Procurement of flood wave or tsunami analyses for mountain landslides in lakes and fjords

Description

NVE needs detailed modeling of flood waves (tsunamis) generated by mountain landslides in fjords and lakes. The wave runup will be used for hazard zones and in some cases evacuation zones for unstable rock-slopes that are monitored in real time. NVE would like to sign a framework agreement with one supplier. Lot 1: NVE needs detailed modeling of flood waves (tsunamis) generated by mountain landslides in fjords and lakes. The wave runup will be used for hazard zones and in some cases evacuation zones for unstable rock-slopes that are monitored in real time. NVE would like to sign a framework agreement with one supplier. NVE is responsible for monitoring and giving warnings of mountain landslides in Norway. It includes funding and coordination of the national mapping program for large unstable rock slopes, which could develop into rock avalanches. The mapping is done by the Geological Survey of Norway (NGU). Hazard zones on land for potential rock avalanches are modelled by NGU, while secondary effects such as displacement waves in fjords or lakes until now have been modelled by Norwegian Geotechnical Institute (NGI) on demand. Flood waves created by mountain landslides have historically been one of most deadly natural hazards in Norway. Danger zones are currently used from different natural hazards whilst planning areas in order to prevent loss of life and damage to property. Also hazard zones from displacement waves (from rock avalanches in lakes and fjords) are required for areal planning in the Norwegian building codes (TEK 17). The modelled wave runup will also be used as basis for evacuation zones if the monitoring/early warning systems indicate a high risk of a rock avalanche to occur. Specific hazard levels are required for the hazard zones in TEK 17; the probabilities are 1/100, 1/1000 and 1/5000 per year. We have so far modelled the tsunami hazard zones for eight individual unstable rock slopes, of which most have more than one failure scenario with different volumes and failure probabilities. During the last years a probabilistic approach has been used in the modelling, where uncertainties in the rockslide annual probability, volume and slide evolution has been combined with uncertainties in the modelling parameters to create hazard zones that comply with the probabilities required for the building codes. NVE is open for a discussion on how to deal with uncertainties in the input data and modelling parameters. NGI has modelled displacement waves with both large scale physical models and numeric models and compared the results to historic events. The mapped unstable rock areas typically lie in high relief mountain areas with narrow fjords and lakes. It is important to use a numerical model suitable for such environment, where wave interference is an important factor. Reliable hazard zones for displacement waves are important to prevent loss of lives and property. It is important that the mapped zones are not conservative but as realistic as possible, as land use is restricted in the hazard zones. A conservative or “worse case” zone can be mapped and used as an evacuation zone in some cases. NVE is responsible for delivering: 1) Unstable scenarios, with volume(s), geometry (slip plane), and probability. 2) A detailed DEM and as detailed bathymetry data as available. 3) Modelling results of the rock avalanche progression with velocity and geometry can be provided if required. Required delivery from the consultant: Wave runup lines or polygons in predefined inhabited areas in a suitable GIS-format. We would prefer the lines to be connected to probability and to be in accordance with the requirements in TEK17. A report for each specific rock-avalanche case to document the modelling work. Scope of the work: We expect that between two and four locations a year will require flood wave modelling in the coming years. The cost is estimated to be NOK 300,000 - 400,000 for each location. The maximum cost is NOK 7 million. The contract duration is 2 years, with an option to extend for 1+1 year.