterfield Heights based on Sewells Point readings, it would be ½-foot too low," Spencer said. 
The data from the additional sensors will inform all kinds of projects, and has given city planners a better idea of mean low water and mean high water around the city. 
The measurements will help the city determine how a floodwall and berm built on the Elizabeth River might affect wetlands. The data will support design and planning projects such as the city- wide Coastal Storm Risk Management Study or flood infrastructure construction projects -- or even a waterfront casino. 
"Now we can have a much better designed project in construction, using more precise data," Spencer said. "They are precise because we are measuring the water closer to the location we are building in. That’s key."

Highest readings

The data provides useful information for all kinds of people and projects. Take a look at this chart that shows the highest readings over the last year.

Lowest readings

Low water readings are important, too. They provide information for planners and work crews, such as when to work on flooding infrastructure like flood gates.

More information = more preparation

Additionally, these sensors have become part of the StormSense project to provide a more comprehensive at-a-glance view of real-time flood conditions in Hampton Roads.
StormSense has installed more than 40 water-level sensors through cooperative agreements with municipal governments throughout Hampton Roads. The system also pulls in data from 25 more sensors outside its network from NOAA and USGS.
These additional inputs have allowed local governments to prepare for flooding with more advance notice and to predict water levels with greater accuracy. "Thanks to these sensors," Spencer said, "modeling in Norfolk is street-level accurate up to 36 hours in advance."
That means emergency operations, fire/rescue and police can anticipate flooding and close roads in advance. It also means that city officials have more warning and better information about when and how to close the Downtown flood gate near Nauticus.
"It's more anticipatory than reactionary," he said. 

"Hey, smarty, what's the tide?"

Placing this sensor data in the portal means that researchers may easily and freely obtain information that supports their work to mitigate flooding in our region. It also makes the data available to savvy entrepreneurs to conduct independent research.
Eventually, data from these sensors will support all kinds of efforts to mitigate the effects of flooding. Perhaps someday soon you'll simply ask your smart speaker for tide and water level information in your neighborhood. Or you'll use driving and traffic apps to navigate flooded streets and alternate routes in real time. 
"Data like this can help build products like that, and some of these are already in the works," Spencer said.

Take our data. Please!

So please -- take this data and use it. Whether you are a waterfront homeowner curious about how these gauges measure water levels near your home or elsewhere in the city, or a research scientist studying sea level rise and flooding, we WANT you to find uses for this data. 
And we will keep using this data ourselves to make the best possible decisions to keep residents and property high and dry in Hampton Roads. 


We are so glad you're here! 

Feel free to view, download and analyze this data. We provide this data as an affirmation of our commitment to transparency and community collaboration. We hope that you will use this data to improve your community, spark a business idea or just satisfy your curiosity.  Data will be updated and expanded often as we work to build a comprehensive open data portal. Click the logo above to check out all the data the City of Norfolk has to offer.
Questions? Please contact us at 757-664-4007 or email opendata@norfolk.gov.