Reservoir Bank Research Articles

Study on the Damage Mechanism of Bank Slope-Bridge Pile Foundation Interaction under Reservoir Water Level Cycle

The physical and mechanical properties of the reservoir bank slope deteriorate under the fluctuation of water level, causing bank debonding and slippage, which can produce different degrees of damage to the bridge foundation, piers, and superstructure, a condition that is difficult to treat. In this paper, for a Yangtze River Bridge bank slope instability problem in the Three Gorges reservoir area, a numerical model of the bank slope and bridge was established using the finite element-SPH conversion coupling algorithm, and the pile pier damage development law and damage mode (deformation and stress–strain curves of the bank slope and pile foundation) were obtained according to the geological conditions of the bridge location. Additionally, combined with the characteristics of bank destabilization in the reservoir area of the Three Gorges Yangtze River Bridge, landslide management is proposed by using soil drainage and anti-slip pile reinforcement measures. In addition, for the characteristics of bridge pier deflection, a comprehensive deflection correction reinforcement method of pushing deflection correction, adding pile foundation, expanding pile bearing, and increasing pier cross-sectional area is proposed, so as to provide a theoretical basis for the prevention and control of reservoir bank landslides, the service life of pile structure, and the disposal of diseases.

Prediction model of particle loss based on seepage tests of sediment in water-level-fluctuation zone of reservoir

Particle erosion is one of the important factors in the deformation and failure of sediment in the reservoir slopes during reservoir operation. The determination of the sensitive factors and the degree of loss of party les from reservoir banks is an important prerequisite for studying the stability of reservoir banks. The degree of particle loss has become a key indicator in studying the deformation failure process of reservoir slope sediment. Based on field investigation and statistics, the coarse-grained skeleton of slope sediment was divided into five types. An orthogonal design method was used to design the test specimens. In this study, a multi-valve parallel particle erosion test system was developed, and a preparation method of sediment samples was proposed. The variation of grain positions in the sediment sample is analyzed using digital image processing technology. The sensitivity factor of fine particle loss rate was obtained by the range analysis method. Based on seepage test results, a prediction model of particle loss rate was proposed. The prediction model was verified by comparing it with experimental data from two mounded slope sites, Baijiabao landslide and Kaziwan landslide in the Three Gorges Reservoir area. The results show that the relative density is more sensitive than other factors in affecting the particle loss rate. The particle loss is one of the non-negligible reasons for the sediment strength deterioration of the reservoir water-level-fluctuation zone. The results of the study can provide useful references for future studies on the macroscopic and microscopic structural characteristics of bank slope sediment during reservoir operation.

Thermo-hydro-poro-mechanical responses of a reservoir-induced landslide tracked by high-resolution fiber optic sensing nerves

Thermo-poro-mechanical responses along sliding zone/surface have been extensively studied. However, it has not been recognized that the potential contribution of other crucial engineering geological interfaces beyond the slip surface to progressive failure. Here, we aim to investigate the subsurface multi-physics of reservoir landslides under two extreme hydrologic conditions (i.e. wet and dry), particularly within sliding masses. Based on ultra-weak fiber Bragg grating (UWFBG) technology, we employ special-purpose fiber optic sensing cables that can be implanted into boreholes as “nerves of the Earth” to collect data on soil temperature, water content, pore water pressure, and strain. The Xinpu landslide in the middle reach of the Three Gorges Reservoir Area in China was selected as a case study to establish a paradigm for in situ thermo-hydro-poro-mechanical monitoring. These UWFBG-based sensing cables were vertically buried in a 31 m-deep borehole at the foot of the landslide, with a resolution of 1 m except for the pressure sensor. We reported field measurements covering the period 2021 and 2022 and produced the spatiotemporal profiles throughout the borehole. Results show that wet years are more likely to motivate landslide motions than dry years. The annual thermally active layer of the landslide has a critical depth of roughly 9 m and might move downward in warmer years. The dynamic groundwater table is located at depths of 9–15 m, where the peaked strain undergoes a periodical response of leap and withdrawal to annual hydrometeorological cycles. These interface behaviors may support the interpretation of the contribution of reservoir regulation to slope stability, allowing us to correlate them to local damage events and potential global destabilization. This paper also offers a natural framework for interpreting thermo-hydro-poro-mechanical signatures from creeping reservoir bank slopes, which may form the basis for a landslide monitoring and early warning system.

