Oct 18 2007 - Young River update

Graphical representation of the Young River landslide dam.

On October 9, GNS scientists installed a lake-level monitoring system in the new lake and carried out a terrestrial laser scan survey of the landslide to more accurately determine its volume.

The lake-level monitoring system measures the water level at 5 minute intervals. Data is currently stored by the equipment on-site, and requires manual downloading. Radio communications to enable the data to be transferred from the dam to GNS Science offices in real time are being investigated. The equipment will measure the rate of lake draw-down should the dam breach, and will provide information on the outlet discharge should there be rapid dam failure.

The terrestrial laser scan (TLS) survey of the landslide dam (deposit) and source area used a RIEGL LMS-Z420i scanner, designed specifically for rapidly acquiring hi-resolution three-dimensional topographic data and images. The survey of the dam collected over 2 million points, and has been used to generate a three-dimensional model of the landslide deposit (see accompanying images). This model has been compared with the pre-failure topography, to accurately calculate the landslide and lake volumes. This information greatly improves our knowledge of the Young River landslide, and provides essential information in assessing its future stability as a dam.

Details of the landslide and lake from the TLS survey are:

A further TLS survey will be carried out in the coming weeks to accurately monitor any changes to the dam morphology.

Young River valley: after the landslide.

Young River valley: before the landslide.