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The whims of the Nile
© Marc Ryckaert
Research

The whims of the Nile

A Leuven research team is extracting sediment core samples that are teaching exactly how the Nile ran in ancient Egypt.

10 minutes
09 September 2020

In and around Dayr al-Barsha in Egypt, a Leuven research team is not only extracting archaeological finds from the soil, but also sediment core samples that are teaching exactly how the Nile ran in ancient Egypt. It turns out the river was less predictable than we previously thought. And that insight is of great importance to the work of Egyptologists.

An interdisciplinary team led by Egyptologist Harco Willems has been conducting archaeological research into ancient Egyptian rock tombs in the Dayr al-Barsha area for the past twenty years. The site is most famous for the beautifully decorated tomb of Djehutihotep, a provincial governor who lived in Middle Egypt 4,000 years ago. The excavations carried out by Leuven yield new finds every year, and the researchers are also using digital archaeology to reconstruct the site.

The corona crisis was a setback for the team. They still travelled to Cairo at the beginning of March in the hope of starting the annual excavation campaign, but they were unable to continue on to the archaeological site. They returned to Leuven just in time before the airport was closed.

Fortunately, Earth scientist Willem Toonen had in recent years collected significant data for use in his research. He uses core samples to map out how the landscape – and in particular the location of the Nile – has evolved over the centuries. Egyptologists working throughout the Nile Valley can benefit from insights gleaned from this approach.

The Leuven team at work in Dayr al-Barsha.
The Leuven team at work in Dayr al-Barsha.

Outsider

The first series of exploratory drillings – carried out by professor Gert Verstraeten – were primarily intended to map the ancient river landscape on the east bank of the Nile. Among other locales, he drilled in the modern village of Dayr al-Barsha to find out exactly where the bank of the river was in earlier times.

When Willem Toonen joined the team in 2015, he too took core samples in the village, with the hopes of finding archaeological traces. The holy grail in that quest is a colossal statue of Djehutihotep, which is depicted on a wall of his tomb. Given the detailed description it contains, the statue probably actually stood on the banks of the Nile at the time, but no trace of the statue has been found to date.

Building on the work of Professor Verstraeten, Willem Toonen also wanted to map the historical location of the Nile in a broader sense, featuring extensive drilling research on the western flood plain on the other side of the Nile. This makes Willem something of an outsider during the excavation campaigns. Whilst the Egyptologists walk from base camp to the archaeological site in the morning, he chooses his own path in a pick-up truck loaded with drilling equipment and heads into the green valley.

Also on board the truck is a crew made up of a few enthusiastic locals who have become accomplished drilling experts. With their help, Willem drills a borehole every 200 metres, working his way down 10 to 15 kilometres-long transects that extend across the Nile valley. ‘We use a mechanical hammer that is made to break up asphalt, but in our case it has a one-metre-long hollow sample casing attached to it,’ says Willem. ‘We drive that pipe into the ground and then extract it again with a large manual jack. We repeat this until we’re down to a depth of 10 metres.’

In addition to the mechanical percussion drill, this ‘Edelman hand drill’ is also sometimes used.
In addition to the mechanical percussion drill, this ‘Edelman hand drill’ is also sometimes used.

‘This way I can get soil samples up to one metre long, which I then describe sedimentologically: what depth do we encounter which sediment types, such as sand or clay, what are the characteristics of the sediment, etc. Amongst other things I study grain size, sorting and colour, all relying on numerous field methods. For the colour, for example, I use the same sort of colour chart that you might find in paint shops. It’s a fan of colours that I place next to the sample. When I find the corresponding colour, I write down the code. I just do that on site, because I don't have a laboratory at my disposal and the authorities won’t allow us to take sediment samples out of Egypt.’

