Failure mechanism of a large-scale composite deposits caused by the water level increases

The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case,the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation,the failure mechanism of the composite deposits during reservoir water level variations was studied.The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process.The first slip deformation is greatly affected by the buoyancy weight-reducing effect,and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation.The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope.During the impoundment process,the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation.It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low.But the damage caused by local bank collapse of the deposit slope still needs attention.The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.

IMPACTS OF FUTURE SEA LEVEL RISE ON SALT WATER INTRUSION IN THE CHANGJIANG RIVER ESTUARY

Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water.The implications of sea level rise for increasing salinity have been examined in the Changjiang(Yangtze)River estuary.By correlative analysis of chlorinity,discharge and tidal level and calculation of two-dimensional chlorinity,distribution of the Changjiang River estuary,the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50-100 cm.The intensity of salt water intrusion in the future will be far more serious than current trend.

Estimation of Peak Water Level in Pearl River Estuary under the Background of Sea Level Rise

[Objective] The study aimed to predict the peak water level in Pearl River Estuary under the background of sea level rise. [Method] The changing trends of peak water level at Denglongshan station and Hengmen station were analyzed firstly on the basis of regression models, and then sea level rise in Pearl River Estuary in 2050 was predicted to estimate the 1-in-50-year peak water level in the same year. [Result] Regression analyses showed that the increasing rate of peak water level over past years was 6.3 mm/a at Denglongshan station and 5.8 mm/a at Hengmen station. In addition, if sea level will rise by 20, 30 and 60 cm respectively in 2050, it was predicted that the 1-in-50-year peak water level will reach 3.04, 3.14 and 3.44 m at Denglongshan station, and 3.19, 3.29 and 3.59 m at Hengmen station separately. [Conclusion] The estimation of peak water level in Pearl River Estuary could provide theoretical references for water resources planning.

Impact of Grouting and Loading of Building Construction on the Water Level of Tangshan Mine Well

The water level rising rate of Tangshan mine well significantly accelerated in 2010,and the ascensional range was obviously higher than that of the same period in previous years.From the view of groundwater dynamics and loading effects,and based on the water pumping( pouring) water test model and semi-infinite elastic space theory model under uniform load,the effects of grouting and loading of nearby building construction on the well water level were analyzed. Results show that grouting at a distance of 200 ~ 700 m to the well,with amount of 2500m3 per day and duration of 270 d,can cause an 8 ~ 11 m rise of well water level; and loading of large-area building construction can cause about a 4m rise of well water level. Through the analysis of these factors,we find that the water level anomalous rising of Tangshan mine well was relevant to grouting and loading of the nearby building construction. This study provides a scientific basis for anomalous rising analysis of water level of Tangshan mine well.

FORECAST OF IMPACTS OF SEA-LEVEL RISE ON THELOW COLONIZED ISLANDS AND THEIR SURROUNDING WATERS IN THE CHANGJIANG RIVER MOUTH

As a worldwide authoritative, IPCC forecasted in 1990 that the world- s sea level would most probably rise by 0. 66 m by the end of the 21 st century. Combined with the local depression caused by the sink of the earth’s crust and the human activity, the relative sea level in the Chanaiiang River mouth will rise by about 1. 0 m during the same peried. Based on this figure, the article forecasted the impacts of sea-level rise on the safety coefficient of coastal structures and civil facilities, loss of wetlands, flood hazard as well as water intrusion. The results show that: 1 ) 40% as large as the present engil1eering mass should be added to the coastal structures in order to maintain the safety coefficient; 2 ) a dynamic loss of 60 km2 of wetlands, as much as 15% of the present total area, would be caused; 3) to hinder the increase inflood hazard dy11amic capacity to drain water must increase by at least 34 times as large as the present; 4) to maintain the present navigation conditions, about 100 million yuan (RMB) is needed to reconstruct over 30(X) bridges and 30 sluices;and 5 ) the disastrous salt water intrusion caused by the sea-level rise could be encountered by the increase in water discharge from the Three Gorge Reservoir in the dry season.