Catalogue of specimens of Odacantha melanura (Linnaeus, 1767) (Coleoptera, Carabidae) deposited in the State Museum of Natural History NASU, Lviv, Ukraine

Tribe Odacanthini is a tribe of ground beetles in the family Carabidae subfamily Lebiinae, there are more than 43 genera and 680 described species in Odacanthini (Lorenz, 2021). Genus Odacantha includs 15 extant species known so far. European-Asian genus Odacantha, in Ukraine is represented by single species Odacantha melanura (Linnaeus, 1767). Species distributed in Western Palearctic from medle parts of Spain, Italy and Balkan Peninsula till to southern provinces of Fennoscandia, to East reached Amur River, recorded in Caucasus and Iran (Burakowski et al., 1974). Odacantha melanura (Linnaeus, 1767) is a winged, spring breeder and occurs in the Scirpus, Typha and Phragmites thicketon the banks of reservoirs and bogs (Hůrka, 1996). In Ukraine Odacantha melanura (Linnaeus, 1767) recorded in Podillia (Tovtry ridge, Pantalykhy steppe, Butsyky) (Nowicki, 1864), Horodok vicinity (Malkovychi) (Łomnicki, 1868), Butsyky (Łomnicki, 1870), banks of the Dnipro River near Kyiv (Hochhuth, 1871), Podillia (Nowicki, 1873), Ivano-Frankove (Zalissia) (Król, 1877), Lviv (Vulka near Sobka pond), Ivano-Frankove (Zalissia) (Łomnicki, 1890), Ternopil (Rybiński, 1903), up to Kharkiv and Kherson gubernias (provinces) (Якобсон, 1905), Kamianets-Podilskyi (Якубовский, 1914), Uzhhorod and all Transcarpathians lowland (Roubal, 1930), Crimea (Эйдельберг, Мальцев, Перваков, 1988), Forest (Novgorod-Siverske Polissia) and Forest-steppe zones of Left-Bank Ukraine (Kirichenko, Babko, 2004 (2005)), Mezynskyi National Nature Park (Шешурак, Назаров, 2021). In the collection of the State Museum of Natural History, National Academy of Scienses of Ukraine (SMNH) are stored 19 specimens collected in western part of Ukraine, Poland and Austria. Collection material represents the following physiographic regions: Temprate broad-leaf forests zone: Roztotsko-Opilska Upland oblast (Roztochchia district (9 specimens), Opillia district (1)), West Podillia Upland oblast (3), Ukrainian Carpathians: Ciscarpathians Upland oblast (1). The findings are collected by the following collectors M. Łomnicki, J. Mazurek, dr. Łuczakowski , A. Stöckl, H. Eder, Yu. Polianskyi, A. Winkler, V. Zanko in the period of ~1868 – first half of XX century.

Deterioration Effect of Sandstone Tensile Strength and Its Mesoscopic Mechanism under Dry-wet Cycles

The rock mass in the hydro-fluctuating zone of the reservoir bank slope is under dry-wet cycles for a long time, which will cause the deterioration of rock mass and induce geological disasters. In this study, a series of dry-wet cycle tests on the argillaceous quartz sandstone in the Three Gorges Reservoir area was carried out. Then, after different dry-wet cycles, the sandstone specimens were used to conduct the Brazilian splitting, scanning electron microscope, and 3D laser scanning tests. Herein, we provided detailed physical and microscopy image data to analyze the deterioration effect of tensile strength and mesostructure deterioration process of sandstone. With the increase of dry-wet cycles, the tensile strength of sandstone initially decreases rapidly, and then the decline rate tends to slow down. The evolution laws of fractal dimension and porosity are also significantly consistent with the deterioration of tensile strength. Moreover, further mesostructural analysis has revealed the repeated “absorption and swelling-dehydration and contraction” of clay minerals. This results in the breakage of framework mineral quartz and the expansion and connectivity of internal cracks, which ultimately deteriorates sandstone’s tensile strength.

