The 2021 Atlantic Hurricane Season lasted from June 2021 to November 2021 and was the third most active season on record for the Atlantic region. This season, Hurricane Nicolas struck Harris County in mid-September, causing storm surge and wind damage resulting in an estimated cost of $950 million to $2.2 billion in damage.
With the end of the 2021 Hurricane Season behind us, now is a good time to reflect on tropical storms and the mitigation efforts underway. This blog post, which is based the Analyst's Office report featuring the Coastal Texas Study and the Galveston Bay Park Plan, examines past tropical storms activity in Harris County, how tropical storms produce storm surges, and describes the two regional projects designed to mitigate the impact of storm surge to Galveston Bay and the region.
Understanding Storms and Storm Surge
Hurricanes are strong tropical cyclones. A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has a closed low-level circulation.
Tropical cyclones are typically categorized based on their wind speeds using the Saffir-Simpson Hurricane Wind Scale to differentiate the hurricane intensity, and are classified as follows:
- Tropical Depression: A tropical cyclone with maximum sustained winds of 38 miles per hour (mph) or less.
- Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph.
- Hurricane: A tropical cyclone with maximum sustained winds of 74 mph or higher up to 110 mph, corresponding to a Category 1 or 2 hurricane.
- Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph or higher, corresponding to a Category 3, 4, or 5 hurricane.
One of the most destructive threats from a tropical cyclone is the storm surge generated. Storm surge describes the abnormal rise in water generated by a tropical cyclone; it is caused by strong winds and low pressure from a storm. Projections demonstrate increases in storm surge associated with storms due to the rising sea levels expected over the next 100 years.
Impact on Harris County
At the start of each Atlantic Hurricane Season, the National Hurricane Center provides 21 storm names to differentiate between tropical cyclones each season. The 2021 Hurricane Season concluded with 21 named storms and seven hurricanes, four of which were major hurricanes. In addition, the 2021 Season marks the first time two consecutive hurricane seasons (the 2020 and 2021 seasons) had at least 21 named storms.
The National Oceanic and Atmospheric Administration (NOAA) projects that on average, for every 100 years, 15 hurricanes will hit Harris and Galveston counties, four of which will be major hurricanes.
These expected storms may produce storm surge, and when coupled with the anticipated sea-level rise, which by some estimates could be as high as two-to-four feet in the Gulf Coast over the next 100 years, that storm surge is a considerable threat to the coastal parts of Harris County and the Houston Ship Channel, a state and national economic driver.
Storm Surge Mitigation Plans
Projects to mitigate storm surge in Galveston Bay have been discussed for decades, starting with the USACE Texas Coast Hurricane Study in the late 1970s, and more recently, with the 2009 Texas A&M University of Galveston’s “Ike Dike” and the 2016 Gulf Coast Community Protection and Recovery District’s (GCCPRD) “Coastal Spine.”
Currently, two storm surge mitigation projects are under consideration for Galveston Bay:
The Coastal Texas Study, which was developed by the US Army Corps of Engineers, is a “Multiple Lines of Defense” strategy that uses natural and man-made infrastructure to keep surge from coming into the bay during a storm and to protect the west side of Galveston Bay and the backside of Galveston Island from in-bay storm surge. The strategy also seeks to restore over 6,600 acres of coastal ecosystems and provide 2.9 miles of coastal storm risk reduction on South Padre Island. The current Coastal Texas Study models a potential 10-foot reduction in storm surge, reducing storm surge for Galveston Bay by more than 50%.
The Coastal Texas Study will cost approximately $28.9 billion and take 19 years to complete, with an estimated completion date of 2043. Maintenance and operation costs estimated to be $131 million per year while the gates are operational. The source of funding for the Coastal Texas Study is still under discussion.
The GalvestonBay Park Plan (GBPP) is a dual-purpose barrier islandsystem and park designed by Rice University’s Severe Storm Prediction,Education, & Evacuation from Disasters Center (SSPEED Center). According tothe team that developed the Park Plan, it is designed to protect West GalvestonBay and the Houston Ship Channel from a 25-foot storm surge event generatedfrom large Category 4 hurricanes. The Park Plan is also intended to complementthe Coastal Texas Study and to afford initial surge protection for theGalveston Bay and protection for Galveston Island.
The Park Plan still requires the completion of studies to aidwith determining cost, feasibility, and timeline.
The threat of storm surge to the coastal areas in Harris County and to our region’s economic driver, the Houston Ship Channel, looms. The Coastal Texas Study and the Galveston Bay Park Plan are on very different timelines to address this anticipated threat.
The Coastal Texas Study’s final feasibility study is currently planned to be completed and sent to Congress in 2022 for authorization in the 2022 Water Resource Development Act (WRDA). Congress will then need to appropriate funds, expected as early as 2023, following Congressional authorization.
The next step for the Galveston Bay Park Plan is for advocates to solicit funding from local partners to complete a feasibility study for the project.