Geoecological risks in the valleys of small rivers of the forest-steppe zone of the Russian plain (on the example of the Chuvash Republic)

. The Chuvash Republic belongs to the territories with a high frequency of occurrence of emergency situations of moderate severity. This is due to the intensive economic development of the region. The probability and intensity of the manifestation of georisks is different for individual landscapes, therefore it needs a detailed study. The study includes the study of the probability of the development of slope, climatic, hydrological risks, and the risk of wildfires on the territory of the Chuvash Republic. The analysis showed that the slope type of geoecological risk is confined to the river valleys of the region and has maximum values in the north of the Chuvash Republic. A high risk of flooding and flooding exists in the valleys of major rivers of the region (Volga, Sura) and their tributaries of the first order. On other watercourses, the hydrological risk is not significant. Climate and weather risks are associated with hurricane winds and dry winds. The southeastern part of the region suffers the most from them. The risk of fires depends on the composition and age of the stand. The maximum risk values are typical for the Prisursky forest area (southern and southwestern parts of the region). Based on the data obtained, the classification of the districts of the Chuvash Republic by the size of the georisks was carried out. Four groups of districts were identified according to the probability of natural emergencies and the main factors of their occurrence were described.


Introduction
The Chuvash Republic belongs to the territories with a high frequency of occurrence of emergency situations of moderate severity caused by hydrometeorological and geological hazards.The occurrence and development of emergency situations can cause significant damage to both man-made complexes and natural ecosystems.High rates of development of the territory of the Chuvash Republic led to the mosaic of the few remaining natural geosystems.The highest mosaic is characteristic of the landscapes of the valleys of small rivers in the region.Emergencies can affect territories of the studied region that are very valuable from the point of view of biodiversity conservation.Therefore, it was decided to analyze the main types of natural and man-made risks in order to identify the degree of probability of occurrence, the area of spread of emergency situations that can affect the development of ecosystems of river valleys of the Chuvash Republic.

Materials and methods
It was decided to analyze geoecological risks in order to identify the most vulnerable natural-territorial complexes from the point of view of emergency situations for their subsequent development of recommendations to increase the stability of landscapes.The most stable landscapes of river valleys from the point of view of risk development can be intensively used.And those exposed to degradation risks should be included in the territories of special protection and compliance with the non-interference regime [1][2][3][4][5][6][7][8][9][10].
The methodological basis was the most relevant at the time of research methods for assessing geoecological risks: 1) the risk of slope processes [5]; 2) hydrological risks [7]; 3) climatic and weather risks [4]; 4) fire hazard risk [1], [2].In the course of the research, the Internet resources of the world's leading publishing houses, abstract journals of environmental topics, statistical reporting on the territory of the Chuvash Republic, Stock and archival documentation of the Territorial Geographical Fund of the Chuvash Republic, the Ministry of Natural Resources and Ecology of Chuvashia were studied.
Equipment was used to register the location of the boundaries of natural and naturalterritorial complexes, software for the compilation of complex and specialized maps "MapInfo", "Surfer".
The following methods were used for field studies of landscapes of river valleys of the Chuvash Republic: 1) comparative geographical: selection of standards, "keys" in the field study of the territory, selection of the most typical objects, landscapes in the Chuvash Republic; 2) landscape mapping and landscape profiling: study of the properties and structure of modern geographical landscapes of the territory of the Czech Republic, comparison of maps and profiles of different times.
3) landscape-geobotanical (on the territory of specially protected natural territories of federal significance: landscape survey, determination of endaphic properties of PTK; 4) decoding of AFS topocards: identification of modern and indigenous landscape structure [8], [10].
The process of constructing graphical models of the studied objects was carried out on the basis of the developments of leading modern scientists [6], etc.
The object of the study was the river valleys of the Chuvash Republic.The Chuvash Republic is located on the eastern part of the Russian Plain, where several natural zones meet: taiga, mixed and broad-leaved forests, steppes.Therefore, a unique combination of diverse landscapes is presented on a small territory of the region.The combination of various landscape zones on a small territory provides high natural stability of geosystems [9].However, the influence of anthropogenic factors can lead to deterioration of landscapes.Such a variety of landscapes and a developed diversified economy allows us to consider the Chuvash Republic as a model region for the Russian Plain.
According to the scheme of physical and geographical zoning of Russia, the territory of Chuvashia is included in two provinces: the subtaiga zone (zone of mixed and broad-leaved forests) of the low-lying Trans-Volga region (Trans-Volga region of Chuvashia) and the forest-steppe province of the Volga upland with deciduous and coniferous forests, foreststeppe and steppe.These provinces, in turn, are part of the area of erosive uplands and plains of the physical and geographical country -the Russian Plain.There are 6 physical and geographical regions on the territory of Chuvashia: Zavolzhsky, Privolzhsky, Central, Zasursky, Prisursky, South-Eastern (fig.1).

