人工堤坝影响下的黄河三角洲海岸带生态特征分析

在滨海地区,堤坝干扰对自然植被景观及土壤属性的梯度变化规律有重要的影响.本文采用统计分析和梯度分析的方法,在RS信息提取和GIS空间分析技术的支持下,从植被群落的变化入手,从样地尺度上研究堤坝对黄河三角洲海岸带土壤环境的影响并揭示堤坝干扰下,土壤属性的梯度变化规律.研究表明:(1)堤坝影响海岸带地区自然植被的盖度,并且...     

混凝土大坝原型测量及抗震分析

以丹江口大坝、葛州坝闸墩坝、新丰江大坝和潭岭大坝强震观测为例 ,介绍了混凝土大坝原型观测中所使用的仪器、测量方法 (强震观测和微振观测 )及获取的初步成果 ,扼要介绍了混凝土大坝抗震分析的内容 (包括结构动力特性分析、坝体稳定性分析和强度验算 )和方法 (拟静力法和反应谱法 ) ,最后 ,详细介绍了利用强震记录对新丰江大坝和潭岭大坝进行抗震分析的结果 ,并由此看出强震观测对于大坝抗震的重要性     

Effects of spillway types on debris flow trajectory and scour behind a sabo dam

Debris flows are one of the common natural hazards in mountainous areas. They often cause devastating damage to the lives and property of local people. The sabo dam construction along a debris flow valley is considered to be a useful method for hazard mitigation. Previous work has concentrated on the different types of sabo dams such as close-type sabo dam, open-type sabo dam. However, little attention has been paid to the spillway structure of sabo dam. In the paper, a new type of spillway structure with lateral contraction was proposed. Debris flow patterns under four different spillway structures were investigated. The projection theory was employed to predict trajectory of debris flow out from the spillway and to estimate the incident angle and terminal velocity before it plunged into the scour hole behind the sabo dam. The results indicated that the estimated data were in good agreement with the experimental ones. The discrepancy between the estimated and experimental values of main parameters remained below 21.82% (relative error). Additionally, the effects of debris flow scales under different spillway structures were considered to study the scour law. Although the debris flow pattern and scour law behind the sabo dam under different operating conditions was analyzed in this paper, further study on the scour mechanism and the maximum scour depth estimation based on scour theory is still required in the future.     

IMPACT EVALUATION OF HAIZUKA DAM ON ITS UP STREAM： A CASE STUDY IN HIROSHIMA PREFECTURE, JAPAN

Japan ranks fifth in the world for the number of large dams. Environmental impacts of large dams are known, such as enormous losses of water or disruption of fish spawning, however, impacts of the dams on their up streams are functions of topography of the up stream. Haizuka Dam is located in Hiroshima Prefecture, Japan and its implementation will start in 2006. This large dam influences its up stream through dam making activities, which occurs in order and with different spatial presences that were categorized into chronological and spatial impacts. In this case study, spatial impacts were further divided into horizontal and vertical ones. The horizontal impacts were identified as new roads, diversion tunnel, dam lake, and submerged cultivated land, while vertical impacts were recognized as submerged historical monuments, slope protections, dam body, and deforested area in the reservoir. There were convergences of spatial and temporal impacts, however, the extent of the impacts was limited to the lake boundary.     

Optimizing hotspot areas for ecological planning and management based on biodiversity and ecosystem services

The significance of biodiversity and ecosystem services are gradually recognized by human as an approach towards sustainability, so it is important to understand relationships and congruence between them to support conservation planning, especially in the hotspot areas with a prominent role in conservation. However, the management of most conservation hotspots mainly focused on biodiversity, and rarely concerned with ecosystem services. With the aim of proposing criteria for conservation strategies that contribute to the optimization of biodiversity and ecosystem services, in this study, a Geographic Information System(GIS)-based approach was designed to estimate and map the biodiversity and ecosystem services in Chongqing Municipality of China. Furthermore, the distributions of hotspot areas for biodiversity and ecosystem services were mapped based on the relationship between cumulative ecosystem services and areas. Finally the statistical analysis was processed focused on specific conservation objectives. The results showed that hotspot areas can conserve the most biodiversity but with the least ecosystem services under the conservation plans target to biodiversity conservation. In contrast, depending on the ecosystem services of interest, hotspot areas can conserve the largest ecosystem services but with the least biodiversity. By integrating biodiversity and ecosystem services into conservation plan, we found that the conservation and regeneration of these small areas, would contribute to a conservation of 44% of the biodiversity hotspot and 14%–42% of the ecosystem services hotspot. Moreover, the current nature reserve selection was not maximize the biodiversity and ecosystem services compared to integration strategy, indicating that hotspot areas conservation and selection is vital for optimization protection of biodiversity and ecosystem services, and has practical significance for natural resources and ecosystem management.     