Study on Early Identification of Landslide Perilous Rocks Based on Multi-Dynamics Parameters

The dynamics parameters cause sudden change during the damage of the structural plane of landslide perilous rocks, and these can be easily accessed. Therefore the changes in dynamics parameters can effectively achieve early identification, stability evaluation, and monitoring and pre-alarming of the perilous rocks. Seven kinds of dynamic indexes, such as pulse indicator, margin index, the center of gravity frequency, root mean square frequency, impact energy, relative energy of the first frequency band, and damping ratio, are introduced and the early identification of landslide perilous rock is achieved based on the support vector machines (SVM) model, improved by particle swarm optimization algorithm. A laser vibrometer collected seven dynamic indexes of two rock masses on the reservoir bank slope in Baihebao Reservoir, China. Based on the particle group optimization algorithm optimization support vector (PSO–SVM) perilous rocks recognition model, and seven dynamic indicators, the stability of two rock masses was recognized with high efficiency and accuracy. The identification results were consistent with the landslide perilous rock identification results based on natural vibration frequency, and the results verify the accuracy of the PSO–SVM perilous rocks identification model. The results show that the sensitivity order of each identification index is: root mean square frequency > margin index > relative energy of the first frequency band > center of gravity frequency > impact energy > pulse indicator > damping ratio. The accuracy of the multi-dynamics parameters landslide perilous rock mass identification model can be improved by selecting appropriate dynamic indexes with good sensitivity. The research results have high theoretical significance and application value for early identification of landslide perilous rocks, stability evaluation, and safety monitoring, and early warning.

Physical and Numerical Simulation of the Mechanism Underpinning Accumulation Layer Deformation, Instability, and Movement Caused by Changing Reservoir Water Levels

Large-scale physical models of landslides can potentially accurately reflect the interactions between many internal and external factors and elucidate the process of slope deformation and failure. In order to reveal the mechanism of deformation of the reservoir bank accumulation layer, in this study, a large-scale physical test model with a similarity ratio of 1:200 was constructed based on the actual engineering geological section. Two reservoir water level cycle fluctuation conditions were simulated, and the reservoir water level drop rate was strictly controlled to be two times the rise rate. This study analyzed pore water pressure and deformation characteristics in the accumulation layer in relation to fluctuating reservoir water levels. The results showed that the rise in reservoir water level will make landslides more stable. The periodic sudden drop in water level seriously endangers the stability of landslides. The deformation and failure of landslides are more likely to occur in the weak interlayer area. The failure mode of the accumulation body in the test was traction failure. It is suggested that the front part of the accumulation body can be reinforced in practical engineering. To reveal the progression of instability and movement during accumulation layer large-scale landslides, a numerical model was constructed using the material point method. The accumulation layer sliding process could be divided into three stages: acceleration sliding, deceleration sliding and stabilization. After destabilization, the river channel may be altered by the landslide mass to form a landslide dam, potentially threatening the integrity of the dam via impulse waves generated during destabilization. The research results provide technical support for reservoir scheduling in major water conservancy and hydroelectric power station reservoirs as well as engineering risk assessment and prevention.

