Alabama Archaeology at Risk:
A Review of the Applications and Potential for the Mitigation of
Alabama’s Coastal Archaeological Sites
Rising tides and climate change are constant topics of debate as we are facing increasing temperatures and the degradation of many natural resources. The extent of which varies all throughout the planet, but it is clear that the frequency and intensity to which we experience storms and natural processes has grown in startling rates. Hurricanes are more frequently plowing over the Caribbean, Atlantic, and Gulf and floods, once thought to only be temporary, are now becoming permanent fixations to our modern environments. While researchers work to mitigating the immediate and long-term effects of these storm systems for different communities, heritage management is increasingly finding itself with more work. When we think of archaeology, it is not difficult to envision these sprawling sites such as St. Augustine and Jamestown, but we often forget that archaeology embodies much more. What happens when the floods come close, or the shoreline erodes? Sites are erased or fall underwater, leaving the amount of information we can derive incredibly limited or nonexistent. In southern Alabama, we have heritage sites spanning the entirety of Indigenous and American history. Could these sites be facing a greater risk for preservation than ever before? In this paper, I will demonstrate that the archaeological record of Alabama’s coast is at risk of destruction by hurricanes and flooding and can be ameliorated by applying modern practices in remote sensing.
Remote sensing is merely a different way of viewing the world and provides a new way to understand the processes that shape it in a grander scale. Different agencies and researchers are adopting remote sensing to aid in disaster management, agriculture, and archaeology. It is an all-encompassing process that allows one to peel beneath the layers of clouds and ground cover to find new ways to document resources. Using both the Digital Index of North American Archaeology, which uses state site files, Alabama has a total of 27,583 archaeological sites, 463 of which are in Mobile County, and 530 of which are in Baldwin County (Digital Index of North American Archaeology, 2018). Furthermore, the archaeologists who manage the DINAA have found that 3,964 archaeological sites in south Alabama are at risk of future sea level rise (Anderson et al 2017: 7). The number of sites on Alabama’s coast is not nearly as vast as other coastal areas, but it is known that the region is pivotal in understanding several aspects of indigenous, colonial, and industrial American history. Both Baldwin and Mobile counties make up 3,671 mi2 of land, which means that for every 0.27 mi2 of land, there is an archaeological site that needs protection.
Bayous filling the low-lying coast have always provided resources and refuge for Alabama’s inhabitants, from the indigenous to the industrial, but could these places, now being home to more than 600,000 people between Mobile and Baldwin counties be poised to disappear from coastal erosion? Satellite imagery available through Google Earth and NASA’s EOSDIS provide a several-decade glimpse at coastal conditions in the counties of Mobile and Baldwin (see Figure 1). Along the coastal shore, estuaries and inner rivers of the two southern counties, preservation takes a tool for they are experiencing these similar elevated issues. Clear indicators of flooding are prevalent throughout several communities in the immediate vicinity of the rivers. Sites, sometimes now situated in residential areas, are at the front lines of major destruction, with the only traces left now fallen to the floods (see Figure 2). For the greater Southeast, similar issues are occurring with news station reporting on dugout canoes coming unearthed from lakebeds (Daley 2017). As archaeologists and the stewards of heritage management are becoming increasingly aware of the issues facing the protection of sites as disasters strike, they are increasingly going to incorporate technologies that can assist at a greater length, potentially even technologies like remote sensing.
Technological Overview
Modern technologies have allowed archaeologists to fully uncover the past to a greater degree using a variety of different methods of remote sensing including (but not limited to): LiDAR, Hyperspectral Aerial Photography, and more. Additionally, remote sensing technologies have become a standard in modern disaster mitigation and aid in tracking many different aspects of disasters effects. Historically, these technologies stem from when Allied Forces in World War II began using offset photographs of major areas of interest with stereo photo pairs to enhance intelligence gathering activities (Harder & Brown 2017: 117). While aerial photographs were not uncommon at that time, the way in which they were taken and used was what would influence the development of technology in that direction. Little did the first users know, they would later influence the inception of remote sensing technologies used throughout the sciences.
