An Integrated Approach For Assessment Of Levees In The Lower Rio Grande Valley

Abstract

The U.S. Army Engineer Research and Development Center (ERDC) and the U. S. Section of the International Boundary and Water Commission (U.S. IBWC) have undertaken an integrated condition assessment of 270 miles of U.S. IBWC levees and their foundations in the Lower Rio Grande Valley of Texas. The purpose of this assessment is to detect levee reaches that lack integrity, need repair, and/or require replacement. The approach utilizes airborne followed by surface geophysics, geologic studies, ground truth sampling, and an Enterprise Geographic Information System (eGIS). Airborne geophysical survey methods included multi-frequency electromagnetic (EM) induction, magnetics, digital video, and light detection and ranging (LiDAR) acquired at speeds up to 70 knots. By employing these techniques, levees were investigated from surface to depths of 100 ft. Ground surface geophysical investigations providing high-resolution definition of anomalies included a full suite of electrical, electromagnetic, magnetic, and ultimately seismic techniques. Geologic studies included mapping of paleochannels, geomorphic surfaces, and identifying borrow sites. Ground truth information was obtained using ERDC’s Site Characterization and Analysis Penetrometer System (SCAPS) employing an instrumented cone and selective sampling tools. Data are efficiently managed for easy retrieval through the eGIS. Upon completion, the entire levee system will be mapped and displayed in terms of good, marginal, acceptable, and high-risk zones, to prioritize long-term monitoring and levee-rehabilitation needs. It was concluded that airborne reconnaissance geophysics followed by high-resolution surface geophysics was indeed a viable, economic approach to levee condition assessment.