Reliability evaluation of reservoir bank slopes with weak interlayers considering spatial variability

Reservoir bank slopes with weak interlayers are common in the Three Gorges Reservoir area. Their stabilities are affected by multi-coupled factors (e.g., reservoir water fluctuations, rainfall, and earthquakes in the reservoir area). Meanwhile, the differences in mechanical parameters of reservoir banks make it more difficult to determine the dynamic stability of bank slopes under complex mechanical environments. In this paper, the multiple disaster-causing factors and spatial variability of the landslide were comprehensively considered to study the long-term evolution trend of the bank slopes with weak interlayers. Specifically, the limit equilibrium method combined with the random field was performed to calculate the reliability. Furthermore, the long-term effects of dry-wet cycles on reservoir bank landslides and the sensitivity analysis of the statistical parameters of the random field were discussed. The results show that the earthquake action had the most significant impact on the failure probability of the landslide. The failure probability was more significantly affected by the vertical fluctuation range of the parameters and the coefficient of variation of the internal friction angle. The increase in failure probability under the action of dry-wet cycles was mainly caused by the reduction of the parameters of the weak interlayer. The reliability evaluation method of reservoir bank slopes can be applied to predict the long-term stability of the coastal banks.

Structure Integrity Analysis Using Fluid–Structure Interaction at Hydropower Bottom Outlet Discharge

Dam reliability analysis is performed to determine the structural integrity of dams and, hence, to prevent dam failure. The Chenderoh Dam structure is divided into five parts: the left bank, right bank, spillway, intake section, and bottom outlet, with each element performing standalone functions to maintain the overall Dam’s continuous operation. This study presents a numerical reliability analysis of water dam reservoir banks using fluid–structure interaction (FSI) simulation of the bottom outlet structures operated at different discharge conditions. Three-dimensional computer-aided drawings were used to view the overall Chenderoh Dam. Next, a two-way fluid–structure interaction (FSI) model was developed to explore the influence of fluid flow and structural deformation on dam systems. The FSI modeling consists of Ansys Fluent and Ansys Structural modules to consider the boundary conditions separately. The reliability and performance of the reservoir bottom outlet structure was effectively simulated and recognised using FSI. The maximum stress on the bottom outlet section is 18.4 MPa, which is lower than the yield stress of mild steel of 370 MPa. Therefore, there will be no structural failure being observed on the bottom outlet section when the butterfly valve is fully closed. With a few exceptions, the FSI models projected that bottom outlet structures would be able to run under specified conditions without structural collapse or requiring interventions due to having lower stress than the material’s yield strength.

Study on Calculation Method of Stability of Damaged Sliding Dangerous Rock on Reservoir Bank

The rapid destruction of dangerous rock produces a large amount of energy, causing heavy casualties and economic losses every year. There are various failure modes and stability calculation methods of dangerous rock. The common failure modes of dangerous rock are tipping mode, sliding mode and falling mode. For large tower pillar dangerous rock with degraded foundation, it is unreasonable to use conventional stability calculation methods to calculate the stability of dangerous rock. This paper takes Jianchuandong dangerous rock in Wushan County as the research background, considering the expansion of rock cavity of damaged dangerous rock base and the deterioration of rock mass in the base of large tower column reservoir bank, and establishes the stability calculation method of dangerous rock suitable for the damage deterioration of the base. It is innovative on the basis of the traditional stability calculation method of dangerous rock, which has important practical significance and theoretical basis for the calculation of the stability of unconventional dangerous rock.

Experimental Study on Creep Characteristics of Unloaded Rock Masses for Excavation of Rock Slopes in Cold Areas

