Record May Snowfall Precedes Risk of Ten-Year Flood in Norway

Sjusjøen resident and NVE’s local precipitation gauge Ellen Tømte Hagen (33) has not seen such large amounts of snow in May in the ten years she and her family have lived on the roof of the country’s largest cottage municipality Ringsaker.

On 1 May, she measured 152 centimeters of compact snow at the fixed measuring point Storåsen, just over 900 meters above sea level. Not since 1985 has there been so much snow here in the green spring month.

On 15 April, the measuring stick showed 172 centimeters – a snow record on Lake Sjusjøen since 2008.

On 10 May it was still 132 centimeters.

– The night before was the first time I heard water dripping from the roof. It has been freezing at night until the last few days. We weigh the snow, and the weight shows that there is a lot of wet snow that becomes more water than dry snow, says Tømte Hagen to Dagbladet.

Ten-year flood

Water from melting snow on Sjusjøen flows into Mjøsa and further into Glomma.

Already Tuesday or Wednesday over the weekend alerts NVE (Norwegian Directorate of Water Resources and Energy) about the risk of ten-year floods in Eastern Norway.

Most exposed from the start: Glomma and the Drammensvassdraget.

– There will already be serious consequences with an orange flood level in a few days, and people in exposed, lower-lying areas must prepare for it now. For example, moving valuables up from cellars, moving caravans by the river bank and securing boats. Farmers must get rid of round bales that are close to normal water levels, says Anne-Live Øine Leine on duty at the NVES flood warning to Dagbladet.

There, the flood warning telephone is “hot” during the day.

Not sure about the weather

– From last Wednesday, the forecasts for rain and temperatures have changed daily. It creates uncertainty about when and where the floodwaters will come, says Øine Leines.

In the latest flood warning NVE calculates that there is one and a half to three times more snow than normal in several mountain areas.

In addition to Glomma and the Drammensvassdraget, NVE initially warns of abnormal water flow in Gudbrandsdalslågen, Trysilelva, Numdedalslågen and Skiensvassdraget.

And NVE asks people around lowland lakes below 500 meters above sea level to be especially vigilant now before the snow suddenly becomes floodwater:

Mjøsa, Krøderen, Øyeren, Randsfjorden, Sperillen and Tyrifjorden.

The 2000s have seen many devastating floods directly triggered by snowmelt and rain.

The most destructive flood in modern times was in 1995. The flood has been given the historical name Vesleofsen, and was a so-called 100-year flood.

– Are we risking such conditions this spring?

– No, there are no signs now that point to that, replies the watchman to NVE’s flood warning.

The name Vesleofsen, which claimed one life when a car was swept away by the flood at Lillehammer, has a direct link tol the country’s worst flood – Storofsen.

Cold degrees in the mountains in southern Norway until 22 May and late, massive snowmelt triggered the big flood in 1995.

Worst since the Black Death

Storofsen is over 200 years back in time – in 1789.

Historians are reasonably agreed that this flood is the worst natural disaster in Norway since The Black Death in 1349-50.

Also in 1789, there was a lot of winter snow in the mountains. But there was a long period of rain in the middle and end of July that put the forces of nature completely out of control.

At least 61 people lost their lives. Several thousand animals drowned, at least 3,000 residential houses were smashed by the flood and at least 1,800 farms were washed into the rivers.

Gudbrandsdalen and Østerdalen were critically affected, and many had to find new farms and livelihoods far from their original homes.

17 meter over

There lies the historical background for the Gudbrandsdal dialect still appearing in Målselvdalen and Bardudalen in Troms.

Measurements in 1789 show that Mjøsa flowed out nine meters above normal level (“only” seven meters below Lillofsen in 1995), Øyeren went 13 meters above its banks and Nedre Glomma 17 meters.