Landslides in our country are increasingly reminding us that nature does not forgive the lack of prevention. After the incident near Pamporovo, the topic has come to the fore again, and experts warn that the risk is not only in mountainous areas and along the Black Sea coast. There are also underestimated dangerous terrains around Sofia - in areas with active construction, complex relief and drainage problems. Assoc. Prof. Dr. Eng. Ivan Mitev, Executive Director of the Bulgarian Chamber of Mining and Geology (BMGC), spoke to FACTS.
- Mr. Mitev, we have seen what a landslide is, I am referring to what happened near Pamporovo. Have landslides become more frequent in Bulgaria in recent years and to what extent does climate change play a role in this?
- The reasons cannot be reduced to just one factor. Landslides are the result of an accumulation of factors. The influence is exerted by climatic features, geological structure, slope of the terrain, presence of groundwater, drainage, human activity and climate. But it is a fact that more intense precipitation and sudden changes in weather increase the risk, especially where the terrain is already unstable. Climate change does not create landslides by itself, but can accelerate processes that already exist.
- Which are the riskiest regions in the country in terms of landslides and are there places that, in your opinion, are underestimated as a danger?
- The riskiest regions in terms of landslides in our country are the regions in the Rhodope Mountains, the Northern Black Sea Coast and parts of the Danube coast. In the Rhodope Mountains, the problem is related to the complex relief and large slopes, and on the Black Sea coast and the Danube, to erosion and unstable slopes. As a result of coastal erosion, the land borders of Bulgaria are changing and the territory is decreasing. Coastal erosion is also associated with the displacement of the Danube riverbed.
In terms of landslides, smaller local areas around populated areas remain underestimated - for example, some areas around Sofia such as the areas of Pancharevo, Kokalyane, Bankya and Vladaya.
There, the risk is not so visible, but with intense rainfall and active construction, serious problems can also arise.
- After the incident near Pamporovo, there was again talk of a lack of prevention. Does Bulgaria have a real early warning system for landslides?
- There is monitoring of registered landslides, but the problem is that not every risky terrain is identified in advance. When a section is already listed as landslide-prone, there is order, there are expert opinions and measures. It is more difficult with new or unrecognized processes.
- To what extent do poor drainage and unmaintained infrastructure contribute to the activation of landslide processes?
- Water is one of the main factors. When there is no good drainage, when ditches, ravines, supporting structures or road infrastructure are not maintained, the risk increases. The accumulation of water changes the behavior of soils and rocks and can accelerate a process that would otherwise develop more slowly.
- Are geological risks often underestimated in the construction of roads, hotels and residential buildings and is there sufficient control?
- I would not say that there is a lack of control or that geological risks are deliberately underestimated. The problem is rather in the organization of the investment process itself. Currently, geological surveys run parallel to design, and they should precede it. This is the essential difference. When there is an investment intention, regardless of whether it is a road, hotel, residential building or other infrastructure facility, the design is commissioned first and the surveys begin together with it. Thus, they remain limited within the framework of the specific project and its easement. And geological processes do not have such boundaries.
The landslide may be outside the route itself, but subsequently affect the entire facility.
This is also the reason why in some cases there are so-called “geological surprises“ during construction or years after it. Not because there are no surveys, but because they are aimed at the specific design solution, and not at the overall characteristics of the area. For example, in the case of infrastructure projects, the route is studied within the assigned scope, but not all the processes around it that may develop over time.
Another important point is that practice allows for different approaches and projects are often implemented in short terms due to financing and public needs. This leads to faster progress in the investment process, in which geological surveys remain part of it, instead of being an independent basis for decision-making. Therefore, geological, engineering-geological and hydrogeological surveys should be a separate preliminary stage.
First we need to know the terrain, and then choose the technical solution.
When we have previously clarified geological conditions, we can develop different options, predict risky areas and avoid many of the problems that subsequently increase the cost and delay construction. There are no ideal conditions in nature and risk will always exist. But when the terrain is studied in detail from the beginning, solutions are more sustainable, and the probability of emergency situations is significantly reduced.
- What are the clearest signals that a terrain is potentially dangerous – are there signs that people and local authorities should monitor?
- A landslide rarely starts with a large collapse. Usually the terrain gives indications in advance - through cracks, movements, water and deformations. This does not automatically mean a disaster, but it is a signal that an expert assessment should be sought.
- Are the geological surveys in our country of sufficient quality, or are they in many cases done formally in order to fulfill administrative requirements?
- There are good specialists and good practices, the problem is in the scope and timing of the assignment. When the survey is limited, it does not always give a complete picture of the area.
- Does the state have the capacity and means to strengthen dangerous areas, or is it often reacted after an incident occurs?
- Capacity is being built with the necessary funds. Currently, through the state structures “Geoprotection“, a not bad organization has been created for collecting information and making decisions in already established problem areas in the country. With this, the administrative order is relatively secured. But in order not to move after the events and register them as such, it is necessary to prioritize prevention activities and, accordingly, to provide funding for this. This way, we will limit the effect of classifying these events as disasters, because in many cases they are a consequence of a lack of prevention.
- What measures should Bulgaria take to avoid new blocked roads, destroyed infrastructure and risks to human life due to landslides?
- First of all, there are preliminary geological and hydrogeological surveys before design, especially for roads, resort areas, residential construction and large infrastructure. Second, there are clear technical specifications for different types of construction, because a small building and a highway cannot be approached in the same way. And third, there is constant monitoring, good maintenance of the drainage infrastructure and strategic planning of the territories. The better we know the land on which we build, the less we will rely on luck.
---------------------
Assoc. Prof. Dr. Eng. Ivan Mitev graduated in engineering geology and holds a PhD, specializing in geotechnics and underground construction. He is currently a lecturer in the Department of "Underground Construction" of the University of Mining and Geology "St. Ivan Rilski" and Executive Director of the Bulgarian Chamber of Mining and Geology (BMGC).