1. Headcut gets taller & ACM mat flips out of the upstream key trench of the downstream pipe crossing, which causes problems. Project is years old.

2. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
Looking newly exposed river weights show that since March 2009 another 8 inch headcut has moved upstream to the ACM.
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

3. Analysis by Dr. Chester Watson of stage data from the gage on the first bridge downstream of the pipeline crossing shows that the gage has dropped an average of 0.2 ft/per year for the last 15 years, which translates into the 3 ft of headcut observed at the downstream end of the ACM at the pipeline crossing.

4. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
ACM that has flipped out of its US key on the downstream pipe crossing.
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

5. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
Looking US. Bank erosion US of the tree is a concern if it breaks thru the clay outcrop. Bank pins will be installed to ascertain rate of bank erosion. However, erosion on this bank appears less severe now than April 1, 2004.
Bank erosion
Clay outcrop
Next picture
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

6. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
It appears that stone is missing, but in reality there is up to 2.5 ft of sediment over the top of the existing stone on the right bank of Thompson Creek.
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

7. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
Looking stone that has launched as designed. Veg growing in the LPSTP highlights long-term stability. However, when more LPSTP launched upstream compared to downstream, the resulting curve (shown) is guiding water toward the left bank
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

8. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
Looking US. Flow is deflecting off of the left bank (white arrow & exposed LPSTP) & heading toward the right side of the DS pipe crossing (black arrow).
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

9. Looking US @ ACM that has flipped out of its US key.
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

10. 6.5 YEARS LATER-HICKAHALA CR. @ PIPELINE. PIX-DERRICK 3-31-2010
The survey shows that water is flowing under the pipe at the arrow. This means the pipe is suspended in flow & in trouble
6.5 YEARS LATER-HICKAHALA PIPELINE. PIX-DERRICK

11. It’s a rental!!
Pix by Derrick
March 18, 2009

12. AT-GRADE GRADE CONTROL STRUCTURE ON HICKAHALLA CREEK NEAR SENATOBIA, MS. (upstream of the pipeline crossing)
Mini case study: 1 of 12

13. AT-GRADE GRADE CONTROL, FLAT SLOPED SAND BED STREAM
Crest of stone equal to invert of stream
Sheet pile
Headcut advancing
Stone has adjusted and arrested the advancing headcut
Cover over
Stone has adjusted
Mini case study: 2 of 12

14. AT-GRADE GRADE CONTROL, SAND BED STREAM
Crest of stone equal to invert of stream
Sheet pile cutoff wall
Headcut advancing
Stone has adjusted & arrested the advancing headcut
Cover over
Stone has adjusted
Mini case study: 3 of 12

15. At-grade, grade control structure, Hickahala Creek, MS, {rural, sand bed, slope<1%, pool-riffle-pool, straightened, incised} as-built in 1989, note concrete cap on sheet-pile cutoff wall
Mini case study: 4 of 12

16. At-grade, grade control structure, Hickahala Creek, MS, as-built in 1989, note concrete cap on sheet-pile cutoff wall
Mini case study: 5 of 12

17. Sheet-pile cutoff wall
Mini case study: 6 of 12
At-grade grade control, Hickahala Creek, MS. Functioning as designed (to arrest headward migration of knickpoints) picture taken April 2004

18. Hickahala at-grade GC at high flow, April 6, 2005
Mini case study: 7 of 12
Hickahala at-grade GC at high flow, April 6, 2005

19. Sheet-pile cutoff wall
Mini case study: 8 of 12
At-grade GC, Hickahala Creek, MS. April Compared to the 2004 pictures, some stone has been displaced on the DS side of the sheetpile cap.

20. Sheet-pile cutoff wall
Mini case study: 9 of 12
At-grade GC, Hickahala Creek, MS. April Close-up of displaced stone on the DS side of sheetpile cap.

21. Sheet-pile cutoff wall
Mini case study: 10 of 12
At-grade GC, Hickahala Creek, MS. April Stone on DS face has self-adjusted to form a pool-riffle-pool configuration.

22. Sheet-pile cutoff wall Mini case study: 11 of 12
At-grade GC, Hickahala Cr. Except for some movement of stone on the DS side of the cutoff wall, there is little difference between the April 2007 & April 2010 pix.

23. Sheet-pile cutoff wall
Mini case study: 12 of 12
At-grade GC, Hickahala Creek, MS. April Structure is similar to April Left bank erosion has increased, right bank is stable.

24. AT-GRADE GRADE CONTROL, FLAT SLOPED SAND BED STREAM
Crest of stone equal to invert of stream
Sheet pile
Headcut advancing
Stone has adjusted and arrested the advancing headcut
Cover over
Stone has adjusted

25. AT-GRADE GRADE CONTROL, SAND BED STREAM
Crest of stone equal to invert of stream
Sheet pile cutoff wall
Headcut advancing
Stone has adjusted & arrested the advancing headcut
Cover over
Stone has adjusted

26. At-grade, grade control structure, Hickahala Creek, MS, {rural, sand bed, slope<1%, pool-riffle-pool, straightened, incised} as-built in 1989, note concrete cap on sheet-pile cutoff wall
Mini case study: 1 of 7

27. At-grade, grade control structure, Hickahala Creek, MS, as-built in 1989, note concrete cap on sheet-pile cutoff wall
Mini case study: 2 of 7

28. Sheet-pile cutoff wall
Mini case study: 3 of 7
At-grade grade control, Hickahala Creek, MS. Functioning as designed (to arrest headward migration of knickpoints) picture taken April 2004

29. Hickahala at-grade GC at high flow, April 6, 2005
Mini case study: 4 of 7
Hickahala at-grade GC at high flow, April 6, 2005

30. Sheet-pile cutoff wall
Mini case study: 5 of 7
At-grade GC, Hickahala Creek, MS. April Compared to the 2004 pictures, some stone has been displaced on the DS side of the sheetpile cap.

31. Sheet-pile cutoff wall
Mini case study: 6 of 7
At-grade GC, Hickahala Creek, MS. April Close-up of displaced stone on the DS side of sheetpile cap.

32. Sheet-pile cutoff wall
Mini case study: 6 of 7
At-grade GC, Hickahala Creek, MS. April Stone on DS face has self-adjusted to form a pool-riffle-pool configuration.

33. Sheet-pile cutoff wall Mini case study: 6 of 7
At-grade GC, Hickahala Cr. Except for some movement of stone on the DS side of the cutoff wall, there is little difference between the April 2007 & April 2010 pix.

34. Sheet-pile cutoff wall
Mini case study: 6 of 7
At-grade GC, Hickahala Creek, MS. April ERR is similar to April Left bank erosion has increased, right bank is stable.