Lomonosov Moscow State University Faculty of Geography Land

Lomonosov Moscow State University Faculty of Geography Land Hydrology Department VARIABILITY ASSESSMENT OF FLOOD HAZARD INDICATORS ON THE NORTH CAUCASUS Authors: Anastasiia A. Mironenko Ekaterina P. Rets Natalia L. Frolova 2020

2. The study relevance • Natural flood in the North Caucasus is a frequent occurrence. Only for the years 1991 -2005 112 floods that caused damage to the economic regions of Russia occurred in the North Caucasus (Semenov, Korshunov, 2007), which is about 20% of the total number of hazardous floods in Russia. Of these, 43 floods fell on the territory of the Krasnodar Territory, 26 - Dagestan, 12 - Chechnya. Moreover, research data indicate increased floods in the European part of Russia over the past 110 years (Frolova et al. , 2016). (http: //www. krasfun. ru/2012/07/poezdka-vkrymsk/comment-page-1/) (https: //pics. ru/samye-razrushitelnye-navodneniya-5 sovetov-kak-spastis-ot-stihii) (https: //www. dialog. ua/news/60823_1435239944) 2

3. The study purposes The study aims to conduct a comprehensive assessment of the danger of flooding in the rivers of the North Caucasus. Main research tasks: 1) A comprehensive assessment of the floods formation factors on the North Caucasian rivers; 2) Hydrological database creation necessary for assessing flood hazard in the North Caucasus; 3) Review of existing approaches to flood hazard mapping, choice of approach for the North Caucasus; 4) Current variability assessment of flood discharge characteristics; 5) Calculation and mapping of flood hazard indicators in the North Caucasus. 3

4. Initial data and study area Ø Maximum for the entire observation period, urgent annual water levels with the dates of their passage; Ø Historical highs of water levels (HWL); Ø Marks of levels of dangerous and adverse events on the rivers; Hydrological gauges: Ø 232 with historical water levels; Ø 146 with urgent annual water levels. Hydrological gauges involved in the research 4

5. Methodology for determining the floods risk and its mapping 5. 1. Overview of existing flood hazard mapping approaches Three main approaches: üThe use of integrated indicators that take into account the contribution of several hazard factors (hazard and flood risk maps, vulnerability and exposure of the territory to floods) - (Gallopin, GC, 2006; Gladkevich et al. , 2012; Zemtsov et al. , 2012; Frolova et al. , 2016 ); What approach to choose for the North Caucasus? üConstructing a series of maps reflecting the distribution of a particular flood hazard indicator - (Lugeri et al. , 2006); üUsing the results of hydrological modeling - (Belikov, Militeev, 1992; Cutter et al. , 2008; Alexeevsky et al. , 2016). 5

5. Methodology for determining the floods risk and its mapping 5. 2. Choosing an approach to mapping flood hazard in the North Caucasus and its rationale 1) 2) Construction of maps series reflecting the distribution of a flood hazard particular indicator; Potential flood zone construction (Flood Damage Modeling tools - Rahman, Thakur, 2018; Rosser et al. , 2017; Mc. Coy, 2017) 6

6. Algorithm for constructing of potential flood zone : testing on historical water levels 1) Doubling of points on both sides of the channel in the alignment of hydrological posts; 2) Determination of the flood surface levels (FSL 1, FSL 2, . . . , FSL 232) in the alignment of each gauge: FSL = Н 0 +HWL, where Н 0 - the zero of the fasting graph in the BS, m, HWL - the level of maximum water rise; 3) Construction of a common flood surface over the entire territory of the North Caucasus by interpolation between the values of FSL 1, FSL 2, . . . , FSL 232; 4) Subtraction from the heights of the DEM of the flooding surface (DEM- FSL) to determine the potential zones of flooding in rivers that are not covered by hydrological observations; 5) Building a map of potential flood zone. The scheme of potential flood zone constructing 7