A key factor that allows for the observation of multiple sites simultaneously is the adoption of these new widespread technologies with Google Earth, ArcGIS, and more. Remote sensing, which will be further elaborated on later, allows for the direct observation of archaeological features based off of satellite imagery. If you are using both historical maps and recent satellite imagery, one can illuminate landscape change with a long-term comparison (Stewart 2001: 361). This can show many things such as a change in the availability of water features, the encroachment of the rising tides to the coastline, and even changes in urban development. Different methods can be applied with remote sensing, but all in all, it allows for a greater interpretation of archaeological sites.
Remote sensing allows to fully understand the various dynamics of geographic regions and features that inhabitants would have had to adapt to. This can include anything like the susceptibility to flooding, drought, hurricanes, and tornados. The larger landscape in remote sensing also can yield important information for settlement patterns. One of these ways we look for potential features is by surveying the area of interest. Ancient remains have distinctive spectral signatures left throughout the landscape, and after surveying one would need to look at different methods of image enhancement to find the best fit (Parcak 2009: 84). Remote sensing in archaeology can help pinpoint many features, but each landscape requires a different set of tools. Modern remote sensing work in the Americas has been known to include anything from ground-penetrating radar (GPR) surveys, such as the one at the Mississippian site of Lake Jackson at Tallahassee, FL, to Light Detection and Ranging (LiDAR) surveys, now commonly seen in Central America (Seinfeld, Bigman, Stauffer, & Nowak 2015: 1) (Kvamme 2017: 222). Combining a multitude of different methods, both off the ground and on the ground and different layers of image enhancements can help illuminate different aspects of intrasite organization. It is becoming more widely available and accepted for use and suggest that future archaeological work is going to increasingly use remote sensing techniques to aid in excavation and monitoring.
Imaging additionally provides a greater opportunity for disaster resources and planning committees as they look for new ways to save our communities. With the abundance of satellites facing earth, we have started to cultivate new ways in how we manage our environments. Remote sensing has always been of interest to NASA, as they have recently highlighted some of their new innovations with the technology. Forest fires stirred up from dry weather conditions grow at exponential rates, but remote sensing from unmanned aircraft is helping pinpoint weak spots for effective incident management (National Aeronautics and Space Administration, 2018: 29). Not only does this add to the variety of potential remote sensing technologies, but it also adds to how we envision different aspects of our environment.
Undoubtedly remote sensing can provide profound applications for how we perceive disasters as they happen. Recent hurricanes have acted as catalysts for the communities they have hit. The United States Geological Survey and National Aeronautics and Space Administration acquired stunning imagery from the Landsat 8 satellite before and after Hurricane Florence showing the dissolved organic matter being discharged from waterways in Cape Lookout in North Carolina (Patel & Carlowicz 2018). Additional images from an adjacent area and before and after the same storm also show major swelling in the water systems. These images provide somewhat haunting illustrations of the sheer power of these high magnitude storms. Earlier images from the Landsat 8 satellite at those sources show full drainage systems forming in areas where the most water seen is usually that of a small stream.
For cultural resources management, the sheer amount of work to be done can be quite daunting, especially if one tries to act quickly. In disaster management, you have a similar situation, but with many more variables to consider. Many different organizations are attempting to figure out how to best mitigate any loss, and due to the sheer size of affected areas in hurricane events, Tomnod created a crowdsourcing platform to help pinpoint areas in need. As Hurricane Maria tore through the Caribbean, it had scarred the island of Puerto Rico leaving rubble thrown across the landscape, and satellite imaging companies worked together to open a crowdsourced platform to help map where debris is an attempt to better pinpoint areas in need (Tomnod 2018). With crowdsourced archaeological projects such as GlobalXplorer, there is a clear advancement in the potential for making observations off of satellite images. If known sites are facing risks, imagine what we will lose without the pinpointing of additional sites.
