Tag Archives: John Anderson

Stopping Erosion by Dr. John Anderson

Conservation, Sustainability, ,

Yesterday, Saturday January 24th, my wife Doris and I attended the town hall meeting at Sea Isle and wandered around the various booths reading the comments posted for each group. At the Environment Booth I was struck by one comment in particular that read “Stop Erosion”, which provoked me to sit down and write up this summary of the problem. Stopping beach erosion is about as complicated as stopping volcanoes from erupting and earthquakes from quaking and the sooner we accept this reality the sooner we will get on with the business of sustainable development in Galveston. I welcome questions and comments and am happy to provide scientific documentation of the statements I have made in this summary.

  1. For those who would question the importance of sea-level rise in controlling coastal retreat (erosion), consider that in the past 17,000 years, since the last major glaciation, sea-level has risen approximately 100 meters causing the shoreline to retreat approximately 80 miles from it previous location at the edge of the continental shelf to its current location.


  2. The current rate of shoreline retreat, which averages 3 feet/year along the west end of the island but in places is as much as 10 feet/year, is slow compared to times in the past when sea level was rising at a more rapid rate, at times as much as 50 feet/yr.
  3. The rate of rise in any given location is combination of eustasy (global sea level rise) and subsidence. This is called relative sea-level rise. Eustasy is fairly constant across the northern Gulf of Mexico but subsidence is highly variable. In western Louisiana the rate of subsidence is in places as much as 30 times faster than the rate of eustatic rise. Our neighbors to the east are already contending with problems that we will face by the end of this century. The rate of subsidence in Texas is significantly lower but locally is still a major contributor to shoreline change. Unfortunately, we have relatively few locations where elevation changes are being monitored and those are not all in the most ideal locations. There are ways to acquire long-term subsidence measurements but little work has been done in the field. Remember, we spend all our money in Texas dumping sand on the beach and pitifully little goes to address the real issues of why the coast is changing. If we don’t know why, we can’t begin address the problem.
  4. Sediment supply is as important as sea-level rise in controlling coastal change. If sediment is added to the coast fast enough to keep up with the rate of sea-level rise the shoreline will remain stable and even grow. This is how Galveston Island formed at a time when sea level was rising and why beaches adjacent to the north and south jetties have grown since the jetties were constructed. Sediment supply to the upper Texas coast is minimal. So, even a slow rise in sea level results in shoreline retreat. We still do not have an accurate sediment budget for the upper Texas coast. The recent study by the Corps of Engineers was a poor attempt to quantify the sediment budget and until the budget is improved it will not be possible to predict the response of the Gulf and Bay shorelines to accelerated sea-level rise. I have a PhD student, Davin Wallace, who is currently working on a more accurate sediment budget for the Texas coast.
  5. Many of the current maps that show coastal inundation through time are highly inaccurate because they simply flood the landscape with different scenarios for sea level rise. They do not account for subsidence or sediment supply. For the most part, they are best-case scenarios.
  6. The current Galveston Island Geohazard Map is a more accurate approach to predicting coastal change because it relies on historical rates of shoreline change to predict future change. However, it assumes a constant rate of sea level rise and does not take into account changes in sediment supply through time. Neither does it account for the impact of hurricanes. So, it is a best-case scenario and should be immediately adopted by the city until we have a better handle on subsidence and the sediment budget.
  7. Eustasy is controlled by the temperature of the oceans (remember water expands when heated) and the contribution from glaciers and ice sheets. There is no question but that the oceans are getting warmer as the atmosphere warms, and this is the main contributor to the current acceleration in sea-level rise. In addition, 80% of the glaciers on Earth are melting. The net result is that the rate of sea-level rise has nearly doubled (from an average of 1.8 mm/yr to nearly 3.0 mm/yr) this century. The contribution of ice sheets to sea-level rise is the greatest uncertainty when it comes to predicting future rise, but it is by far the most important in terms of magnitude. If the Antarctic Ice Sheet were to melt global sea level would rise 60 meters (~200 feet). While this is not going to happen in the next few tens of millions of years, the most current scientific evidence suggests that the West Antarctic and Greenland ice sheets are going to contribute to sea-level rise this century. At the most recent meeting of the American Geophysical Union in San Francisco one of the keynote speakers at the meeting (Dr. Eric Rignot) summarized the current scientific information on ice sheet mass balance and concluded that global sea-level rise will likely reach 5 mm/yr by the end of this century. Dr. Rignot is one of the best, most respected scientists in the field and I see no scientific justification to doubt his predictions.
  8. Let’s put Dr. Rignot’s sea-level prediction into perspective. If we want to view the world of coastal change at a time when sea level was last rising at a rate of 5 mm/yr we have to turn back our geological clocks 7,000 years. I have spent the past three decades studying the evolution of the Texas coast before and after 7,000 years. Take it from me, this was a time when our coast, including estuaries, was changing at a rate most people cannot (don’t want to) imagine. This is not science fiction, this scientific consensus based on the peer-reviewed literature. This is why we have to fight to educate people about the seriousness of the situation. We can no longer tolerate ignorance, indifference and greed on the part of those who control the destiny of our coast. We owe it to our children and grandchildren to fight for a more sustainable coast.

