Often in litigation, especially in flood claims, determining the vertical elevation of a land or water based structure or object is important. In a recent flood case, the elevation of the top of an earthen embankment and associated dam structure was important in determining whether a defendant was liable. The allegation was that the dam collapsed and contributed to downstream flooding because it was not properly maintained. The defense was that it collapsed because the rain storm was greater than the capacity of the dam and embankment, and the failure was the result of an Act of God. The contention was that the rain overtopped the dam and embankment.
Determining the elevation of the embankment before the flood was a critical factual issue. Among other things, plaintiff’s experts accessed the LIDAR database, developed and maintained by U.S. Geological Survey (USGS). According to the National Oceanic and Atmospheric Administration (NOAA) website, LIDAR, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These light pulses — combined with other data recorded by the airborne system — generate precise, three-dimensional information about the shape of the Earth and its surface characteristics.
USGS has surveyed many parts of the United States from the air with LIDAR technology and the data from those surveys is available free of charge. This data provides very accurate information regarding the elevation of the things surveyed. USGS’s 3D Elevation Program (3DEP) initiative is being developed to respond to growing needs for high-quality topographic data and for a wide range of other three-dimensional representations of the nation’s natural and constructed features. The primary goal of 3DEP is to systematically collect enhanced elevation data in the form of high-quality light detection and ranging (LIDAR) data over the conterminous United States, Hawaii, and the U.S. territories, with data acquired over an eight-year period.
The geographic area in question in the litigation was surveyed from the air prior to the flood and during the time that the defendant was supposed to be maintaining the facility. Plaintiff’s expert superimposed the raw USGS LIDAR data onto a contour map and located the dam and embankment and determined with virtual certainty the relative pre-flood elevations of the dam and embankment in relation to the known water surface elevations. This data reinforces the other bases for his opinions and he can say now testify convincingly that the conditions support the plaintiff’s position and not the defense position.
LIDAR can be a new, effective, and accessible tool for experts to utilize in property damage litigation.