Regional Overview
Changing climates is one of the largest contributors to the increasing frequency of high-intensity hurricanes and severe storms. While it may not be a mystery to anyone in the southeastern United States that we have been battered year after year of some of the strongest storms on record, the extent of effects varies, especially for the Alabama coast. Researchers have pointed out though that the known hurricane record for the Alabama coast is too short chronologically to estimate the recurrence of the most destructive hurricanes (Liu & Fearn 1993: 793). Hurricanes do not hit the Delta frequently like other areas of the Gulf coast though (Figure 3). Additionally, Hurricanes are not the only processes that can cause damage to archaeological sites. Flash Floods pose a threat, but despite the fact that they stem from thunderstorms, their slow-moving nature can allow a river to exceed its capacity for infiltration and generate high amounts of runoff and discharge (Alexander 2001: 129). These processes are common in the Gulf Coast. Many areas are filled with low lying bayous and rivers for which archaeological sites are located, meaning they are positioned in areas that make them susceptible to damage
Within the two coastal counties of Mobile and Baldwin, they include a diverse array of water systems aside from the Bayous. Mobile Bay is characterized as a low energy sector in the Gulf, with sediment discharge coming from several rivers into an estuarine Delta (Holmes & Trickey 1974: 122). Raging waters exit the Delta seasonally at the end of winter/beginning of spring. This annual flood bottlenecks around the tall bluffs that keep the flood from engulfing the Delta completely (Morgan 2003: 90). Flooding happens frequently in the region. Some of the areas earliest European explorers had even made note of what the landscape looked like as they began to explore the river systems in the early 1700s. Iberville’s brother, Le Moyne de Bienville had observed several sites that were abandoned from war, that were now flooded by six inches in high water – additionally he noted that most settlements were on islands and mostly dense for thirteen leagues (leagues referring to an antiquated unit a measurement, measuring distance with one league equaling one hour) (McWilliams 1991: 168). Flooding is common to the area all throughout its history, causing people to continuously adapt as they built and rebuilt their homes in areas that soon would become underwater.
Understanding the frequency of hurricane and flooding events are important for understanding the dynamics of geomorphology. Using tidal overwash in Lake Shelby’s sediment, researchers theorized that those layers of sediment can assist in creating a strike and intensity chronology for hurricanes (Liu & Fearn 1993: 794). For many parts of the region, the landscape seems stabilized aside from the greater intensity of floods that have battered sites in the Delta for the past decade (Figure 2). These floods are not too uncommon though. For the past 300 years in the Delta, it was known to annually flood, because of its low-lying environment being roughly 10 ft above mean sea level, with tidal fluctuations of 2 ft (Holmes & Trickey 1974: 122). This doesn’t make the land seem as if it is at too much risk, but surges can easily rise and create floods into different regions that could last for several days. With the area being highly susceptible to floods, even based on its previous history, it is easy to imagine that a great deal is at risk of destruction.
The Mobile-Tensaw Delta offers an interesting look at these processes too. With sites important for understanding the evolution of human activity in the area like Bottle Creek, several Forts, and high density of mounds and middens spread throughout the Delta island, we could have a very different understanding of the geomorphology of the land. Numerous Delta islands exist in the Mobile Bay region and are annually flooded from February to April (Knight, Jr. 1984: 204). In a most basic sense, these low-lying areas in proximity to the river or estuarine systems are becoming floodplains as temperatures continue to rise. With areas like this, we see spillage in excess of channel capacity will enter the floodplains, which are periodically inundated with water. The excess water will move and level deposits of clay, sand, and silt (Alexander 2001: 121). Generally speaking, floods are predicted in ten, fifty, and one-hundred-year intervals, with the latter two usually being considered catastrophic and the ten-year floods being labeled as moderate and able to occur several years in a row (Christopherson 2003: 365). Annual floods like the ones we see in the Mobile-Tensaw are common to most deltaic regions, but the extent to which it will flood varies. If we continue to see long-term floods like that of Bryant’s landing in figure 2, other local archaeological sites will soon fall underwater and become eroded over time based off of river deposition and transport (as mentioned earlier, Mobile and Baldwin counties together have 993 archaeological sites on the known state file listed by the DINAA).
