A Farmer-Friendly Dam Safety Evaluation Procedure As A Key Part of Modern Australian Water Laws

Abstract

The largest dams are generally built and managed by Governments; individual owners build small dams. Over time, many dam safety aspects have changed, such as population distributions, meteorological information, engineering methods and design standards, together with the condition of the dams, raising serious doubts about dam adequacy. For the larger dams response has been to spend vast amounts on remedial works. Unfortunately, only a few countries have developed mature safety assurance schemes for smaller dams: these are comparatively reviewed here identifying elements of “minimum” and “best” practice, and providing policy models and guidelines of “appropriate” practice for varying circumstances. Farmers often overlook common law obligation to review/design dams in line with current standards because of high engineering consulting costs. A cost-effective spillway design/review procedure that is applicable to South Eastern Australia, but is transferable to any other region world-wide, is also reported here: this procedure is integrated with the policy models and guidelines, aiming to minimize cost burdens to dam owners, encourage better dam safety management, and provide an acceptable level of safety assurance to downstream communities.     

Australian Community Responses to Upgraded Farm Dam Laws and Cost-effective Spillway Modelling

Recent attention to farm dams and dam safety in Australia and elsewhere reflects both safety and sustainability issues, and is driven by the fact that since built, many dam safety aspects have changed, e.g. population distributions, meteorological information, estimates of rainfall and runoff, engineering methods, and design standards and techniques. Farmers in Australia have often overlooked the common law obligation to review/design dams in line with current standards because of high engineering consulting costs: this leaves them vulnerable to litigation if their dam fails and the downstream community is susceptible to unacceptable risk levels. The seriousness of this problem has been demonstrated by case studies undertaken in the policy-absent State of South Australia and the policy-driven State of Victoria. In each state, ten hazardous private reservoirs were investigated for spillway adequacy in line with state-of-the-art practice. The investigation follows the release of an innovative Australian developed cost-effective spillway design/review procedure that has been made available and promoted in both states to minimize cost burdens to dam owners and encourage better dam safety management. Recent surveys undertaken in South Eastern Australia to test community attitudes to the procedure and implemented dam safety and water allocation policy in Victoria are also reported. These surveys together with the ‘spillway adequacy’ investigations clearly demonstrate that farmers require more than awareness and encouragement to ensure they look after their dams properly.     

基于“漫而不溃”理念的新疆小型水库土石坝应对洪水风险新策略

新疆已建、在建山区小型水库149座,其中拦河坝为土石坝的小型水库120余座。近年来,气候变化条件下洪水风险呈更加严峻之势,小型水库采用土石坝坝型的运行与溃坝风险较大。针对泥沙淤积使防洪库容减少、表孔宣泄遭遇枯木树枝堵塞、水库遭遇超标准洪水、坝体年久失修或结构失稳等小型水库土石坝的洪水风险问题,需增加土石坝工程的超泄能力,避免造成溃坝等洪水风险,以增加工程的安全性。以某山区小型水库为例,通过加宽溢洪道、增加底孔泄流、坝体部分溢流、坝体全断面溢流等方案分析,研究了不同组合泄洪形式的可能性,提出了基于“漫而不溃”的土石坝加固理念与措施,以应对气候变化条件下超标准洪水的宣泄,可供类似工程设计参考。     

数值模拟在横山岭水库除险加固中的应用

通过对横山岭水库溢洪道下泄洪水进行三维数值模拟,得出了设计洪水会淹没、冲刷坝脚,给大坝造成安全隐患的结论.并利用数值模拟技术验证了对溢洪道下游阻水山体采取开挖的疏导措施可以避免洪水威胁大坝的安全.通过这次泄洪流场模拟,开拓了三维数值模拟技术在大坝安全鉴定和除险加固中的应用.     

近期我国土石坝溃决或出险事故及其启示

受极端气候影响,近年来溃坝和出险事故时有发生,一些规律性趋势逐渐清晰,对超标准洪水影响、土石坝漫而不溃、应急响应机制等一些新问题新方向有待深入研究。基于最新溃坝和出险案例,从防洪标准、监测预警、应急响应、应急处置等方面总结经验教训,得出在水库大坝安全管理和防洪度汛方面的启示,进一步提出加强溃坝风险防控的思考和建议。快速降低库水位是应对超标准洪水的关键措施,土石坝可以做到漫而不溃,土石坝结构设计应充分考虑极端强降雨工况,流域梯级水库防洪能力亟待加强,管理设施对紧急情况下应急能力影响很大,低水平的管理会严重影响防洪安全。     

