The Extremes ofthe Extremes: Extraordinary Floods (Proceedings of a svmposium held al Reykjavik. Iceland. July 2000). I AI IS Publ. no. 271. 2002. 173
The large flood of 1860 in Norway
LARS ANDREAS ROALD Norwegian Water Resources and Energy Directorate (NVE), Box 5091 Majorstua, N-0301 Oslo, Norway e-mail: [email protected]
Abstract In 1860 a large and widespread flood occurred over eastern Norway causing extensive damage. The extent and causes of this flood are examined. The period between 1846 and 1870 had an over-abundance of large floods, which is typical for cold periods with a significant contribution from extensive snowmelt. Flood warnings were issued before the 1860 flood and several measures were taken to reduce the flood damage.
Key words Hood hydrology; case study; flood causes; damage mitigation; Norway
INTRODUCTION
East Norway has been affected by a number of widespread flood events, causing extensive damage. Most devastating was "Stor-Ofsen", which occurred 20-23 July 1789, killing 68 people and more than 4000 farm animals. Another large event occurred in 1860, with a duration of more than one month. This flood has the second highest observed level in Lake Mjosa and in Lake 0yeren, and with a flood volume much larger than "Stor-Ofsen". In 1995 another large event "Vesle-Ofsen" occurred in east Norway, causing damage worth 220 million US dollars.
DATA
Daily water levels are available for a number of sites on major rivers in south Norway. The flood level is also known at a number of additional sites. Rating curves have later been established at some of the sites. By assuming that the rating curves may be backdated to 1860, estimates can be made of the maximum discharge. The locations where water level data or discharge data are available are shown in Fig. 1. Precipitation and air temperature data are available from the University observatory in Kristiania (Oslo). The large flood also affected parts of Sweden and meteorological data have been obtained for Falun from the Swedish Meteorological and Hydrological Institute (SMHI), as well as runoff data from Fâggeby in Dalâlven.
THE FLOOD EVENT
The daily water levels observed at sites with daily observations are shown in Fig. 2. The 1860 flood had two peaks, around 10 June and around 17-21 June. The discharge 174 Lars Andreas Roald
exceeded 2000 nrV1 at Sarpsfoss from 31 May to 8 July, as shown in Fig. 3. The resulting flood affected an area from the River Vorma/Lâgen to the eastern part of the River Skienselv basin (Johnson, 1861). High flood levels were also observed in several rivers further west as well as a number of rivers draining towards the bottom of fjords in west Norway. The flood also extended into Sweden, where the flood at Fâggeby was the largest on record. The culmination discharges are summarized in Table 1. Flood frequency analysis indicates that the maximum flood volume flood over 30 days had a return period in excess of 500 years at Sarpsfoss and Fâggeby, based on the general extreme value distribution estimated by the probability weighted moment method. The 1-day return period is shorter, indicating that the duration was exceptional.
Station name
Bjorneskallen Lillestram Sarpsfoss Minne Hamar laker Morkfoss Langnes Losna Solbergfoss Bergerfoss Vikersund Spirillen Kvaerkhengsletj Strandefjord Labru Loveid ovf. Hjellevatn Lundevatn Selbusjo
Scale Fig. 1 Location map of water level and discharge stations affected by the 1860 flood. The area affected by the flood is shaded. The large flood of 1860 in Norway 175
CAUSES OF THE FLOOD
The period from 1846 to 1870 was a cool period with extensive snowfall in several winters. Large floods occurred in 1846, 1850, 1853, 1858, 1860, 1862, 1863, 1866, 1867 and 1869 in some rivers of southern Norway. There are indications of secondary advances of glaciers in west Norway during the period, as can be seen from a number of moraines (Andersen & Sollid, 1971). A common factor of the floods is late spring melt combined with fairly heavy rainfall. The winter 1859/60 had extreme snowfall in an area from the Gudbrandsdal Valley extending towards the southernmost part of Norway. The snowfall was low north of the mountain divide towards Trondelag. The two flood peaks were caused by heavy rainfall in combination with intensive melting. The melting started in late April in areas at altitudes below 700 m. The first peak was caused by fairly high temp eratures, combined with about 50-60 mm precipitation between 26 May and 2 June. The ground became saturated, providing optimal conditions for an extreme flood in the case of a new precipitation event. Extremely warm and humid air masses arrived on 15 June with extreme precipitation and a strong wind from the southeast. The temperature rose to 26°C in Kristiania and probably to 13°C in the high mountain basins (Hogâsen, 1998). The melting became extreme. The precipitation was high in Kristiania (84 mm), and exceptional in the Gudbrandsdal Valley. The precipitation was generally high in
2,31.3 River Glomma at Sarpsfoss 2.26.0 River Giomma at Lake 0yeren at Lillestrom „ 2.101.0 River Vorrrta (Giomma) at Lake Mjosa at Kamar .™™.™,., 12.16.0 River Orammenselv at Lake Tyriljorden at Vikersunrj 12.11.0 River Randselv (Drammenselv) Bergerfoss 16.17,0 River Skienselv at Hjelievatn at Skien
10. —i
I860 Fig. 2 Observed water levels during the flood in 1860. 176 Lars Andreas Roald
0 • n——i— r r — .May Jun Jul Aug Sep I860 Fig. 3 Observed discharges during the 1860 flood in Norway and Sweden. valleys running toward the northwest. The main event lasted from 15 to 17 June. Heavy precipitation is also the explanation of the flooding on the south coast and in west Norway. The circulation pattern giving the second event has been associated with almost all the extreme flood events observed in east Norway as well as large floods in Sweden. The precipitation was less in Sweden, and the major flood in the first event occurred in connection with snowmelt.