These flooding and erosion processes are also commonplace and present an elevated risk during storm surges from hurricanes. On top of intense winds blowing over structures, floods hit as waves and inundate all they touch. Geological work on Alabama’s Gulf has shown that the typical radius of destruction in high-intensity hurricanes is 50 km, relative to the wind field surrounding the eye (Liu & Fearn 1993: 794-795). Liu & Fearn additionally hypothesized that there were deposition layers from the immediate beach found in Lake Shelby, showing that a hurricane had caused such destruction that it was changing how sediment had formed at that time. It was soon found that there were noticeable differences in the sand layers that confirm Liu and Fearn’s hypothesis – the layers resemble sand found only on the beach and most likely came from high-intensity (Cat. 3 and above) hurricane strikes (Liu & Fearn 1993: 794). With that knowledge they learned and recreated a history of hurricane strikes in the proximity of Gulf Shores, where several archaeological sites correlated to indigenous prehistory are found.
Many of those sites on the Gulf shore are that of mounds and middens made mostly of sand and mollusks. These anthropogenically built mounds are susceptible to the same damages of the regular beach too. Mound sites, such as the one at Graveline, MS, can generally retain a discernable shape; however, hurricanes, looting, and erosion play a role in expediting site destruction (with looting causing most of the damage) (Blitz & Downs 2015: 4). When we think about these sites and where they are located, we must also think about how these settlements would be formed because it was not as if they randomly chose places. The bluffs on the western and eastern shores of the Delta were flood protected, leading the inhabitants a safer area to settle (Knight, Jr. 1984: 204). The indigenous and later colonial inhabitants would make choices as to where these settlements went based off of what could provide the most safety for them. Generally, one would build settlements in areas that provide the greatest amounts of protection. But more modern processes in the past few hundred years have begun the show a different story.
Archaeologists continue to find more and more evidence of flooding, damage, and inundation at archaeological sites. Fuller notes that while examining the stratigraphy of an excavation unit in the more southern bayous of Mobile County, it was found that prior to construction there was a mixture of several yellowish and grayish sand layers with cultural materials indicating a redeposit through erosion and periodic flooding at the site (Fuller 2003: 35). This shows the extent to which remains are affected as their environmental redeposit them through flooding and erosion processes. In the stratigraphy of Andrews Place Shell Midden (1Mb1), clean beach sand served as the bottom layer; however, there was a layer of gray ‘muck’ that sealed two alligator skeletons was found in the central part of an excavation unit, representing the bed of an old bayou (Wimberly 1960: 38). Additionally, On the shoreline of the Dog River plantation, a brick-lined well was exposed by storm erosion in the spring of 1999 (Gums 2007: 4). Notes were made at Bottle Creek stating that it becomes inundated with water during peak flood season, covering nearly all except for Mound A (and occasionally Mound B) (Morgan 2003: 92). The current environmental dynamics of Mobile and Baldwin County are showing more than the archaeological sites in the known state files are becoming more at risk. Assuming Delta flood patterns mirror those recorded in the Iberville journals, and those mirror that of prehistory, one could suggest that the Delta could really only be uninhabitable during the peak of flood season (Morgan 2003: 95). As sites are facing risk and it is increasingly becoming reported in Cultural Resource Management reports, it requires some more long-term thinking. As progressive technologies become available and the understandings that of the dynamics between flooding and archaeological sites are furthered, what can we do to preserve our history?
Current Disaster Response in Heritage Management
Disaster mitigation in heritage management is still growing. Governmental resources are allotted to attempt to assist at a greater scale through programs like Federal Emergency Management Agency (FEMA) and National Oceanic and Atmospheric Association (NOAA) (Martinez, 2018) (National Oceanic and Atmospheric Association, 2017). The recent push to assess heritage resources in the wake of events is a new practice. In the past, with storms such as Hurricane Hugo, there was never any full-scale effort into research the effects the storm had on the documented and undocumented heritage sites (Dunnavant, Flewellen, Jones, Odewale, & White 2018: 159). Heritage resources are falling victim to major storms as historically there was no full understanding of how they are being affected. However, archaeologists realized the impact and the detriment to which sites experience and shifted their attention to how to fix this in areas susceptible to disaster. Around the 2010 Earthquake in Haiti, there was more of a full-scale effort to support preventative methodologies to be put in place and adapting the heritage laws to support sustainable heritage management policies (Dunnavant et al 2018: 159). As practices were evolving and archaeologists were attempting to find the best fit, it was not until Hurricane Sandy that exact systems were starting to be adopted.
