It was a fortuitous combination of timing, serendipity, and experience in forensic engineering that enabled the author’s recognition of the configuration of the ruined structures in the river and those on the Yaxchilan’s Grand Plaza. These events initiated the archaeo-engineering investigations for reconstructing Yaxchilan’s lifeline over the Usumacinta River. This was an ingenious feat of Maya technology that may prove to be their most creative engineering project. Their solution for the river crossing was the construction of a long-span suspension bridge—a structure that was destined to be recognized as the longest bridge in the ancient world.
Today, little remains of this unique achievement in civil engineering. However, by analyzing and recognizing clues scattered throughout archaeological records, combined with contemporary evidence generated by field surveys, aerial photography, remote sensing, and computer applications, the collected data was synthesized and used to develop topographic data and three-dimensional computer simulations that led to the virtual reconstruction of the bridge. Forensic engineering techniques were used to conceptualize the geometry of the bridge structure, identify the construction materials, and postulate engineering techniques used to construct the bridge, as well as determine the critical role the bridge played in the political and economic activities of the city-state of Yaxchilan.
Figure 10-4: Satellite map of omega in Usumacinta River at Yaxchilan. Courtesy of Google Earth.
Close Encounters With Maya Technology
In February 1989, I was part of an archaeological expedition traveling deep into the Usumacinta River basin lying between Mexico and Guatemala. Our goal was to traverse the Pasión and Usumacinta rivers in native cayucos. That portion of the rivers that could be navigated by boats, while Avon rafts were required traversing the section of rapids in the lower Usumacinta River. The itinerary included visits to Ceibal, Altar de Sacrificios, Yaxchilan, Piedras Negras, and Palenque. Our group was a mixed bag of Mayanists: an archaeologist, an artist, a London School of Economics professor, eco-tourists, a civil engineer, and our leader, who was a nurse, in addition to the river men who were the crew on the boats, cooked our meals, and watched our backs. The 10-day odyssey consisted of river travel, overnight camps on the river banks, and self-guided explorations at each of the sites.
We had jumped off at the river port of Sayaxché, Guatemala, located on the shores of the Pasión River. On the third day of travel, after visiting several sites, we were on the downriver segment of the trip, drawing close to our next destination, the ancient city of Yaxchilan. The brown, swirling waters of the Usumacinta swept past as we made our way downstream through the tropical wilderness. It was a scene out of a fantasy. We were surrounded by the dense rainforest. Spider monkeys were swinging from vines while toucans and macaws flitted through the towering tropical hardwoods. I was reclining in the bow of the 75-foot-long boat, anticipating my first glimpse of the ancient city of Yaxchilan. My forward position in the cayuco placed me in the shelter of the thatched roof of our native craft. This spot on the bow afforded relief from the searing tropical sun for me and my cold can of Gallo cervesa.
The afternoon sun was reflecting from the glimmering water, and the glare made it difficult to see even with the maximum UV protection on my sunglasses. The captain steered right as we entered the nearly 360-degree omega in the Usumacinta. “Look sharp,” said Tammy Ridnour, the leader of the outfitters of the expedition. “Yaxchilan is on the south bank.” The captain steered to port. My first glimpse of the unique riverine city was the tall palace structures located high on the green hills overlooking the river. As we prepared to land on the north river bank, I noted a large cylindrical ruin of worked stones rising 3 meters above the water on the left side of the river. The configuration of the ruins seemed familiar to me. I looked to the right and observed a similar but less-defined structure that aligned with the south ruins. “Hey!” I blurted out. “These ruins look like the structural piers for a bridge!”
“Impossible,” said a voice behind me. The archaeologist had spoken. “That is impossible. The Maya were a Stone Age culture, and they did not have the capabilities to build complex structures.” I turned and pointed to the tall structures on the hill and asked, “Then who built those buildings?” His response was “They are simple stone and mortar construction, typical of a Stone Age culture.” That ended the archaeological discussion. I was sure that a bridge had spanned this river, and I was determined to search for the answer.
