In August 2005, Hurricane Katrina hit the Gulf Coast of the United States, becoming America's costliest and one of its worst natural disasters. Nearly 2,000 people died in the wake of the hurricane and flooding, with the deadliest toll in New Orleans. Katrina's storm surge damaged 53 levees in the New Orleans area, leaving 80 percent of the city underwater.
Shortly after this catastrophic event, the Interagency Performance Evaluation Task Force (IPET) was formed to investigate why the New Orleans area's hurricane protection system failed.
The group, involving more than 150 scientists and engineers from government, academia, and private industry, is divided into several subgroups, including the "Geodetic Elevation and Water Level Datums" team, composed of members of the US Army Corps of Engineers, US National Oceanic and the Atmospheric Administration (NOAA), and contractors.
Through research on various hurricane protection structures and analysis of historical data, the team found inconsistencies in the elevation values used during the design and construction of hurricane protection systems. The group also found that there was a lack of coordination in the New Orleans district of ensuring a common vertical datum (reference point for elevation or depth measurements) and recommended that the USACE's elevation datum guidance should be
According to the report, specifically, the results of the team's research on geodetic elevation and water level data, the military is re-evaluating its programs across the country to ensure they are consistently referenced to the vertical datum of the current national spatial reference system, such as North America's vertical datum of 1988 (NAVD88). The effort is the Comprehensive Evaluation of Project Benchmarks (CEPD): A vertical benchmark for flood protection, comprehensive evaluation guides revetment, hurricane protection, and navigation projects.
The Corps' New York District used Rogers measurements to conduct research on Staten Island's tidal interactions. Burt Winnes, a certified hydrographic surveyor and project manager for the Construction Society Program at Rogers Surveying, noted that the company is working on seven Army Corps of Engineers in the New York/New Jersey area.
Winnes explained that the National Network's datum was established in 1929 to determine mean sea level, and in his area Sandy Hook, New Jersey, is the local datum. The intent is to motivate, however, to establish a NAVD88 baseline within each Corps item, and then to establish mean low water (MLLW) within each baseline. Unlike mean sea level, which varies depending on location in a particular body of water, NAVD88 is the reference and is not affected by water level. NAVD88, the more useful and recognized datum, was built using the original 1929 datums as well as additional datum and elevation point generated networks.
For the Army Corps of Engineers to be addressed by Rogers Survey, the initial step is to determine the reference location, preferably on a bulkhead or dock, where the HOBO® water level data loggers U20-001-01, U20-001-02, U20-001-03 , U20-001-04 (from Onset) can be deployed most easily.
For the first now completed project, located on the Shrewsbury River in New Jersey, ten water level data loggers were deployed individually suspended from electrical wires on PVC pipes at key locations along the river. A HOBO water level logger U20-001-01-Ti, U20-001-02-Ti, U20-001-03-Ti, U20-001-0-4-Ti is also deployed above the water surface to record air pressure. In turn, the barometric pressure readings will be subtracted from the blood pressure readings recorded by the ten-type data logger, thus in the data set the water-induced pressure
Water level data loggers U20L-01, U20L-02, U20L-04, logging every six minutes, calibrated tidal boards (basically large rulers) at least twice a 30-day tidal cycle at a time – near deployment start, again To the end, before the logger is retrieved. Data download and calibration of readings from tide plates using Onset hobo ware® Pro graphics software, analysis of which water level data (time and NAVD88 water level readings) export to Excel for further analysis and reference to the nearest NOAA tide gauge station (refer to the nearest 19-year tide era), and subsequent calculations and other relevant information
Although Rogers Surveys is able to deploy all ten water level data loggers in most convenient locations, such as bulkheads or docks, recent projects have required a vessel to be used for logger deployment and retrieval. In a few cases divers have had to install sand spikes into the seafloor, attaching a small PVC pipe containing the data logger
Winnis said that HOBO's water level data loggers U20-001-01, U20-001-02, U20-001-03, U20-001-04 items are especially useful because they are user-friendly and flexible because They are small and thus can be easily deployed. The affordability of the data logger is an attractive feature as well, especially if multiple loggers are required. Winnes also noted that data retrieval is easily accomplished with a pocket-sized device known as the "Data Shuttle U-DTW-1," which downloads data from the website to the computer after the logger.
Work in the field has been completed on all seven Corps sites, including projects on New York's East River and New Jersey's Sandy Hook Bay. Winnis points out that now one crunches numbers and creates reports re MLLW. To learn more, contact Beijing North Dahe Instrument Co., Ltd. These corrective actions, learned after dealing with the lessons of Hurricane Katrina, will not only get everyone on the same page about vertical datums – in this case, this New updates and accurate information will help reduce damage from future disasters involving the incredible power of water.
