Historic flooding continues along the Arkansas River with heights not seen since 1945.
Levees located in Fort Smith and Van Buren were built after the 1945 flood to minimize the extent of the flooding to save property and lives.
Both levees will be tested to their design limits this week.
Here's what we know about the Van Buren Levee System
- Construction started in 1947 and was completed in 1949. It was funded in part by the Flood Control Act of 1944.
- For the flood wall, the average height is 12ft above ground elevation and is a "T-structure" made of reinforced concrete.
- The actual embankment levee is 14 feet in height and has a crown width of 10 feet.
- As of 2017, 4,538 people are at risk, 697 structures are being protected worth an estimated $291 million dollars.
- The system is 21.52 miles with 21.28 miles of embankment.
- There are 4 closure structures.
The Van Buren Levee and floodwall were last evaluated in 2009 and were certified by FEMA later that year.
The critical water elevation for water overtopping the levee is between 417-418ft elevation. A forecast river crest of 42.5ft leaves the levee with roughly 3ft to spare.
The critical level to watch on the Arkansas River is 46ft. As long as it stays below that level, the levee is expected to perform well according to it's recent evaluations and the Corps of Engineers Risk Assessment.
According to the most recent evaluation the levee is currently a low risk for failure; "the levee is expected to perform well under significant loading" noting past performance of the levee that "it has performed well with loading of approximately 50% of levee height in the past".
Given a flood of this magnitude unknowns remain but the most recent evaluation noted: "Although there is some uncertainty in performance related to the aged culverts, embankment seepage and floodwall seepage these concerns are somewhat offset by the levee materials leaning towards impervious and the multiple short egress routes. ".
The risk level scale for levees runs from 1 to 5.
- (1) Very High Risk
- (2) High Risk
- (3) Moderate Risk
- (4) Low Risk
- (5) Very Low Risk.
The Van Buren Levee System risk level is a 4.
The lower risk has been communicated by local government as well as emergency management.
That said, we are now in uncharted territory. The Arkansas River hasn't been this full in the history of modern record keeping.
If you live in the vicinity of levee continue to monitor the situation carefully and follow emergency management directives if you are asked to evacuate.
The state of the levee gives us much to be hopeful for as flood waters continue to climb.
-Garrett