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Near Infrared, Far Away in Time

Ljubljana Marshes were once a vast and shallow lake, and in late neolithic humans came to make the lake their home. They built houses on stilts called pile dwellings in the middle of the lake, enjoying the protection of a difficult access and the abundance of resources like water, fish and edible water plants.

Ljubljana Marshes and river Ižica today, as seen from a kite

At least, that's the prevailing paradigm, a story we were taught in schools. However, certain clues emerged in the last decade that challenge the established narrative of early farmers living in the middle of the lake.

A wooden wheel, later determined to be the oldest extant wooden wheel in the world, was discovered on the site of a pile dwelling Stare Gmajne near Vrhnika in 2002. Carbon dating put its construction in 3.200 BCE, right at the time when the purported lake covered the Marshes. The question - why would the pile-dwellers need a wheel in the middle of the lake?

The oldest wooden wheel in the world

In 2008 a LIDAR survey of the area of pile dwellings norhteast of the village of Ig (a UNESCO World Heritage site!) was made, and it revealed a complex dynamics of ancient rivers and streams; archaeologists dr. Mihael Budja and dr. Dimitrij Mlekuž Vrhovnik analyzed the data and came to a conclusion that the ancient pile dwellers constructed their houses on stilts on the banks of rivers and streams flowing through the Marshes - there was no permanent lake and no pile dwellings in the middle of it.

LIDAR data of the Ižica floodplain showing ancient streams. The Maharski prekop pile dwelling site is marked in red. From Budja and Mlekuž 2008.

We kind of stumbled into the lake / no lake debate when we did some kite aerial photography around the pile dwellings area and noticed a dark streak on one of the photos:

This dark line on the left is a palaeochannel, a silted-up stream that was active over 5.000 years ago.

After some research we decided to come back and do a more thorough kite aerial photo session, using both a regular camera and a near-infrared one.

Visible light (above) and near-infrared panoramas of the Maharski prekop pile dwelling area

Those ancient streams and riverbeds are sited up today, but they still get waterlogged, so plants are not growing well there. That difference in growth can be rendered visible in NDVI images constructed from visible light and near-infrared photos.

NDVI - normalized difference vegetation index - image of the Maharski prekop pile dwelling area

The images show a true maze of overlapping streams that flowed around the pile dwelling thousands of years ago

NDVI, visible light and near-infrared images of the Maharski prekop site. The excavated pile dwelling is marked in red; it was constructed on the banks of ancient streams.

The whole area is covered with silted-up streams. We could identify the larger ones in this kite aerial panorama animation - Maharski prekop pile dwelling site is marked with a red dot:

The lake / no lake debate rages on and is far from over. We hope that our small, amateurish effort and our kite aerial photos can contribute to it and to help find the answer to the question - did the ancient pile dwellers live in the middle of the lake, or on the riverbanks flowing through the marsh?

Kite aerial photos shot with Nikon P330 (visual) and modified Pentax WG-10 (near-infrared). The cameras were flown on a delta kite, expertly piloted by an aspiring kite pilot and kite maker Maša. Special thanks to dr. John Wells (who provided the infrared-modified camera) and dr. Dimitrij Mlekuž Vrhovnik for his kind encouragement.