预见冰雪崩的雷达数据

Author:Lorenz Meier

The risk of natural hazards and the associated damage are globally on the rise. Extensive protection structures are costly and may not prevent damage by themselves. Spatial planning and preventative measures have become the most important actions for successful civil and assets protection. Permanent monitoring of the specific hazard processes allows for early detection of an imminent risk or the continuous modification of the hazard situation. The potential damage caused by an event can be remarkably reduced with warning and alarm systems – if set up and used correctly.

The Swiss-based technology company Geopraevent is an expert in this field. Geopraevent develops, installs and operates customised alarm and monitoring systems for various natural hazards, such as avalanches (snow and ice), rock fall, debris flows or floods. The applied technologies include different types of radar, e.g. the interferometric radar supplied by Italy-based leading provider of Ground Penetrating Radar and interferometric technology solutions IDS GeoRadar. Geopraevent currently runs more than 60 systems globally, many of them in high mountain environments. Recently, one of them clearly demonstrated the ability topredict an imminent event and react early: the failure of the Trift Glacier on Weissmies situated above the village of Saas Grund in Switzerland’s region of Wallis。

在高山环境中挑战监控任务

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.

2014年夏季，位于魏斯米斯西北部的Trift冰川显示出冰雪崩活动的增加。悬挂的冰川以前从下面得到冰的支撑，由于陡峭地区占主导地位的冰川质量损失而失去了稳定。瓦利斯当局的广州接近Geopraevent，要求监视冰川运动，以便在可能发生的冰倒入导致大冰/雪地雪崩的情况下实现早期行动。Geopraevent的专业工程师立即访问了测量地点，并向当地决策者和负责部门提供了glacier velocity data在安装当天晚上。

整合到岩土分析中的干涉雷达数据提供了判断情况所需的详细信息。干涉测量雷达是一种可靠的技术，用于短期或长期监测多个位移的尺度，无论可见性和天气条件如何。雷达以高精度测量空间分辨的变形速率。IDS GEORADAR IBIS FM雷达是交付的系统reliable 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 itsonline data portal。这为VAW/ETH教授的Martin Funk Group和当地的Geoformer GmbH的工程师提供了足够的数据解释现行危险对于悬挂冰川下方的区域。

“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,”said Richard Steinacher, physicist and project leader at Geopraevent.

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。In the beginning of September, it was clear that the glacier would fail soon.

为了在夜晚和恶劣天气中提供速度数据，Geopraevent于9月7日重新安装了干涉范围^Th。Velocities were on the order of 80 cm per day and accelerated to more than 2 m per day on Saturday, September 9^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。因此，有220名endangered village part of Saas Grund were evacuated。大多数不稳定如预测的那样，冰量崩溃了, around Sunday, 6 a.m.. Fortunately, the ice 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.

Real time safety monitoring and long-term planning

IDS GEORADAR IBIS-FM系统从空间或时间的角度收集有关斜率行为的定量信息。它为实时即将发生的失败提供可靠的早期检测警报，并在长时间内进行准确的地理参考输出，使用户能够将雷达数据整合到斜坡故障机制的岩土技术分析中。

“The IBIS-FM radar accurately monitors multiple scales of displacements in real time, from early detection of slow movements to fast accelerations associated with slope collapse. The great operative range, up to 4500 metres allows to safely deploy the system in comfortably accessible areas without exposing people and equipment to hazardous zones,”said Paolo Papeschi, IDS GeoRadar GEO business unit manager.“Thanks to the most advanced automatic algorithms in the market, IBIS-FM delivers reliable and accurate data in all weather conditions. Monitoring experts can respond to slope hazards faster ensuring the safety of operators and the public.”

Geopraevent also 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。雷达允许尽早预测新的摇滚并采取适当的措施；预计2017年9月15日的岩石秋季活动大约提前一天。