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article: Apr 1 2008 - Young River update
Monitoring of the young river landslide dam and lake continues.
Graph showing the fluctuation in water level of the Young River lake derived from the GeoNet lake-level sensor. The sensor was installed in October 2007 (recording the lake level at 5 minute intervals), and radio communications to the sensor were installed in November 2007.
Photograph looking north towards the dam crest along the outflow channel, March 4 2008.
Photograph looking north of the Young River landslide, dam and lake, March 4 2008.
In November 2007 GeoNet installed radio communications to the lake-level sensor, allowing data from the dam to be accessed from GNS Science in Avalon near Wellington. These data are proving very useful for both GNS assessing changes in lake level due to rainfall and Otago Regional Council for their management of the hazard.
A second laser-scan survey of the landslide (by GNS on November 1 2007) covered a much larger portion of the landslide and was combined with a control survey using satellite global positioning system (GPS) equipment. This allowed the landslide and lake volumes to be more accurately estimated.
| Dam height (maximum) above the original river bed: | 70 metres |
| Landslide volume: | 11 million cubic metres |
| Lake volume (at dam crest level): | 21 million cubic metres |
Lake water continues to flow over the dam crest and has caused some erosion of material from along the outflow channel during periods of high rainfall. A laser-scan survey of the outflow channel was repeated on March 4 2008 to enable assessment of the amount of this erosion.
