Restoring and Preserving the Incan Cultural Wonder of Saqsaywaman

Lohr, Kenneth, Civil Engineering - School of Engineering and Applied Science, University of Virginia
Miksad, Richard, Department of Civil Engineering, University of Virginia

The study of Saqsaywaman started by looking at the collapsed terrace walls then expanded to the drainage basin that flow to the terrace walls, and finally expanded to the water flow over the entire site of Saqsaywaman. The topographical survey conducted at Saqsaywaman, Peru in July of 2013 reveals several key factors that affect the current wall collapse crisis. Over 4,000 survey points were collected using a total station. Those points were then used in order to create a three-dimensional model of the site of Saqsaywaman. This model was used to analyze the topography and runoff patterns on the site. The rational method was first used to estimate the water runoff for the site based off the 27 drainage basins and sub-basins. The runoff is estimated as a percentage of the total rainfall that lands on the site. Through a ground cover analysis the percentage of runoff to rainfall was found to be 37 percent. The maximum total runoff for a storm with a rainfall intensity of 0.2 meters per hour is 7500 cubic meters per hour.

Many of drainage ports at Saqsaywaman are not currently performing any hydraulic function because the water inlets are not located at ground level. Some of the inlets are buried while others are floating above the current ground surface. It is hypothesized, that all of the port inlets were once at ground level only there can serve any hydraulic purpose. The hydraulic flow rates of the ports have been analyzed and the average maximum volumetric flow rate for an average port is around 6500 cubic centimeters per second.

The current drainage channels recently constructed are not uniformly designed and have several problem areas that are over capacity during large rainstorms. This has caused large amount of water to overflow the channels in several locations, concentrating the damage to the walls. The other attempts to help fix the problem are at best preventative steps to help prevent further damage but all fail to correct the source of the problem.

The real source of the problem is the excessive amount of runoff and the northward flow. The amount of runoff has increased over the years due to ground cover changes as more impervious surfaces have been put in place. The current topography causes the water runoff to flow north towards the main terrace walls that were never designed to receive water runoff. This is causing the walls to collapse, taking with it the historical beauty of this cultural heritage site.

A new analysis, based off evidence of terraces above the walls at Saqsaywaman, shows that the flow patterns would change dramatically if the site was terraced. The flow patterns would direct all the water to the south, east, and west instead of to the north as seen with the current topography. There are some remnants of these terraces in the form of topographical clues, stone rubble piles, and old maps that suggest these terraces once existed.

Based on this study it is recommended that the drainage channels be upgraded to meet storm water runoff needs in order to prevent further damage to the site in the short term. In the long term, it is recommended that the topography of the site be returned to its original form which should help to alleviate water runoff problems.

MS (Master of Science)
Rational Method, Saqsaywaman, Surveying, Drainage Port
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