Seasonal freeze–thaw environments are one of the key factors that aggravate the mechanical strength decay of excavated and unloaded rock masses on reservoir banks in cold areas. To study the time-dependent mechanical properties of an excavated and unloaded rock mass on a bank slope under freeze–thaw action, triaxial unloading tests were carried out on sandstone, freeze–thaw tests simulating freezing strength were conducted, and triaxial creep tests were implemented with graded incremental loading on unloaded specimens subjected to freeze–thaw action. The test results showed that the total deformation of the unloaded specimens is significantly increased compared with the conventional specimens, and the lateral direction is more likely to produce creep behaviour than the axial direction. The level of confining pressure determines the level of creep deformation of unloaded specimens and affects the variation law of creep rate. The creep behaviour of the unloaded specimens is aggravated by freeze–thaw action and, the longer the freezing period, the larger the creep strain share, and the creep rate increases significantly. The creep damage pattern of the unloaded specimens subjected to freeze–thaw action is mainly manifested as shear damage, and the creep process intensifies the derivation of tension-type cracks in the specimens. The higher the confining pressure of the unloaded specimen, the more obvious the plastic characteristics and the weaker the brittle characteristics during creep failure. The freeze–thaw action significantly reduces the long-term strength of the unloaded specimen, which is approximately 50~55% of the instantaneous strength. The long-term strength decays significantly with an increasing freezing period, and the research results can provide a theoretical reference for the evaluation of the long-term stability of excavated and unloaded rock masses in cold areas.

Study on deformation mechanism and parameter inversion of a reservoir bank slope during initial impoundment

Study on deformation mechanism and parameter inversion of a reservoir bank slope during initial impoundment

Propagation Mechanism of Deep-Water Impulse Waves Generated by Landslides in V-Shaped River Channels of Mountain Valleys: Physical Model of Regular Rigid Block

Landslide-induced impulse waves in alpine valleys are a significant risk to large-scale dam and reservoir engineering projects in the surrounding area. In this study, a 1 : 200-scale physical model of landslide-induced impulse waves in a V-shaped river channel was established, and 18 groups of tests were conducted to evaluate the influence of different parameters, such as the volume and shape of the landslide body, water entry velocity, and water depth of the reservoir. Based on the test results, a dimensionless formula was established for the first wave height of impulse waves caused by a deep-water landslide in a V-shaped channel. An energy conversion law was determined for the impact of landslide-induced impulse waves on the reservoir bank. Finally, a distribution law was obtained for the initial maximum pressure caused by landslide-induced impulse waves along the water depth on the opposite bank. The theoretical predictions of the dimensionless formula showed good agreement with the experimental results, and the energy conversion rate of the landslide-induced impulse waves initially increased and then decreased with an increasing Froude number. The maximum dynamic water pressure showed a triangular distribution with increasing water depth below the surface of the still water body. The impact pressure of the impulse waves on the slope on the opposite bank increased with the water entry velocity. This study provides a scientific basis for the risk prevention and control of landslide-induced impulse waves in river channels feeding into reservoirs.

Revealing the time lag between slope stability and reservoir water fluctuation from InSAR observations and wavelet tools— a case study in Maoergai Reservoir (China)

ABSTRACT Reservoir water fluctuation in supply and storage cycle have strong triggering effects on landslides on both sides of reservoir banks. Early identification of reservoir landslides and revealing the relationship between slope stability and the triggering factors including reservoir level and rainfall, are of great significance in further protecting nearby residents’ lives and properties. In this paper, based on the small baseline subset time series method (SBAS-InSAR), the potential landslides with active displacements in the river bank of Maoergai hydropower station in Heishui County from 2018 to 2020 were monitored with Sentinel-1 data. As a result, a total of 20 unstable slopes were detected. Subsequently, it was found through a gray correlation analysis that the fluctuation of the reservoir water level is the main triggering factor for the displacement on unstable slopes. This paper applied wavelet tools to quantify the time lag between slope stability and reservoir water fluctuation, revealing that the displacement exhibits a seasonal trend, whose high-frequency signal displacement has an interannual period (1 year). Based on the Cross Wavelet Transform (XWT) analysis, under the interannual scale of one year, the reservoir water fluctuation and nonlinear displacement show a clear common power in wavelet. Additionally, a time lag of 65–120 days between slope stability and reservoir water fluctuations has been found, indicating that the non-linear displacements were behind the water level changes. Among the factors affecting the time lag, the elevation of the points and their distance to the bank shore show Pearson’s correlation coefficients of 0.69 and 0.70, respectively. The observed time lag and correlations could be related to the gradual saturation/drainage processes of the slope and the drainage path. This paper demonstrates the technical support to quantitatively reveal the time lag between slope stability and reservoir water fluctuation by InSAR and wavelet tools, providing strong support for the analysis of the mechanisms of landslides in Maoergai reservoir area.