The cayuco slid onto the edge of the river bank. The beach-like river bank extended inward for 10 meters then upward to a vertical bank rising 8 meters to the level of the Grand Plaza. It was time to disembark, unload our gear, climb the steep path to the top of the river bank, and set up camp. We pitched our tent, toured part of the site, and were then served an excellent dinner prepared by Jose, the capitano, and his crew. Bedtime always came early for me and Vernon Harris, my long-time friend and tentmate, and I zipped up our tent and we slipped off into dreams of Maya glories.
The next day I returned to the beach and observed the ruins on the south side of the river. Close observation confirmed my first-glance analysis. The cylindrical shaped structure was approximately 10 meters in diameter and was elevated 3 meters above the waterline (Figure 10-5). The ruin was constructed of worked stone. It was difficult to see much of the pier structure on the north side because of the high water level. I took photos of the south structure and sketched the ruin. I vowed to carry out further investigation relative to the nature and characteristics of this important pre-Columbian structure. To initiate the investigation and analysis of the structure, I would require a comprehensive review of the archaeological studies of the site, three-dimensional surveys of the bridge support structures, and topographical mapping of the site. After two days, our group surrendered our boats at Yaxchilan and boarded Avon rafts to traverse the river rapids down to Piedras Negras and then to Palenque.
Figure 10-5: Photo of bridge ruins in Usumacinta River in 1989. Author’s image.
Our new crew of riverboat men was a talented group of expatriate Americans. They included a college professor, once teaching at the University of the Yucatán, whose life had been set adrift by Hurricane Gilbert; a California surfer dude; and our experienced expedition leader, Tammy. I thought we were ready for anything—well, almost anything—until we were “captured” by Guatemala guerillas at Piedras Negras.
Piedras Negras is a magnificent Maya city down river from Yaxchilan. The site is located in Guatemala, and during the late 1980s, the site was a refuge for guerrillas fighting against the establishment. Piedras Negras is situated in some of the densest tropical rainforest in the Yucatán. The structures at the site had been consolidated by archaeologists, studied, and then left to the vagaries of the rainforest. The site did not have the advantage of live-in guardians provided by the government that are present at Mexican sites. In short, the site was unoccupied, or so we thought.
I did not notice the first guerrilla until he stepped out of the underbrush with his AK-47 at chest level. He did not have to speak, as I immediately stopped; he was silently joined by two more comrades armed with M-16s. My Spanish was very basic, and I felt we needed a diplomatic native speaker who also knew the territory. Enter Jim Dion, the down-on-his-luck college professor, who had been active with the rebel movement and assisting villages in developing potable water systems. Jim was familiar with the leaders of the movement; he had to be “the man.” I raised my right hand to the warriors while tuning and requesting Jim Dion to come forward. Jim stepped up and saved the day.
I could ramble on with a long dialogue of the encounter between the lambs and the guerrillas. The guerillas did not believe that we were archaeological tourists; they said we did not look like mild-mannered tourists and were convinced we were agents of the CIA. They were not, of course, happy with the CIA. Jim casually took a seat on a fallen log and chatted with the leader. The other two armed men stood vigilantly by his side. All three were hard-bitten vet
erans of the long war and were born killers. It sounds silly in retrospect, but white plastic caps were in place over the ends of their weapons. I had the fanciful illusion that we were safe unless they removed the caps. Jim charmed the leader with his excellent Spanish and intimate knowledge of their cause and its leaders. The conversation and Jim’s revelation as a friend of the cause was welcomed.
