OP-ED: Ancient Engineering, Climate and Navigation along Rivers
Written by Harry Valentine
David Bernoulli (1700 – 1782) is recognized as the “father of modern hydraulics”. He developed mathematical equations that pertain to hydraulics that are used at the present day, including in maritime engineering. However, over 1,000-years before the birth of Bernoulli, the engineers of the Mayan Empire had developed significant breakthroughs in the field of hydraulic engineering that have withstood the test of time. They built special tunnels of steadily decreasing cross-section, to divert water from rivers into reservoirs located at higher elevation, right under the Mayan compounds.
They also learned to control flooding at the lower elevations, by building rock dams at regular intervals at higher elevations along tributaries of those rivers. Evidence of their feats of hydraulic engineering still exists across parts of Central and South America. There may be scope at the present day to re-introduce some ancient Mayan engineering techniques to assist in maritime navigation along several navigable rivers around the world. Changing weather patterns have caused drought in some regions and reduced river navigation depth, while excess rainfall in other regions has raised water levels and literally flooded dock areas.
The Modern Era:
There is scope to apply the Mayan rock dam precedent to partly alleviate river navigation problems caused by erratic weather patterns. One modern technology involves a large inflatable tube that may be secured to a riverbed and pumped with water, to reduce the cross sectional area of a river at a given location. That reduction in cross sectional area will result in less water volume flowing at higher velocity over the restriction as water begins to “back-up” upstream of the dam and increasing navigation depth.
Under excess rain conditions in highland watershed areas, the installation of modern versions of rock dams along river tributaries would cause navigation depth to increase at higher elevations. A series of such dams prevented the Mayan farmlands from being flooded long ago. In the modern era, that approach can reduce flooding of dock areas at river ports at downstream locations. At other locations and during drought conditions, the increase in navigation depth may occur further downstream, including near the mouth of a river.
The Mayan rock dam approach may be used near the mouths of rivers where upstream drought periodically reduces navigation depth far downstream. Under such conditions, ship companies have to partially unload freight to increase draft to reach an inland port, transferring part of the payload at considerable expense to other watercraft or to the railways. Depending on ship traffic volume and the amount of tonnage and containers they carry, there may be scope to use Mayan engineering techniques to increase river navigation depth near the river mouth.
A series of adjustable dams located upstream of the mouth of a river would reduce the volume flow rate of water into the ocean. Water would “dam-up” behind each dam and increase navigation depth, including to an inland port. The dam technology may take many forms. It may include building navigation locks at regular intervals along relatively narrow waterways. The locks may include water saving technology such as side reservoirs along with water turbines that drive water pumps.
Such technology would use part of the water stream that flows downriver, to pump a small volume of water upstream of the active lock or into the active lock. While such technology can reduce water usage by some 66% to transit a pair of ships sailing in opposite directions, there is also the option to use grid electric power to pump water uphill at regular intervals to assure sufficient navigation draft. Such an option may be considered along relatively narrow waterways. In such applications, ship propellers may duplicate as mega-size water pumps that may assure navigation depth upstream.
Submerged Locks and Dams.
Many navigable rivers widen on approach to the river mouth. The width and depth of the channel allows for the implementation of numerous options to reduce water volume flow rate. On a wide river, the use of buoys may demarcate the navigation channel while an underwater ridge of rock or a series of inflatable tubes may be secured to the riverbed, transverse to the river flow between the navigation channel and the nearest riverbank. The reduction in cross sectional area would occur outside of the navigation channel.
A pair of ridges of rock may be installed on the riverbed, parallel to and along the outer boundary of the navigation channel. In heavy traffic areas that involve parallel navigation channels designated for upstream and downstream traffic, a third parallel ridge would separate the channels over the distance of several ship lengths. The installation of inflatable tube technology at both ends of each navigation channel would assist in reducing water volume flow rate.
As a ship approaches the section of channel between the ridges, water would be pumped from a tube to allow the ship passage then re-inflate with water after the ship has passed. The extended length of the submerged locks and the coordinated deflating and inflating of the water tubes/bags would allow ships to sail through the submerged locks at steady speed. A series of such locks may be installed along several rivers around the world, to assure sufficient navigation draft for ships and barges that sail the inland waterways.
The hydraulic techniques developed by the engineers of the Mayan empire may have application in modern inland waterway transportation. Their techniques could manage downstream water depth during periods of excess rainfall over the upstream watershed areas, as well as manage downstream water depth during periods of drought. Over the period of the same year, some rivers will experience flooding during one season and drought during another season.
Over several centuries, the Mayan hydraulic approach reduced downstream flooding while heavy rains fell over the upland areas. There is scope to modify and refine the Mayan approach during the modern era and adapt their technology to assure sufficient navigation depth along waterways during rainy and dry seasons. There are also numerous variations as to how modern engineers may modify the Mayan approach of reducing water volume flow rate along a river, for the purpose of assuring sufficient navigation for inland ship traffic.
Harry Valentine can be reached at firstname.lastname@example.org for comment.