Geotimes - November 2007 - Comment
A COMMENT ON ...
Coastal Development: The Galveston Case, Part II Jim Gibeaut
Last month, in part one of this series, the author commented on how geoscientists can participate in coastal development discussions using advances such as geohazards maps. Read the story at Geotimes online, atwww.geotimes.org/oct07.
Barrier islands and coastlines are dynamic places, constantly changing. What may be a dune one year may be a flat beach a few years later with a new dune meters to hundreds of meters away. What may be a freshwater marsh may become a saltwater marsh, or vice versa. Change is the norm. Change in these environments can become a problem, however, when humans build to the edges of these environments. Therefore, we must figure out how to help preserve these coastal environments, which are not only scenic and provide key ecological and recreational opportunities, but also provide protection from storms and dampen the impact of sea-level rise.
Today, firmly planted buildings occupy the space where mobile dunes would be, and concrete structures built to prevent beach erosion, called bulkheads, and filled lots have blocked the landward and upward migration of wetlands. Buildings and infrastructure that were constructed appropriately inland of protective dunes or fringing saltwater wetlands may have appeared reasonable when they were erected, but they are now in a hazardous and environmentally destructive location. Along portions of the Texas coast, this is the situation, and houses have been falling into the ocean for the past three decades. Along many deltaic and bay shorelines, the wave- and storm-surge buffering and flood-absorbing effects of wetlands have decreased as the wetlands themselves have disappeared.
This means that like many of our coastal barrier islands, Galveston Island, Texas, is more vulnerable to storm damage today than it should be. Some of the deterioration of the natural system has occurred as a result of blatant and direct destruction of dunes and wetlands to make way for more houses, hotels and golf courses, but much has and will continue to occur because development occupies the space where these protective environments need to migrate in response to sea-level rise and erosion. This is a topic not often discussed. But geoscientists know that even if we had ironclad rules preserving wetlands, beaches and dunes as they exist today, we would still experience a net loss of these protective environments in the future due to the effects of sea-level rise and erosion intersecting development. In our planning, therefore, we must use projections of future conditions and develop land-use policies that recognize the dynamics of these environments.
We recently completed the Galveston Island Geohazards Map for the city of Galveston. The map shows areas that vary in their susceptibility to, and function for, mitigating the effects of geological processes, including sea-level rise, land subsidence, erosion and storm-surge flooding and washover. The current wetlands, beaches and dunes are mapped as having the highest geohazard potential both in terms of their exposure to hazardous conditions and their mitigating effects of those hazards for the rest of the island. These existing “critical environments” are generally protected under existing regulations. However, the areas that we project will become wetlands, beaches and dunes in the next 60 years are not protected. These areas are the most difficult to deal with from a policy point of view, yet we must address what happens there if real progress is to be made in how we live with coastal change.
The projections are made for 60 years because this is a timescale people often plan for in their personal lives, and because it is a period where our methods for projection are most pertinent. So how should we consider these areas in our management policies?
A relatively easy prospect is to make hazard maps required reading for property buyers. Include maps as another page to be signed during the real estate transaction. Hopefully, this will prompt buyers to make more informed decisions about their investments and discourage those who plan on retiring there or reaping income from a property a few years down the line, from purchasing land in precarious coastal locations. This would also temper public support for unsustainable, expensive and often environmentally destructive erosion control strategies if we all know that property owners knew the risks when they made the purchase.
The 60-year landward edge could be treated as a setback line for new construction. This would provide a buffer where beaches and wetlands can migrate for awhile. But unless there is a policy that can force the removal of a structure before it is in the zone where wetlands or dunes would develop, then it is just a matter of time before many newly developed areas replace our dunes and wetlands, just like today. Another approach is to allow construction right up to the critical areas but require buildings to be removed when they are found to be preventing the migration or formation of the protective environments — but I’m not sure how likely people would be to move something just built a decade or two earlier.
Whatever the choice, it is clear that we need to build into our policies a dynamic that matches the changing conditions along our coast, and we need to make sure the public is aware of the situation. In so doing, we will have communities that are more resilient to hazards while maintaining environments important to ecological health.
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.