The integrity of levees, earthen dams and flood-control infrastructure is an essential component of homeland safety. The failure of such systems due to a natural or man-made hazard such as a hurricane storm surge, flood, earthquake, deterioration, or terrorist attack can have serious repercussions, sometimes with unanticipated consequences on human life, property and the country’s economy. The failure of levees during hurricane Katrina in 2005, which led to the catastrophic flooding of New Orleans, is a highly illustrative example. The national flood-control infrastructure is aging and its structural health is deteriorating. The ASCE’s 2009 Report Card for America’s Infrastructure gives the condition of our nation’s dams a grade of D and levees a grade of D-. The current consensus among the engineering and decision-maker communities is that a major effort must be undertaken urgently to upgrade and rehabilitate the national flood-control infrastructure.
Assessing the health and predicting the performance of geosystems, such as flood-control levees, are challenging tasks. Geomaterials are an ultimate example of a complex random medium that exhibit intricate response and degradation mechanisms. Currently, most infrastructure assessments are based on infrequent visual inspections of the surface condition of levees and dams, which in reality reveal very little about the internal condition and performance of these structures. It’s similar to a medical doctor conducting an annual checkup based solely on the external appearance of a patient. This project aims to develop a new, more effective means to continuously monitor and analyze, in real time, the internal and external health of levees and dams. The proposed framework is cost-effective, robust, minimally invasive, and should boost the safety and reliability of our national flood-control infrastructure.
The project’s capstone experiment includes participating in a $5 million test by the U.S. Army Corps of Engineers that involves intentionally breaching, or loading until failure, a full-scale levee.
The project team at Rensselaer is led by Professor Mourad Zeghal, associate professor in the Department of Civil and Environmental Engineering. Co-investigators on the project are Tarek Abdoun, professor and acting department head of the Department of Civil and Environmental Engineering, and Birsen Yazici, associate professor in the Department of Electrical, Computer, and Systems Engineering at Rensselaer. Professor Abdoun led Rensselaer’s physical modeling team that clarified the failure mechanisms of some of the New Orleans levees during Hurricane Katrina, providing critical feedback to the corresponding numerical analyses. Professor Yazici is leading an $800,000 U.S. Air Force research project to create a new laboratory for developing and testing next-generation radar systems. Geocomp Corporation in Boxborough, MA is the second organization in this Joint Venture grant. Geocomp will play a major role in promoting the proposed sensor-based model-aided health assessment approach to various infrastructure projects in the field.
Among the long-term monitoring techniques proposed for the levee assessment framework is InSAR, or satellite-based interferometric synthetic aperture radar measurements. InSAR will capture and analyze high-resolution satellite images of levees and dams, and measure how far these structures have shifted or subsided due to environmental changes such as rain, floods, tremors, or even aging. InSAR measurements are accurate down to the millimeter scale.
The proposed framework also calls for sensor arrays to be installed into the ground beneath and around levees and dams. These SAPP (Shape-Acceleration-Pore Pressure) arrays, manufactured by Measurand Inc. in New Brunswick, Canada, are inexpensive and will help to accurately measure soil deformation, vibration, and pore pressure at critical points of a flood-control system. To bridge the gap between InSAR satellite data and below-ground SAPP measurements, the researchers will augment the framework with a network of high-resolution GPS sensors to track the physical movement of structures.
Data collected from the three systems will be integrated into an automated “smart network” that provides, for the first time, a long-term continuous assessment of the health of levee systems from both underground and aerial perspectives. In case of a levee failure, data collected by the proposed automated monitoring system will be used to organize a quick emergency response to repair levees and minimize the extent of flooding. Collected data will also be paired with computational simulation techniques to build accurate, predictive models of how different levees should react to different environmental conditions. Such models will be invaluable for developing plans to mitigate levee damage and respond to disasters. The new framework will also provide quantitative assessments that will better allow federal and local governments to prioritize where infrastructure repairs are most needed.
The proposed health assessment framework has the potential to revolutionize our ability to monitor, manage and ensure the safety of levees and other systems of a flood-control infrastructure. This framework provides a comprehensive multi-scale monitoring and analysis for real-time health assessment of this infrastructure. In particular, the goals of this project are to develop and implement: (1) multiscale (global and local) sensing and optimal monitoring strategies, (2) a hierarchy of multiscale data-reduction and identification tools of geosystems, and (3) innovative model-based tools for fusing and mining of observational and computational data to assess the health of these systems so that their safety can be more effectively managed.
This framework utilizes small system deformation due to natural cycles of loading and unloading (rain storms, flood cycles, tides, etc.). Thus, federal and local governments will be able to prioritize and implement repairs and rehabilitation as well as assess the effectiveness of these repairs before major events. This approach would significantly reduce the risk of having a catastrophic failure of a flood control system similar to that of Hurricane Katrina. In case of a levee failure, data collected by the proposed monitoring system will be used to organize a quick emergency response to repair levees and minimize the extent of flooding. The proposed new sensor and monitoring tools as well as the multi-scale health assessment framework will be implemented and benchmarked through an ambitious field implementation plan in critical areas such as the New Orleans area. The benchmark plan will also include a $5,000,000 full-scale test of a levee that will be loaded until failure by the US Army Corps of Engineers (USACE) within the next two years.
The monitoring and assessment of the health of flood-control levee systems is highly vital to homeland security. Places like New Orleans, Northern California, and a number of cities and towns along the path of numerous rivers are under a significant hazard associated with levees that may fail under severe conditions. The goals mentioned above will transform the field of geohazard mitigation to enable more global and holistic approaches, and thereby enable a better control and more reliable flood-control infrastructure. This project will build on the strong track record at Rensselaer and Geocomp in the fields of levee design, sensors performance monitoring of infrastructure, and geohazard mitigation.