Matters lightened up, they apparently were glad to meet a sympathizer of their movement. They spoke of their fight for freedom and how they had won the war, but the army leaders would not grant amnesty. They lived there in the ruins of Piedras Negras, where the precious Maya ruins afforded protection from air force attacks. They asked us not to mention this encounter when we reached Guatemala City, or they would make trouble. If pressed, we were to say we had encountered the guardians of the orphans and widows. We parted ways in the ruins. They said they would keep watch on us overnight and decide our fate, and their instructions were to stay near our tents, which were set up on the shore of the river. Sundown came and we bedded down, taking turns standing watch during the night. We were nervous. Dawn broke with a torrential rainstorm and heavy fog. We quickly and silently packed up and slid our rafts into the water, not knowing what to expect from the line of rainforest trees. We launched our rafts downriver in the misty downpour, never looking back toward the guardians of the orphans and widows.
The archaeological tour was very enlightening, and on my return to Atlanta, the thought of the Maya bridge at Yaxchilan kept playing out in my mind. I was fascinated by the riddle of the “rocks.” I began to research archaeological studies that had taken place at the site. I knew that someone during those studies had left clues to the riddle. If so, the clues would be in plain sight. Archaeological research, analysis, and engineering hypotheses were carried out in my engineering firm during the period from 1989 to 1994, with several return visits to the city of Yaxchilan to gather site data, confirm alignment of structural components, and survey critical elements of the structure. My first priority was to develop graphical and analytical data relative to the site, including aerial photography and remote sensing. Furthermore, research into the archaeological records of studies of the site would provide an overview of the graphic history of the site and initiate the archaeo-engineering research.
History of the Yaxchilan Site
The city of Yaxchilan is situated along the banks of the Usumacinta River and was the power base of a city-state that included a vast domain located south of the river. The majority of the temples and palaces of the city were located on the terraced hillsides, as well on sites that bordered its Grand Plaza. Maya city planners developed the Grand Plaza along the banks of the river, and it served as the focus of daily activity of this rich and powerful city-state. This navigable river served as a transportation conduit for the city. The riverfront and the Grand Plaza was parallel to the river and was the focus of activity for river travel, land transport, political activities, commercial trading, and everyday domestic life.
The area around Yaxchilan receives one of the heaviest yearly rainfalls in the Yucatán Peninsula. During the rainy season this excessive precipitation promoted an abundance of agricultural products that contributed to the wealth of Yaxchilan but elevated the water of the Usumacinta to flood levels for as long as six months of the year.
Yaxchilan became one of the most powerful city-states during the Maya Classic Period. The warrior-king, Yat-Balam, founded the city in the fourth century AD. This powerful king and his descendants ruled Yaxchilan until its decline five centuries later. During their reign, they built gleaming temples atop the terraced hills and luxurious palaces along the Grand Plaza. Magnificent structures were constructed on massive terraces carved into the surrounding hills.
The steep hills and broad river provided a natural defensive barrier for the city. The river formed an omega-shaped meander encompassing the city on the west, east, and north, and the steep hills protected the narrow south side. These barriers created a natural fortress that protected the city from military invasion. The hills formed a palisade and the river formed a moat. However, in order to efficiently operate this city of 50,000 people, it was necessary to have an all-weather passage across the treacherous Usumacinta River to connect this vibrant urban place to their assets in the villages and hinterlands across the river (Figure 10-4).
Archaeological Data of Yaxchilan
Due to its remote access, the art and architecture of the site at Yaxchilan have suffered minimal looting, and a solid chronological and historical background has been established through studies and interpretations of hieroglyphic inscriptions. Research has indicated that the Maya carefully recorded the history of this city during a period of 500 years. Modern archaeologists have studied Yaxchilan for more than 130 years. Numerous photos, site maps, renderings, drawings, narrative observations of the site, the buildings, and hieroglyphic art are included in the corpus of archaeological studies, but these academic studies totally overlooked the need for the lost landmark of bridge engineering that was critical to the survival and success of this “island” city.
It was Alfred Maudslay who made the first archaeological visit to the site in 1882. He references the ruins of the stone and concrete bridge piers located in the river in Biologia Centrali-Americana. He writes that the “pile of stones” was situated in the river was used as a landmark for the site. This landmark ruin appears in a photograph, taken by Maudslay, and is located on his map of the site depicted in this publication. Maudslay apparently felt that the “pile of stones” had special significance to the site.