Case analysis of water exchange between the Bohai and Yellow Seas in response to high winds in winter

Based on the data from a special project titled China's Offshore Marine Integrated Investigation and Evaluation as well as Regional Ocean Modeling Systems(ROMS)diagnostic numerical model,we studied the influence of high wind processes on the circulation and water exchange between the Bohai and Yellow Seas(BYS)in winter.The results show that the vertical structure of the Yellow Sea Warm Current(YSWC)is relatively uniform under condition of high winds,showing obvious barotropic features.However,this flow is not a stable mean flow,showing strong paroxysmal and reciprocating characteristics.A comparison of the changes in sea level suggests that the intensity of the northwards upwind flow is consistent with the abnormal fluctuations in the sea level.It indicates that the upwind flow is closely related to the water exchange between the BYS.The impact of high wind processes on the water exchange between the BYS is enormous.It can make the flux through the Bohai Strait,as well as that through the mouth of each constituent bay(i.e.,Liaodong Bay,Bohai Bay,and Laizhou Bay)far greater than usual,resulting in a significant increase in the water exchange rate.The exchange capacity,which is about 8%of the total volume of the Bohai Sea,can be completed in a few days.Therefore,the water exchange of the Bohai Sea may be completed by only a few occasional high wind processes in winter.

Counteracting the Effects of Sea Level Rise in Southeast Florida

Over the past 100 years, worldwide surface temperatures have increased at an unprecedented rate, contributing to warming of the oceans, melting ice fields and glaciers, and other adverse climatic effects. Southeast Florida＇s vulnerability derives from its geographic location, low elevation, porous geology, unusual ground and surface water hydrology, subtropical weather patterns, and proximity to the Atlantic Ocean. The region is especially susceptible to sea level rise. After several millennia of stable sea levels prior to the 20th century, sea levels have been rising at accelerating rates due to thermal expansion of the oceans and from land-based ice melt The Everglades ecosystem and the water supplies for southeast Florida are particularly vulnerable as neither can be protected without significant expenditures of public dollars, and even these efforts may not prove to be successful. New approaches may be required to improve the resilience and prolong the sustainability of the region＇s water resources and ecosystem. The efforts to adapt to sea level changes in both the urban area and ecosystem as outlined herein are date and incident based-climate changes may occur earlier or later so instead of spending limited public dollars early, expenditures can be adjusted given future information.

Study on the Lowest Navigable Water Level

The design lowest navigable water level is a primary index to the channel grade division.But differ- ent method can get different calculated result,and that even brings contradiction to decide the navigation grade.In this paper the differences between guaranteed rate method and guaranteed rate-frequency method on the fundamental concept of guaranteed rate and the calculated result are carried out.According to the theoreti- cal expression forms of the two methods,the reason leading to the difference is an...

Water Intrusion in the Chesapeake Bay Region: Is It Caused by Climate-Induced Sea Level Rise?

Sea level rise due to climate change is a contentious issue with profound geographic and economic implications. One region in the USA identified as being particularly susceptible to seal level rise is the Chesapeake Bay region, and it has been estimated that by the end of the century Norfolk, Virginia could experience sea level rise of 0.75 meters to more than 2.1 meters. Water intrusion is a serious problem in much of the Chesapeake Bay region. The question addressed here is whether this water intrusion is the result of climate-induced seal level rise or is being caused by other factors. Our findings indicate that the water intrusion problems in the region are due not to “sea level rise”, but primarily to land subsidence due to groundwater depletion and, to a lesser extent, subsidence from glacial isostatic adjustment. We conclude that water intrusion will thus continue even if sea levels decline. These findings are critical because the water intrusion problems in the Chesapeake Bay—and elsewhere—cannot be successfully solved unless their causes are correctly identified and appropriate remedies are devised. For the Chesapeake Bay region, the required remedy is the reversal of groundwater withdrawal rates, which has been used successfully elsewhere in the USA and other nations to solve water intrusion problems.