梯级水库群系统洪水演进模拟及防洪安全评估

针对梯级水库群系统中上级水库泄洪对下级水库带来的水力传递影响,以评估水库群系统的安全隐患为目标,以澜沧江中游干流5个水库组成的梯级库群系统为例,运用同频率地区组合法推求库群系统的设计洪水过程。以此作为库群系统的输入条件,采用MIKE 11模型模拟当库群系统发生稀遇洪水时的沿程最高水面线,并与坝顶高程比较,对库群系统中大坝的防洪安全状况进行评价。结果表明:当库群系统发生5 000年一遇以下洪水时,各坝址处最高水位均低于坝顶高程;当发生10 000年一遇洪水时,其中两个水库(漫湾和景洪)的最高水位接近其坝顶高程,存在发生漫坝的风险,给整个库群系统的防洪安全带来一定隐患。研究成果对于提高库群所在的澜沧江中游地区的应急防洪能力具有重大的现实意义,为库区下游的安全生产和经济发展提供重要的保障。     

水库洪水风险图的制作

制作水库洪水风险图，要进行水库校核洪水淹没计算和水库溃坝洪水淹没计算，然后对洪水淹没损失进行评估，最后采用地形素图绘制成洪水风险图，并完成编制说明     

Multi-Objective Optimization of Fusegates System under Hydrologic Uncertainties

Fusegates are independent units held only by the gravity installed on the free spillway of existing dams in order to increase reservoir storage and/or discharge capacity. Increasing reservoir storage in many dams can partly sacrifice dam’s reliabilities. So considering the failure risk of a dam together with the amount of increase in the reservoir capacity can prevent selecting fusegates which seriously endanger a dam safety. However, Lack of accurate information on various damage functions and difficulty in quantifying failure consequences are among principal limitations that hinder practical application of conventional approaches which account failure risk in real world hydrosystems problems. This study develops two effective multi-objective frameworks to optimize fusegates’ configuration in order to eliminate the need for such hard-to-get mathematical damage functions and provide valuable information on the failure risk, total cost, and increased water volume of a reservoir. The proposed models find trade-off solutions between two sets of conflicting objectives. The first competing objectives is investment cost and water storage and the second conflicting goals are water storage and failure probability under the inherent and parameter hydrologic uncertainties. Complicated flood routing phenomenon within a reservoir equipped with fusegates is explicitly taken into account to attain a more cost-effective and reliable design without jeopardizing the dam safety. Applicability and performance of the developed optimization schemes are discussed and demonstrated on a real life case study. The multi-objective optimization results represented as an ensemble of diverse trade-off solutions provide decision makers with more insight and understanding of system behavior and different design alternatives.     

基于WebGIS技术的水库安全管理系统设计与实现

水库安全度汛一直是我国防汛抗洪的难点和重点,中小型水库的安全度汛已成为当前全国防汛工作的一个薄弱环节.随着国家对水利行业的逐步投入,江西省大部分中小型水库已经安装了水位、雨量等监测设备,其中少部分中小型水库还安装了大坝渗压、渗流等自动监测设备.江西省水利厅基于网络地理信息(WebGIS)技术,建设了一套全省中小型水库安全管理系统,实现了库区降雨量、水位、大坝渗压、渗流、浸润线的水库自动化监测和可视化管理,为水库的安全管理与运行调度提供及时、准确、直观的信息.     

长河坝水电站泄洪建筑物的布置研究

长河坝水电站挡水建筑物为心墙堆石坝,最大可能洪水逾10000m^3／s,泄洪功率大,坝身不能过流,按照常规,心墙堆石坝泄洪建筑物应布置岸边溢洪道或泄洪洞。根据长河坝坝址区的地形、地质条件,对全泄洪洞方案和泄洪洞与溢洪道相结合方案进行技术经济比较后,最终推荐了全泄洪洞泄洪方案.     

子威水库泄洪方式与洪水调节分析

泄水建筑物是水库枢纽的重要组成部分,是影响大坝特征水位选择和水库防洪安全的重要因素,而泄洪方式的选择和洪水调节计算是设计的重点。为解决水库枢纽所在支沟来水量不足问题,子威水库采用主坝、副坝结合的布置方式,通过库区内的连通隧洞将副坝所在主沟水量引至主坝进行补水。考虑地质条件和工程投资限制,主坝不设泄洪设施,提出了主坝泄洪采用库区内连通隧洞引洪至副坝溢流坝进行下泄的方式,同时结合了水库枢纽泄水建筑物的布置形式,提出了子威水库枢纽主坝和副坝联合洪水调节的计算方法,可为中小型水库泄洪建筑物工程布置与调洪计算提供借鉴。     

气候变化下山溪性河流水库防洪减灾措施

近年来极端气候变化频发,引发局地短时强降雨,易造成超标洪水,严重威胁山溪性河流上的水库安全,由此而导致的大坝漫(溃)坝案例已有发生,且危害巨大,防范和化解此类重大灾害是新时期水库设计和安全运行管理的关键问题。通过归纳总结已建土石坝工程实例,认为水库漫顶溃坝风险主要来源于水文资料短缺、洪水成因复杂和突发性强,水情监测预警预报不到位,抵御超标准洪水时调洪能力有限等不利因素。因此,关注设计洪水的合理性分析及安全性评价,建立对超标准洪水的分析预测和监测预警,合理规划泄洪建筑物的规模以及抗冲结构设置,加强水库排沙预泄措施和梯级水库的联调联控等综合调洪能力的提高,提升非常情况下的应急安全管理能力等,是病险水库除险加固以及新建水库工程设计及运行管理的必需措施。     

