Hidden Engineering: The Design Secrets of Ancient Empires

The majestic terraces of Machu Picchu are world-renowned. Built around 1450 AD, they remain remarkably well preserved and draw 1.5 million visitors every year. But this incredible monument to ancient genius and engineering would not exist without the lesser known subsurface design. In the world around us, from ancient to modern, the secrets that lead to longevity are often hidden from view. 

Water is a force of life and a force of change that every civilization in the history of the world has had to deal with. My work as a licensed professional water engineer includes predicting and controlling flooding. (Yes, flooding happens even in drought-stricken Utah).  Erosion control is an important part of my work and the basis of why many ancient sites still survive today. Ancient engineers understood the world they lived in and innovated in powerful ways to survive in harmony with the elements.

To understand the importance of these innovations it’s important to understand some basic hydrology principles. When it rains, water that doesn’t seep into the ground pools up and eventually runs off. The more we change a surface, such as covering a field with a parking lot, the more we force water to run off instead of soaking into the ground. A lot of rain, especially in a short time, on a sloped or impervious surface can lead to a lot of runoff flowing at high speeds - the recipe for erosion and flooding. The goal of stormwater infrastructure is to safely collect that runoff in gutters which flow to pipes which then flow to something designed to collect the water, like rivers, detention ponds, or stormwater tanks. 

The recent flooding in Yellowstone shows how impactful the force of water can be. In the space of a weekend, raging flood waters washed out highways, tore buildings from foundations, and inundated towns. And while engineering cannot feasibly design to anomalous storms (most storm design is to the 100-yr, 50-yr, or 10-yr storm) good design practices can improve the probability of long lasting design. 

Flooding between June 10-13, 2022 in Yellowstone let to historic flooding and destruction. Here the northeast entrance road was completed washed out. Photo by Jacob W. Frank and National Parks Service.

The ancient Incan civilization carefully planned and built Machu Picchu nearly 600 years ago, and yet according to Ken Wright, a civil engineer and expert researcher of Machu Picchu, “The Inca were better urban drainage engineers than we are at the present time, because they planned ahead.” (NOVA 2009) He estimates that 50-60 percent of the engineering effort is underground. 

The terraces on the  steep slopes help prevent erosion by slowing runoff velocities, but a major key to their continued survival is the subsurface layers of rock chips and stones, gravel, and sand in the terraces. Such materials allowed for the passage of water that was then collected and turned into fountains on lower terraces. Foregoing terraces would have allowed rainfall to collect and pull off the topsoil, eroding the arable land. Overlooking the subsurface drainage would have made the terraces unstable and liable to collapse.

Machu Picchu has withstood centuries thanks to carefully planned engineering. Ken Wright estimates 50-60 percent of the engineering effort was spent on what is now underground. Photo courtesy of wikimedia commons.

A civilization that by all evidence did not have a “written language, use of the wheel, or availability of iron or steel” (Wright 2013) managed to preplan and engineer one of the most incredible sites known to humankind. Wright’s research at Machu Picchu highlights the careful preparation and technical planning used at each construction site.

This kind of foresight isn’t limited to the Incas. There is evidence of ancient stormwater engineering in most early civilizations, from Ancestral Puebloans to Imperial China. Canals, reservoirs, dams, drainage pipes and channels, culverts, bridges, diversion structures, and water gates are not new inventions. We pull from the wisdom of the past when we design for the future. 

Petra was built by the Nabateans in 312 BC. A walk down the “Siq”, the narrow canyon, opens dramatically in front of the “Treasury”. Photo courtesy of wikimedia commons.

The Nabatean civilization is one of my favorite examples of this. Those who have seen the Indiana Jones and the Last Crusade movie will be disappointed to know that at the end of the “Siq” canyon, located in Petra, Jordan, there is not in fact an old knight guarding a collection of various goblets nor a treasure vault. However, those with a nerdier engineering persuasion can find a treasure of an entirely different sort. 

Note the water channels on both sides of the path through the Siq. These are human-made, not a natural accident. Photo courtesy of wikimedia commons.

The steep canyon walls of the Siq are reminiscent of a Moab slot canyon, except with traces of an ancient civilization carved into the walls. In approximately the 4th century BC, Nabateans carved channels into the stone walls of the canyons, which carried water from flash storms in the mountains to reservoirs and cisterns - the ancient version of buried water tanks. At first sight, these aqueducts are not particularly notable compared to the intricate wall art or the chiseled architecture of the mausoleum, but they were the key to building a thriving kingdom in the unforgiving desert. The stormwater they preserved would sustain the community through the dry summer months. Perhaps the most telling sign of Nabatean brilliance is that some of their water systems have been updated and are still in use today. (Ortloff 2014)

(The Nabateans were also perhaps the earliest to use an ancient form of concrete to create hidden cisterns along their trading routes in the deserts between what is now Syria and Jordan in 6500 BC. This technology later made its way through Egypt and then to Rome.) 

