Drought may be cracking Groningen’s medieval churches

Medieval churches in the Dutch city of Groningen may be cracking due to a combination of factors, according to a recent study. The research, conducted by Deltares and the Hanze University of Applied Sciences, found that drought, along with earthquakes and human activity, is contributing to the deterioration of the wierden, or man-made dwelling mounds, under the churches.

The study, commissioned by the province and the Old Groningen Churches Foundation, focused on two churches in Oostum and Den Ham, northwest of Groningen. The damage to the church at Oostum began in 2018, two years after previous earthquake-induced repairs. Despite no major quakes in the area since, the damage appears to be worsening.

Church researcher Floris Boogaard noted that the church's clay foundation expands when wet and contracts during drought, while peat in the ground compacts as groundwater levels fall. He emphasized that drought is the most significant factor, as dry periods have become significantly longer, impacting the church's structural integrity.

Boogaard cautioned that the climate change is causing these longer dry spells, exacerbating the problem. The researchers are still analyzing the two-year study and stress the need for longer-term research before drawing definitive conclusions. They warn that other historic buildings could face similar issues and suggest that stability in water levels around the churches could be a solution.

One possible approach is to dig pits around the churches to collect rainwater, allowing it to slowly permeate the ground.