Degradation of Typical Reverse Sand-Mudstone Interbedded Bank Slope Based on Multi-Source Field Experiments.

The bank slopes in the Three Gorges Reservoir area (TGRA) have experienced obvious deterioration under the action of the periodic fluctuations in the reservoir water level. Generally, laboratory tests have been used to reveal the evolution trend of the slope banks. However, this method has a certain degree of cross-scale problem, especially for the mechanical state in a complex environment. Therefore, in this study, we took the Yangjiaping bank slope in the TGRA as an example and proposed a comprehensive on-site detection method to further reveal the rock mass degradation phenomenon of this typical reverse sand-mudstone interbedded bank slope. Specifically, multi-scale laser scanning, cross-hole acoustic wave detection, and inclination measurements were performed to analyze the fractures, quality, and deformation of rocky banks. The results showed that the deterioration of the bank slope manifested as the expansion, deepening, and widening of the cracks, as well as the peeling off and loosening of rocky banks. Large-scale laser scanning revealed that the deterioration zone was deformed along large fracture zones and layers. Unlike limestone slopes, the intact sandstone underground might be degraded by changes in water. There are few inclinometers and no deformation or weak deformation, which requires long-term monitoring. The relevant research methods provide an important reference for determining the instability and failure trend of the reservoir bank slopes.

Deformation Monitoring and Trend Analysis of Reservoir Bank Landslides by Combining Time-Series InSAR and Hurst Index

Landslides along the Three Gorges Reservoir in China pose a threat to coastal residents and waterway safety. To reduce false positive misjudgments caused by a sudden local change in the landslide deformation curve, in this paper, we propose an effective method for predicting the deformation trend of reservoir bank landslides. We take reservoir bank landslides in the Wanzhou District of the Three Gorges Reservoir area as the research object. The Time-Series Interferometric Synthetic Aperture Radar (InSAR) method and 62 Sentinel-1A images from 2018 to 2022 were selected for landslide deformation monitoring, and the Hurst index was calculated to characterize the deformation trend. Furthermore, we propose a method for predicting the deformation trend based on the statistical distribution of deformation rates and the physical significance of the Hurst index. After the field survey and Global Positioning System (GPS) verification, the Time-Series InSAR results are shown to be reliable. We take the Sifangbei landslide as a representative case to analyze the validation results. It is found that the determined Sifangbei landslide deformation trend is consistent with the conclusions for the region. In addition, the deformation trend of a reservoir bank slope has obvious spatial and temporal differences. Changes in the reservoir water level and concentrated rainfall play roles similar to those of catalysts. The proposed method, involving the combination of Time-Series InSAR and the Hurst index, can effectively monitor deformation and predict the stability trend of reservoir bank landslides. The presented research results provide new ideas and solutions for landslide prevention and risk mitigation in reservoir areas.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

InSAR-Based Active Landslide Detection and Characterization Along the Upper Reaches of the Yellow River

