1. Norwegian practice - new research
2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002
Risk analysis
Norwegian practice - new research
by Grethe Holm Midttømme
The Norwegian Water Resources and Energy Directorate (NVE)
Photo: NVE

2. The Norwegian Water Resources and Energy Directorate (NVE)

3. Development of RA for dams in Norway - brief overview
Norwegian practice
Development of RA for dams in Norway - brief overview
1987: First project initiated by NVE and EBL (RA for 2 dams)
: A few projects on RA for dams, spillway gates and penstocks, among others a project on estimation and comparison of the probability of failure in large rockfill dams using event trees (Johansen et al. 1997, Hydropower’97)
: Several risk analyses performed, mostly probabilistic event tree analyses, e.g. RA of the rockfill dam Valldalen (Funnemark et al. 2000, Q.76, ICOLD congress Beijing)
Very few analyses include consequence analyses, i.e. assessment of probability of failure is emphasized
G.H.Midttømme - 2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002

4. Development of RA for dams in Norway - brief overview (continued)
Norwegian practice
Development of RA for dams in Norway - brief overview (continued)
In general:
Dam owners seem to use PRA’s mainly as a systematic way of identifying deficiencies and ranking safety improvements, e.g. as part of a dam safety reassessment
PRA methodology usually include: site inspections, hazard identification, construction of event trees, probability assessment (statistics and engineering judgment) and evaluation of results
A method for consequence analysis adapted to Norwegian conditions has been developed (Funnemark et al. 1998, ICOLD European Symposium on Dam Safety in Barcelona 1998)
G.H.Midttømme - 2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002

5. Regulations and guidelines
Norwegian practice
Regulations and guidelines
Revision of the first dam safety guidelines (1981) included a working group on risk analysis and emergency action planning
1997: Guidelines on application of RA for dams (NVE)
1999: Guidelines on the use of PHA for emergency planning (EBL)
2001: New regulations on dam safety (§2.8 - NVE may demand risk analyses conducted by the responsible dam owner)
2001: Practical guidelines describing how to perform event tree and fault tree analyses (EBL)
NVE-guidelines issued in 1997 describes only what kind of RA-methods are available and when RA are relevant to use.
G.H.Midttømme - 2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002

6. Regulations and guidelines (continued)
Norwegian practice
Regulations and guidelines (continued)
There are plans for developing new guidelines on application of RA (NVE) ->
focus will probably be on qualitative methods and analyses for EAP
Planned ICOLD-bulletin on Risk Assessment in Dam Safety Management and
ongoing projects related to risk analysis will be looked at
NVE-guidelines issued in 1997 describes only what kind of RA-methods are available and when RA are relevant to use.
G.H.Midttømme - 2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002

7. New research
Recent dr.ing. studies at the Norwegian University of Science and Technology (NTNU), Trondheim
Hilde Marie Kjellesvig: Dam Safety - The Passage of Floods that Exceed the Design Flood, Thesis published July 2002
Parts of the research work has been done in close cooperation with the project ”Stability and Breaching of Embankment Dams”
Grethe Holm Midttømme: Flood Handling and Emergency Action Planning for Dams, June 2002
G.H.Midttømme - 2nd IMPACT WORKSHOP, Mo i Rana, Sept. 2002