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Floods map

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Floods

The aim of the flood map is to give an insight into distribution of flooding risk on the territory, and level of its danger to human activity and facilities of national economy. The map was compiled on the basis of reference materials of the national water resource inventory [Long-term…, 1986; Resources …, 1973], data on the flooding damage, and archival and cartographic materials.

Flood hazard is characterized by their genesis, recurrence, impact, damage, possibility and appropriateness of forecasting a dangerous situation. T.A. Borisova determined the integral risk of floods from the territorial assessment of risk caused by floods [Borisova, 2013] using private maps of disturbances of land of different categories and population (based on the estimation of physical, economic and social risks). Flood danger for the rivers of Southern Baikal flowing from the Khamar-Daban Ridge is determined through an expertise as there are no appropriate calculated data.

Severe floods take place at the Selenga, Khilok, Uda, Upper Angara, and Barguzin rivers. The depth of floodplain inundation does not exceed 0.5-1 m during common floods and reaches 1.8-3 m during severe floods. The height of the water layer increases downstream the rivers: for example, its height at the Selenga river near the settlement of Ust-Kyakhta is 1 m and near the city of Ulan-Ude increases up to 3 m. The longest floods (30-90 days) are observed in the valley of the Selenga river and downstream the  river. Shorter floods (up to 25 days) are recorded in the basins of the Barguzin, Upper Angara, Uda, Dzhida, and other rivers. The duration of floods at small rivers, flowing directly to Lake Baikal, is, as a rule, 3-7 days.

The increase of water levels and flow rates in the rivers under study are observed during spring floods caused by thawing of snow cover and glaciers and during summer rain floods. High water floods are not characteristic of rivers located in the southern part. Spring floods are observed in the rivers of the Selenga basin, as well as in the streams running from the Khamar-Daban and Primorsky Ridges. The rivers with spring-summer floods are located in the northern part of the territory (Upper Angara, Barguzin, Turka, Tyya, Rel, Goudzhekit, and others).

Breakup of the ice is often accompanied by ice jams resulting in sharp short-term water level increases. Such local floods are confined to certain areas of narrowing riverbeds or river oxbows. Areas where ice jams are most likely to occur are noted on the Selenga River (Omulyovka Mountain – village of Voznesenovka – Mostovoy sidetrack – settlement of Reid, etc.).

Rain floods usually start from the decrease of spring flood and are observed during the entire summer period. The highest water levels are usually recorded in July-August. The highest intensity of the water level increase is registered at the rivers of the Selenga basin. For instance, during the highest flood in 70 years on the Dzhida River (19/1) it was 4.5 m per day (Khamney level gauge) and 2.79 m per day (Dzhida level gauge). Besides, rapid water level increases of a number of mountain stream tributaries (Khamney, Kurba, Ona, etc.) are associated with their location in the permafrost zone which considerably decreases the infiltration capacity of the soils. Fluctuations of water levels in the Selenga river and in the lower reaches of its tributaries are smoother, which is attributed to the spreading of floods and regulatory influence of the plains. However, the damage from the floods in this area is the most severe as the floodplains are the deepest and flooding is the longest. Moreover, this territory is highly developed economically and densely populated.

Maxima of rain floods on the territory under study significantly prevail over the maxima of spring floods in both absolute value and their number of the total annual maxima [Kichigina, 2000]. The first ones are the most dangerous for the flood formation. The exception is some rivers in the northern regions (Upper Angara, Barguzin, Rel, and Tyya) where the spring flood is the main water regime phase. The map represents the distribution of cross-sections with the dominance of rain flood maxima and with comparable contribution of spring and rain flood maxima. Rain floods cause huge damage as they are widely spread, repeat many times and have a high rate of formation. They can flood both separate small basins and vast territories. Their timely and precise forecast is, as a rule, low. For example, the destructive rain flood that happened in July of 1966 caused a 3 m water increase in the Tuul river, and for several hours the city of Ulaanbaatar submerged and 130 people drowned.  Only for the Republic of Buryatia the damages in the Selenga river basin amounted to about 1.4 billion roubles in 1971, 0.7 billion roubles in 1973 and 40 billion roubles in 1993 (based on current prices). In Mongolia the damages are considerably lower due to the specific settlement patterns and the unique features of the economic use of alluvial lands.