Landslides have attracted extensive attention and research worldwide because of their tremendous destructiveness, and many catastrophic landslides have occurred along river corridors and reservoir bank slopes. The detection and detailed monitoring of potential landslides are prerequisites for landslide disaster prevention, with recent advance in spaceborne Interferometric Synthetic Aperture Radar (InSAR) having effectively addressed this challenge. In this study, a wide-area landslide detection and monitoring framework, combining multiple InSAR techniques, is proposed to investigate active landslides along the upper reaches of the Yellow River from Longyang Gorge to Liujia Gorge (UYRLL), north-west China. A total of 597 active landslides have been mapped in this region for the first time. Our analyses suggest that a large percentage of the detected landslides are distributed at an elevation of 2,000-3,000 m with slope angles of 5-30°and their spatial distribution density is correlated with regional tectonic activity. Multi-Temporal InSAR (MTI) techniques have also been adopted to analyze the surface motion characteristics of two typical landslides (i.e., the Lijia landslide and the Xijitan landslide), showing that these two landslides are dominated by linear motion. The landslide movements also contain slight non-linear oscillations, inferred from wavelet analysis to be associated with reservoir water area changes and seasonal rainfall. The proposed framework herein can be extended to the detection and monitoring of active landslides in other areas with similar geomorphic features, and the above findings on landslide characteristics can also contribute to landslide prevention and mitigation in the upper Yellow River area.

Evolutionary trend of plant community and adaptive strategies of dominant plants in the water-level-fluctuation zone of the Three Gorges Reservoir

三峡水库周期性蓄水显著改变了消落区植物群落组成及多样性,植物群落的演变过程能反映和影响整个消落区生态系统的变化,但目前还缺乏长期连续的观测数据记录,因而本研究基于2009-2021年6月的固定样方长时间序列监测数据和优势植物叶片功能性状数据,分析了消落区3个高程(145~155、155~165和165~175 m)区域植物群落多样性和优势植物重要值的变化趋势,通过冗余分析和蒙特卡罗检验揭示了水库运行特征参数和气象因子对消落区植物特征的影响。研究发现:1)消落区3个高程区域,优势植物差异明显,145~155和155~165 m区域以狗牙根、香附子和苍耳等为主,165~175 m区域以狗牙根、野胡萝卜和鬼针草等为主。145~155 m区域植物群落Shannon-Wiener多样性指数(1.47±0.47)和Pielou 均匀度指数(0.67±0.07)显著低于165~175 m区域。2)2009-2021年期间,高程145~155和155~165 m区域Shannon-Wiener多样性指数和Pielou 均匀度指数呈波动下降趋势,优势植物狗牙根和香附子的重要值呈增加趋势。3)RDA分析表明,与水库运行特征密切相关的淹没时间、周期性淹没次数和高程均能显著影响消落区优势植物重要值的大小。狗牙根、喜旱莲子草和苍耳等物种重要值与周期性淹没次数呈正相关,狗尾草和水蓼的重要值与淹没次数呈负相关。野胡萝卜、鬼针草和黄花蒿等物种重要值与高程呈正相关,狗牙根、香附子和水蓼的重要值与高程呈负相关。4)不同植物的适应策略各有不同,消落区植物狗牙根的比叶面积最大,为(32.8±7.2)mm²/mg,鬼针草和苍耳次之,分别为(30.6±3.9)和(30.0±3.0)mm²/mg,均小于未淹没对照区植物的比叶面积。5)狗牙根耐水淹能力强,以S策略投资为主(53.4%),苍耳的比叶面积大,以C投资策略主(61.3%)。小白酒草(64.6%)和鬼针草(50.9%)以R策略为主,种子小数量多,喜旱莲子草也以R策略为主(71.3%),具有发达的根茎。本研究结果可加深对大型水库消落区植物群落演变趋势及优势植物的生态适应策略的科学认知。;The periodic impoundment of the Three Gorges Reservoir has significantly changed the composition and diversity of plant communities in the water-level-fluctuation zone (WLFZ), and its succession process can reflect and influence the changes of the whole reservoir bank ecosystem. At present, there is still a lack of long-term continuous observational records. Based on the monitoring data of fixed sample sites from June 2009 to June 2021 and leaf functional traits of dominant plants, this study analyzed the change trend of plant community diversity and the important value of dominant plants at the altitudes of 145-155 m, 155-165 m and 165-175 m in the WLFZ, and revealed the influence of reservoir operation characteristic parameters and meteorological factors on plant characteristics in the WLFZ through redundancy analysis. The results showed that: 1) dominant plants varied obviously in different elevation areas. The dominant species exhibiting higher important value (IV) at the altitude of 145-155 m and 155-165 m were Cynodon dactylon, Cyperus rotundus and Xanthium sibiricum with the higher water-tolerant capacity, while C. dactylon, Daucus carota and Bidens pilosa were dominant at the altitude of 165-175 m. The Shannon-Wiener diversity index of plant communities (1.47±0.47) and the Pielou index (0.67±0.07) at the altitude of 145-155 m were significantly lower than those at the altitude of 165-175 m. 2) From 2009 to 2021, the Shannon-Wiener diversity index and Pielou index at the elevation of 145-155 m and 155-165 m decreased, while the importance value of C. dactylon and C. rotundus increased. 3) RDA analysis showed that the flooding time, number of periodic flooding and elevation can significantly affect the IV of dominant plants. The IV of species such as C. dactylon, A. philoxeroides and X. sibiricum were positively correlated with number of periodic flooding. The IV of Setaria viridis and Polygonum hydropiper were negatively correlated with number of periodic flooding. With increasing elevation, the IV of D. carota, B. pilosa and Artemisia annua increased, however, the IV of C. dactylon, C. rotundus and P. hydropiper declined. 4) The adaptation strategies of different plants varied. Specific leaf area (SLA) of C. dactylon (32.8±7.2) mm²/mg was the largest, followed by B. pilosa (30.6±3.9) mm²/mg and X. sibiricum (30.0±3.0) mm²/mg. The SLA of these plans in the WLFZ were lower than those of plants in the unflooded area. 5) The investment proportion of S strategy of C. dactylon was 53.4% with high flooding-resistant ability. The investment proportion of C strategy of X. sibiricum was 61.3% with the largest leaf area. The proportions of R strategy of Comnyza canadensis and B. pilosa were 64.6% and 50.9% that have a lot of small seeds. The proportions of R strategy of A. philoxeroides was 71.3% with developed roots. The results of this study may deepen the scientific understanding of the change trend of plant communities and the ecological adaptation strategies of dominant plants in the WLFZ of large reservoirs.

