The upgraded full-scale avalanche test-site Ryggfonn, Norway.

Abstract

Measurements of full-scale avalanches are expensive and time consuming, but are indispensable to gain in-depth understanding of the flow behavior of avalanches. They are needed to crosscheck the scaling used in small-scale experiments and also form the basis for developing and calibrating numerical models. The recent partial upgrade of NGI’s Ryggfonn test-site is focused on the processes occurring during interaction between avalanches and a catching dam in the runout zone. These processes are crucial for the efficiency of this type of avalanche mitigation measure, which has been the focus of several small scale experiments in recent years. But qualitatively and quantitatively good observations from real avalanches for a crosscomparison are rare. Therefore, two new masts were constructed at Ryggfonn. One is located about 10 m upstream of the foot of a catching dam and has a height of 15 m. The other stands on the crown of the dam and is 6 m high. In this way, we also hope to complement the SLF full-scale tests at the Vallee de la Sionne test-site. Instrumentation on the new masts consists of load-cells and LED velocity sensors, each type with a vertical spacing of 0.5 m. In addition, flow-height switches are placed with 0.25 m vertical spacing. Thus, the instrumentation is quite similar to the instrumentation used in Vallee de la Sionne, which will hopefully allow better cross-comparison of measurements. We present the upgraded set-up and show preliminary results from the first measurements.