When sites were continuously being battered by storms across the world, archaeologists increasingly were attempting to aid recovery of sites as they found themselves at odds with the destruction. Following Hurricane Sandy, a two-phase system was set in order to mitigate any future loss including (1) identifying, photographing, and mapping exposed features, and (2) surveying for NRHP eligibility (Dunnavant et al 2018: 160). Following the work done to mitigate loss on the During the Phase 1 reconnaissance from Hurricane Sandy, researchers made note that the exposed deposits could not always be reconnected to a particular site without extensive evaluation and comparison to the state record, therefore they had these sites labelled as Hurricane Damage Archaeological Deposits (HDADs) (Ives, McBride, & Waller 2018: 69). Phase II surveying post-Sandy was mainly focused on conducting surveys for eligibility for inclusion into NRHP through test pits in order to proceed with further evaluation (Ives et al 2018: 71). This model works well for getting to make sites known and for documenting damage extents following the strike of a hurricane. Additionally, this process put forward and adopted by others allows for there to be more efficient efforts in mitigating loss.
To ensure the efficiency of this method, archaeologists considered the limitations of team size and time when handling the amount of work that needs to be done. As they began their phase II surveys they analyzed shoreline erosion in order to make note of site loss and determine eligibility for the NRHP, while furthermore in their documents they made suggestions of further work using a site rank system that is directly tied to erosion-related loss (Ives et al 2018L 72-74). Using a site rank system, while discussed later, would further solidify the methods in which they use to assess damage and chose sites to further work on.
The increasing occurrence of these disasters continues to show archaeologists the importance and the scale of work that needs to be done. The archaeologists working on the damaged Danish West Indies site note that there is a greater need for preemptive measures, and by mapping these resources that are being found, they can further monitor, document, and assess any changes that are found on the sites (Dunnavant et al 2018: 168). These more recent methods served as a great foundation as further analyses were developed. Using the idea of a site rank system is beneficial because it allows to further determine which sites are more at risk and gives a better idea of what should be expected in disaster response for heritage management.
Vulnerability Modeling
Building upon these historical methods, archaeologists have also come to suggest the potential for a predictive analysis and assessment of site vulnerability. With the increasing awareness of the potential disaster that is faced with the archaeological record. For Vulnerability assessments, it is known that you have to differentiate between events, risks, and vulnerability. Further explaining that events do pose risks in terms of slope failures and storms, vulnerability determines sensitivity, and a threat poses a risk that could affect a site i.e. soil erosion (Daire et al 2012: 174). The variety in which sites experience changes related to natural disasters like hurricanes and floods is vast. Many different variables lead to many different outcomes; however, they do share similarities that can be further examined to understand and assess the damage.
As similar as events may be based off the diverse variable in natural processes, narrowing events to hurricanes and flooding or sea level rise can help begin to pinpoint the dynamics of a disaster to an archaeological site. A vulnerability is generally related to scale, regional variations, whereas threats depend on sensitivity, frequency, and the intensity (Daire et al 2012: 176). Daire’s team suggests a Vulnerability Evaluation form that uses the following criteria: Infrastructure, traffic, activity (Human), the distance between geographical hazards, biological hazards, weathering, resistance (remains), resistance (sediment), physical protection, and legal protection (Daire et al 2012: 177). Daire has additionally set up a form using the aforementioned variables that produces a number that sets up a vulnerability score, based off of their equation seen in figure 4 (for more see Daire et al 2012: 179). This uses a similar idea seen earlier with the multi-phase surveys post-hurricane Sandy; however, these uses more information that further envelops the various processes that can harm a site. Using this system is beneficial for assessing and creating models for site vulnerability to sea level rise and can be similarly applied to natural disasters.