Results
Natural and man-made risks can be divided into 2 main groups: man-made and natural.The analysis of technogenic risks consisted in identifying territories where existing landscapes can be affected in one way or another in case of emergency situations of anthropogenic origin.There are 38 potentially dangerous objects on the territory of the Chuvash Republic, including: Class 1 -2 objects; Class 2 -1 object; Class 3 -14 objects; Class 4 -10 objects; Class 5 -11 objects [2].The northern part of the republic (Cheboksary, Mariinsko-Posadsky, Morgaussky and Tsivilsky districts) is most at risk of emergency situations.This is due to the presence of most of the potentially dangerous objects in this territory, including hazard classes 1 and 2 (JSC "Khimprom", JSC "UK Hydro OGK", JSC "Cheboksary HPP").The second group of districts in terms of the potential for emergency situations includes Kanashsky and Vurnarsky districts, characterized by a dense transport network and the presence of the "Vurnarsky Chemical Plant".In the rest of the republic, the risk of emergency situations of technogenic origin is not great and is mainly confined to pipeline routes, railways and highways.During the analysis of natural and environmental risk, it was revealed that the absolute risk indicators of man-made disasters that can lead to the degradation of large-area PTCs are not high.Its maximum values are typical for the northern part of the republic -in the capital Cheboksary district.
The main types of natural risks of a geological and geomorphological nature include landslide and erosion risks.drip-rain destruction, causing significant damage to the economy of the republic.However, the values of erosion washout for most natural geosystems do not exceed the value of natural renewal of the soil cover.Thus, of the geological and geomorphological types of risks, it is the formation of landslides that cause the greatest damage to the landscapes of the Chuvash Republic.The development of modern landslide processes can negatively affect the slope, terrace and floodplain landscapes of the valleys of the above-listed areas [2].
Currently, due to the strengthening of the negative role of floods, an increase in the number of abnormal flood events, the assessment of the hydrological risk of flooding of the territory by internal waters is relevant.A high risk of flooding of floodplains and floodplain terraces are characteristic of the following rivers: Sura (4.8 km long near the village of Sursky Maidan); Bazdna (33.6 km long in the territorial segment from the confluence of the Orbezdna River to the mouth of the river); Kirya (20.4 km long from the village.Krasnobor to the mouth of the river); Alatyr (16 km long from the western borders of the Chuvash Republic to the mouth of the river); Kubnya (21 km long, floods along the administrative border of the Yantikovsky and Urmarsky districts); Bol.Tsivil (45,2 km long from the confluence of the left tributary of the Sorma River to the confluence with the Tsivil River), Tsivil (40.6 km long from the confluence of the B.Tsivil tributary to the mouth of the river).The average danger of flooding is typical for the rivers Parat, Sorma, Lyulya, Kirya, Unga, Vyla, Ryksha, Algashka, the middle course of the Bazdna River.In these rivers, the spring ice drift takes place at high levels.During high water, there is an intense collapse of the banks on one side and an increase in the floodplain in the floodplain.On the Sura rivers, the Tsivil process is accompanied by congestion, causing flooding of large areas and destruction of the banks [2].
Thus, the valleys of small rivers of Chuvashia belong to objects with low vulnerability of landscapes.The probability of violation of natural geosystems within their limits is low.The floodplain landscapes of the Sura and Volga rivers, the Kubnya, Tsivil, Bazdna, Kirya and Alatyr rivers are most at risk of degradation due to a sudden rise in water levels.In the territories highlighted above, due to hydrological, geomorphological indicators, unique biocenoses are observed.Therefore, it is recommended to pay special attention to the conservation of biotopes of the valleys of the rivers listed above.
From the climatic group of factors, the possibilities of occurrence of droughts and dry winds were considered.Most of the territory of Chuvashia is within 15% of the frequency of atmospheric droughts in summer.However, this indicator is poorly differentiated for the studied region.Therefore, further analysis of the listed indicators is not essential.The development of tornadoes is also episodic and has no obvious patterns of distribution in the republic.
One of the factors derived from climatic groups is the risk of fires.To analyze the potential risk of destruction or degradation of existing landscapes, it was decided to analyze the possibility of the occurrence and development of fires on preserved natural geosystems.The territory of the state forest fund was analyzed.In the course of the research conducted on the territory of the state forestry Fund of the Chuvash Republic, 4 categories of fire danger were identified: from the absence of the possibility of fires to high fire hazard (low, medium, high, critical).The category with a high fire danger includes cowberry pine forests, coniferous young trees, spruce forests and pine forests through which railway tracks pass.The types of forest listed above are characteristic primarily for plantations of the Prisursky forest area (Alatyrsky, Ibresinsky, Sumerlinsky and Krasnoarmeysky) districts.There are no significant tree plantations belonging to the category with a very high fire danger on the territory of the Chuvash Republic.However, under long-term climatic conditions favorable for the occurrence of fires (such as the anomalous year 2010), the potential fire hazard increases.Thus, the most susceptible to destruction or degradation due to the occurrence of fires are pine forests and spruce forests of the Prisursky forest area, through which large E3S Web of Conferences 431, 04007 (2023) ITSE-2023 https://doi.org/10.1051/e3sconf/202343104007highways pass.These are coniferous plantations of Ibresinsky and Alatyrsky districts.There is also a high climatic fire hazard.The most secure in this respect are the deciduous plantings of the northern part of the Chuvash Republic.Therefore, in order to preserve the unique forest biotopes, first of all, coniferous plantations of the Prisursky and Zavolzhsky forests should be protected.

