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Excavating an archaeological site reveals the past, but it also changes the landscape that has preserved it for centuries. Researchers from Istanbul Technical University and American partners have used computer models to show how archaeological excavation and soil erosion interact at the Resuloğlu mound in central Anatolia. Their study, published in the journal Geoderma Regional, sheds light on a long-standing dilemma in the discipline.
A site threatened by erosion before excavation
The Resuloğlu mound, in north-central Anatolia, holds a settlement dating from about 2300 to 2100 BCE, that is, the Early Bronze Age. Excavations took place there from 2003 to 2019.
The site posed a particular difficulty: erosion was already shaping the landscape long before modern interventions. It had even helped expose tombs, which weighed in the decision to excavate. Archaeologists therefore faced terrain that was already in motion.
When excavation reshapes the terrain
According to the study, excavation introduces new disturbances: it exposes archaeological structures, alters the shape and properties of slopes, and moves material. Spoil heaps are often deposited downslope, which can divert water flows and create new vulnerable areas.
This finding illustrates a central dilemma of archaeology: uncovering heritage can alter environmental conditions and threaten the future stability of the site.
Reconstructing the landscape before and after excavation
To measure these changes, the team combined historical aerial photographs, drone surveys, satellite images, soil and weather data, excavation archives and a detailed analysis of the relief. Aerial photos from 1990 were used to reconstruct the landscape before excavation, and drone images from 2019 the landscape after.
The researchers then used QGeoWEPP, an interface for QGIS of the WEPP (Water Erosion Prediction Project) model. Eight slopes were simulated, six disturbed by excavation and two undisturbed reference slopes, using twenty-four years of climate data, from 2000 to 2024. Unlike simpler models, this approach tracks the path of water and sediment slope by slope, which makes it possible to identify erosion hotspots.
Effects varying from slope to slope
When excavation removes the soil cover and exposes hard archaeological surfaces, comparable to a paved surface, water infiltrates less and runs off more. On a funerary slope, the modelled average annual runoff rises from 12.6 to 20.1 millimetres, and soil loss from 1.1 to 2.1 kilograms per square metre.
Conversely, depositing spoil can improve infiltration where the soil layer is thick, but loose, fine materials remain fragile on steep slopes without vegetation. On a settlement slope, average soil loss climbs from 1.1 to 4.9 kilograms per square metre. The effects therefore vary considerably from one slope to another.
Planning excavation to better protect the site
Beyond the diagnosis, the value of the method lies in its capacity to anticipate. Archaeologists and conservators could assess vulnerable slopes, choose where to place spoil and identify areas to stabilise before digging. At Resuloğlu, the team found that storing equipment on steep slopes increased erosion risk; they suggest placing it on gentler slopes or reusing it to backfill excavated structures.
Kemal Koçaklı, of the Eurasian Institute of Earth Sciences at Istanbul Technical University, sums up the stakes: "The aim is not to tell archaeologists not to excavate, but to give them a tool to excavate with less impact." According to him, the model makes it possible to test different scenarios on screen before fieldwork begins.
Protecting the whole landscape, not just the trench
The study reminds us that an archaeological site is not limited to its visible ruins. At Resuloğlu, neighbouring gullies, livestock movement, water points and the placement of spoil all influence erosion processes. The authors therefore argue for conservation that takes the entire landscape into account.
They acknowledge, however, that their results rest mainly on modelling rather than direct erosion measurements on the site. Field observations of runoff and sediment should, in their view, improve the accuracy of the predictions.
Frequently asked questions
Why can archaeological excavation cause erosion?
When it removes the protective soil layer and exposes compacted surfaces, excavation limits rainwater infiltration. More water then runs off across the surface and carries more sediment. Depositing spoil on steep slopes can also worsen the problem.
What is the Resuloğlu mound?
It is an archaeological site in north-central Anatolia, Turkey, occupied from about 2300 to 2100 BCE. Excavations took place there from 2003 to 2019, and erosion had already helped expose tombs.
How can erosion at an archaeological site be modelled?
The team used QGeoWEPP, an interface for the WEPP model, which simulates the movement of water and soil slope by slope. The data combined aerial photographs, drone surveys, satellite images and twenty-four years of weather data.
Can this method help plan excavations?
The authors believe so: it could identify vulnerable slopes and help choose where to place spoil before work begins. It remains based on simulations, however, and will need to be checked against field measurements.
Sources
Original summary written with the help of artificial intelligence from the sources cited, checked automatically, then translated from the French original. Information and quotations belong to their authors. Read the French original.