7. Potential flood zone of North Caucasian Rivers 8

8. Assessment of the current variability of flood discharge characteristics Urgent annual water levels Periods of comparison: 1936 -1975 и 1976 -2015 Spearmen-test Fisher-test Homogeneity criteria Red – decrease in rate, green – increase in rate, cross - uniformity violation isn`t statistically significant 9

Urgent annual water levels Periods of comparison: 1936 -1975 и 1976 -2015 Wald-Wolfowitz- Kolmogorov. Smirnov-test Independence criteria Red – differences in distributions are significant, green – insignificant 10

9. Assessment of the risk of flooding on the rivers of the North Caucasus 9. 1. Exceeding levels of adverse and dangerous events Dangerous events – phenomena that can cause significant material damage or pose a threat to human life and health; Adverse events – phenomena that have not reached the level of dangerous events, but significantly complicate the activities of certain sectors of the economy and cause damage to the population and economy. Data: data on the dangerous and adverse events levels of 89 hydrological gauges, 42 of which are located in the Kuban basin and on the rivers of the Black sea coast of the Caucasus, 31 - in the Terek basin, 15 - in the Kuma basin. Methodology: determination of the number and frequency of exceedances of dangerous and adverse events marks during the period of observations at hydrological gauges. 11

Adverse с events level exceeding Number of cases Incidence, % 12

Dangerous events level exceeding Number of cases Incidence, % 13

9. Flood hazard assessment on the rivers of the North Caucasus 9. 2. Calculation of maximum water levels with probability of occurrence P=1% Maximum water levels P=1%, m Advers e events Hazard events Adver Hazar se d events event , % s, % № River Gauge code Catchment area, km² Opening date Closing date Years of observati on 1 Amta Burgusta s. Ketchenery 84004 99, 2 17. 09. 1957 - 58 52 - - 2 Kuma st-tsa Bekeshevskaya 84026 434 06. 04. 1931 - 84 - 1 1 1, 9 Terek st-tsa Grebenskaya 84133 36100 08. 05. 1925 - 90 16 4 3 6, 5 4, 8 Belka g. Gudermes 84284 1190 09. 08. 26 - 89 57 9 4 14, 8 6, 6 … 106 … 146 14

9. Flood hazard assessment on the rivers of the North Caucasus 9. 3. An attempt to build a zone of potential flooding in the North Caucasus based on maximum water levels P=1% Fragment of the simulation results of the flood zone of the North Caucasus rivers according to the urgent annual water levels P=1% data (a) and its comparison with the modeling data on the historical maximums of water levels (b) a) b) 15

Conclusions 1) An extensive database of hydrological data has been created necessary to assess the risk of flooding in the North Caucasus rivers; 2) At all posts there is an increase in the mathematical expectation of urgent annual water levels from the first to the second period (the exception is the Argun River in the alignment of the village of Sovetskoye). A decrease in dispersion is characteristic of rivers in the south of the Black Sea coast of the Caucasus, the Psheha and Belaya river, the middle reaches of the Kuma, the upper reaches of the Baksan and Terek, Fortanga, Sulak and individual sections of the Samur river. The remaining posts recorded an increase in dispersion, which is the predominant trend in the rivers of the North Caucasus; 3) The safety of the population adjacent to certain sections of the Vulan, Mzymta, Belaya, Afips, Ubinka, Pshish, Psekups, Laba and Kuma districts causes concern when passing maximum water levels above AE marks, the frequency of which exceeds 50% of cases. When comparing the maximum water levels and the levels of HH, it was found that the highest degree of flood hazard is inherent in areas adjacent to the Ubinka, Pshish, Psekups, Laba and Kuma; 4) In the framework of the study, a model of the potential flood zone of the North Caucasus rivers was proposed and tested, based on data on the historical maximums of water levels. The construction of the flood zone according to the maximum water levels of 1% security requires a more detailed cartographic basis, access to which is currently limited. 16

Thank you for attention! 17