“数字台湾”与中央山脉保育轴之划设、经营和管理

本研究系应用数字地球系统理论于中央山脉保育轴经营管理机制建置 ,并依 IUCN之保育区划设标准 ,作为未来研订中央山脉保育计划之分区准则与数字台湾系统建立之发展模式。数字台湾之观念乃源于数字地球突破传统信息空间、政策经营之多向度信息整合 ,同时考虑克服科技应用与时间效益以及决策兼蓄解决传统资源管理在空间地理与生态艺术上之综合性问题。     

滑坡堰塞坝堆积形态影响因素离散元分析

滑坡是形成堰塞坝的最主要原因,在地震、降雨、冰雪融水等作用下均可形成滑坡堰塞坝,而滑坡堰塞坝的堆积形态、范围等对评价堰塞坝的稳定性有着重要的影响。通过离散元方法(DEM),系统分析了三维条件下滑动距离、滑面出口宽度、滑面倾角、河床倾角、河谷形状对堰塞坝堆积形态的影响。研究结果表明:滑动距离和出口宽度对坝体高度影响最大;随出口宽度和坡面倾角的增加,坝长和坝宽分别呈线性增大和减小趋势;滑动距离可以有效控制滑体速度,进而影响堆积角大小;河床倾角主要影响坝长;对坝高、坝长、上下游绝对倾角正切值和堆积角正切值进行回归分析表明,数学模型契合程度高,说明其形态可以预测;引入2个参数λ和χ,对堰塞坝堆积特征进行了描述;河谷形状的影响主要体现在随着河谷底部宽度的增大,滑体爬高爬坡能力增强。研究成果对根据实际地形预测滑坡堰塞坝堆积形态进而评估坝体的安全性具有重要意义,可以为进一步开展堰塞湖溃决研究提供一定的参考。      

The siltation of debris flow behind check dam in the midstream of Bailong River

Siltation gradient and siltation length are important parameters for designing gravity check dams for debris flows, which directly affect the accuracy of estimates of interception capacity. At present, siltation gradient calculations are based primarily on empirical values, and range from 0.4 to 0.95 times the channel slope coefficient. The middle reaches of the Bailong River are one of the four areas in China that are most severely affected by debris flow hazards. Gravity dams are widely employed in this mountainous area. However, field studies of their capacity are lacking. In this paper, the operations of check dams were investigated. Based on field investigation results and theoretical analysis, calculations for siltation gradient, siltation length, and dam storage capacity are established. The impact of debris flow density, channel slope, and particle size weight percentages are discussed. The calculations show that the theoretical values for siltation gradient are consistent with measured values with 83.6% accuracy; and theoretical values of siltation length are consistent with measured values with 91.6% accuracy. The results of this research are an important reference for optimal height and spacing of dams, estimation of dam storage capacity, and disaster prevention.     

Experimental study on characteristics of trapping and regulating sediment with an open-type check dam in debris flow hazard mitigation

Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the sediment-trapping and flow-regulating characteristics of a beam dam. To determine the coefficients of the empirical equations, flume experiments were conducted to simulate the trapping and regulating processes. The flow pattern, trapping, and regulating characteristics were investigated when debris flows passed through a beam dam. Debris-flow bulk density and peak discharge, and sediment-trapping ratios, were measured directly and indirectly. The results showed that three blocking actions occurred, and that blockage-breaking considerably influenced the trapping and regulating performance of the beam dam. The relative opening size and the sediment concentration were the two main factors affecting the performance of the beam dam. The ratio of trapping sediment decreased with relative opening, and increased with sediment concentration as well as reducing ratio of bulk density and reducing ratio of peak discharge. The sediment concentration and relative opening were the leading factors influencing the trapping and regulating sediment of a beam dam, followed by flume gradient. The results showed that the calculated values obtained using empirical equations were in good agreement with the values derived from the experiments, and that the deviation was acceptable. Finally, taking Zechawa Gully as an example, using the empirical equations we designed the opening size of a beam dam aimed to trap sediment and regulate peak discharge of debris flow in the main gully.     