Additional modelling for site vulnerability is generally based off of proximity to other natural resources. As researchers have put together an interactive database that uses the state site files for the southeast, the Digital Index of North American Archaeology (DINAA) was developed in part to having an interactive tool for state planning resources. Research has shown that because of known site proximity and projected sea level rise, Alabama will lose 3,964 archaeological sites and 283 NRHP sites assuming there is a sea level rise that affects the first 200 km off of the coast (Anderson et al 2017: 6-8). On an even larger scale, the coastal southeast in the DINAA shows that 19,676 archaeological sites will be submerged based off of current sea level rise rates for the end of the century. This issue doesn’t consider preventive measures to protect sites, but it clearly shows that coastal sites stand in great numbers in the southeast alone, and without even considering hurricanes and flooding, sites are already facing the potential for major loss.
Similar to this issue of site loss, there has been additional interest in addressing this issue of sea level rise by providing a model for site vulnerability on a regional scale in Australia. Researchers had come up with a model called the Coastal Site Sensitivity Index (CSSI) that analyzes sites in marine and coastal contexts using GIS-based practices of shoreline change before confirming through ground truthing (Knott, Szabo, Ridges, & Fullagar 2017: 81). The CSSI is built off of variables such as wave height, tidal range, the relative rise in sea level, slope, geology, geomorphology, shoreline exposure and the distance to the shoreline to create an equation that further ranks site vulnerability (Knott et al 2017: 82). Using this idea of ranking and assigning a value to vulnerability seems to continue to pop up in literature. Assigning these rates is good because it further allows to scale loss and determine what areas are at the most risk. These regional rates also can help pinpoint patterns to understand what kind of features are facing the most damage. This equation further allowed them to look into a major area of interest and find that moderate to high sensitivity site were located on quaternary sediment layers (Knott et al 2017: 90). Interestingly enough they began to notice that the sediments in certain contexts are facing a higher rate of vulnerability. It is understood that different sediments are more or less susceptible to these damages, but this illustrates that despite the overarching problem, these issues are all occurring at different rates based on different aspects like structural integrity and sedimentology.
Some methods of remote sensing have been adopted more strictly into field methods for disaster management based on this idea of vulnerability modelling. Using previous methods of groundwater and sea level rise modeling, 1m resolution LiDAR models with .15-m vertical accuracy, and regional specific information, Johnson and their crew were able to create sea level rise scenarios at .5 m intervals to determine the area’s most susceptible to loss (Johnson, Marrack, & Dolan 2015: 241). Granted, LiDAR information is generally expensive as are other remote sensing methods, building digital models to understand the intervals of change to sites is interesting, especially when considering some of the previous methods of vulnerability scores. Following an analysis of the 2011 impacts of a tsunami in their study area, they were additionally able to further determine the exact types of effects they would be facing from rising waters, including damage to structural integrity, sand deposit displacement, and erosion and exposure of unknown cultural deposits (Johnson et al 2015: 242). This in its essence is similar to the vulnerability scores mentioned before, except provides a more visual model for understanding the potential effects on a precise scale. Using these maps and LiDAR information to map these features provides a unique way in which to understand what features can be expected to be damaged and what areas warrant more archaeological work.
Predictive modeling in Erosion rates
While somewhat similar, vulnerability modeling considers more so the forces acting strictly on land as well as the impacts that specific sites will face. Additional methods use the same general concepts, but more so analyzes changes in shoreline as an active force of change when natural processes take place. To model vulnerability to archaeological sites via shoreline change, researchers in the Canadian Arctic found that shoreline erosion was the most immediate cause of loss in archaeological materials (O’Rourke 2017: 1). Methods like O’Rourke’s use the same concepts in remote sensing but focus more so on historical imagery. To get a better understanding of the changes found on the coast, O’Rourke had collected 150+ archival air photos and satellite images to analyze the coastal change rate and model the extent of historical shoreline change (O’Rourke 2017: 2). Historical Imagery has been collected since the Second World War, and the photos taken of different areas can truly illustrate the exact impacts of shoreline changes. It further solidifies the concept that is explained and also allows for geologists to build and learn a rate of change to which the shoreline faces.
