
As the ominous, and literal, dark cloud of Hurricane Gustav threatens the city of New Orleans, preparation and preparedness remain great issues of concern for the vulnerable city. With 75% of the city flooded and over 1800 deaths resulting from the 2005 natural disaster and the failure of the city's engineered levee system as well, questions lingered on how such a failure could occur and how to prevent it in the future.
According to U.S. Geological Survey (USGS) articles published in the agency's online newsletters, shortly after the devastating storm ran ashore on August 29, 2005, scientists collected high-resolution scans of several levee breaches along various canals, which resulted in severe flooding and damage. The scans, collected at the request of the U.S. Army Corps of Engineers, used a "ground-based terrestrial laser-mapping system" to survey the breaches and examine how both structural and soil degradation contributed to the monumental failure. After analysis by a number of agencies was complete, the finding were presented to the US senate. Several months later, a USGS team returned to the city to collect and ultimately attach Global Positioning System (GPS) data to the scans. GPS uses 24 satellites that circle the globe every 12 hours at 12,000 miles above earth, continually collecting and transmitting the satellites exact time and location in space (Pine, 83). When the satellites' radio signal is transmitted to receivers, a variety of precise information can be collected, tracked, mapped and categorized.
The USGS team visited the same area where the scans were originally collected used GPS to assign geographic coordinates to the scans. Because the original scans were often collected in the path of emergency responders and thus at a rapid pace, accurate "registration points", or actual geographic coordinates, were not included at that time. In order to revisit the sites, the team examined the scans for potential location points that might still be available as many of the areas had been under repair and altered since original collection. After determining 3-dimensional structures that would hopefully still be available, the USGS team headed out to collect the points. With the use of GPS points, data was assigned to within centimeter accuracy of the registration point.
Upon completion of the registration process, the information was provided to numerous agencies in order to aid in the repair process of the levee system. Specifically, the data was used in conjunction with geographic information system (GIS) to depict the conditions in areas where the levees failed as well as with geotechnical drilling information to examine how the terrain and geology impacted the levee failure. The registered points will also be used to help with current concerns of inaccurate floodwall elevation data. Due to soil variance causing the current, "fixed" benchmarks to sink sometimes more than a foot, the newly collected GPS points will provide a more accurate measurement of the floodwall elevation.
Although too late for the victims of Hurricane Katrina, hopefully science and government still have time for future generations of the gulf coast region.
Sources: soundwaves.usgs.gov/2006/05/>
soundwaves.usgs.gov/2005/01/ >
Pine GIS and GPS, 2007
Photo from cmurray - breach at 17th street canal, 2005