Hazard mitigation planning for debris flow based on numerical simulation using Kanako simulator

Debris flow often causes enormous loss to life and property,especially on alluvial fans.Engineering structures such as retention check dams are essential to reduce the damage.In hazard mitigation evaluation and planning it is of significance to determine the location,size and type of dam and the effects of damage mitigation.We present a numerical simulation method using Kanako simulator for hazard mitigation planning of debris flow disaster in Tanjutani Gully,Kyoto City,Japan.The simulations were carried out for three situations:1) the simulations of erosion,deposition,hydrograph changing and inundation when there were no mitigation measures;2) the simulations of check dams in four locations(470 m,810 m,1,210 m and 1,610 m from the upstream end) to identify the best location;3) the simulations of check dams of three types(closed,slit and grid) to analyze their effects on sediment trapping and discharge reduction.Based on the simulations,it was concluded that two closed check dams(located at 470 m and 1,610 m from the upstream end) in the channel and a drainage channel on the alluvial fan can reduce the risk on the alluvial fan to an acceptable level.     

GIS-BASED ANALYSIS OF URBAN LAND-USE CHANGES—A Case Study of Haizhu District of Guangzhou City, China

This paper describes a GIS-based spatial analysis method that combines qualitative analysis and quantita-tive analysis to characterize land-use patterns and predict the trend of future land-use changes in Halzhu District ofGuangzhou City, China. Spatial technique is introduced to manage land-use data and derive information of land-usechanges. Through the case study for the selected area, it is demonstrated that the method and technique introduced in thepaper can be effectively utilized for the analysis of urban land-use changes. Based upon this analysis, the paper also pro-vides discussions and recommendation on urban land-use planning, urban planning and land management. Both land-usemaps of Haizhu District of Guangzhou in 1995 and 1997 and the remote sensing images of 1999 are utilized in the cur-rent research. It is convenient to get various statistic data and to combine attribute data with spatial data so as to analyzeland-use changes in a geographic context, which is especially suitable for the need of urban construction department, ur-ban management department and urban planning department.     

Fish Assemblage Responses to a Low-head Dam Removal in the Lancang River

Dam removal is becoming an effective approach for aquatic biodiversity restoration in damming river in order to balance the aquatic ecosystem conservation with large-scale cascade damming. However, the effects of dam removal on fish communities in Asian mountainous rivers, which are dominated by Cypriniformes fishes, are still not well known. To determine whether dam removal on a mountainous river benefit restoration of fish diversity, we investigated the response of fish assemblage to dam removal using a before-after-control-impact design in two tributaries of the Lancang River(dam removal river: the Jidu River, and control river: the Fengdian River). Fish surveys were conducted one year prior to dam removal(2012) and three years(2013–2015) following dam removal. We observed rapidly and notably spatio-temporal changes in fish biodiversity metrics and assemblage structure, occurring in the Jidu River within the first year after dam removal. Overall, fish species richness, density and Shannon-Wiener diversity all increased immediately in above-and below-dam sites, and maintained a stable level in subsequent years, compared to unchanged situation in the control river. All sites in the Jidu River experienced shifts in fish composition after dam removal, with the greatest temporal changes occurred in sites below-and above-the former dam, resulting in a temporal homogenization tendency in the dam removed river. These findings suggest that dam removal can benefit the recovery of habitat conditions and fish community in Asian mountainous rivers, but the results should be further evaluated when apply to other dammed rivers since the dam age, fluvial geomorphology and situation of source populations could all affect the responses of fish assemblages.     

