Author’s note: This is the fourth article in a series describing nine changes that we would propose to the U. S. Army Corps of Engineers Tentatively Selected Plan, based upon our Ike Dike-related research over the last decade.

The first article (“Army Corps’ coastal spine plan needs some changes,” The Daily News, Dec. 12) discussed moving the corps’ proposed levee and flood-wall land barriers from behind the coastal highways to the coast and constructing the protection needed as natural appearing fortified dunes.

The second (“Further changes needed to improve the Army Corps’ coastal spine plan,” Dec. 23) discussed changes necessary to reduce surges in Galveston Bay — such as adding a western section as fortified dunes on Follet’s Island and a gate San Luis Pass — and instituting best practices for bay water management in estimating bay surge.

The third article (“Creating the best coastal spine for Texas, Part III,” Dec. 24) dealt with rethinking the size, complexity and even need for the Galveston ring levee and gates and structures at Kemah and Dickinson Bayou.

This article addresses two additional needed changes.

• Change No. 7: Reduce or eliminate the north-south eastern barrier running up from High Island. Recent modeling shows that any water getting into Galveston Bay from hurricane surge generated east of the coastal barrier enters an eastern bay region with low water heights.

This is because waters in eastern Galveston Bay have already been reduced by the approaching hurricane’s outlying winds, which blow the bay water from the east to west. For now, we believe the barrier can be eliminated or greatly reduced in height.

• Change No. 8: Modify the Bolivar Roads water barrier to reduce the size of the ship gates and allow more flow through the environmental section.

The tentatively selected plan’s navigation gates are too large and certainly too deep. The gates are designed at 1,200-foot width and 60-foot depth.

This is for a 530-foot-wide channel (800 feet wide with shallower barge lanes) with a present water depth of 43 feet to 45 feet. Plans for improving navigation in the channel seem concentrated on deepening some shallower areas in the upper channel to the 43-to-45-foot design depth and improving mobility by taking out some curves and kinks.

Any significant deepening would require dredging the channel for many miles out onto the Texas shelf, as well as dealing with the myriad of pipelines crossing the channel. The navigation gate is the single most expensive part of the plan, about $5 billion, and while some allowance for widening and deepening is understandable, the present design can be usefully downsized.

The environmental gates allow for two major functions, assuring sufficient flow in and out of the bay to maintain conditions in the bay necessary for ecosystem health, and allowing exchange of sea life between the Gulf and bay, especially larvae.

The present plan can be improved to allow more flow by substituting barge gates with larger flow openings for some gates in the present design. Also, accordion or inflatable gates could be used near Bolivar. This would allow totally open waters in the eastern section of Bolivar Roads, where most larvae exchange occurs.

William Merrell, president emeritus, regents professor and Mitchell chair: Center for Texas Beaches and Shores, Texas A&M University at Galveston

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