Anticipating the ice avalanche with radar data

作者：Lorenz Meier

自然危害和相关损害的风险在全球范围内上升。广泛的保护结构是昂贵的，可能不会自行损害。空间规划和预防措施已成为成功的民事和资产保护的最重要行动。对特定危害过程的永久监控允许早日检测到迫在眉睫的风险或危险情况的持续修改。如果设置并正确使用，则可以通过警告和警报系统大大减少事件造成的潜在损害。

总部位于瑞士的技术公司Geopraevent是该领域的专家。Geopraevent开发，安装和操作定制的警报和监视系统，以适应各种自然危害，例如雪崩（雪和冰），岩石跌落，碎屑流或洪水。应用的技术包括不同类型的雷达，例如基于意大利的领先地面穿透性雷达和干涉技术解决方案IDS Georadar提供的干涉测量雷达。Geopraevent目前在全球范围内运行60多个系统，其中许多在高山环境中。最近，其中一个清楚地表明了预测即将发生的事件并提早反应：Trift冰川在位于瑞士瓦利斯地区SaaS Grund村庄上方的Weissmies上的失败。

Challenging monitoring task in an alpine environment

The well-known summits of Fletschhorn (3993 metres), Lagginhorn (4010 m) and Weissmies (4017 m) separate the Saas-Valley from the Simplon Valley in southern Switzerland. Easily accessible from the cable car station located at Hohsaas, in Canton of Wallis, the Weissmies is one of the most frequently climbed peaks in the area.

In summer 2014, the Trift Glacier, located on the north-west face of Weissmies, showed increased ice avalanche activity. The hanging glacier, formerly supported by ice from below, had destabilised due to glacier mass loss predominating in steeper areas. Canton of Wallis authorities approached Geopraevent with the request to monitor the glacier movement to enable early actions in case of possible ice failures resulting in a large ice/snow avalanche. The specialised engineers of Geopraevent visited the measurement site immediately and supplied the local decision makers and responsible authorities with冰川速度数据on the evening of the day of installation.

Interferometric radar data integrated into geotechnical analysis provides the detailed information required to the experts judging the situation. Interferometric radar is a reliable technique for short or long-term monitoring of multiple scales of displacements regardless of visibility and weather conditions. The radar measures spatially resolved deformation rates with high accuracy.IDS GeoRadar IBIS FM radaris the system deliveringreliable and accurate data of displacements in real time despite the atmospheric correction needed in high altitudes。In addition, a high-definition camera was installed at this location and proved to be an excellent alternative for automatic long-term deformation analysis if weather is not an issue.

Critical landslide and ice avalanche monitoring for safety

Despite the turbulent atmosphere over the glacier that can hamper the measurements at times, reliable measurements have so far been obtained daily. To account for the highly variable alpine conditions, Geopraevent added an extra processing step that verified the plausibility of the data before making it available to the customer via its在线数据门户。This provided sufficient data for VAW/ETH Professor’s Martin Funk group and the local geoformer GmbH’s engineers tointerpret the prevailing hazardfor the area below the hanging glacier.

“After almost three years of continuous radar monitoring, statistics showed that the radar delivered viable deformation data on 95 per cent of days. Radar measurements only failed temporarily during heavy snow storm due to surface changes caused by snow and rain,”Geopraevent物理学家兼项目负责人Richard Steinacher说。

与其余的冰川以每天约10厘米的速度移动相比，不稳定的部分最初以每天约25 cm的速度明显更高的速度移动。在2014年至2017年之间，通常会提前几天从雷达数据中预测数十个小而无害的冰雪崩。

Saving lives by forecasting the inevitable

After 2.5 years of successful operation, the interferometric radar was replaced by a high-resolution camera in early 2017 for visual deformation analysis. This camera delivered excellent results that tracked the movements of the glacier daily if visibility conditions permitted. The camera analysis revealed a distinct acceleration of the glacier starting around August 20^th。在9月初，很明显，冰川很快就会失败。

To provide velocity data also during night and bad weather, Geopraevent re-installed the interferometric radar on September 7^th。速度为每天80厘米，9月9日（星期六）每天加速超过2 m^th。Breakoff-predictions on that day suggested that an ice volume of up to 400’000 m³would fail in the early morning of Sunday, September 10^th。Consequently, 220 inhabitants of theendangered village part of Saas Grund were evacuated。Most of the unstableice volume collapsed, as predicted周日,大约6点. .幸运的是,冰detached in several small portions within ten minutes as revealed by the radar interferograms. No damage occurred and by 8 a.m. all inhabitants could return to their homes.

实时安全监控和长期计划

IDS GeoRadar IBIS-FM system collects quantitative information on slope behaviour from either a spatial or a temporal point of view. It provides reliable early-detection alerts on impending failures in real time, as well as accurate geo-referenced outputs over long periods of time allowing users tointegrate radar data into geotechnical analysis of slope failure mechanisms。

“ IBIS-FM雷达可以实时准确监测多个位移的尺度，从早期检测到缓慢运动到与斜坡塌陷相关的快速加速度。伟大的手术范围，最多4500米，可以安全地将系统部署在舒适的可访问区域，而无需将人员和设备暴露于危险区域，”IDS Georadar Geo业务部门经理Paolo Papeschi说。“由于市场上最先进的自动算法，IBIS-FM在所有天气条件下都能提供可靠和准确的数据。监测专家可以更快地对斜坡危害做出反应，从而确保操作员和公众的安全。”

Geopraeventalso installed an IDS GeoRadar system above Bondo in the region of Bergell, in Canton of Graubunden, Switzerland, after a massive landslide occurred in August 2017. The radar, installed on 3 September 2017, monitors the Pizzo Cengalo permanently anddetects millimeter-movements in all weather conditions。The radar allows to predict new rockfalls early and initiate appropriate measures; a rock fall event on 15 September 2017 was predicted about one day in advance.