Author’s note: This is the third in a series describing nine changes we would propose to the U. S. Army Corp of Engineer’s Tentatively Selected Plan based upon our Ike Dike-related research over the past decade.
In our first commentary (“Army Corps’ coastal spine plan needs some changes,” The Daily News, Dec. 12) we discussed Change No. 1: Move the corp’s proposed levee and flood-wall land barriers from behind the coastal highways to the coast and construct the protection needed as natural appearing fortified dunes.
In the second commentary (“Further changes needed to improve the Army Corps’ coastal spine plan,” The Daily News, Dec. 22), we discussed changes necessary to reduce surges in Galveston Bay, namely Change No. 2: Add a western section as fortified dunes on Follet’s Island and gate San Luis Pass; and Change No. 3: Institute and account for best practices for bay water management in estimating bay surge.
The water levels allowed in the bay directly impact a number of protection issues, including the heights of or even the need for secondary barriers such as the Galveston ring levee and structures at Clear Creek and Dickinson Bayou. This leads to the subjects of this column.
Changes No. 4, 5 and 6: Rethink the size, complexity and even need for the Galveston ring levee and gates and structures at Kemah and Dickinson Bayou.
These additions to the basic coastal spine are designs that evolved from rejected non-spine options that attempted to deal with the full force of storm surge in unprotected areas as opposed to a surge that’s already reduced by a properly designed and operated Ike Dike. With the presence of a coastal spine these additional features may not be needed or can be reduced in size and complexity.
The proposed Galveston ring levee is a ring around the eastern part of the city of Galveston now protected by the seawall. The seawall would be heightened and the proposed ring levee would have a substantial height of 18-feet on the backside of the city.
The proposed levee is expensive and would require high maintenance. It has many points of potential failure — 46 two-lane highway gates, six four-lane highway gates, four railroad gates and three pumping stations. Its 18-feet height creates a nightmare overflow scenario if it, or the seawall, were ever breached. Suitable protection can be achieved by less intrusive means.
In addition to the Galveston ring levee, supplements to the basic coastal spine protection are proposed for the west side of Galveston Bay, including the possibility of 17-feet high gates at Clear Creek/Kemah and Dickinson Bayou. Large gates will be expensive, high maintenance, and require considerable additional infrastructure to reduce flooding. As proposed, a gate at Kemah would divert the Clear Creek flooding path through Shore Acres unless a barrier is built there.
In its Tentatively Selected Plan, the corps wisely notes that nonstructural alternatives might be considered (note that the corps includes raising individual structures in its non-structural alternatives) for the west side of Galveston Bay. This combined with modest structural improvements would provide suitable protection from surge and nuisance flooding for Galveston Bay’s west side, as well as the back side of the city of Galveston.