Flooding Hazard Assessment of Built-Up Lands Using Modern Geographic Information Systems

Introduction. The construction and operation of buildings and structures on the banks of rivers and other water reservoirs with rapidly changing water level are associated with the hazard of territories flooding and underflooding, which can lead to major material damage and even endanger the life and health of people. It’s very important to make a reliable forecast of floodable and underfloodable zones and to develop possible engineering protection measures for such territories, as well as evacuation or rescue plans for cases of emergency. In this article by the example of 2 allocated for construction potentially flooded plots in the Tuapse district of the Krasnodar region, the quantitative flooding hazard assessment is carried out based on the use of the geographic information system QGIS.Materials and methods. In the study there were used: the analysis of existing methods for assessing underflooding and flooding of territories; the long-term observation materials of the water level in rivers and of the largest floods on the studied plots; the analysis of methods of engineering protection of territories from underflooding and flooding; the hydrogeological and hydrological processes modeling using the modern geo information system QGIS; the development of recommendations for engineering protection of the built-up lands and for design of buildings’ and structures’ bases and foundations.Results. As a result of modeling of the underflooding and flooding processes of 2 plots of the prospective built-up lands of the Tuapse district of Krasnodar region in the geo information system QGIS, the boundaries of potential flooding zones and varying probability water rise levels have been identified. Graphical results of modeling in the QGIS system have been presented and graphs of flooding and underflooding levels have been plotted in given sections and along plot’s outline.Discussion and Conclusions. The boundaries of the most hazardous built-up lands have been identified and the engineering protection measures have been reasoned for them. Recommendations have been developed on design and construction of buildings and structures on the plots taking into account the forecasted hazards of underflooding and flooding.