The Gulf Coast Community and Recovery District includes Brazoria, Chambers, Jefferson and Orange counties, which joined Galveston County to form the coalition.
The Galveston County Daily News reported Thursday that Harris County recently became part of the group.
The counties are expected to launch a study of the so-called Ike Dike concept devised by Texas A&M University at Galveston professor Bill Merrell after the September 2008 hurricane.
Merrell proposes extending Galveston's seawall to the west end of the island, building a similar barrier on Bolivar Peninsula and installing giant gates at the entrance of the Houston Ship Channel.
Galveston County Judge Jim Yarbrough says the group's first meeting should be in mid-March.