INFLUENCE OF SEA LEVEL RISE ON SHANGHAI ASTRONOMICAL TIDE AND STORM SURGE AND ESTIMATION OF PROBABLE WATER LEVEL

A nonlinear two-dimension dynamic model of storm surge (SS) and astronomical tide(AT) was used to investigate the effects of SS and AT on expected sea level rise (SLR) at principalcoastal stations in the Shanghai region and to estimate numerically the probable maximum water lerel for2010 - 2050. Evidence suggests tha SLR causes reduction of SS; that its influence on SS depends on theintensity and path of a tropical cyclone and the station locality; tha the SLR’s effects on AT vary periodi-cally, with the peried being the same as tha of the AT’s: and that as the SLR increment grows, its impactincreases; below mean sea level (MSL) the effect is positive at rising tide and negative at ebb tide, andvice versa for the effect above MSL. Study of the probable maximum water level (by assuming SLR, SSalong favorable tropical cyclone’s path, its possible maximum intensity and effectivee spring AT at a rangeof set paths of Cyclones 5612, 8114, 9417) showed that the probable maximum water level is 740, 745,and 751 cm in the years 2010, 2030, and 2050, respetively, over the target region.

Prediction of China's Submerged Coastal Areas by Sea Level Rise due to Climate Change

Based on the simulation with the Ocean-Atmosphere Coupled Model CCSM and Ocean Model POP under the green- house gas emission scenario of the IPCC SRES A2 （IPCC, 2001）, and on the earth crust subsidence and glacier melting data, the relative sea level change is obtained along the coast of China in the 21 st century. Using the SRTM elevation data the submergence of coastal low land is calculated under the extreme water level with a 100-year retum period. The total flooding areas are 98.3× 10^3 and 104.9× 10^3 km2 for 2050 and 2080, respectively. For the three regions most vulnerable to extreme sea level rise, i.e., the coast of Bohai Bay, the Yangtze River Delta together with neighboring Jiangsu Province and northern Zhejiang Province, and the Pearl River Delta, the flooded areas are 5.0× 10^3, 64.1×10^3 and 15.3 × 10^3 km2 in 2050 and 5.2 × 10^3, 67.8×10^3 and 17.2 × 10^3 km2 in 2080, respectively.

Study of Water Flow in a Single Clay Crack

A model has been constructed to study water flow in a single clay crack, and a new concept of the critical rise rate of water level in the crack has been put forward. When the water level rises faster than this critical rate, the flow in a crack will increase, and vice versa. The flow in a crack is not in proportion to the water level. The maximium water flow in clay is 30-40 times smaller than that in a rock fissure under the same condition. In the process of water discharge, the flow in a crack will lessen gradually, and the crack will grow narrower by 3.0-4.0cm, with its depth reducing by over 50%.

Saline Intrusion Response to Sea Level Rise and Its Implications on Water and Coastal Management: A Case Study in Brazil

Global temperature is predicted to increase in the end of the century and one of the primary consequences of this warming is the sea level rise. Considering the vulnerabilities on coastal systems and water resources, it is important to evaluate the potential effects of this rising in coastal areas, since the saline intrusion on rivers would be intensified, leading to problems related to water quality. In this context, the present work aimed to verify saline intrusion changes along an important river, S&#227o Francisco Canal, located in Rio de Janeiro State, Brazil. For this purpose, a hydrodynamic modeling was performed using SisBaHiA, considering different sea levels and tide conditions. According to the results, it was verified the intensification on saline intrusion and higher salinity values due to a sea level rise of 0.5 m. These results show that new licenses for water withdrawals must be carefully analyzed as the fluvial flow plays an important role to contain the saltwater intrusion on the studied river. Accordingly, it is recommended the evaluation of climate change effects in order to choose best strategies to reduce coastal vulnerability, and the use of this theme on environmental licensing and territorial planning, integrating water planning with coastal management.