On the southern coast of Lake Baikal (from the Mysovka River mouth to the Angara River outlet), on the south-eastern slope of the Baikal Ridge and in a number of the Selenga River tributaries, floods are often aggravated by mud flows [Makarov, 2012]. Mud floods are caused by heavy rains at the sites with significant slope steepness and easily washed-away loose soil. Mud flow processes mostly develop in the near-mouth areas of the rivers of the northern slope of the Khamar-Daban Ridge and along the Circum-Baikal railway. Mud flows have very destructive force, and they are able to cause significant damages. The increase of water level in such small rivers as the Pokhabikha, Tiganchikha and others can be caused by thawing of ice crust formed as a result of freezing of their river beds.

In general the rivers in the Baikal basin are related to high flood probability ones. Small floods on certain rivers are registered almost annually. Recurrence of severe floods over the period from 1936 to 2012 amounts to 5-12%. According to statistics the most severe last century’s floods were registered in 1932, 1936, 1971, 1973, 1993 and 1998.

The height of the water level on the floodplain and the duration of high water stand are important characteristics. The height depends on both severity of a flood and hydrological and morphological properties of a river. During floods on the Selenga river near the village of Ust’-Kyakhta is comes to 1-2 meters; in the conditions of a narrowing valley and a sufficient stream supply by the Dzhida and Chikoy rivers near the village of Novoselenginsk it sharply rises and may exceed 4 meters. By the city of Ulan-Ude it drops down to 2.2 meters and to 1 meter in the vast delta.

The duration of high water stand varies. Long-term water floods on a floodplain (25-40 days) are observed in the valley of the Selenga river and in the lower course of the Chikoy river. Shorter-term floods (up to 25 days) are registered in the basins of the Barguzin, Upper Angara, Uda and Dzhida and other rivers. On small mountain streams floods usually do not exceed 3-7 days.

3 to 5% of the basin’s territory is exposed to recurrent floods. However, these are largely the most developed and settled lands. For instance, within the Russian part of the Selenga river basin about 4.000 sq km of inundated landscapes may be exposed to flooding; 231.600 hectares or 9.5% are agricultural lands. On the rivers of the northern part (the Barguzin, the Upper Angara) almost 2.000 sq km are flooded, a quarter of them agricultural lands.

The list of settlements on the territory of the Baikal basin, which are at risk of flooding, was compiled using summarized archival and reference data. In total, 75 settlements were included into the flood zone. The settlements with the highest risk of flooding are marked on the map.

References

Borisova, T.A. (2013). Natural-anthropogenic risks in the Lake Baikal basin. Chief Ed. A. Tulokhonov, Novosibirsk: Akad. Izd-vo “Geo”, 2013, 126 p.

Kichigina, N.V. (2000). Genetic and statistic analysis of maximal flow of rivers in South-East Siberia. In: Natural and socio-economic conditions of Siberian regions. Novosibirsk: Izd-vo SO RAN, pp. 19-22.

Makarov, S.A. (2012). Mud flows in Cisbaikalia. Irkutsk: Izd-vo Instituta geografii im. V.B. Sochavy SO RAN, 111 p.

Long-term data on regime and resources of surface land waters. (1986). Leningrad: Gidrometeoizdat, issue 13, 346 p.; issue 14, 282 p.

Surface water resources of the USSR. (1973). Leningrad: Gidrometeoizdat, 1972, vol. 16, issue 2, 586 p.; vol. 16, issue 3, 400 p.

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Fogs map

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Fogs

Fogs at Lake Baikal form corresponding to sea fogs: they correlate with the relatively consistent seasonal drifting of air masses and with the seasonal distribution of winds. However due to the isolated inland location of the lake and the influence of the surrounding continental landmass, the Baikal fogs are to be classified as a separate type of advection fogs of large inland lakes and water reservoirs. The number of foggy days is the highest along the Northeast coast of Lake Baikal, and the lowest in the Central and the Southwest parts of the lake. The fogs lie mainly in the curves of the coastline, bays, coves, mouths of the rivers, flowing into Lake Baikal, and the numerous creek valleys that open towards the lake. In the annual cycle, the fogs are most frequent in July. The Northern stations report higher frequency of fogs in summer and register a single sharp peak in July. The Southern stations report lower frequency of fogs in the annual cycle, while the annual peak is extended over June, July and August.

At Lake Baikal, condensation prevails in summer, and evaporation – in winter. In the warm season, fogs are formed by passing of a warm front, or within a diffused pressure field above the wet underlying terrain. These fogs are formed by condensation of vapor in a mass of air warmed up above the land as it passes over the cold water. Summer fogs are very dense and persistent, especially in the first half of summer.

