The $20 million U.S. Army Corps of Engineers/Texas General Land Office Coastal Texas Planning Study covered the Texas coast and examined both storm surge protection and ecosystem restoration. The report is out for public comment through Jan. 13.
The corps and land office have made a real effort to explain their outcomes to the public through visuals and interactive programs. This is a welcome addition to a now 1,000-page report that was missing in the first version. Overall, this second report is much improved and shows the results of a lot of hard work on a complex problem.
However, the design can and must be made better.
The first thing that strikes us is the poor overall performance of the corp’s design for its estimated expenditure of $26.17 billion. The plan states expected damage reduction of only 60 percent over the 50-year period of economic analysis.
The principal issue causing these large damages is a failure to hold to the coastal spine “Ike Dike” principles of strong protection at the coast and keeping water out of Galveston Bay.
The corps has used the coastal spine concept but made it weaker by not gating San Luis Pass and proposing very weak protection for the land barrier on west Galveston Island and Bolivar Peninsula.
The original Ike Dike plan first proposed in 2008 had all protection at about 17-foot height throughout the spine and gated San Luis pass. The corps plan varies considerably in height and strength of protection. The Bolivar roads gates are at 21.5-feet height and the present seawall raised to 21 feet.
But the principal coastal land barriers are two sand dunes at 12 and 14 feet. These sand dunes have effective protection much less than those heights.
The corps’ dune response modeling shows that the dunes would be below 12 feet for 75 percent to 80 percent of the time. This very weak dune component allows water into the bay during storm events and won’t hold up over the multiple years between nourishment.
Because the regional storm surge protection modeling was done assuming the dunes afforded 12 feet solid protection, the expected regional surge damages are actually greater than already poor stated results.
The other source of water into the bay is an open San Luis Pass. Not closing the pass during storm or high water events allows forerunner surge in the bay, as well as regular storm surge which directly affects structures on the West End of Galveston Island and on the mainland north side of west bay.
It also disallows sealing the bay at low tide with an approaching hurricane to reduce bay elevations as much as possible. Every contribution to water height in the bay increases the surge in the bay and thus increases the need for and strength of the bay lines of defense.
Future articles will focus on three areas of concern: natural sand dunes as designed are simply not strong enough, the need for San Luis Pass gating to reduce surge effects throughout west and Galveston Bays, and the approach to Galveston Ring Barrier protection.