Date post: | 12-Nov-2014 |
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Technology |
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Floods and the flood protection in Rovaniemi and Kittilä
• The river Kemijoki •The longest river of Finland, 550 km
•The Kemijoki’s drainage basin is the Finland’s second biggest, 50 000 km²
•Hydroelectric power production was started in 1948, there are found 8 hydroelectric power-plants in river Kemijoki
• The river Ounasjoki • The longest tributary of the river Kemijoki • The Finland’s longest river which flow free, length is 298 km
•The Ounasjoki drainage basin is almost 14 000 km² and it cover 27 % of the Kemijoki’s drainage basin
Floods
• The biggest floods arise after snow melting in spring• When discharges together in Kemijoki and Ounasjoki are
about 4 000 m³/s, Rovaniemi begins to suffer from flooding.
• When discharge in Ounasjoki is about 850 m³/s, Kittilä begins to have flood damages
• Risks for flooding are also caused by ice jams
• The lastest big flood was • in Rovaniemi in 1993
• in Kittilä in 2005
Saarenkylä in Rovaniemi in year 1973
Saarenkylä in Rovaniemi in year 1973
Kittilä in 2005
Kittilä in 2005
Kittilä in 2005
Flood area in Kittilä in year 2005 modeling on the air map
-Blue describes the flood area-Red line is the border of an area, where an accurate digital elevation model is available
The flood hazard map in RovaniemiHQ 1/100 year, discharge 5 102 m³/s
Saarenkylä’s flood area once in 100 years
Climate change and floods
• Climate change will not impact very much on flooding • The risks for flooding are same than today
• Floods in spring will first increase, but when climate become warmer floods can little decrease
• Floods will little increase in summer and autumn
The flood protection alternatives
• The flood embankments– Easy to carry out and good
choice in some places– Hide beautiful river view– Not be suitable in places
where is fine-grained land
• The flood embankments are planned in Kittilä
• Rovaniemi has made the preliminary plans of the flood embankments
The flood embankments in Kittilä
The preliminary plans of the flood embankments in Saarenkylä
The flood embankment
The flood protection alternatives•Dredging
•Improves flowing in river•Difficult and expensive to carry out•Need more investigations and many permissions before it can be carried out in Kittilä or Rovaniemi
The flood protection alternatives
• Reservoir for flood protection– Reservoir is big pool, where snowmelt water is stored if big
flood threatens– Reservoir is good choice but it is very expensive and slowly to
carry out– Two reservoir have as preliminary been planned for above
municipality of Kittilä
• The law of the river Ounasjoki and natural protection areas cause legal troubles if we want to carry out dredging or reservoir
Flood protection alternatives
• Change the regulation’s orders• That means: the old regulation’s orders are updated and
the capacity of the lake Kemijärvi is raised (Kemijärvi is situated about 100 km to the north from Rovaniemi, upriver to Kemijoki)
• Simultaneous flood peaks of the rivers Ounasjoki and Kemijoki in Rovaniemi can be avoided by the regulation of Kemijoki
• Impacts of the regulations are useful in the flood protection, but regulations help only few days because of the small capacity of Kemijärvi
Other alternatives on the flood protection
• Temporary flood protection structures• Sandbag walls and other structures• Structure’s material has to be fast built, easy to carry to
flood area and withstand water pressure
• Developing flood protection communication and co-operation between all actors
• The combination of different alternatives could be the best choice in flood protection
The temporary flood embankment in Kittilä
The sandbag wall in Kittilä
Thank you for your attention!