The following report appears as a News Note in the June 1998 issue of Geotimes. It is reprinted here with permission.
With everything from floods to tornadoes to a rainy day being attributed to El Nino this year, geoscientists have been busy monitoring and forecasting the impacts of the storms associated with the phenomenon. Scientists with the U.S. Geological Sur vey (USGS) have been instrumental in gauging stream flows and predicting floods as well as monitoring landslides. The USGS has recently joined forces with the National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Admini stration (NOAA) to assess coastal erosion from this winter's storms.
El Nino is an abnormal warming of the ocean across the eastern tropical Pacific (approximately 8 degrees F above normal this year) accompanied by weak trade winds that affects weather patterns worldwide. Due to technological advances, including ocean d ata buoys and satellites, NOAA was able to accurately forecast that this year's El Nino would be the largest since 1982-1983, and prepare to mitigate the predicted effects.
Flood monitoring and warning
With the early prediction of El Nino by NOAA, USGS scientists were able to take preliminary action by preparing experiments on stream-channel changes and groundwater recharge, in order to take advantage of the expected heavier-than-normal precipitation. T he USGS also communicated historical information on flooding and streamflows during previous El Ninos to water managers, primarily in the West. This data provided clues on where flooding was most likely to occur.
The USGS has over 7,000 stream-gauging stations located throughout the United States, about half of which are connected via satellite to transmit the information in "real time" to local agencies. In addition to these stations, hydrologists went into th e field to measure stream discharge during peak flow times. These measurements were then used by the National Weather Service and others to accurately predict floods and were posted in real time on the Internet. This information is often difficult to gather -- USGS field crews lower weighted measuring devices into swollen streams from bridges or as they hang from small cable cars. According to USGS hydrologic technician William Boults, "You are abou t 15 feet above the raging waters in a cable car with a 100-pound weight, your feet dangle over the water -it can be scary!"
Last fall, the USGS combined the newly-digitized USGS National Landslide Overview Map, which delineates areas where large numbers of landslides have occurred and areas that are susceptible to landsliding, with NOAA's National Climate Outlook Maps, which s how contours of probability that El Nino-induced precipitation will be above, near, or below normal. The resulting national maps, which were updated every three weeks, indicated where there may be overlap between areas of high potential landsliding and pr edicted above-normal precipitation, a prime condition for landslides. The USGS alerted communities in areas that were found to have a greater than normal probability of landslides and also provided information to the public on how to recognize a landslide and what to do if one occurs. In addition to using the maps, scientists were out in the field monitoring the movement of land and providing the information to local and state governments, who would then make the decision whether or not to evacuate the ar ea.
Although the fast-moving debris flows in California ended in March, the intermountain states of Nevada, Utah, New Mexico, and Colorado have prepared for snowmelt landslides, which are expected to occur primarily in late spring or early summer. In addit ion, scientists are still busy doing reconnaissance work for a 10-county study in the San Francisco Bay area. A joint effort of the USGS Geologic and Mapping Divisions, the intensive study will measure economic loss and land movement in the area. The resu lts, which will be incorporated into maps that are usable at the homeowner level, will be released this summer.
In April, the USGS Centers for Coastal Geology joined with the NASA Goddard Space Flight Center and NOAA's Coastal Service Center to begin research to produce a highly detailed map of the west coast, from Washington to Southern California. Using an Airbor ne Terrain Mapper (ATM) flown on a NOAA plane and a Global Positioning System satellite receiver, researchers will be able to survey the beach elevations to an accuracy of four inches. These results will be compared to a smaller, pre-El Nino baseline surv ey that covered three regions of the West Coast. The USGS will be instrumental in mission planning and converting the information to a format that can be used by state and federal agencies to help plan coastal development. John Brock, Coastal Remote Sensi ng Program Manager with NOAA, believes this information will "help to support sustainable coastal development and improved coastal management." Information on the ATM can be found on the NASA Internet home page.
The research conducted by USGS scientists will not only help those affected by this year's El Nino, but also will continue to increase the accuracy of prediction and lessen its effects in future years.
Please send any comments or requests for information to the AGI Government Affairs Program.
Contributed by Kasey Shewey, AGI Government Affairs Program
Last updated May 29, 1998
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