Characteristics and interpretation of the seismic signal of a field-scale landslide dam failure experiment

Outburst floods caused by breaches of landslide dams may cause serious damages and loss of lives in downstream areas; for this reason the study of the dynamic of the process is of particular interest for hazard and risk assessment. In this paper we report a field-scale landslide dam failure experiment conducted in Nantou County, in the central of Taiwan.The seismic signal generated during the dam failure was monitored using a broadband seismometer and the signal was used to study the dam failure process.We used the short-time Fourier transform(STFT) to obtain the time–frequency characteristics of the signal and analyzed the correlation between the power spectrum density(PSD) of the signal and the water level. The results indicate that the seismic signal generated during the process consisted of three components: a low-frequency band(0–1.5 Hz), an intermediate-frequency band(1.5–10 Hz) and a highfrequency band(10–45 Hz). We obtained the characteristics of each frequency band and the variations of the signal in various stages of the landslide dam failure process. We determined the cause for the signal changes in each frequency band and its relationship with the dam failure process. The PSD sediment flux estimation model was used to interpret the causes of variations in the signal energy before the dam failure and the clockwise hysteresis during the failure. Our results show that the seismic signal reflects the physical characteristics of the landslide dam failure process. The method and equipment used in this study may be used to monitor landslide dams and providing early warnings for dam failures.     

Seismic deformation and seismic resistance analysis of Shapai Roller Compacted Concrete Arch Dam based on field monitoring and dynamic finite element method

Shapai Roller Compacted Concrete(RCC) Arch Dam is the highest RCC arch dam of the 20th century in the world with a maximum height of 132m,and it is the only concrete arch dam near the epicentre of Wenchuan earthquake on May 12th,2008.The seismic damage to the dam and the resistance of the dam has drawn great attention.This paper analyzed the response and resistance of the dam to the seismic wave using numerical simulations with comparison to the monitored data.The field investigation after the earthquake and analysis of insitu data record showed that there was only little variation in the opening size at the dam and foundation interface,transverse joints and inducing joints before and after the earthquake.The overall stability of the dam abutment resistance body was quite good except a little relaxation was observed.The results of the dynamic finite element method(FEM) showed that the sizes of the openings obtained from the numerical modeling are comparable with the monitored values,and the change of the opening size is in millimeter range.This study revealed that Shapai arch dam exhibited high seismic resistance and overload capacity in the Wenchuan earthquake event.The comparison of the monitored and simulated results showed that the numerical method applied in this paper well simulated the seismic response of the dam.The method could be useful in the future application on the safety evaluation of RCC dams.     

Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.     

Experiments on Channel Evolution due to Dam Removal in Taiwan

Due to safety concerns and habitat restoration for landlocked salmon,a 13-m high check dam on Chijiawan Creek was removed in late May 2011 in Taiwan.We conducted experiments to understand channel evolution of different scenarios.We further compared our experimental results of riverbed elevation changes with the analytical solutions derived from the diffusion equation and field dynamics as well after the creek experienced the first flood event.The results indicated that magnitude of discharges and notch size are dominant factors in resulting channel evolution.While the largest differences between grain size distribution are associated with discharge,the largest differences in net change in upstream volume are associated with notch size.While the theoretical equation could help understand the channel change after dam removal,it only explained the evolution closer to the dam.The physical experiments,on the other hand,provided insights especially with regard to comparing alternative proposed management actions.The discrepancies between predicted and actual outcome highlight more needed inputs for future dam-removal assessments.     

Rapid geometry analysis for earthquake-induced and rainfall-induced landslide dams in Taiwan

Stability analysis of the dam is important for disaster prevention and reduction. The dam＇s geometry plays an important role in understanding its stability. This study develops a rapid landslide dam geometry assessment method for both earthquake-induced and rainfall-induced landslide dams based on nine real cases collected in Chinese Taipei and 214 cases collected worldwide. For simplification purposes, a landslide dam is classified into triangular or trapezoidal. The rapid landslide dam geometry assessment method in this paper uses only satellite maps and the topographic maps to get landslide area, and then analyze the dam geometry. These maps are used to evaluate the area of the landslide and the slope of the river bed. Based on the evaluation information, the proposed method can calculate dam height, the length of the dam, and the angles of the dam in both upstream and downstream directions. These geometry parameters of a landslide dam provide important information for further dam stability analysis. The proposed methodology is applied to a real landslide dam case at Hsiaolin Village. The result shows that the proposed method can be used to assess the landslide dam geometry.     