Discussion
The distribution of types of natural risks is heterogeneous both geographically and in relation to different landscapes.The coincidence of landslide and erosion risk to the slope type of terrain is highlighted (the maximum development was in the northern part of the republic), the risk of flooding of floodplains of the largest rivers in the republic (floodplains of the Sura river, valleys of the rivers Tsivil, Kubnya, Bazdna) (figure 1).directions.The risk of occurrence and development of fires depends on the species composition of stands and is of maximum importance in over-standing pine forests in the presence of railway communications in the nearby territories of the Prisursky forest area (Ibresinsky, Alatyrsky, Sumerlinsky districts).
Based on the data obtained, groups of administrative districts were identified, if possible, emergency situations of a critical nature in them that could affect natural and territorial complexes important from the point of view of biodiversity conservation.The first group of districts includes Alatyrsky, Mariinsko-Posadsky, Morgaussky, Cheboksary districts.Natural and anthropogenic risks reach critical importance for the vast majority of river valleys: there is a combination of erosion and landslide risks with man-made, hydrological and climatic.Certain types of emergencies can affect all parts of river valleys.
The second group includes Ibresinsky, Poretsky, Yadrinsky and Kozlovsky districts.The selected areas are characterized by critical indicators of natural and man-made risks in several types.For example, for Ibresinsky it is the risk of flooding of floodplains and high fire hazard, for Kozlovsky it is the risk of floods, erosion and landslide risks.The development of emergency situations can lead to the degradation of significant natural geosystems, primarily floodplain and slope.

Conclusion
The highest values of potential risks in the Chuvash Republic are characteristic of the northern regions: a combination of erosion and landslide risks with man-made, hydrological and climatic.This is due to the intensive economic development of unstable and easily disturbed landscapes of river valleys.The use of unstable slopes of river valleys in construction and other industries can lead to the development of landslides and other slope processes.
The vast majority of administrative districts are characterized by the presence of one type of geoecological risks.These are mainly central areas, characterized by a developed diversified economy.This includes erosion, hydrological and climatic risks.The absence of geoecological risks is typical for the river valleys of the southeastern part of the region.These are areas focused on the agricultural sector of the economy.
It should be noted that even in the allocated territories, the potential for emergency situations that can lead to the degradation of significant landscapes is not great in absolute terms.
In order to clarify the possibility of geoecological risks in the river valleys of the Chuvash Republic, detailed studies of specific objects are needed.

Fig. 1 .
Fig. 1.Geographical location of the Republic of Chuvashia The strong dissection of the relief, the presence of sufficient moisture contribute to the development of landslides on the Tatar deposits of Perm, in the Upper Jurassic deposits, and in the Lower Cretaceous deposits.The right bank of the Volga River (Cheboksary, Yadrinsky, Morgaussky, Mariinsko-Posadsky, Kozlovsky districts) and the left bank of the Sura River in the south of the republic (Alatyrsky, Poretsky, Sumerlinsky districts) are distinguished by high risk indicators of landslides.In the region, all types of erosion are actively occurring everywhere: planar flushing, trickle, microruche, gully and E3S Web of Conferences 431, 04007 (2023) ITSE-2023 https://doi.org/10.1051/e3sconf/202343104007

Fig. 2 .
Fig. 2. Groups of districts by geoecological risksIndicators of the risks of weather anomalies spread latitudinal with a minimum in the center of the republic and an increase in the likelihood of drought in the north and south