Switzerland: Landslides, flooding affecting Graubunden (Grisons) and Valais cantons, June 23 /update 1

Severe weather overnight June 21-22 in Graubunden (Grisons) and Valais cantons has caused flooding and landslides. Authorities report that 124 mm (4.88 in) of rain fell in parts of central, eastern, and southern Switzerland. The town of Zermatt in the Valais has also been cut off as roads in the area have been closed, and trains between Visp and Zermatt have been halted. As of June 23, authorities have evacuated some residents and are still searching for three missing people. The Swiss meteorology services Meteo Swiss have warned of further scattered showers through June 24. Officials could update and possibly extend the coverage of weather alerts over the coming hours and days.

Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides cannot be discounted in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall. Disruptions to electricity and telecommunications services are possible where significant winds, flooding, or landslides impact utility networks.

Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather could also trigger flight delays and cancellations at regional airports. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas that see heavy rainfall and potential track inundation.