Transport officials say the weekend's flooding caused an unprecedented number of gravel road collapses.Heavy rains flooded the roads in Multia.Yle News16:48Heavy rainfall at the turn of the week cut off 16 gravel roads across Finland, with the worst damage reported in Pirkanmaa and Central Finland.According to the Finnish Transport Infrastructure Agency, three separate road collapses occurred in the Central Finland municipality of Multia, which recorded the country's highest daily rainfall total of 114.2 millimetres.Road maintenance specialist Jarkko Pirinen said the scale of the damage was exceptional."There has never been this many gravel road collapses caused by a single rainfall event," Pirinen said.He explained that while road authorities work to maintain the network, it is impossible to prevent every collapse. Finland has thousands of kilometres of gravel roads, and increasingly intense summer downpours linked to climate change are difficult to predict.A collapsed road was repaired in Ylöjärvi, a city in the Pirkanmaa region of western Finland on Sunday."The intensity of the rainfall is the real challenge. One hundred millimetres of rain in a day is roughly equivalent to more than a metre of snow falling during winter," Pirinen said.According to Pirinen, heavy downpours are becoming increasingly common. Events that once occurred only every 10 to 30 years can now happen annually.He added that many of Finland's gravel roads and drainage systems are decades old and were built for different weather conditions. As this heavy rainfall becomes more frequent, the ageing infrastructure is coming under increasing strain, but the country's vast gravel road network makes large-scale upgrades difficult.