Hurricanes are just one type of natural disaster that can severely impact coral reef habitats. Their strong winds create powerful wave action capable of tearing a reef apart. Run-off from massive quantities of rainwater dumped on land carries sediments, chemical waste, and debris out to sea. The potential for destruction underwater is as real as that on land.
So, how do the reefs of Flower Garden Banks National Marine Sanctuary stand up to the onslaught? We've had a few opportunities to find out.
Hurricane Harvey (2017)
In late August 2017, Hurricane Harvey dumped an unprecedented amount of rain on the Houston/Galveston area of Texas, prompting concerns about excessive freshwater influence on the sanctuary. A Rapid Response team of scientists visited the sanctuary in September 2017 under a National Science Foundation grant to see if they could identify any such impacts, but found that the massive amount of freshwater deposited by Hurricane Harvey never quite reached the sanctuary.
The only visible evidence of Harvey's passing was large ripples in the sand patches. All of the water turnover during Harvey also brought temperatures down to 81F, greatly reducing the threat of bleaching that year.
Rippling in the sand seen near East Flower Garden Banks Buoy #5 after Hurricane Harvey. (Image: FGBNMS/Hickerson)
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Hurricane Ike (2008)
In September 2008, the eye of Hurricane Ike passed directly over East Flower Garden Bank en route to Galveston, TX where the sanctuary offices are located. Although this was rated a Category 2 storm according to wind speed, it's enormous size caused it to move water like a Category 4 storm.
In October 2008 sanctuary staff were finally able to secure a small vessel to take them for a quick look at the condition of the reefs. What they saw was reminiscent of the aftermath of Hurricane Rita in 2005. Some boulders of coral up to 4 meters across had been torn loose from the reef and tossed about, sometimes landing more than 25 feet away. Others had been toppled in place. As much as 3 feet of sand was scoured away from coral formations along the sand flats, then piled deeper in other areas. And, several mooring buoys were gone.
While this initial assessment is important, it will be followed up with a more comprehensive evaluation once a larger vessel and other necessary resources are available.
For more information and photos of Hurricane Ike's effects, visit our 2008 Post-Ike Reef Assessment and Hurricane Ike Images pages.
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Hurricanes Katrina and Rita (2005)
In August and September of 2005, Hurricanes Katrina and Rita came roaring into the northwestern Gulf of Mexico.
Hurricane Katrina passed well to the east of Flower Garden Banks National Marine Sanctuary and is believed to have had minimal impact on the reef. Unfortunately, due to recovery efforts immediately following Katrina, we were unable to secure a vessel to check on the sanctuary before Rita came howling through.
The eye of Hurricane Rita passed 35 miles to the east of East Flower Garden Bank as a Category 3 storm, with much of the rest of the storm directly over the sanctuary.
The first post-hurricane visit to the sanctuary didn't occur until October 2005. Several more trips were then taken during the following year to continue monitoring the initial hurricane impacts. A final report was generated in February 2007.
Satellite photos in the weeks after the storm showed a huge slug of brown water reaching from the coast over 115 miles out to the sanctuary. Water quality sensors on site confirmed that this was indeed freshwater, but what nutrients or chemicals it contained we may never know. Needless to say, even coral reefs far from shore may be impacted by storm runoff.
While some of Rita's physical impacts at the sanctuary were significant, affecting items as deep as 72m, positive changes also occurred. The most significant benefit was the cooler water Rita left in her wake. Cooler temperatures were exactly what bleaching corals needed to aid in their recovery.
Click here to download a copy of Hurricane Rita Impacts at the Flower Garden Banks National Marine Sanctuary (1.3MB pdf) which includes dramatic before and after photos at various locations in the sanctuary, as well as satellite images and data on temperature and salinity changes.
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