Disaster Risk Reduction: The Early Warning System at Devdoraki Gorge
The Caucasus, like many mountain ranges worldwide, is being disproportionately affected by ongoing climate change. Devastating debris flow events originating at the glaciers in the summit area of Mt. Kazbeg have in the past blocked the Terek River valley and heavily affected the main road to Russia, a gas pipeline, a hydro-powerplant and the border control. After the debris flow event in May 2014, the National Environmental Agency (NEA) decided to plan protection measures for the main infrastructure and its beneficiaries. Based on a detailed hazard assessment provided by the Swiss company GEOTEST Ltd., the Government of Georgia decided to implement an early warning system (EWS) to monitor glacial activities in the upper part of Mt. Kazbeg enabling them to warn and protect those living in the valley below who are at risk of harm from debris flows. The system was installed by GEOTEST in autumn 2016.
Hazard assessment and design of Early Warning System
The EWS at Devdoraki Gorge is an efficient measure to close the road and warn people of the different elements at risk when an event occurs. It will not prevent the road from being blocked, but the risk of people dying due to a catastrophic event can be minimized significantly. The economic risk (road block) can only be eliminated by a technical solution (such as a tunnel).
A profound knowledge of the ongoing processes is essential for the proper design of an EWS. The information gained from a detailed hazard assessment was necessary to elaborate realistic hazard scenarios and to determine major parameters for the design of the EWS.
There was only one possible location for the installation of an EWS to sufficiently meet requirements and the dimensions of the gorge, as well as the rough climate during winter, were major challenges for the installers. At the location where the alarm station is installed, the gorge is about 50 m deep and 250 m wide.
The Devdoraki EWS
The system consists of two main stations:
- A monitoring station to observe the glaciated summit area of Mt. Kazbeg;
- An alarm station at Devdoraki Gorge which will detect debris flows and send a direct warning to the border police and SMS to persons in charge at the NEA.
Both stations are connected to a password-protected data portal where the NEA can check pictures, river flow heights, and temperatures, as well as the health-status of the stations. The stations work automatically and sending status reports around the clock.
Monitoring station at 3,000 m a.s.l.
The monitoring station for observation of glacial development on Mt. Kazbeg is situated on an exposed mountain ridge at 3000 m a. s. l.. Glacial movements are monitored by two solar-powered cameras. Pictures are transferred via GSM and radio connection to the main station in the valley. Local authorities are able to determine the glacial movement based on feature tracking within the images.
The installation of the station was challenging because of logistics, rough weather conditions and short time frames to get the work done. All equipment, Swiss experts and specialists from the NEA were transported to the mountain ridge by helicopter.
Alarm station at the Devdoraki Gorge
For the detection of catastrophic events, automated closure of the road and the alerting of local authorities, a large scale monitoring and alarm system was installed in the lower part of the debris channel approximately 3.5 km away from the damage potential (road). The alarm system is equipped with:
- two gauge radars suspended on cables spanned across the channel to measure flow height and debris flow magnitude.
- two webcams with live-access and infrared floodlights allowing night alarm verification.
- Trigger lines, which will raise the alarm when torn from the switch.
In a spectacular one week installation mission, the EWS-components were fixed on the suspension cables by rope access. Well trained Swiss experts worked on the cables hanging more than 50 m over the Gorge.
Conclusions
The EWS at Devdoraki Gorge is based on terrestrial stations. It is a reliable and efficient tool for local communities / authorities to reduce risks. With the early warning system installed, it will be possible to plan and build long-term protection measures.
GEOTEST Ltd, Switzerland is one of the leading Swiss geological-geotechnical and engineering and consulting companies with 140 employees specialized in environmental and natural disaster risk reduction. It investigates and assesses areas endangered by natural hazards, simulate process scenarios with numerical models and plan effective and efficient protection measures. It has over 50 years experiences in the field of natural hazards, landslide and debris flow mechanisms. Based in Switzerland, it has a number of natural hazard related projects in Europe (Germany, Austria, Greece), South America (Chile, Brasil), China, and Georgia.
Daniel Tobler is a geologist and member of the Executive Board of GEOTEST Ltd. He is currently working as natural hazard expert in the Engineering Geology Department. Daniel’s primary work projects are linked to natural hazard assessments (i.e. rockfall, landslides, glacial lakes), planning of mitigation measures and risk management. For the last few years he has been involved in various projects related to climate change and its influence on high mountain areas around the globe.
Daniel Tobler, Stefan Tobler, Irakli Megrelidze