Sand that speaks volumes

Based on what has been found, Willem makes a reconstruction of the ancient landscape. ‘Units of sand (“unit” here referring to a horizontal layer of sediment shaped by one geologic process and displaying similar characteristics throughout – ed.) are generally formed by fast flowing water moving in a channel,’ he explains. ‘Clay in turn is sediment that deposits in standing water and thus indicates a lake or a flood basin – the Nile experienced a flood every year. If the drillings give the impression of a spatially confined zone of sandy units with layers of clay stacked on both sides, I know that the Nile once flowed here.’

As a rule of thumb, it is assumed that every thousand years one metre of clay forms in the Nile Valley. The depth of the sediments can therefore give Willem a rough idea of their age. ‘For example, if I find sand two metres below the surface, then I know it is about 2,000 years old and therefore dates back to Roman times. If it’s at much greater depth, it’s a lot older, for example from the Old Kingdom – the time when the Great Pyramids of Giza were built.’”

Ceramic fragments that he occasionally finds during the drilling can help to date the sediments more precisely. ‘Usually they’re small fragments, but sometimes we also find larger pieces with a characteristic "slip", a distinctive surface layer that makes it possible to date fairly accurately. This can also be done on the basis of other characteristics, such as the material from which the pot is made or traces of certain production techniques. The ceramologists in our team can tell you approximately how old a ceramic fragment is and what type of pot it was originally.’

‘For example, in the subsoil of Ashmunayn – in the middle of the Nile Valley, about 10 kilometres west of Dayr al-Barsha – we found hundreds of ceramic fragments in several of our cores. It was already known from ancient texts and previous archaeological finds that the provincial capital from the Old Kingdom was located there about 4,500 years ago, but now we have factually shown that there was habitation there at that time. It’s also the place where the governors buried in Dayr al-Barsha came from.’

Detail of a core sample from the floodplain of the Nile. In some places, a rapid succession of sand layers can be found instead of the usual clay deposits. Those layers of sand are characteristic of changing water flow velocities, and so indicate that the Nile once flowed there.
Detail of a core sample from the floodplain of the Nile. In some places, a rapid succession of sand layers can be found instead of the usual clay deposits. Those layers of sand are characteristic of changing water flow velocities, and so indicate that the Nile once flowed there.

Giant leaps

Toonen's findings shed new light on the evolution of the course of the Nile. Until recently, most Egyptologists relied on a landscape model developed in the 1970s by the German-American geographer and archaeologist Karl Butzer, referred to as the Eastern Migration Premise. Butzer argued that the Nile had meandered by eroding its outer bends and in doing so shifted over time to the east of the valley.

‘Basically he didn't do anything wrong,’ says Willem Toonen, ‘but his model was based on a number of historical maps, textual sources, aerial photographs and only six core samples. All in all, a fairly limited data set, and yet many have come to see his proposition as a certainty, probably due to the absence of alternative suggestions. However, the findings of our current study, and those of a number of other studies in the wider region, do not fit that traditional model at all.’

Ceramologists Stan Hendrickx and Kylie Cortebeeck investigate pottery fragments that Willem Toonen extracted from boreholes at Ashmunayn. Their analysis confirmed that it was the location of the provincial capital in the Old Kingdom.
Ceramologists Stan Hendrickx and Kylie Cortebeeck investigate pottery fragments that Willem Toonen extracted from boreholes at Ashmunayn. Their analysis confirmed that it was the location of the provincial capital in the Old Kingdom.

With his core samples, Willem Toonen has obtained a more accurate picture of the giant leaps of the Nile. Because that word seems to be the right one to use. ‘In a large part of the area where the Nile once flowed and must have moved according to the Butzer model, we found no sands. The river could never have been located there. Yet, we did find sand deposits in approximately one-kilometre wide zones at Ashmumayn and near Dayr al-Barsha. So we know that the Nile once ran in these two places, and never occupied the areas in between.’