Do Forest Landscape Pattern Planning and Optimization Play a Role in Enhancing Soil Conservation Services in Mountain Areas of Western China?

The relationship between landscape patterns and soil conservation, as well as the need for nature-based soil erosion control and landscape pattern optimization, have increasingly gained attention in the scientific and political community in the past decade. With the implementation of a series of afforestation/reforestation projects in the western China, the optimization and management of forest landscape patterns will become more important for soil conservation. In this study, the Bailongjiang Watershed(BLJW), in the western China, was used as a case study to explore the relationship between the forest landscape pattern and soil conservation services using mathematical and spatial statistics methods. A spatially-explicit model called the sediment delivery ratio(SDR) model of the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST) was used to assess the soil conservation service in each sub-basin of BLJW in 1990, 2002, and 2014, and landscape indices were used to describe changes in forest landscape patterns in each sub-basin. Nine forest landscape indices, including the percentage of landscape(PLAND), largest patch index(LPI), edge density(ED), landscape shape index(LSI), mean patch shape(SHAPE_MN), patch cohesion index(COHESION), landscape division index(DIVISION), splitting index(SPLIT) and aggregation index(AI), were significantly correlated to the soil conservation service. PLAND, AI, LSI and SPLIT of forestland were determined to be the more important landscape indicators. The results also indicated that soil conservation was substantially scale-dependent. The results demonstrated that landscape type diversity greatly affected watershed soil conservation and can be used for forest landscape restoration and management. Furthermore, spatial statistics analysis indicated that the Spatial Lag Model(SLM) was superior to the Ordinary Least Squares(OLS) for soil conservation regressions in 1990 and 2014, while OLS was more appropriate for the regression in 2002. These findings will be useful for enhancing soil conservation and for optimizing mountainous forest landscape patterns for afforestation/reforestation and regional development. Future planning and implementation of ecological restoration should focus more on strategic spatial planning and integrated landscape management with full consideration of future climate, water availability/consumption, hydrological regime, topography, and watershed features, especially on afforestation and revegetation projects in western mountainous China, where the socio-ecological system is fragile and poor.     

Variations and trends of trans-boundary runoff in the longitudinal range-gorge region

The mountainous hydrological process usually shows high variation to climate change and human action. In the Longitudinal Range-Gorge Region (LRGR), Southwestern China and Southeast Asian, the transboundary runoff variations are much more sensitive and complex under the interaction of climate change, “corridor-barrier” functions in LRGR, and dams building. In this paper, based on the long hydrological records (1956-2013) from three mainstream hydrological stations in Nu River, Lancang River, and Red River, the region runoff variations were analyzed. The results show out: i) the regional runoff changes were strongly influenced by the “Corridor-Barrier” functions in LRGR from west to east, the variability extent of annual runoff increased, but tended to decrease after 2009 and the reduced extents also increased; ii) the annual runoff change in the three rivers had high concentration degrees; iii) there were periodicities of 33 years of runoff change in Nu River and Lancang River, and 30 years in Red River, and the lower flow period would continue for 8-9 years in Nu River and Lancang River but only for 4 years in Red River; iv) since 2010, as the two mega dams of Xiaowan and Nuozhadu built in Lancang River mainstream, their variations of annual runoff were quite different. The research results could offer a scientific base for sustainable utilization, conservation, and management of the regional water resources     

Characteristics of Large Low-frequency Debris Flow Hazards and Mitigation Strategies

A low-frequency debris flow took place in the north coastal range of Venezuela on Dec. 16, 1999,and scientists all over the world paid attention to this catastrophe. Four characteristics of low-frequency debris hazard are discussed: long return period and extreme catastrophe, special rare triggering factors,difficulty in distinguishing and a series of small hazards subsequent to the catastrophe. Different measures, such as preventing, forecast - warning,engineering, can be used for mitigating and controlling the catastrophe. In engineering practice, it is a key that large silt-trap dams are used to control rare large debris flow. A kind of low dam with cheap cost can be used to replace high dam in developing countries. A planning for controlling debris flow hazard in Cerro Grande stream of Venezuela is presented at the end of this paper.