For additional reading consult Dr. Eric Rignot’s research.

John Anderson

Maurice Ewing Professor of Oceanography

Department of Earth Sciences

Rice University

Houston, Texas 77251-1892

Shifting Sands – A View from John Anderson

Politics, Recreation, Sustainability,

For years John Anderson has been warning Galveston leaders of the risk of unbridled coastal development (particularly on the west end of the island), and the futility of engineered solutions (geotubes, beach renourishment) to stave off the encroachment of the Gulf. Ike has generated another round of debates about what can be done to refashion and redirect development on the island. John wrote the following editorial to address these issues that are facing our island again.

Sustainable Development of the Upper Texas Coast: A Call for More Science Input in Post-Ike Recovery

Hurricane Ike was a stark reminder of the risk of living on barrier islands. Yet, even as the loss of human life and material damage are still being assessed, City of Galveston officials and even former US presidents are talking about rebuilding a bigger and better Galveston. The fate of Bolivar Peninsula, however, remains more problematic. What is the future of the upper Texas coast, especially this century, and can Galveston Island sustain the unbridled development that existed prior to Hurricane Ike?

The reality is Galveston Island and Bolivar Peninsula were already experiencing significant changes long before Hurricane Ike, changes brought about by increasing rates of sea level rise and a limited amount of sand within our coastal system. We have tried to slow the rate of change by placing sand-filled socks along stretches of the beach on both Galveston Island and Bolivar Peninsula and placing relatively small amounts of sand on isolated beaches all up and down the coast. These projects were not working to slow beach erosion before Ike and they certainly did not help in reducing storm damage on Bolivar Peninsula, where the brunt of Ike was felt.

Yet, it is a virtual certainty that people will continue proposing even stronger geotextile tubes, offshore barriers and other strategies for combating the forces of nature. Before we buy into these panaceas we need to all take a short ferry trip over to Bolivar Peninsula to see what could have been if Ike had not in the final hours before land fall made that faithful turn to the east. Observe that not only did the Geotubes fail, but as they failed they created weak spots along the coast were breaching resulted in even greater damage inland.

See how few houses within two hundred meters of the coast survived the storm. Note that the elevation of the beach was lowered by several feet. And, while you are there, consider the fact that the beach ridges, which provided the only natural protection to waves and surge, were destroyed leaving the barrier lower and flatter and even more vulnerable to the next storm. Those ridges formed over centuries, they are not coming back any time soon. I would advise against encouraging re-development on Bolivar Peninsula by building a bridge to the peninsula.

As you ride the ferry back over to Galveston give some serious thought to the fact that this could have been us. Fortunately, there are some important geological differences between Galveston Island and Bolivar Peninsula and Follets Island. But that does not mean that Galveston will not see even more devastating storm impact in the future. The question is, how will we prepare for this impact?

