Harris Galveston Subsidence District Harris Galveston Coastal Subsidence Districts. http://hgsubsidence.org Harris-Galveston Coastal Subsidence Districts. Harris Galveston Subsidence District Harris Galveston Subsidence District Harris-Galveston Subsidence District's http://www.hgsubsidence.org/ Harris-Galveston Subsidence District Harris-Galveston Subsidence District Harris-Galveston Subsidence District http://www.hgsubsidence.org/ Harris Galveston Subsidence District http://www.hgsubsidence.org/