Dike study could help validate new flood-control monitors

Civil engineers from Rensselaer Polytechnic Institute were part of an international research team that collapsed the full-scale dike, which was embedded with advanced sensors and traditional measurement instruments.

According to a statement, the dike was situated in a specially constructed basin, which the researchers filled with water. The slow addition of water into the basin increased the pressure on the dike. Water forced its way into the dike and eventually softened the bottom of the dike and shifted the earth underneath, prompting the overall structure to collapse.

The study was led by Dutch research institute Deltares, in partnership with Rensselaer and 14 other companies and universities from around the world. It was the research team’s third full-scale levee test collapse this summer. The full results of the tests will be presented at the Flood Risk Conference in November 2012 in Rotterdam, the Netherlands.

‘The failure of flood-control infrastructure is very real and can lead to catastrophic flooding as we unfortunately witnessed in 2005 during Hurricane Katrina,’ said Tarek Abdoun, associate dean for research and graduate programmes in the School of Engineering at Rensselaer. ‘A large-scale test [such as] this can help supply us with invaluable data to inform and validate our efforts to create a long-term, real-time monitoring system that can assess the health of levees and help identify the vulnerability of levee or dam sections before they fail.’

The collapsed dike was fitted with a large number of different sensors, including shape-acceleration-pore pressure (SAPP) arrays that were developed through a partnership between Rensselaer and industrial collaborator Measurand. SAPP sensor arrays are designed to be installed into the ground, beneath and around levees and dams. The arrays measure soil deformation, vibration and pore pressure at critical points of a flood-control system.

The project, funded by the US National Institute of Standards and Technology’s Technology Innovation Program, pairs SAPP measurements with GPS and InSAR, or satellite-based interferometric synthetic aperture radar measurements.

Claimed to be accurate down to the millimetre, InSAR captures and analyses high-resolution satellite images of levees and dams and measures how far these structures have shifted or sunk due to environmental changes such as rain, floods, tremors or even ageing.

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 and the ground surface.

‘Through our joint-venture partnership with Geocomp, a dense grid of instruments including SAPPs, GPS and radar reflectors has been installed at the London Avenue Canal in New Orleans. The real-time data collected from this site, and others in the New Orleans area, will make performance information available during this and upcoming hurricane seasons, in addition to providing calibration data for health assessment algorithms,’ said Rensselaer research assistant Prof Victoria Gene Bennett.

Data collected from the SAPP, InSAR and GPS systems is integrated into an automated smart network that provides a long-term continuous assessment of the health of levee systems from both underground and aerial perspectives.

In the case of a levee failure, data collected by the automated monitoring system will be used to organise a quick emergency response to repair levees and minimise the extent of flooding.

Collected data is also being paired with computational simulation techniques to build accurate, predictive models of how different levees will react to different environmental conditions.