Earthen embankment levees are key components of flood management infrastructure. The National Levee Database contains records for 6,857 levee systems comprising 24,518 miles of levees. Inclusion of additional woody vegetation in levee projects is limited by the hindrance vegetation poses to visual inspection. A cost-effective technology to inspect levees and floodplains under various types of vegetative cover could increase flood management system reliability while protecting and facilitating environmental resource values. Geiger mode lidar was developed for defense and intelligence applications because of its exquisite single-photon sensitivity and high data collection rates but has experienced only limited application to civil works. In state-of-the-art Geiger-mode lidar systems, avalanche photodiodes detect single photons and record their time of arrival with sub-nanosecond resolution. Thousands of these sensitive detectors are combined into an imaging array which is synchronized with pulsed lasers operating at rates of 90 kHz. In post-processing these weak signals are aggregated into reliable measurements of the 3D structure of the scene, including elements that are highly occluded, such as the ground under bushes and trees. Detailed, precise 3D surfaces of floodplains and levees are generated. When applied to levee inspections, sophisticated software including AI is used to process the large volume of data produced by Geiger mode lidar overflights and to separate returns from closely-spaced objects to produce accurate terrain maps. Machine comparison of successive lidar surveys (automated geometric change detection) would potentially surpass the capability of human visual inspections to detect erosion, settlement or other changes in levee embankments and adjacent floodplains. Results of a pilot study comprising data collection and processing of a levee and vegetated floodplain along the Lower Mississippi River just north of Vicksburg, MS are presented.