This means that the Nile did not gradually shift over to the east, but suddenly changed its position. Or rather, created a new channel for itself. ‘At some point during a flood, the river found a new, more favourable path after it breached a bank; we call that an avulsion. This new channel could have formed in a span of 100 to 200 years, which in geological terms qualifies as ‘suddenly’. As a result, Ashmunayn was no longer located alongside the river, whilst Dayr al-Barsha found itself lying on the banks of the new river.’

This historical map of the Nile valley from the time of Napoleon has been overlain with the old Nile courses that the Leuven team found. The orange track shows the main channel of the Nile during the Old Kingdom, when the river passed Ashmunayn (the circle). That river course redirected to the purple course, which runs along Dayr al-Barsha (the square). The black arrow indicates the river migration according to Butzer's model, but the reconstruction by Willem Toonen and his colleagues thus shows that the Nile has 'skipped' large areas and therefore did not disturb the soil archive there. The green track is a Nile run from the Greco-Roman era.
This historical map of the Nile valley from the time of Napoleon has been overlain with the old Nile courses that the Leuven team found. The orange track shows the main channel of the Nile during the Old Kingdom, when the river passed Ashmunayn (the circle). That river course redirected to the purple course, which runs along Dayr al-Barsha (the square). The black arrow indicates the river migration according to Butzer's model, but the reconstruction by Willem Toonen and his colleagues thus shows that the Nile has 'skipped' large areas and therefore did not disturb the soil archive there. The green track is a Nile run from the Greco-Roman era.

Necropolis on the Nile

Core samples taken by Willem Toonen for a different project in the Luxor area confirm this model of riverbed displacement by avulsion. Within Egyptology, it offers a completely new view of the way the river landscape changes over time, an insight that has important consequences.

For Egyptologists it is important to know where the Nile has flowed through the ages. There is usually little for them to investigate in places where the river flowed, as erosion has disrupted or completely washed away the soil archive. But in contrast to Butzer's predictions, there are entire areas in the current floodplain where the soil might contain preserved historical material and are therefore potentially of high archaeological value.

For the Leuven Egyptologists in Dayr al-Barsha, the new view of the course of the Nile fits in better with the puzzle they are putting together. ‘The branch of the Nile that Willem traced goes straight to another burial ground that belongs to our concession, 5 kilometres from Dayr al-Barsha,’ says Professor Harco Willems. ‘It was the burial place for the provincial governors when the Nile still flowed at that spot, and so there was a direct waterway between the provincial capital and the cemetery. The drillings confirm that the river channel later silted up. Then they chose Dayr al-Barsha as the new location for a burial ground.’

Why did the Egyptians want a place near the Nile to bury their high status dead? ‘The wheel had not yet been invented, so for elite burials they needed the river in order to transport various items by ship, including the coffins, which sometimes weighed a tonne. But in the case of Dayr al-Barsha, the fact that elite tombs were preferably carved high in the rocks in impressive locations certainly played a role. In other words, the place had several advantages.’

We can learn lessons from this research about the impact of climate change on the 'behaviour' of rivers, and about the relationship between nature and humanity in the past.

Climate lessons from the soil

Leuven researchers want to continue drilling in the coming years in order to broaden and refine this image of the historic landscape. They are also working on a proposal for a European training network so that colleagues working in other parts of Egypt can exchange knowledge and research techniques and contribute to the landscape reconstruction.

We can also learn lessons from this research about the impact of climate change on the 'behaviour' of rivers, says Willem Toonen. ‘For example, there have been repeated periods of great drought in Ancient Egypt; the most famous was at the end of the Old Kingdom. The floods of the Nile, which were important for agriculture, did not occur for several centuries – possibly resulting in famine and political unrest – and branches of the river became difficult to navigate and silted up.’

‘We can learn a great deal from this about the relationship between nature and humanity in the past. Our research can help to tell that didactic story. Many people still see archaeology as a kind of hobby, but the insights we gain from it are very relevant to our own time. And that certainly applies if you want to know how people and nature react to each other, even today.'