Community Resilience: Data Surge! Better Storm Records Will Improve Predictions
By Spencer Rogers
A full original version of this story appeared in the spring 2016 issue of Coastwatch.
North Carolina Sea Grant is a partner in national efforts to improve storm-surge data gathering and understanding. Those efforts are advancing thanks to the increased attention from the U.S. Geological Survey, or USGS, to storm surge in and following Superstorm Sandy in 2012.
Until recently, local, state and national officials did not have precise measurements of the water flow during storms. Rather, they relied on “watermarks” as historical records, a system with at least two major drawbacks.
Rogers, at left, and Andrew Kennedy of Notre Dame University set gauges at the Rodanthe Pier on Hatteras Island prior to Hurricane Irene. Photo: Michael Halminski
The first problem was that no single agency was in charge. Nationally, many folks collected storm-related water data, including USGS, the U.S. Army Corps of Engineers, the National Weather Service and various researchers at state agencies and universities, including Sea Grant program staff and researchers. No single system or protocol was used to measure watermarks, or to maintain the records.
Also, the marks only recorded the highest water during a storm. While that is good information, it is much better to identify the rise and fall of storm surge and waves during and after storms.
Better Storm Records
Beginning with Hurricane Rita in 2005, USGS began extending its century of work in measuring streams and rivers to deploying pre-storm gauges. North Carolina started deployments in 2006, with several years in which we did not have severe storms to test the process.
When Irene threatened North Carolina in 2011, three groups — Sea Grant, the University of North Carolina at Chapel Hill’s Institute of Marine Sciences and the USGS — were ready to cover deployment in different parts of the state. This was a great advance over hurricanes impacting North Carolina from before the 1990s all the way up to Hurricane Isabel in 2003, when we really needed the gauge-based measurements, but had to rely on watermarks.
After Sandy —first designated a hurricane, then a superstorm — hit the East Coast in 2012, USGS was tasked with collecting storm-surge and other water data. At the time, the USGS storm-surge gauges would only sample every 30 seconds; unfortunately, more accurate wave sampling requires about one-second sampling.
Based on our experiences in North Carolina, we encouraged them to move from slower stream-flow measurements to the wave gauges for storm surge.
USGS agreed and was able to start purchasing wave gauges to meet nearshore and inshore needs. For Hurricane Joaquin in 2015 and a 2016 winter storm, we saw successful deployments.
Measurements of water levels and wave heights in specific storms obviously are important as part of a storm record. But that data also will be used in models for forecasting impacts of future hurricanes or other coastal storms that threaten our coasts. Unlike the earlier error-prone watermarks, gauges provide a hydrograph for calibrating storm-surge models, improving these predictions.
In North Carolina and other states, these data are used in emergency management and planning, such as floodplain mapping. Those records also are key factors in predictions that are used in flood-resistance designs for new buildings and retrofitting of existing structures.
Now, with equipment and deployment much better refined, the key issue is optimizing data collection. With the requisite data, coastal flood damage could be predicted at the community — or even building — scale. Communities then could craft responsive design guidance to ensure future development is sustainable, one building at a time.
Learn more about current gauge data and modeling needs as well as results of a community-scale analysis on the Bolivar Peninsula in Texas using gauge data from Hurricane Ike in 2008.