Crawfish Tales
A Quarterly Publication of the National Weather Service Lower Mississippi River Forecast Center
Slidell, Louisiana

David Reed, Hydrologist In Charge Vol. 6 No. 4, Summer 2003 Ethan A. Jolly, Editor

Features New Status Maps on the LMRFC Web Site Know Your River Systems: Black & White Rivers

From the HIC

We have had a busy summer with continued showers and heavy rainfall over the LMRFC area and rainfall from Tropical Storm Bill. As we near the most active part of hurricane season, we will continue to keep a watchful eye on the tropics.

In addition to the operational work, we continue to work on development activities to improve our forecast system and enhance our ability to provide data and information to our customers and cooperators. We will continue to make enhancements in our website. Our lead story in this newsletter helps to highlight

our listening to our customers and providing them information that is needed to meet their customer demands. We are also working to develop datasets to support our Advanced Hydrologic Predictions Services efforts to improve our forecast system.

Feedback is always welcome. Please let us know if there are additional products or services you need from the LMRFC. We always enjoy hearing from our cooperators and partners.

- Dave Reed

New Status Maps on the LMRFC Web Site

Frequent conference calls and requests for information regarding the status of rivers during flood conditions over the RFC area demonstrated the need for an effective way to provide this information to customers. In response to these needs, LMRFC now produces web graphics that show the current status of rivers within the RFC area. Prior to this, customers had no way to quickly assess the state of the rivers in the RFC area.

The LMRFC webpage at now has a graphic that depicts the flood category (minor, moderate, major and record) of the highest forecast river stage at each RFC forecast point (fig. 1). This map provides an indication of the magnitude of flooding, if any, and has links to more detailed information and maps of individual forecast groups.

Figure 1: LMRFC status map. Graphic is located on the LMRFC web front-page and is updated twice hourly
Southern Region (SR) 3 hour Flash Flood Guidance
Click for larger image

Drill downs of individual forecast groups (fig. 2) include categorical information with current stage readings, date/time of the reading, river forecast name, and flood stage. Additional information on the maps includes state boundaries with names, county outlines with names, rivers and reservoirs, and interstates. Some support stations with current river stages are also included but categorical information is not listed because these are not official forecast points.

The RFC overview image is automatically created on a PC with a Visual Basic executable using ArcObjects. The executable requires ArcGIS 8.x and runs outside of ArcView allowing it to run much quicker with less system resources.
Drill-down images of individual forecast groups are created on the HP-Unix system with shell scripts and utility programs. Scripts format the data and print text and colored symbols to a background image previously created in ArcView. Categorical and current stage data are extracted from the database with shell scripts and formatted into text files. The current stage data may not be quality controlled. Graphics are updated at 20 and 50 past the hour, twenty-four hours a day.

Figure 2 : Drill-Down Graphic of Pearl River Basin
SR month-to-date observed precipitation
Click for larger image

The drill down maps contain links to hydrographs and text forecast for each forecast point (fig. 3). The LMRFC recently implemented a new and improved forecast hydrograph graphic obtained from the ABRFC. These graphics are also used at the SERFC. The new format now includes observed six-hourly precipitation amounts along with forecast precipitation flood stage flood stage and flood of record.

Figure 3 : Forecast Hydrograph with Text Product
SR normal rainfall from PRISM data set
Click for larger image

- David Welch

Know Your River Systems: Black and White RIver Systems

The Black and the White River Basins cover a combined area of 27,818 square miles across South Missouri and Northern Arkansas. The Black River Basin covers 8,558 square miles across southeast/south-central Missouri and north-central Arkansas and includes the Black, Current, Jack’s Fork, Eleven Point, Spring and Strawberry sub-basins. The upper White Basin covers 11,284 square miles across southwest Missouri and northwest Arkansas and includes the

Figure 1: Black and White River Systems
West Tennessee and St. Francis River Systems
Click for larger image

White, Kings, James, North Fork White, Buffalo, and Bryant Creek sub-basins. The lower White Basin covers 7,976 square miles across north-central through east-central Arkansas and includes the White, Little Red and Cache sub-basins. The upper and middle reaches of the Black Basin and all of the upper White Basin lie within the Ozark highlands, while the lower reaches of the Black Basin and much of the lower White Basin lie within the relative flat land of the Mississippi Alluvial Plain.

Numerous man-made lakes and reservoirs are located within the Black and White Basins. The U.S. Army Corps of Engineers, state or local agencies or power companies control most of these lakes and reservoirs and use them primarily for flood control, hydroelectric power generation, water supply and recreation purposes. Much of the lower White River is also navigable and used seasonably by barge companies.

Average annual rainfall across the White and Black Basins ranges from 42 inches in southwest Missouri to 50+ inches in east-central Arkansas where the White, Arkansas and Mississippi Rivers merge. Response times for forecasted river basins across the area varies depending on terrain. Consequently, the higher relief features of the upper Black adn upper White Basins have several fast response rivers (crests within 12 to 24 hours). The lower White Basin has the majority of slower response rivers (crests greater than 48 hours) owing to the flatter terrain. The table below shows all of the forecasted points within the Black and White basins.

Table 1: Record and Recent Flooding
Black River Basin
River Location Flood Stage (ft) Record Flood (stage/date) Recent Flood (stage/date)
Annapolis, MO 8 27.4 11/14/93 21.5 - 05/13/02
Black Poplar Bluff, MO 16 21.6 12/02/82 18.5 05/09/02
Black Corning, AR 15 16.9 6/13/45 13.3 12/20/01
Black Pocahontas, AR 17 25.9 04/17/27 23.2 05/21/02
Black Black Rock, AR 14 30.3 04/15/27 24.8 05/19/02
Jack’s Fork Eminence, MO 12 19.6 11/19/85 12.5 05/17/02
Current Doniphan, MO 13 25.5 12/03/82 20.6 05/10/02
Eleven Point Ravenden Springs, AR* 15 29.1 12/03/82 17.9 05/09/02
Spring Imboden, AR 18 38.12 12/03/82 21.5 03/26/02
Upper White River Basin
River Location Flood Stage (ft) Record Flood (stage/date) Recent Flood (stage/date)
Berryville, AR 31 36.0 05/07/61 19.8 12/17/01
James Galena, MO 15 33.5 09/25/93 22.0 05/09/02
Buffalo St. Joe, AR 27 53.8 12/03/82 31.5 03/20/02
Buffalo Gilbert, AR* 30 59.2 12/03/82 30.0 03/20/02
North Fork Tecumseh, MO* 20 28.1 11/19/85 22.5 05/08/02
White Calico Rock, AR* 19 52.9 01/31/16 22.5 03/21/02
White Batesville Bridge, AR 15 20.0 05/04/90 18.2 03/21/02
Lower White River Basin
River Location Flood Stage (ft) Record Flood (stage/date) Recent Flood (stage/date)
Newport, AR 26 35.9 04/17/45 27.3 03/29/02
White Augusta, AR 26 41.0 04/20/45 33.5 03/30/02
White Georgetown, AR 21 32.8 02/01/49 23.5 04/01/02
White Des Arc, AR 24 37.4 02/02/49 27.6 04/02/02
White Clarendon, AR 26 43.3 04/23/27 29.1 12/28/01
Little Red Judsonia, AR 30 39.5 06/15/45 29.8 03/20/02
Cache Patterson, AR 8 16.0 04/19/27 12.7 12/19/01
* Flood Only Points
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