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首页> 外文会议>Association of State Dam Safety Officials, Inc. 2002 Annual Conference Sep 8-11, 2002 Tampa, Florida >REDUCED DESIGN FLOODS ― WHAT ARE THE SAVINGS?
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REDUCED DESIGN FLOODS ― WHAT ARE THE SAVINGS?

机译：减少了设计流程―节省了多少钱？

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摘要

When rehabilitation measures are required to allow a dam to safely pass the mandated IDF, a reduction of the IDF may be merited to reduce the cost of rehabilitation. Prior to performing rigorous (and often costly) analyses to reduce the IDF, the dam owner and engineer should perform a preliminary assessment to identify the likelihood for justification of a reduced IDF, potential cost savings, and other possible consequences of a reduced IDF. Some guidelines for deciding whether and IDF reduction may be valuable are provided below. Justifying a reduced IDF through incremental inundation analysis may be difficult if: 1. There is significant existing development downstream (reduction through RBA may also be difficult in this situation) 2. The reservoir is relatively large in relation to the drainage area contributing to the dam. 3. The dam is a gravity dam with a shorter hypothetical failure time, creating higher computed flows from the breach Even if none of these conditions exist, reducing the IDF may still not be recommended if: 1. Future development in the downstream floodway is likely. 2. The rehabilitation strategy (even for lesser floods) is embankment armoring, where cost savings are not significant for a reduced IDF. 3. The dam's spillway capacity is nearly adequate and nominal raising will allow the dam to pass the mandated IDF. For many dams, the cost of detailed analyses to reduce the IDF may approach the cost of this raising. 4. In addition to inadequate spillway capacity, the dam has other deficiencies (say seepage or stability concerns), requiring extensive rehabilitation measures. In these cases, the incremental cost savings of a reduced design flood diminish. Additionally, rehabilitation such as embankment armoring may incorporate stabilization or seepage control measures while also providing increased spillway capacity. 5. The owner cannot tolerate loss of the reservoir if the IDF is exceeded. This is especially true when the reservoir is a major asset that provides revenue, such as a hydroelectric power or water supply dam. Spillway expansion can increase downstream flooding for events less than the IDF; causing more damage than without expansion. This may provide justification for a reduced IDF; however, it may also influence the selection of rehabilitation strategy. Embankment armoring and gravity dam stabilization both allow safe passage of the IDF without changing the hydraulics of the structure. Reducing the IDF for these tow upgrading methods does not typically provide significant cost benefit. Finally, the owner and engineer should recognize the potential liabilities involved with an IDF reduction through incremental inundation analysis. While it may be shown that the dam does not "significantly" contribute to downstream flooding during an extreme event, it is very likely the dam owner could still be found responsible for damages incurred during a dam breach flood where the IDF is exceeded.
机译：当需要采取修复措施以使大坝安全通过授权的IDF时，可以减少IDF以降低修复成本。在进行严格的（通常是昂贵的）分析以减少IDF之前，大坝所有者和工程师应进行初步评估，以确定降低IDF的合理性，节省的潜在成本以及降低IDF的其他可能后果。下面提供了一些决定降低IDF的价值的准则。如果满足以下条件，则很难通过增量淹没分析来证明减少的IDF：1.下游有大量现有开发项目（在这种情况下，通过RBA进行削减也可能很困难）2.与导致大坝的流域相比，水库相对较大。 3.该大坝是重力坝，其假想故障时间较短，因此从裂缝处产生了更高的计算流量即使不存在以下条件，在以下情况下仍不建议降低IDF：1.下游洪水道的未来发展可能。 2.复原战略（即使是针对较小的洪水）是堤防，在这种情况下，节省的费用对于减少以色列国防军而言意义不大。 3.大坝的溢洪道能力几乎足够，标称升程将使大坝通过授权的IDF。对于许多水坝而言，为减少IDF而进行详细分析的成本可能会接近提高成本。 4.除了溢洪道容量不足外，大坝还存在其他缺陷（例如渗漏或稳定性问题），需要采取广泛的修复措施。在这些情况下，减少的设计洪水所节省的增量成本就会减少。另外，诸如路堤装甲的修复可以结合稳定或防渗措施，同时还提供增加的溢洪道能力。 5.如果超过了IDF，所有者将无法容忍水库的损失。当水库是提供收入的主要资产（例如水力发电站或供水大坝）时，尤其如此。溢洪道的扩建可增加事件发生的下游洪灾，其发生率少于以色列国防军。造成的破坏要比不进行扩张造成的破坏更大。这可以为减少IDF提供理由。但是，它也可能影响康复策略的选择。路堤的装甲和重力坝的稳定都允许IDF安全通过，而无需改变结构的液压系统。对于这些丝束升级方法，降低IDF通常不会带来明显的成本收益。最后，所有者和工程师应通过增量淹没分析来识别与减少IDF有关的潜在责任。尽管可能显示出该水坝在极端事件中对下游洪水没有“显着”贡献，但很可能仍会发现该水坝所有者仍对超出IDF的水坝溃决洪水造成的损害负责。

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