IntroductionLocal and state emergency managers need a preparedness plan and access to the best weather information available in order to respond to threatening weather hazards within their jurisdiction. Experimentation began at FSL in 1992 to modernize the dissemination of data for local emergency response agencies. This led to the realization that a decision-making tool akin to a meteorological forecasting workstation would be very beneficial in helping emergency managers make better decisions.
In 1997, FSL began building the Local Data Acquisition and Dissemination (LDAD) system, the community interface and data distribution component of the Advanced Weather Interactive and Processing System (AWIPS). The LDAD system is a vital component for automating Weather Forecast Office interactions with local data observation systems, severe weather spotter networks, cooperative observers, and local emergency management. Commissioned by Congress last July, LDAD consists of a configurable local data acquisition subsystem, a local observation quality control subsystem, and dissemination via fax, file transfer protocol, bulletin board, and direct connect for non-Java-capable computers. (The November 1997 issue of the FSL Forum is dedicated to all of the many topics related to LDAD at that time.)
The LDAD dissemination strategy includes the Emergency Manager Decision Support (EMDS) system, a workstation configuration especially designed to address destructive weather. It will be installed in every National Weather Service (NWS) office to provide emergency managers detailed, easier-to-understand information (not merely data) that is suited for professionals not formally trained in meteorology. The EMDS system (Figure 1) uses graphics, imagery, audio, and text for communicating important weather information to those who make crucial weather-related decisions. To accomplish this, large volumes of a wide variety of data are accessed in real time and integrated into forecasts that provide more detail in the mesoscale. The EMDS system can be used to combine NWS data, Geographic Information System (GIS) data from local sources, and protocol from emergency manager situational plans to provide real-time, concise, and coherent information to the emergency response community.
Figure 1. An example of information provided by the EMDS system that relates to the case study used in this article, the 1997 Fort Collins flood. This screen shows a radar-derived storm total rainfall of 3–4 inches at 9:05 PM MDT in the Spring Creek drainage area, where the maximum amount of rainfall occurred.
In this article we use the 1997 Fort Collins, CO, flash flood to demonstrate the utility of the EMDS as it will be used in the emergency response community. (An article on the Fort Collins event is featured in the March 1998 issue of the FSL Forum.)
Complexities of Forecasting Flash Floods
A flash flood often requires particularly complex and difficult decisions on the part of both the forecasters and the emergency response community. Unlike most other dangerous weather phenomena, flash floods are not simply meteorological events. Accurate NWS forecasts and diagnoses of rainfall accumulation are not enough to forecast an event. Flash floods are hydrometeorological phenomena that involve the complex interrelationships of rainfall, hydrology, and human activity.
Following a series of particularly disastrous flash floods in the 1970s (Rapid City, South Dakota, 1972; Big Thompson Canyon, Colorado, 1976; and Johnstown, Pennsylvania, and Kansas City, Missouri, 1977), there was an increase of research toward understanding the scientific processes responsible for excessive rainfall. These studies by NOAA scientists represent an important step in understanding the problem, but they only address the rainfall aspect of the flash flood phenomenon. Destructive flash floods have continued to strike regularly in all areas of the country since the 1970s, but increasingly so in urban environments. Recent research at FSL and elsewhere has concentrated more on the nonmeteorological factors responsible for flash flooding and the precipitation intensity contribution in hydrologically sensitive basins.
Although the understanding of excessive rainfall events has improved significantly since the 1970s, there has not been a corresponding improvement in the ability to obtain crucial hydrologic information and to communicate with other experts on the flash flood problem. Here we want to illustrate how the EMDS system is designed to address the communication and hydrological aspects of the flash flood phenomenon.
Special Features of the EMDS System
The EMDS system facilitates the communication of vital weather and warning information between agencies such as the NWS and the local emergency response organizations. This exchange of information is beneficial during dangerous flash flood events, especially in view of the rapid and complex evolution of intense rainfall and subsequent hydrologic response.
The EMDS system provides real-time radar, satellite, river and basin information/alerts, moisture and precipitation related images/overlays, text messages, watches and warnings through direct communication links to the emergency response agency, as follows:
Case Study – 1997 Fort Collins Flood
The Fort Collins flood of July 1997 provides an excellent opportunity to study the various elements that come together during a flash flood event. This event also provides a comprehensive look at the various agencies involved in a weather-related emergency, and how crucial data and information should be communicated among these agencies.
On 28 July 1997, Fort Collins was hit by a series of dangerous thunderstorms that generated 10 inches of precipitation in 5 1/2 hours. This storm began at approximately 5:30 PM (all times mentioned are local time, Mountain Daylight Time) and ended around 11 PM. Roughly half of the total precipitation fell in the last 90 minutes of the deluge, and it was the most rain ever to fall on a Colorado urban drainage. This presidentially declared disaster was the worst in the city's history, with five deaths, over 60 people seriously injured, 2,200 homes or businesses damaged or destroyed, and over $500 million in damage, marking it as the second most costly disaster ever to hit Colorado.
