Sunrise over flooded Pivka basin
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Sunrise over flooded Pivka basin

by Cyril Mayaud, Karst Research Institute ZRC SAZU, Postojna, Slovenia

This picture shows the maximum extension of an extreme flood that occured in February 2019 in front of the famous Postojna cave (Slovenia). Uncommonly heavy rainfall combined to snowmelt in the 250 km2 large recharge area of the Pivka River resulted in a maximum discharge above 55 m3/s measured at its two main gauging stations. Because of the limited drainage capacity of the ponor, it caused a huge flood at the entrance of the cave. The water level started to backflood and peaked at 807 cm, which is approximately 7 m above common values. This resulted to large areas around the cave beeing underwater for two days, including a portion of the road visible on the picture as well as most of the parking lots around. While such events were very rare in the past, they tend to occur more frequently since the last 10 years.