If Ike, and other recent storms, has taught us anything it is that there are no quick remedies to combating the forces of nature. The Upper Texas shoreline has been retreating landward in response to natural forces for over a thousand years and it is not in our power to stop the process. So, why do we continue to waste millions of tax dollars on small beach nourishment and other projects that simply do not work? We could build a wall around the island but not without inflicting heavy damage on its natural habitats and ultimately destroying the beaches and wetlands that make the island so attractive. Is that really what we want?

The governing philosophy for the City of Galveston has been that if it raised tax revenue it was good for the island, including allowing people to build houses just landward of the dune line. Many of those houses are now gone or sitting in the surf zone. But many of those houses were being overtaken by the retreating shoreline long before Ike.

Coastal geologists have been calling for City and State government to adopt more realistic coastal development policies for years, but that input has largely been ignored. The City of Galveston was presented with a Geohazards Map for Galveston Island that would prevent building houses too close to the gulf and bay shorelines and would protect valuable natural habitats. This map has been largely ignored in permitting future developments on the island.

Even before Hurricane Ike, the GLO was threatening a dramatic setback policy, perhaps a warning that if the City can’t deal with these issues the state will deal with them. In the aftermath of Hurricane Ike the citizens of Texas have learned that poor development practices on the island will cost them dearly, in particular the huge chunks of state moneys that are needed to pay off the windstorm insurance claims.

I have been reading with interest Eric Berger’s blog on Galveston re-construction and according to my count there is a strong majority of people who feel that they no longer want to see their tax dollars go toward bailing out people who insist on living too near the beach. Galveston will no longer enjoy the luxury of having unsound decisions go un-noticed by those who don’ t live on the island. We are only an island in the geographic sense.

For those who doubt the value of sound science in avoiding catastrophic destruction, I would point to a number of warnings that are stated in my book, published over a year before Ike.

1.That destruction of Highway 3005 on Follets Island and breaching of the island would occur in the next hurricane.

2.Warnings were made to reserve the sand in Big Reef because it would be needed to repair the seawall and other damage after a hurricane. You may recall that this past summer Mr. Patterson had proposed to use that sand to nourish the beach just west of the seawall. Had that been done, much of that sand would have been transported offshore by the storm, a conclusion supported by a number of prominent coastal geologists who visited the site with me shortly after the storm.

3. The vulnerability of Bolivar Peninsula to storm impact was noted. This is due to the relatively low profile of the barrier and its relatively thin sand vaneer compared to Galveston Island. Indeed, there is compelling geological evidence that Bolivar Peninsula was devastated by a powerful storm approximately 600 years ago that destroyed the seaward part of the barrier.

I could go on, but the point here is not to say “I told you so”, it is to demonstrate that it is possible to predict, to some degree at least, storm impact using good science. The question is, will we now continue down a path of denial concerning the potential (inevitable) changes along our coast or will we begin to take a more creative, scientific approach to sustaining the coast for future generations to enjoy.

We can only hope that policy makers will now begin to listen to the scientific community in planning for sustainable development of our coast. While hurricanes raise the greatest public attention to the vulnerability of the coast to change, we must also focus on those changes that are occurring more slowly, over decades. But, these changes are just as real as are those caused by severe storms, and their impacts are just as devastating. We treat the severe traumas but ignore the cancer. Fortunately, the longer term changes are scientifically more predictable than those of hurricanes.

After the Great Storm of 1900 we looked back and asked, “Couldn’t they see it coming?”. Why didn’t they head the warnings? I fear that by the end of this century our grandchildren and great grand children, who will be faced with restoring coastal damage caused by decades of neglect, will be asking themselves “Couldn’t they see it coming?” Did they really think they could reverse the forces of nature?.

 

John Anderson

Maurice Ewing Professor of Oceanography
Department of Earth Sciences
Rice University
Houston, Texas 77251-1892