岳城水库除险加固工程设计

岳城水库运行已40多年，因先天不足，虽经过多次除险加固，仍存在着防洪标准不足和主坝下游坝坡散浸等质量隐患。介绍了提高防洪标准的第二溢洪道设计和工程质量隐患的除险加固设计，尤其第二溢洪道为国内罕见的大流量软基溢洪道，提出了软基溢洪道关键设计点采取的工程措施。     

中小型水库防洪标准对比研究及对策建议

我国中小型水库众多、分布广泛,为社会提供了极大的经济和生态效益,但也有可能因大坝失事给水库下游地区造成人员伤亡和财产损失,成为洪灾风险的来源之一。通过与美国大坝等级划分和入库设计洪水选择指南的对比,指出了我国相关设计规范中,对中小型水库防洪标准的规定相对偏低,与我国当前的经济社会发展水平不相适应;分析论证了我国存在高风险潜在危险的中小型水库提高防洪标准的必要性和可行性,并提出了提高我国高风险潜在危险等级的中小型水库防洪能力的对策建议。     

格尔木河温泉水库应急抢险施工技术

2010年6月格尔木河提前进入主汛期,致使温泉水库入库洪峰流量及库水位均创历史记录, 其砂砾石坝溃决风险很大。在应急抢险中,按照确保大坝不溃、把损失减少到最低程度的原则,确定 了抢挖应急溢洪道,分流超过校核洪水位的洪水,降低库水位保坝的方案。经过抢险施工,排除了险 情,确保了下游人员生命财产安全。     

我国小型病险水库病害特点及除险加固技术

我国小型水库建设标准低，加之管理不善，经过多年运行后，存在防洪能力不足、大坝渗漏、结构不安全、抗震性能差、金属结构老化及安全管理落后等问题。针对以上问题．对相关的小型病险水库除险加固技术进行了探讨，并提出相应的建议。     

白盆珠水库“8.16”事故浅析及防洪应急电源设计

2013年第11号超强台风“尤特”在广东沿海地区登陆,大范围的强降水,造成白盆珠水库下游河道两岸及上坝公路边坡塌方、发电厂房进水、主副坝电源中断、水库大坝泄洪闸门无法开启的严重事故.通过总结事故的教训,对水库原防洪应急电源进行改造设计,确保新建的防洪应急电源符合要求,保障水库大坝及电站运行人员的安全.     

永庆反调节水库枢纽布置设计特点

永庆水库是丰满水电站的反调节水库、枢纽布置时要考虑丰满水电站调峰运行时的下泄流量以及保持不间断地向下游供水等因素，泄水建筑物需具备挡水、供水和泄洪功能、布置比较复杂。文章着重介绍了枢纽布置方案的比选、泄水闸、自由溢流坝、混凝土重力坝及砂砾石坝的设计特点。     

红旗水库枢纽除险加固设计

红旗水库已运行了近50年,在农业灌溉、防洪,生产生活供水等方面发挥了巨大的社会效益和经济效益,但由于水库修建时受年代条件限制,整个枢纽工程存在的安全隐患较多,险情时有发生,急需进行除险加固.本文介绍了红旗水库大坝除险加固设计中的技术处理,包括大坝上游放缓培厚、上下游护坡,大坝灌浆处理;拆除溢洪道进口浆砌石墩以阔宽溢洪道净宽;改造放水设施;增设安全检测系统;修建防汛抢险公路及管理房.经采取以上加固措施后,保证了水库大坝的正常运用.     

溢洪道安设橡胶坝对其水力特性影响的试验研究

针对溢洪道无消能工和防洪能力不足等问题,修建橡胶坝可以提高其潜在效益。为了研究溢洪道控制段内修建橡胶坝对溢洪道水力特性的影响,结合工程实例,从溢洪道的泄流能力、水流特性以及出口消能防冲效果3个方面进行了对比分析。分析成果表明:安设橡胶坝的溢洪道泄流能力减小,但仍大于工程设计要求,可保障溢洪道安全运行;橡胶坝对溢洪道流速有较小影响,坝前流速变化幅度比坝后流速大;橡胶坝塌坝和充水2种工况下的溢洪道水面线变化趋势相近,突变点发生在坡度变化点附近和橡胶坝附近;溢洪道消能防冲能力几乎不受橡胶坝的影响。因此,有条件的溢洪道控制段内建设橡胶坝是可行的。研究成果可为类似工程的设计和中小型水库的除险加固提供参考依据。