Impact of Tidal River Management (TRM) for Water Logging: A Geospatial Case Study on Coastal Zone of Bangladesh

Bangladesh is a floodplain dominated country. Coastal delta areas of Bangladesh convey multiple impacts of climate change worth-hit. Most of the rivers carry a huge amount of sediment from upstream piedmont area. The river bed rises due to insufficient upstream water supply. Similarly, the deposited sedimentation creates a large number of sandbars inside the river. That’s why, water logging and siltation turn into a serious problem in the south-western region of Bangladesh, especially in Satkhira, Khulna and Jessore district. In the middle of September, 2011 the Tidal River Management (TRM) project approved at the study site for four years to develop the water logging problem with basic consideration of silt management. In this circumstance, this study focused on the consequences of the TRM on water logging in the coastal area of Bangladesh. Primary and secondary data have been used. Geospatial analyses have been used following the NDWI in Arc GIS for water logging area detestation using Landsat Enhance Thematic Mapper (ETM) and Landsat Operational land Image (OLI) satellite images. The geo-spatial analysis denoted, about 5090 acres of agricultural land and about 729 acres of homestead land have been water logged during TRM implementation period.

Empirical Assessment of Coastal Environmental Vulnerability to Sea Level Rise

Sea level rise (SLR) could critically endanger the environment along all the world’s sea coasts. Although sudden SLRs of meters-high waves that might have apocalyptic results would generally be limited to specific areas, on-going SLR of dozens of cms over decades is likely to have adverse impact on coastal environments throughout the world. This study’s objective is to assess relative regional vulnerability of global sea coasts to SLR. The study focuses upon key natural and anthropogenic parameters that might either cause or enhance SLR and thus significantly influence regional coastal environments. Careful assessment can enable reasonable estimates of relative vulnerability of such environments. An initial step involves specifying key parameters and assigning their weightings and ratings. To demonstrate the feasibility of this approach, six seacoast regions from various parts of the world have been considered in this paper, assessing their natural and anthropogenic parameters vis-à-vis general global data. The results emphasize the relative vulnerability of these areas’ environments to SLR. Recommendations are then made for improving global SLR modeling and monitoring.

变化条件下长江口防洪御潮及供水保障研究进展与展望

近一个世纪以来,全球气候变暖导致海平面持续上升,增加了整个长江口的水深,抬高了潮汐和风暴潮的基础水位,使得河口咸潮入侵,洪水和风暴潮发生的频率和强度增加。同时,由于长江流域水土保持和水库群建设,进入河口的泥沙量锐减,加剧了河口咸潮上溯,对区域人群生产生活产生一定影响。从全球气候变暖背景下长江口海平面上升和演变规律、长江口人类活动与气候变化影响下的动力要素变化、河口咸潮入侵时空分布和水盐交换机制及供水安全风险、海平面上升对海堤防洪御潮能力的影响、长江口地区防洪御潮韧性等5个方面总结归纳了现有研究成果,提出未来研究的方向,以期对保障河口地区水资源安全利用和防洪御潮能力提升提供参考。

冻融循环作用下路基结构水热汽迁移规律研究

在冻融循环环境下,路基结构内水分迁移是导致道路冻胀、融沉变形的主要原因。为了探究冻融循环条件下路基结构的水热汽迁移规律,模拟了实际工程的路基结构,基于半透膜材料开展了冻融循环条件下的水、汽分离的水分迁移试验,通过监测试样的水热变化、荧光素上升图像、补水量和集水量变化曲线,得到了水分迁移规律,进而分析了土的孔隙结构、升降温速率和温度梯度等因素对水汽迁移和液态水流出特征的影响。试验结果表明,在土水势作用下,马氏瓶的水分首先以水-汽混合的形式在土柱中向上迁移,达到一定高度后,转变为以水汽的形式向上迁移。非饱和土柱的水汽会透过半透膜向碎石层和控温板底迁移,在整个冻融循环过程中,水汽向碎石层和控温板底的迁移量呈现线性增加的趋势,表明水汽迁移在水分聚集过程中的作用不可忽视。碎石层和控温板底液态水的流出主要集中在每个冻融周期的两个阶段,第一阶段为降温阶段,以冷凝水为主;第二阶段为融化阶段,以融化水为主,融化水占一个冻融周期液态水流出量的70%以上。粉质黏土孔隙较小导致水汽迁移主要受体积含气率的影响,随着粉质黏土土柱含水率的增加,水汽迁移量呈减小趋势。而砂土的孔隙较大,水汽迁移主要受水汽扩散增强因子的影响,随砂土土柱含水率的增加,水汽迁移量呈增大趋势。降温速率减小使冻结锋面有一个缓慢下移的过程,减小土体冻结对水汽迁移通道的封闭影响。升降温速率的减小导致碎石层和控温板底的水分聚集量增大。较大的温度梯度导致水汽扩散系数和水汽密度梯度的增加,从而引起碎石层和控温板底的水汽迁移量增大。