On the night of the flood, NWS forecasters contacted county staff to try to get information on what they knew to be a deteriorating situation. The NWS was given outlying flood feedback for the county areas (i.e., rural areas) but not for the city of Fort Collins. Although the radar provided spatially accurate precipitation guidance, unusual tropical conditions led to greater rainfall rates than the radar guidance could accommodate (see the 1998 issue of the FSL Forum). The result may have been even more disastrous except that the weather forecasters on duty issued a warning anyway, based on experience. In the hours that followed, firefighters, police, dive-rescue teams, and private citizens executed 450 rescues, pulling some victims from certain death in 8-feet high raging waters.
Emergency Response Possibilities Using EMDS
If the city of Fort Collins had been supported with better and faster communication links to weather information, along with additional hydrological data other than radar, earlier evacuation strategies may have precluded the need for rapid-water rescues.
The maximum rainfall occurred in the Spring Creek drainage on the southwest side of Fort Collins. A flood retention pond just east of this rainfall concentration had passed its maximum capacity, which caused flooding in a nearby mobile home park downstream, resulting in the loss of five lives there. At 9:05 PM, about three hours into the event, the EMDS radar-derived storm total rainfall indicated 3–4 inches of rain (Figure 1). By 11 PM, 10 inches of rain had actually fallen in the Spring Creek drainage.
Any region can be readily displayed and various parameters can be customized to distinguish the patterns of the event. Figure 2 was created using GIS to graphically depict the Fort Collins watershed, its flood plain, and streets. This would have provided Fort Collins emergency managers with immediate access to weather information tailored to the particular needs of their locale.
Figure 2. A customized EMDS display of the city of Fort Collins shows streets, watershed, and flood plains.
In this case, by monitoring the real-time radar data updates of the EMDS system, Fort Collins rescue personnel could have been kept abreast of the unfolding situation with informational dispatch tones, while emergency responders put contingency plans of evacuation into effect. Long before the EMDS indicated 3–4 inches of rain at 9:05 PM, traffic could have been diverted from the potential flood areas, evacuation begun, shelters prepared, and rescue personnel staged at strategic spots throughout the city.
At roughly 10 PM, the radar-derived storm total rainfall was estimating 5 inches of precipitation over a 12-km2 area. Because of the tropical-like conditions, this was an underestimate. The final total precipitation was 10 inches, as shown on the isohyetal map (Figure 3). Emergency managers are trained to plan for the worst. Even so, three hours into the event (8:30 PM), the Fort Collins emergency managers began responding to 911 calls, too late for orchestrated evacuations. If the EMDS system had been available–with its customized geographical displays and automatic NWS real-time weather updates, emergency responders would have been staged in the vicinity of known flood basins and ready to monitor their situation via hand-held pack sets. At the slightest indication of flooding (backed-up sewers and flooded basements), evacuation plans could have begun. This would have been at approximately 7:30 PM, one hour before emergency personnel responded to 911 calls. Even with the most extreme planning, 10 inches of precipitation probably would not have been expected. However, evacuation would have been the preferred mode of emergency response, whether 5 or 10 inches of precipitation were predicted. Figure 4 shows two scenes of one area during and after the Fort Collins flood.
Figure 3. The isohyetal map of rainfall for Fort Collins showing that 10 inches of rain had fallen in the Spring Creek drainage (by 11 PM).
Figure 4. Two scenes from the Fort Collins flood: (above) a rescuer at work during the flooding of a trailer park area, and (below) an example of property damage afterward in the same area.
SummaryMost disasters in this country are weather related and their onset is sudden. To the emergency manager, however, weather disasters do not just happen suddenly, they evolve. All weather information, whether insignificant or leading up to a true emergency, is met with an action protocol (such as organizing a special action team). Unfortunately, most emergency responders do not have access to all of the NWS information or forecasts that they need. Many communities obtain weather information through contract agencies that do not have the experience and comprehensiveness of the NWS, nor are they aware of the kinds of services that the NWS can offer them.
The flexible nature of the EMDS system coupled with its capability for processing volumes of varied data will expedite emergency response to every weather situation. The simplification of complex weather guidance or emergency management will result in better services to the public. Moreover, once the combined technological advances of the EMDS system are fully implemented, this will dramatically improve the outcome of weather- related emergencies, subsequently saving lives and money.
[Editor's Note: More information on this project, including bibliographies, is available at the FSL LDAD Website ]
( Deborah Miller is a Systems Analyst in the Modernization Division, headed by Dennis Walts. Her contract affiliation is with System Technology Associates, Inc.)