|David Reed, Hydrologist In Charge||Vol. 5 No. 4, Summer 2002||Ethan A. Jolly, Editor|
|AHPS Update||East TN, West NC, SW VA|
|From the HIC|
The long, hot summer is here and there is a lull in forecast activities. This gives us time to review our hydrologic procedures and develop new techniques to provide products and services to our customers and partners. This will make us better prepared to meet the challenges that might occur during this hurricane season and the flood season of 2003.
Much of our efforts will be focused on the Advanced Hydrologic Prediction Services (AHPS). AHPS will be our next generation forecast system that combines better science with improved technology to expand our products and forecast services. The NWS is hoping for significant funding over the next 10 years starting in 2003 to implement AHPS. Much of our efforts over the summer and fall will be to prepare to utilize these funds to improve
and enhance our current hydrologic models and parameters. Much of this issue is devoted to AHPS and some of the products and services expected to be implemented over the next few years.
To help in understanding the hydrology and forecast locations, we will begin a routine article featuring each of our major river basins. This issue will focus on eastern Tennessee drainages since they will be the first to be implemented in AHPS.
Please let us know if we need to provide additional products and services. We always enjoy hearing from our cooperators and partners and meeting your needs.
|Advanced Hydrologic Prediction Service (AHPS) Update|
During the next few years the Lower Mississippi River Forecast Center along with the rest of the National Weather Service will begin implementing its Advanced Hydrologic Prediction Service (AHPS). This program will greatly enhance the hydrologic services the National Weather Service provides.
Each Year, floods kill more people than any other form of severe weather, and cause damages in excess of $3.5 billion. Three-quarters of all presidentially declared disasters are the result of flooding. National implementation of AHPS will save lives and an estimated $240 million per year in flood losses, and will contribute an additional $520 million per year in economic benefits to water resource users.
Some of the new services include:
upgrade of the NWS River Forecast System (NWSRFS) to reduce the time required to produce forecasts and make it easier to implement new models. The models will be calibrated for each basin to ensure the best possible simulation and forecast accuracy using the latest calibration techniques and historical records. Also, sophisticated distributed hydrologic modeling capability will be implemented which accounts for the variability of precipitation and rainfall-runoff characteristics within a basin. This modeling capability will allow short-term forecasts to more realistically reflect the streamflow response to precipitation.
• Probabilistic forecasts, providing graphical forecasts from days to months into the future.
For more information on AHPS, go the National Weather Service AHPS website at:
|Know Your River Systems: East TN, West NC, & Southwest VA|
The mountain/valley landscape of East TN, West NC, and Southwest VA provide the Lower Mississippi River Forecast Center (LMRFC) with fast response rivers and streams. In fact, the majority of LMRFC rivers that crest within 24 hours are located in these areas. This area is the headwaters of the Tennessee River which starts at Ft. Loudoun Dam.
Figure 1 shows the major rivers and streams in the region as well as topography. The French Broad River which originates in the mountains of western NC and the Holston River which has its origins in southwest VA both flow into the reservoir above the dam. This area has many lakes, most man made and most operated and controlled by the Tennessee Valley Authority (TVA) headquartered in Knoxville, TN. The primary purpose of most of the dams is hydroelectric power, but most are multipurpose providing flood control and recreation.
Hydro-Climatology of the Area
Due to the mountains the region, precipitation varies with topography ranging from 65 inches annually in the mountains of
Western North Carolina to less 35 inches annually in some of the valleys of Eastern Tennessee. Another function of the mountains is help create fast response rivers and streams. Most of the rivers and streams, especially those upstream of a dam or control structure, crest within the first 24 hours of a rainfall event. One function of the dams and river control structures is to hold back any wave moving down stream and help minimize any flooding that occurs by releasing water at a controlled pace at a later time.
History of the Region
Many rainfall events have occurred in the region; some localized affecting only a few locations and some widespread affecting the entire area. Many infamous flash floods have occurred in this region. In 1969, the remnants of Hurricane Camille caused flash flooding killing 153 in what is the worst natural disaster to hit the state of Virginia. 31 inches of rain fell in 6 hours in Nelson County, VA killing 121 in the county alone. Very little flooding occurred in the LMRFC area, however Camille showed us what can happen when a tropical system interacts with mountains.
|Table 1 - Record and Recent Flooding|
||Location||Flood Stg (ft)||Record||Recent Flood (stage/date)|
||Oakdale||27||42.3 ft 3/1929||28.7 ft 1/24/02|
||Whitwell||14||19.0 ft 3/1867||16.2 ft 3/18/02|
||Jonesville||18||44.3 ft 4/1977||32.4 ft 3/18/02|
|Arthur||17||39.0 ft 4/1977||29.0 ft 3/19/02|
|N. Fork Holston
||Saltville||12||14.9 ft 3/2002||14.9 ft 3/18/02|
|Gate City||12||19.8 ft 4/1977||19.5 ft 3/19/02|
||Cleveland||14||26.4 ft 4/1977||20.7 ft 3/20/02|
|Speers Ferry||18||36.7 ft 4/1977||32.3 ft 3/19/02|
|Tazewell||12||29.3 ft 4/1977||21.3 ft 3/19/02|
||Embreeville||12||21.5 ft 11/1977||11.6 ft 8/1994|
||Sevierville||11||18.1 ft 3/1965||11.2 ft 3/18/02|
||Blantyre||17||25.5 ft 10/1964||none since 1996|
|Asheville||8||23.1 ft 7/1916||none since 1996|
|Marshall||8||22.0 ft 7/1916||none since 1996|
|Hot Springs||13||22.4 ft 8/1940||none since 1996|
|Newport||10||19.3 ft 8/1940
(22.5 ft estimated in 7/1916)
|11.5 ft 3/18/02|
||Biltmore||12||19.0 ft 8/1940||none since 1996|
|Chickamauga ck||Chattanooga||18||28.7 ft 2/1990||22.8 ft 4/5/00|