Different geographic regions and processes have different types of changes that are faced, but the concepts are the same. To further model this erosion on the shoreline, O’Rourke had to georeferenced all of the imagery and determine the ‘wet-dry’ line that was more readily visible in the imagery to create a standard for referencing any changes (O’Rourke 2017: 3-4). Choosing this wet-dry line that was visible in the imagery provided the best point of reference for viewing the changes and building a reference point for where the sea was at different times. The shoreline in relation to the wet-dry line was what was being studied, and while also being a noticeable reference point, it was what was most susceptible, making it difficult to georeferenced to other imagery. Initially they looked into modelling the EPR (End Point Rate) provided by DSAS software; however, it was unable to effectively account for changes between erosion and deposition in the shoreline trend, therefore indicating that the LRR (Linear Regression Rate) as the most effective in modelling these changes (O’Rourke 2017: 4). The DSAS or Digital Shoreline Analysis System is hosted by the U.S. Geological Survey and gives tools to understand shoreline changes as a whole (United States Geological Survey 2017). In Figure 5, you will see that DSAS software uses historical imagery and builds off of transects in the georeferenced imagery to look at changes over time in different measurement locations. This tool and method of using an LRR provides valuable datasets that can inform city planners and archeologists to understand the way in which coastal historic and archaeological sites face risk.
To understand these different geological forces that cause these changes though, you must first understand the different processes common especially in the Northern Gulf of Mexico. Endogenic subsidence effects work deep in the earth’s crust through forces like faults, i.e. the fundamentals of geological processes; whereas, exogenic subsidence effects refer to the surface processes (Lewis 2000: 527). Now, with an understanding of these processes, one could further pinpoint the kind of evidence that is looked for in disaster management. Exogenic processes are the only kind of issues that would continuously affect an archaeological site in south Alabama. Lewis accounts for estimating the archaeological components of exogenic subsidence effects stating that models should include tidal inundation, dry-land site file information, and a comparison between sites to understand patterns in local site distribution (Lewis 2000: 527-528). It has also been suggested that erosion modeling must further consider different factors such as reef structure, which can erode at different rates than looser soil and landforms (Fitzpatrick, Kappers, & Kaye 2006: 254). But while these suggestions are great, they scratch the surface very little and rely more so on the data at sites that mostly don’t have excavations going on. Shoreline changes are a huge factor and hugely concerning in erosion modelling in a region.
At specific archaeological sites, erosion is a huge concern, but when researchers consider these larger changes to how the site looks, they might forget to consider the exact effect on an artifact and archaeological materials. To model and understand the rate of erosion to archaeological materials, Fitzpatrick and their team determined that data sources should be comprised of Photographs, sitemaps, and archaeological excavation units, where they can look are stratigraphic recording over the course of several years in their 5×5 grid system (Fitzpatrick et al 2006: 257). One trench provided a good example for them, as the determined that to best estimate loss, they must calculate loss by dividing totally weight of archaeological materials, by the weight of excavated soil as well as length of the site on the shore multiplied by average height of shore profile multiplied by estimated annual shoreline loss (Fitzpatrick et al 2006: 257-258). This method is really interesting for it shifts the focus to changes outside of the site based off of erosion to changes inside of the site. This method does allow some room for more remote methods, potentially using different layers that are used in hydrology. By doing so they can better pinpoint other sources of change in the site that may be at risk; however, this method is great in response to the years of changes that they analyzed.
Conclusion
As tides rise, and shorelines change, archaeological sites are posed to deal with natural processes that put them at risk. This study more so was to point out how hurricanes and floods pose risk because while they are natural, they are less predictable and pose large-scale changes in any environment, as seen in figure 6 with Hurricane Michael. Alabama has been fortunate compared to their contemporaries in the Gulf of Mexico, but while it seemingly may have a small amount of coast compared to others, it has an abundance of history that still needs to be fully explored. Archaeologists are increasingly coming to terms with the fast rates of change that are induced when the abrupt disasters strike, and they realize that preemptive measure are needed to fully understand the ongoing processes and the potential that might strike a site. As stewards of heritage, researchers must further adopt new methods using modern technologies like remote sensing to make further work efficient and proactive. While both vulnerability modelling and erosion modelling are similar in nature and in data collection, both provide some of the clearest pictures of changes that are faced as archaeological work progresses.