A prolonged spell of hot and dry weather has brought lost archaeological sites back into view across Wales, with Roman buildings and World War One practice trenches emerging from scorched grasslands. Wales has received only about 5% of its average July rainfall, following back-to-back heatwaves and a drier-than-usual period from April to June. A drought has been triggered in parts of Wales.
The dry conditions have created distinctive crop marks visible only from the air, revealing monuments that include prehistoric long barrows, Iron Age forts, and Roman buildings. Some of these sites have not been seen clearly for two or three decades, according to the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW). The marks are made by vegetation drawing on better nutrients and water supplies trapped in long-gone fortification ditches, leading to green growth that stands out against parched fields.
“A prolonged heatwave has revealed lost archaeological sites across Wales, including Roman buildings and WW1 trenches.”
Archaeologist Dr Toby Driver has been racing against the heat to record and study the monuments. He said that normally he would have to wait every five to seven years for a record heatwave summer suitable for aerial archaeology, but now they come “every year”. This year's flights from Haverfordwest and Caernarfon airport in June and July have yielded photographs of discoveries including a previously unrecorded Iron Age or Romano-British double-ditched farmstead near Llandysul, Ceredigion, and practice trenches beneath a golf course in Deganwy, Conwy.
“This year has been pretty windy across Wales, so some of the longer trips to record cropmarks have made for challenging flying,” Driver said. “Sometimes the cropmarks are so clear they jump out as we orbit the aircraft around to photograph them. But some parts of Wales are now so dry that the cropmarks can be faint and pretty hard to see.”
In those cases, Driver said they digitally rebalance the colour bands of the image, “really making the archaeology ‘pop’ and reveal previously hidden details – these images appear as black and white”. The RCAHMW noted that east and north-east Wales have been very dry since mid-May, while much of west and south Wales stayed fairly damp and green until the series of heatwaves in late June scorched off grasslands across the country.
The cropmarks can disappear as quickly as they emerge once the weather conditions change, leaving archaeologists with a narrow window to capture these fleeting glimpses of the past.