Evaporation fogs occur during the сold season. Until the lake freezes over, these fogs continuously stay above the water surface or can be lifted into low cloud. In winter, the Siberian Highland ground inversions accompanied by significant fall of temperature form radiation fogs. Winter fog formation is most commonly connected with advection of cold air over the warmer water surface. In cold season, as well as during the summer months, other types of fog can occur at Lake Baikal, caused by various reasons: temperature gradient between land and sea, the occurrence of floe patches and clear water surface, clearings in the fast ice of Lake Baikal.

Forecasting Baikal fogs requires an integrated approach with attention to such factors as their movability and the complexity of their formation processes. One has to take into account the general meteorological situation, the character of breeze/monsoon circulation in the area, the influence of coastline. It is important to consider the influence of West winds on the fog formation at the East coast, especially in winter.

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Forest resources and their use map

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Forest resources and their use

The Baikal basin is a truly enormous treasury of "green gold." As of January 1, 2011 the forest area is 32103.6 thousand hectares in the Russian part of the basin and 10354.3 thousand hectares in Mongolia. Total timber reserves in the Russian part of the basin are 2,795,800,000 m3, with a stock of the conifers 2.443.000.000 m3 (87.4 %). In Mongolia the total timber reserves is 1.373.100.000 m3.

The basic map shows the forests of nature conservation and other preservation patterns, as well as merchantable and other forests, suitable for commercial use, and reserved forests. It should be said that the division of forest lands into protected, merchantable and reserved is characteristic only of the Russian Federation. However, in the territory of Mongolia forests of special importance and in need of protection are distinguished, such as forest areas up to 100 hectares, forests on the slopes of the mountain areas of more than 30 degrees, etc.

Protected forests in Russia include forests subject to reclamation in order to maintain environmental, water protection, safety, sanitation, health and other useful features while using these forests providing compatibility with their intended purpose. Within the Baikal basin there is a high proportion of protected forests, due their ecosystemic, environment protection and water protection functions, as well as the important ecological role of montane forests. Merchantable forests are those which should be developed for the purposes of sustainable, maximum-efficiency rate production of high quality wood and other forest resources, as well as their conversion products ensuring the preservation of beneficial functions of forests. As far as the reserved forests are concerned, those are the forests not planned for logging for next twenty years. These forests are mostly located in the northern part of the region, in the permafrost zone, off-road area and are unattractive for development.

The insert map "Timber reserves by groups of the major forest forming species" shows the average reserves of softwood and hardwood forests (m3) per hectare of land covered by them. The average stand of timber per unit of the covered area is one of the indicators characterizing the productivity of forests, depending on growing conditions of stands, their species, and stands sparsity. The average stand of conifers and deciduous trees per hectare in the Russian part of the Baikal basin is 132.5 m3 (the global average is 100 m3/ha ), and it is fluctuating from 79-82 m3/ha (mostly in the steppe regions of Zabaikalsky krai, the Republic of Buryatia (Zaigraevsky, Chita districts) to 160 -170 m3/ha and up in the mid- and north areas (Uletovsky district of Transbaikalia, Kabansky and Severobaikalsky districts of the Republic of Buryatia, Irkutsky and Slyudyansky districts of Irkutsk oblast). Within the Mongolian part of the basin the average reserve of coniferous and deciduous tree stands is 126.6 m3 per one hectare with fluctuations in the aimaks from 81 to 205 m3 per ha. The highest average stand of timber per unit of forest area is characteristic of the northern mountainous areas of Mongolia.

Also this map shows the distribution of the total stand of timber by major groups of forest forming species (in million m3) with the method of cartodiagram. This index demonstrates forest-resource security area, which varies significantly in the districts of the Russian part of the basin and Mongolian aimaks (from 1.5 to 481 million m3). For correct depiction of the amount of total stand of timber within municipalities a conventional stepped scale for the circular cartodiagram was worked out, which enables to judge about the stands of timber for each group using the percentage between the major groups of forest forming species (coniferous, deciduous and shrubs).

Forest use is determined by the activities that have priority development within the forest vegetation areas. Timber harvesting is most developed among all kinds of forest utilization in the Russian part of the Baikal basin regulated by allowable cutting rates. Forests are actively used for recreation, hunting activities, etc.

In the analysis of forest utilization the following trends for all forests of the Baikal basin are revealed in recent years. They are reduction of coniferous stands, mostly maturing and mature stands; replacement of coniferous species by deciduous ones; widespread illegal logging, reduction of forested area due to fires, forest damage by pests, deforestation, and insufficient reforestation.

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