Geotimes - October 2007 - Comment
A COMMENT ON ...
Coastal Development: The Galveston Case, Part I Jim Gibeaut
Even following the disastrous 2005 hurricane season, barrier islands remain under increasing pressure from development in Texas and elsewhere. The pressure is typically from those who don’t yet have their home by the shore (but want one), individuals investing in vacation properties and governments seeking to grow local economies and expand their tax base. And there are always developers ready to fulfill these desires and push the envelope of what is prudent for the community with regard to the impact of storms, sea-level rise and erosion. Local governments should manage their islands with an eye toward minimizing the impacts of these hazards. In so doing, they will also be practicing wise long-term economic and environmental policies for their islands and the rest of the country by decreasing the cost of the inevitable post-disaster response and recovery. Alas, we all know that is a fantasy. This case is magnified in Galveston, Texas.
Geologists know that if one were to create a natural hazards map of the entire United States using about six levels of hazards, then the entirety of most barrier islands would be colored bright red as most dangerous. But we can talk until we are blue in the face and development will still continue to expand and fill in many of these islands, and risky redevelopment after storms will continue. Preaching “abstinence only” will not work; therefore, we should also focus on providing the public and policymakers with the tools to manage these islands.
Nothing beats a map for focusing the collective attention of government, residents, the press and developers on the realities of geohazards facing a barrier island community. We recently completed such a map of Galveston Island for the City of Galveston. The map draws lines in the sand surrounding areas that vary in their susceptibility to, and function for, mitigating the effects of geological processes. For Galveston, these processes include sea-level rise, land subsidence, erosion and storm-surge flooding and washover. Importantly, the mapping recognizes that sea-level rise and shoreline retreat are changing the island; therefore, 60-year model projections of the effects of these changes are incorporated into the map.
The Galveston Island Geohazards Map draws on decades of geological knowledge of how barrier islands behave and puts it in a form that is intuitive to the public and directly useful to planners. Some of the “messages” in the map include: leave salt marshes alone and give them room to migrate inland as sea level rises; set back and move development away from the shoreline to provide space for beaches and protective dunes to form; and steer away from particularly low and unprotected areas subject to flooding and washover. No surprises here for geologists, and I am willing to bet the vast majority of barrier island stakeholders have heard these messages over and over again. The difference the map makes is that it is a tangible link from our knowledge to the issues on the ground, and if one group wants to ignore that knowledge another can raise the map and start talking about the consequences.
How this map will affect the environmental management of Galveston Island is yet to be seen. I can say, however, that in my experience it has already gained more meaningful traction than all the previous talks and reports on the importance to protect “fragile” environments that I know to have passed in front of the community. Some look at the map and say “well, this is only a problem if we don’t do anything to counter the sea.” Yes, beach nourishment, marsh restoration, seawalls and filling to raise the elevation of low areas can mitigate hazards, but the map shows the magnitude of the problem and some of the environmental tradeoffs in relying on an engineering approach.
The projections for change incorporated into the Galveston map do not include effects of increasing rates of sea-level rise as projected by global climate change models. It would be a shame if our efforts to improve how we live along the shore were caught up in the ongoing debate of global warming and the mapping results neutralized. Instead, all we are asking is for people to look at what we have observed during the past 50 to 100 years, project that just 60 years into the future, add a bunch more people to the island and then realize we better start doing things differently.
Of course geologists should continue to speak to barrier island stakeholders on how the current islands were constructed by geological processes acting over thousands of years and about the geologically ephemeral nature of these islands. We can even tell them how it is folly to expand development and to redevelop following storms in the face of global warming. But after you stupefy everyone and leave the room, they will go right back to the practical and immediate development issues at hand. Even if they don’t forget what you said, they will have no way to use your information when debating exactly where and how that new subdivision should be constructed — because in so many cases it will be constructed.
My suggestion: Leave them a geohazards map showing the current situation and changes to expect on a human scale. Stay tuned next month for Part II on coastal development.
Gibeaut is currently endowed associate research professor in the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University at Corpus Christi. The Galveston Island Geohazards Map was developed while he was at the Bureau of Economic Geology of the University of Texas at Austin.