Pont du Gard, pictured here, is one of the most recognizable works of Roman water engineering. The highest tier carried water from natural springs to the city of Nemausus (Nîmes). Photo courtesy of wikimedia commons.

I can’t make it through this article without at least a mention of Ancient Roman engineering. The Roman aqueducts, for example, captured even ancient awe. Geographer Strabo (c. 64 BC to 24 AD) wrote “so plentiful is the supply of water from the aqueducts, that rivers may be said to flow through the city and the sewers, and almost every house is furnished with water‐pipes and copious fountains” (Deming 2020). 

Roads were also arguably the keystone of the Roman empire, allowing expansion, travel, and trade. Romans didn’t invent the road but they mastered the art. Some roads such as Curates street (estimated built 2nd century BC) in Ephesus, Turkey were built with marble on top of well-developed piped storm sewers. 

The Curetes road at Ephesus, Turkey, is an example of a well-engineered Roman road. Photo courtesy of wikimedia commons.

Roads that didn’t have a piped storm system still used layers of materials under the road that provided stability and drainage. The roads were “crowned” or raised in the middle to shed water to either side, much as we still do today, and water was collected in ditches or pipes on the edges, similar to our modern curb and gutter design (Cartwright 2014). The first major Roman road, the Appian Way (312 BC) still survives in part today, and some modern European highways are built in the footprint of ancient Roman roads.

Started in 312 BC, Appia longarum... regina viarum ("the Appian Way, the queen of the long roads”) stretched from Brindisi to Rome. Photo courtesy of NASA.

The examples could go on. The ability to provide water where it is needed and keep it from where it will cause damage is foundational knowledge of every civilization from ancient to today. The ingenuity of ancient people never ceases to capture my attention, respect, and curiosity. 

Drainage channels and terra cotta pipes distributing stormwater were built by the ancient Minoans before 1100 BC and can still be seen today. Newly excavated sites in the Yangtze River Delta in China reveal a massive network of waterworks that not only controlled flooding but delivered irrigation - built nearly 5000 years ago. Qanats, or water tunnels, delivered water throughout Ancient Persia, with some still flowing today.

Flooded section of the Firaun Qanat. Photo by Pafnutius.

Many of the aspects of modern water engineering are not as immediately obvious as those of the past - most of the networks used are buried beneath your feet or take the form of unassuming culverts (those round pipes under roads) or the stone (riprap) under a bridge. But the benefit of these often invisible structures is infrastructure protection, when correctly designed, and long life of design and civilization. 

Often these design elements are not obvious to the eye. Provo residents know Kiwanis Park well for its  soccer fields and mountain views. Are you aware it also acts as an emergency retention pond? In high flows, water can backflow into the basin created by the soccer fields. This allows water to pool in a safe place and not cause property damage or loss of life. Many parks and green spaces are used for this purpose. Next time you’re at a park, look for some of the telltale signs that the greenspace is part of a flood design. Is there a water outlet pipe or structure? Is there a border around the field of little grass hills (swales)? Your local park or even parking lot green space might be serving double duty to keep your home and roads a little safer from floods. 

Kiwanis Park in Provo Utah helps with flooding and water management. Photo by author.

I know most of those reading this will never go on to become water engineers or design a culvert. While I hope I’ve made you a little more appreciative of the history and necessity of water engineering, my deeper purpose is to give you an appreciation for the unglamorous details. Don’t be ashamed of building something that no one might see. Take pride in creating the unglamorous as well as the awe inspiring. Every career has an aspect that isn’t the star of the show or the most interesting conversation at parties. Even in our daily lives, small habits and tasks build the bigger moments. There is incredible value in building infrastructure, metaphorical or literal, even if it never wins awards or acclaim. It is, after all, the unseen foundations of design that allowed ancient engineering marvels and modern civilizations to flourish. When we get the foundation right, we endure. 

References

Cartwright, Mark. 2014. "Roman Roads." World History Encyclopedia. https://www.worldhistory.org/article/758/roman-roads/.

Deming, David. 2020. "The Aqueducts and Water Supply of Ancient Rome." Ground Water, November 152-161. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7004096/.

Mays, Larry W. n.d. Ancient Water Technologies. https://ancientwatertechnologies.com/.

NOVA. 2009. "Ancient Worlds: A Marvel of Inca Engineering." PBS WGBH Educational Foundation. https://www.pbs.org/wgbh/nova/article/wright-inca-engineering/.

Ortloff, Charles R. 2014. "Water engineering at Petra (Jordan): recreating the decision process underlying hydraulic engineering of the Wadi Mataha pipeline system." Journal of Archaeological Science 91-97. https://www.sciencedirect.com/science/article/abs/pii/S0305440314000235.

Wright, Kenneth R. 2013. "Inca Foundations, Site Preparation, and Drainage at Machu Picchu." Practice Periodical on Structural Design and Construction, May.