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Introduction to Texas Sinkholes
Sinkholes are a geologic feature that becomes hazardous when they occur in populated areas. They can be small enough to be nearly inconsequential, or grow to thousands of square feet swallowing entire buildings. They also can happen quickly, giving residents little time to evacuate to safety. When they happen on roads, they are a danger to traffic, primarily because they can happen without notice or warning. Sinkholes are created by a number of natural and man-made activities. In Texas, they tend to fall into one of these three categories:
- Salt-dome dissolution found mostly on the coastal plain
- Limestone and karstic ones in central Texas
- Bedded salt dissolution in west Texas
Since the dawn of oil-drilling technology, sinkholes have become more prevalent in western Texas due to land subsidence as under-ground oil reservoirs are emptied. Without this oil holding the overlying ground up, the likelihood of collapse becomes more of a danger. But not all sinkholes are due to oil extraction. Coal mining has been a factor in land-subsidence across the country. Groundwater use can also be a factor. Natural sinkholes are formed when water dissolves underlying layers of limestone or other water-soluble minerals (like salt domes). In addition, the lack of water can also cause these depressions as in the conditions created due to drought. When oil or coal extraction creates vacancies for water to seep in, limestone and salt dissolution can occur and create favorable conditions for sinkhole development.
Frequently a sinkhole will fill with water and become a pond. Other times, it will present itself simply as a depression in the ground. When a collapse does not occur, karst (commonly known as a cave) is formed. For this entry, we will be focusing on sinkholes.
The map below is a clip from the USGS webpage and shows the areas in Texas that are prone to sinkhole development given that other conditions are favorable. The underlying rock layers of evaporite rocks like salt, limestone, and gypsum make the possibility of sinkhole development possible. Adding factors caused by human activity can effectively exaggerate the danger in these areas.
Texas Sinkhole Data Research
Texas government sinkhole data is nearly non-existent at this time. This fact is reflected in several documents discovered in my research. I uncovered one dataset that showed sinkholes in the county of Val Verde which was published by the National Parks Service. This was the only publicly available data I came across in my search, but it provided a lot of detail in both point location and polygon outlines of the sinkhole features. One can only speculate why this is the only county that had this kind of data available.
I was fortunate enough to contact Dr. Jeffrey Paine of the University of Texas Bureau of Economic Geology, a university professor who is working on compiling a comprehensive database on sinkholes, karsts, and other near-surface speleological activity, but the timeline as to the availability of that data (which I was told will be made public) is undefined as of 8/2020.
As my search was coming up dry, I decided to branch out to areas that were not immediately obvious. Who would have an interest in sinkholes? Who does this kind of thing matter too? Insurance agencies might give me some leads on sinkhole data. I contacted close to a dozen and most of them came back dry. However, Ed Wise from The Wise Group, an insurance agency that covers businesses, personal, life, and professional liability did return my email with an interesting lead. The Texas Rail Road Commission (TRCC) maintains a dataset on abandoned coal mines.
Even though it is not exactly sinkhole locations, it would be valuable in defining what counties I should contact to see if there was any kind of sinkhole or land subsidence data available on the county level. Using ArcGIS, it was simple to highlight the counties with abandoned coal mines in them to see if there was any location data on land subsidence or sinkhole formation. From there, it was back to the internet to see if any of the counties had possibly a 311 database for reporting construction requests or emergency assistance calls (similar to the one that NYC has). 311 databases are incredibly useful in that they standardize all data that is relevant to the public interfacing with municipal agencies. Searching the database is a matter of a simple filter or query on a column. Many times, there will be codes for certain types of requests, but that translation is generally a matter of finding the data dictionary usually associated and easily accessible.
After contacting many of the GIS offices in these counties, I was getting feedback on looking at data sources I already had, or simply that the data did not exist (previously confirmed by my research and communications).
One interesting finding was that the abandoned coal mine layer appeared to intentionally avoid sinkhole-prone geology. Unscientific speculation would suggest that when these mines were created, reliable technology or methods for preventing collapses had not been developed yet so they avoided these areas. It would be reasonable to deduce that any sinkholes outside the displayed geology has a higher probability of being caused by mining activity.
The Texas Rail Road Commission not only had abandoned coal mine data, but also data on all of the oil wells in Texas. Since oil extraction is a known cause of land subsidence, this seemed like a great discovery. The data that the RRC has made available and extensive, indicating the level of activity of the oil sector in this state. Texas has long been associated with oil so this is not a surprise. What is surprising is the lack of data for the environmental impact this sector has had on the land. But even though the data for oil extraction was at hand, it still did not point to any kind of reliable source of sinkhole development.
Overlaying well data on top of SPG data, it is difficult to correlate a relationship between oil extraction activity and sinkhole development. However, there is much professional anecdotal evidence to be confident of a relation between the two activities. In order to proceed with a study that is scientifically and/or statistically viable, sinkhole location data must be acquired.
Sinkholes are a geologic feature caused by natural processes and/or human activity. According to the Federal Emergency Management Agency (FEMA):
“the number of human-induced sinkholes has doubled since 1930, insurance claims for damages as a result of sinkholes has increased 1,200 percent from 1987 to 1991, costing nearly $100 million.”
Obviously this has the effect of disrupting many sectors, not the least of which is real estate. In many states, sinkhole data is easily available by accessing university databases via a keyword search on google. I think the best hope for this data becoming available for Texas is through Dr. Jeffrey Paine of the University of Texas Bureau of Economic Geology. Of the numerous contacts I made, his is the only one that mentions the possibility of there being a comprehensive sinkhole database in the future. Many other attempts bore some interesting leads (like The Texas Speleological Survey (TSS), whose focus was more on “spelunking” and hiking/adventure trips), but none so far has provided the type of data that could be useful in the capacity of https://sinkholemaps.com/
I feel that further research into this state might uncover some leads and even some small datasets, but the time it would take to cover the entire state would not justify the investment. Perhaps a more focused approach to specific areas, potentially requested by users of the website, would be better. One avenue of research not explored is the use of LIDAR and digital elevation models (DEMs). This could provide some indications of sinkhole locations, but it would require a degree of machine-learning scripting and possibly field visits for confirmation. At this time this is beyond the scope of this website.