The Texas Gulf coast is among the most dynamic environments on Earth. Jeffrey Paine talks about the retreating coastline, and the risks and value of human activity there.
|Scooped by Michael Stuart|
What causes the Texas coastline to change?
It’s a combination of natural and human factors that’s led to what some scientists describe as a dramatic shoreline retreat on the Texas Gulf Coast.
Most of us assume that the environment that we’re in is going to be stable over time. But anyone whose been to a beach knows that the beach is a dynamic environment that changes from hour to hour and day to day with tidal cycles and wave energy and wind and storms and all of those features.
In a broader context, the shorelines along the Texas coast have been retreating for most of the last 20,000 years during the last glacial-interglacial cycle. The peak of the last glaciation was about 20,000 years ago. Sea level was approximately 100 to 120 meters lower than it is today and the shorelines were out near the edge of the continental shelf.
So we have global sea level rise, but we also have a contributing factor on the Texas coast, called subsidence, which is a natural compaction of unconsolidated sediments that are underneath us. Subsidence can be accelerated by removal of fluids – either ground water withdrawal or oil and gas production in areas where we have beaches. Land subsidence leads to what’s effectively a higher rate of relative sea level rise – that is, the rates sea level would rise relative to the local land surface can be higher than the globally averaged rates of sea-level rise.
Shoreline retreat is a threat to us only because we have built structures and are living on the coast in greater and greater numbers. If we weren’t there, there really would be no great threats to us from shoreline retreat. But once someone builds a home or a business on the low land along the Texas coast they are at risk from storm surge and from long-term shoreline retreat. There are many examples of homes that were built in an aesthetically desirable location on the first row landward of the beach.
Many of these homes were on the beach itself within years to decades as a result of shoreline retreat and erosion during storms. In Texas, the Open Beaches Act protects public access to the beach. So when structures get out on the beach then something needs to be done, because then they are restricting the public access to that beach.
If I were someone who were considering building a structure on the coast, and concerned about its long-term viability, I would look at some of the data sources that are out there for determining what the long-term rates of change are.
Some areas of the coast are relatively stable. Others are retreating at highly rapid rates, sometimes as much as 15 meters per year or more. So location is important. Port Aransas os Mustang Island is the best example of a stable-populated coastline area on the Texas coast.