水位下降速率对岩溶土洞塌陷的影响分析

水位升降引起的水气压力变化会导致岩溶土洞塌陷。通过开展物理模型试验与FLAC3D数值模拟相结合的方式,模拟相同供水速率不同排水速率下的水位升降波动对岩溶土洞的致塌过程,分析了水位升降波动过程中不同排水速率对既有土洞内水气压力的变化、覆盖层土压、变形的影响,建立了排水速率,覆盖层变形、塌陷与水气压力的关系,提出了水位波动对土洞塌陷的作用规律。结果表明:(1)排水速率对水气压力变化的影响规律基本一致但变化程度不同。水气压力的变化程度、响应时间与排水速率呈正相关。(2)覆盖层变形量、土压的变化与水气压力变化呈正相关,但影响程度不同,排水速率只是加快了其变化程度。(3)土洞变形、塌陷程度是综合因素所致。排水速率、水位波动次数对既有土洞中水气压力变化、以及土体变形效应均具有不同程度的影响。(4)数值模拟结果与试验室模型试验所得结论基本吻合。这些规律为进一步研究水动力因素对岩溶塌陷的作用规律提供了重要的理论支撑,为合理防治、预测岩溶塌陷提供了依据。

三峡水库运行后汉口—九江河段水位变化特征及成因

大型水库的修建引起坝下游的水位调整,进而对河势、航运、防洪及生态等产生显著影响。为探究汉口—九江河段水位变化特征及成因,采用M-K分析法分析1988—2022年汉口、黄石港和九江站的水位变化趋势,并使用基于距平残差的水位变幅分析方法和一维水动力模型,分析河道冲淤、下游水位和阻力变化对不同特征流量下水位变化的影响。研究结果表明:①三峡成库前,除九江站枯水位呈显著性下降趋势,各级流量下的水位均没有显著性变化趋势。②三峡成库后,九江站的水位变化趋势与建库前相同;汉口站、黄石港站在12000 m^(3)/s和20000 m^(3)/s下的水位呈显著性下降趋势,12000 m^(3)/s时降幅分别为0.072、0.045 m/a,20000 m^(3)/s时降幅分别为0.048、0.027 m/a;水位变化的临界转换流量约为30000 m^(3)/s,在该流量附近水位未出现明显变化;当流量大于30000 m^(3)/s时,水位呈非显著性上升趋势,45000 m^(3)/s下的升幅分别为0.037、0.049 m/a。③临界转换流量以下水位下降的主导作用为河道冲刷,临界流量附近的水位未出现明显变化源于阻力增大作用接近抵消了河道冲刷的影响,临界转换流量以上的水位上升源于阻力增大作用更加明显,个别年份的洪水位上升显著源于下游水位顶托作用明显。

污水管道水位流速检测装置设计

在线实时监测市政污水管道内污水的水位和流速能帮助市政管理部门精准掌握污水流动情况,及时了解管道出现的问题,提高工作效率。该文依据绕流理论设计并制作了一种基于浮球的水位和流速检测装置,通过测量浮球随水位变化的相对位移实现水位测量;通过测量流体对浮球的推力实现流速测量。装置的GSM/GPRS模块接收水位和流速的检测数据并传输至远程监控端,实现远程在线监测。在明渠标准实验台对该检测装置的水位和流速测量值进行标定和精度实验,实验结果表明:测量水位的偏差在±3 mm内,误差不大于其满量程的0.5%;流速测量偏差值在±0.04m/s内,误差不大于其满量程的5%。将该检测装置安装在实际的污水管道内,对污水水位和流速进行了为期三个月的实验监测,检测值的远程传输结果符合预期。