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Packery.Com - Information source for the proposed Packery Channel Project...
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Packery
Channel Introduction |
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September 23, 2000 Letter from: Henry L. Berryhill,Jr.- Marine geologist, retired - U. S. Geological Survey To: District Engineer - U. S. Army Corps of Engineers -Galveston, Texas
Dear Sir: The upcoming study of " Packery Channel " by the Corps of Engineers should address in detail four aspects: 1) how an open channel will affect storm flooding on the islands; 2) how it will affect sand budget; 3) how the progressively receding shoreline will affect protection of the seawall; and 4) how far into the Gulf of Mexico should the offshore jetties extend to minimize sand deposition within the dredged inlet. Comments: Aspect 0ne The proposed site for the channel is in a major zone of hurricane storm surge. Currently, when sea level rises in response to surge caused by an approaching hurricane, the sea must erode its way across southern Mustang Island before reaching the bay/lagoon system. This is done by opening the Packery, Newport, and Corpus Christi storm-surge channels. The process takes several hours and thus delays flooding by the same amount of time. It has been calculated that a channel already open would cut evacuation time from the islands by some three hours. This should be addressed in the study
Aspect Two Since opening of the Corpus Christi Ship Channel 70+ years ago, the natural outlet to Corpus Christi Bay has been progressively filled in by sand deposition, a process by which Mustang and Padre Islands have been sedimentalogically melded together.This sand has come principally from : 1) the islands themselves and the inner shelf/surf zone from whence it has been repeatedly deposited as storm-surge deltas; and 2) the southward drift of sand eroded from the backside of Mustang Island. This building process has increased the ability of the islands to hold back flooding - both by increasing the southward extent of Mustang Island and also its width. The dredging of a channel through this area will remove much of the protective sand built up over the years. Maintenance dredging will remove any further build up of sand. Thus, an area of sand accrual with increasd flooding protection will become an area of sand deficiency that will increase vulnerability to flooding.
Aspect Three Protection of the 4,500 ft. long sea wall and the small bulkheaded island of private property immediately behind it is the principal objective of this project, according to Senator Hutchison’s Bill. The sand dredged to open the channel is to be placed in front of the seawall, both to restore the beach and to protect the seawall. Unfortunately, the beach has been removed in the first place by the process of shoreline retreat. The shoreline along this segment of the Texas coast has receded about 200 ft. over the past 30 to 35 years (a measured figure). This magnitude of retreat is predicted to continue and may increase if predictions of future sea-level rise prove correct. The retreating shoreline is progressively outflanking the the seawall, leaving it increasingly more exposed and more vulnerable to the ocean each year. If the structure is still there 30 years hence, what will be the cost of yearly protection when the shoreline will lie some 200 ft. inland of the wall (this will be especially critical to the south)? Larger and larger amounts of sand will be needed - where will it come from, and at what cost ? The inner shelf does not have an adequate long-term supply. Furthermore, along a shoreline characterized by a strong southerly longshore drift, the placing of sand that is in short supply in front of a seawall to protect a small increment of private property, rather than using it instead to enhance dune build-up to protect much larger segments of the islands, is almost criminal.
Aspect Four Calculations by Naismith Engineering in a report done for the Nueces Commnsioners call for offshore jetties 1,450 ft. long as adequate to prevent sand build-up in the inlet. I believe this to be inadequate. The jetties should be a minimum of 2,100 ft. long but preferably 2,500 ft. Closing statements: 1) The big issue when the dredging of Packery Channel was being pushed in the 1980’s was the great benefit to fishing that would ensue as a result of the increased water exchange to the bay/lagoon system. Your study last year, also mandated by Senator Hutchison, indicated that a channel some 12 miles south of the Packery Channel site would provide the best water exchange with Laguna Madre and that a channel at Packery would have little effect. I fully concur. How do last year’s findings relate to this year’s study? 2) Any long-term attempt to preserve a seawall that, in time, will be left sitting farther and farther seaward of the shoreline will be both an expensive and a losing cause. Sincerely yours, Henry L. Berryhill,Jr. Reprinted with permission from Mr. Berryhill
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