A review of the extensive archaeological studies for the site shows that most written texts reveal a piece of the puzzle that indicates the need for an all-weather bridge. However, archaeologists could not conceive that this “Stone Age” culture had created such an amazing engineering feat. Before archaeologists could be convinced that the bridge and the sophisticated technology required for its construction had once existed, they had to be convinced of the need for a long-span river crossing. Archaeo-engineering studies were needed to point out that, in order to survive and operate efficiently, the seat of power in Yaxchilan required a dependable and safe passageway to cross over the river. The swift water levels of the river rise to a height of more than 15 meters during the rainy season; therefore, a river crossing was mandatory to maintain the political and economic power of Yaxchilan.
Archaeo-Engineering Investigation of 1989 Field Data
In March 1989, during our initial visit to the ancient city of Yaxchilan, we first observed the ruins of the pier structures in the river (Figure 10-5). The position and configuration of the pier structures in the river supported evidence that a bridge had once connected the city of Yaxchilan with the north side of the river. This initial observation and the concept of a potential bridge structure created enthusiastic response from my engineering colleagues, but was met with negative responses from the archaeological community. Detailed surveys of the bridge piers were impossible during the initial site visit, because the necessary equipment was not available. The need to carry out a topographical survey and to locate additional structural elements related to the bridge was required for the analysis. Furthermore, observations of the flow characteristics of the river water indicated that the speed of the water on the outer curve was more rapid and forceful than the water movement in the inner curve, due to the action of centrifugal force. It was possible that other, more degraded elements of the bridge structure were secreted beneath the surface on the north side.
In order to establish the existence of bridge ruins below the water surface, aerial photography of the site would be commissioned to provide a comprehensive, high-angle overview of the plaza and the bridge ruins in the river. The aerial investigation was intended to establish and identify a spatial relationship between the visible structure and the submerged ruins of the bridge.
Aerial Photography of Yaxchilan
Low-level aerial survey flights were flown over the site in
March 1991. The Cessna 172 aircraft was flown by Canadian bush pilot Rick Muyres. Maya tool expert Philippe Klinefelter photographed the ruined structures in the river, as well as the structures on the site. The aerial survey effort was successful and my hypothesis of an additional submerged bridge pier structure was verified. The structure of the northern pier has suffered severely from the lateral forces generated by the fast-flowing water on the outside curve of the river. Waterborne debris was thrust against the northern pier by the swift centrifugal flow along the outside edge of the curve in the river. The impacts of large trees transported in the swiftly flowing water have imparted great damage to the northern bridge pier. The south bridge pier maintained a 3-meter height above the river water level. The slower water flow on the inside curve tended to reduce the damage to the south pier.
In the aerial photograph, it is seen that the majority of the masonry structure of the north pier has been degraded, and its stone block work is visible below the water surface arrayed in a spiral debris field extending downstream. The geometry of the remaining south pier and the foundation of the submerged north pier are clearly visible. The planar shape of the submerged north pier is similar in size and geometry to the south pier. This similarity in plan size and distance from the river bank reinforced the evidence of the existence two bridge piers. The Grand Plaza and its tall structures are clearly in view in the aerial photograph.
The 1993 Site Visit Survey of Bridge Components
The collected site data, aerial photography, satellite mosaics, and structural concept of the bridge configuration were assembled and integrated into the hypothesis. The critical data collected since the 1989 site visit were very promising. The aerial photos and site topographical surveys were digitized and resolved at the same scale. We developed a digital composite map of the area of the bridge including the plaza, the river, and the Guatemala side of the river. However, the geometry of the ruined piers had to be verified by field dimensions. Furthermore, a search for other bridge components had to be carried out on the ground. A second site exploration was launched to verify the digital information garnered from aerial photos and topographical maps and to physically carry out ground exploration for additional bridge components.
The Lost Secrets of Maya Technology Page 25