SGER/Collaborative Research: 2008 Midwest Levee Failure Invesigation

这项小型实验研究补助金（SGER）奖是一项立即进行的实地勘察和数据收集工作，旨在收集敏感和随时间变化的易腐堤坝性能（失败和成功）数据，记录2008年6月和7月风暴期间爱荷华州达文波特和密苏里州圣路易斯之间密西西比河沿着防洪堤坝的性能。 本研究的目的是进行综合评价堤防性能受到“极端”的负载，如延长持续时间升高的河流阶段（诱导下渗/内部侵蚀）和漫顶/冲刷侵蚀。 在过去的十年里，人们已经研究了堤坝性能的各个侵蚀特性，并取得了显著的进展，但还没有进行综合研究，将所有侵蚀特性综合在一个模型中。 这项研究提供了迫切需要的全面的现场数据，以验证经验公式和数值模型，已开发的堤坝侵蚀分析。 从中西部堤坝系统的表现中可以吸取潜在的至关重要的教训。 数据收集包括详细的激光成像调查（陆地激光雷达）的缺口和侵蚀/冲刷特征，植被覆盖的表征，堤坝土壤材料的表征（统一土壤分类系统、阿特伯格界限、密度、粒度分布和侵蚀功能仪器评级），根据目击者的叙述以及河流水位测量站，记录堤坝破坏位置的河流水位，以及观察堤坝故障和执行/监督维修的工程师和人员的经验教训。 因此，本研究为堤防抗冲设计提供了全面的现场资料。 美国有数千英里的土堤，许多没有任何工程设计或认证，这些土堤应该为居住在堤坝后面保护区内的居民提供防洪保护。 在按照公认的工程方法设计的堤坝中，很少有堤坝被设计成抵抗最常见的破坏类型，漫顶。 因此，该现场勘察研究的结果可以直接应用于整个美国防洪系统，以评估土堤作为防洪要素的可靠性，并为堤坝改进提供建议，以提高性能可靠性。

This Small Grant for Experimental Research (SGER) award is an immediate field reconnaissance and data collection effort to collect sensitive and time-dependent perishable levee performance (failures and successes) data, documenting the performance of the flood protection levees along the Mississippi River between Davenport Iowa and St. Louis Missouri during the June and July 2008 storms. The objective of the study is to perform an integrated evaluation of levee performance subject to "extreme" loading, such as extended duration elevated river stages (inducing underseepage/internal erosion) and overtopping/scour erosion. Individual erosion characteristics for levee performance have been studied and significantly advanced in the last ten years, but no integrated studies have been performed that synthesize all the erosion characteristics in one model. This study provides desperately needed comprehensive field data to validate empirical formulas and numerical models that have been developed to analyze erosion of levees. There are lessons of potentially vital importance to be learned from the performance of the Midwest levee systems. The data collection consists of detailed laser imaging surveys (Terrestrial LiDAR) of the breach and erosion/scour features, characterization of the vegetative grass cover, characterization of the levee soil materials (Unified Soil Classification System, Atterberg Limits, density, grain-size distribution, and Erosion Function Apparatus rating), documentation of river stage at the location of levee failures from eyewitness accounts as well as river stage gaging stations, and lessons from the engineers and personnel who observed the levee failures and performed/oversaw repairs. Thus, this study provides comprehensive field data for use in advancement of levee erosion-resistance design. There are thousands of miles of earthen levees in the United States, many without any engineering design or certification, that are supposed to provide flood protection for residents living within the protected zone behind the levees. Of the levees that were designed in accordance with accepted engineering methods, very few of the levees have been designed to resist the most common failure type, overtopping. Thus, the results of this field reconnaissance study can be directly applied to the entire U.S. flood protection system to evaluate the reliability of earthen levees as flood protection elements, as well as recommendations for levee improvements to increase performance reliability.