Table 1 Date and estimated maximum flood discharge of the 1860 flood.
Site River Basin area Date Discharge: (km2) (m3 s"1) (1 s"1 km"2) Sarpsfoss Glomma 41 594 24-25 June 3188 77 B laker Glomma 38 092 22 June 3600 94 Losna Glomma/Lâgen 11 087 21 June 1700 227 Lalm Glomma/Otta 3 982 21 June 1580 398 Sperillen Begna 4 581 1470 320 Strandefjorden Begna 1 842 550 300 Labru Numedalslâgen 4 245 17 June 1285 302 Hjellevann Skienselv 10 203 22 June 2650 259 Loveid/Norsjo Skienselv 9 975 22 June 2500 250 Fâggeby Dalalven 25 037 1 June 2644 105 The large flood of1860 in Norway 111
The year 1860 was characterized by heavy precipitation and crop failure in south Norway as well as in much of northern Europe. The year was reported as an excellent year with abundant crops in north Norway. The year has also been reported as a dry year in the USA.
FLOOD DAMAGE
The damage was severe in rivers with a total basin area of 34 000 km2. Some damage was also reported from an area of 10 000 lan2. The damage was extensive on many roads. A large number of bridges were destroyed. The railway was inundated at some locations. Houses were also flooded at a number of villages and towns, and a number of houses were carried away. Farmland was inundated at many places, and some farms were destroyed. The flood eroded the riverbanks near several rivers, and landslides occurred at some locations, killing seven people at Nore in Numedal. A particular problem was large amounts of timber, which was contained by booms in several of the larger rivers. Bridges were destroyed or damaged by drifting timber at Eidsvoll, Honefoss and Kongsberg. The boom at Kvasrk on the River Drammenselv contained an even larger amount of timber. If this boom had broken, the town of Drammen would have suffered extreme damage. Fortunately the timber was contained as the boom did not fail.
MEASURES TO REDUCE FLOOD DAMAGE
Because of the extreme amount of snow it was realized that a large spring flood was inevitable. A local police chief issued a flood warning two months before the flood for the River Drammenselv. Measures were taken to reduce the water level of the reservoir in Lake Farris as the first flood peak started, saving the town of Larvik from damage. Efforts were taken on the River Drammenselv to secure the timber boom, and a telegraph line was set up to report the situation to Drammen. Horsemen brought messages from the boom to a downstream village, which also would be destroyed in the event of failure of the boom. The flood protection works were reinforced during the flood. Piers and houses threatened by the flood were filled with rocks, and some houses and dams were torn down to give the flood free passage.
CONSEQUENCES OF CONSTRUCTION WORKS IN THE RIVER CHANNEL
Some construction work had taken place prior to the flood, and was partly blamed for increasing the flood damage. The level of low flows out of Lake Mjosa had increased, but the outflow capacity had been raised at high water levels. Merchants suffering from the inundation at Hamar, sued for compensation. The streets affected had however been developed well outside the zone previously designed as safe. At other locations it was proved that constructions had contributed to the damage. Construction of reservoirs later reduced the magnitude of floods as shown in Roald (1999) and Tingvold(1999). 178 Lars Andreas Roald
Acknowledgements The author gratefully thanks 0ivind Nordli of the Norwegian Meteorological Institute for providing meteorological data from the Observatory in Kristiania and the evaluation of the snowmelt conditions in 1860, and Sven-Erik Westman of the Swedish Meteorological and Hydrological Institute for providing meteorological and hydrological data from Sweden. Astrid Vokso of the Norwegian Water Resources and Energy Administration prepared the map.
REFERENCES
Andersen, J. L. & Sol lid. .1. L. ( 1971 ) Glacial chronology and glacial geomorphology in the marginal zones ol'the glaciers, Midtdalsbrecn and Nigardshrecn, south Norway. Norsk Geogr. Tidsskr. 25, 1-38. Hogasen, S. (1998) Grovvurdering av vilkar lor snosmelting, etter temperalurslatislikk frâ Universitetsobservaloriet i Oslo (Evaluation ol'the snowmelt, based on temperature statistics from the University observatory in Oslo). Unpublished note. Johnson, G. B. ( 1861 ) Mine Belraklninger og Anskuelser over Communicalionerne i Norge (My considerations and views on the communications of Norway). Cammenmeyer. Kristiania, Norway. Roald, E. A. (1999) Analyse av lange flomserier (Analysis of long-term flood series). HYDRA Rapport no. FOI. Oslo, Norway. Tingvold, J. K. (1999) Effekt av vassdragsreguleringer i Glomma og Lâgen pâ stor flom (Effect of hydropower regulation on large floods in Rivers Glomma and Lâgen). HYDRA Rapport no. F04, Oslo. Norway.