1. Natural Channel Restoration after
Irene and Lee
a Schoharie County Opportunity
Will VanDeValk, Area Engineer
USDA/NRCS
2013 Mohawk Watershed Symposium 1

2. NRCS Emergency Watershed
Protection Program
 Several towns approached NRCS in late 2011 seeking
technical and financial assistance
 State Office staff evaluated sites for EWP eligibility
 10 sites (reaches) on 6 Streams were determined eligible
 Significant Threat to Public Health and Safety
 75% NRCS Funding for construction
(25% Local Match req’d)
 NRCS determined that a holistic approach to stream
restoration is critical to long-term success
2

3. Platter Kill/Flat Creek Road (5,500 LF reach)
 Approx. 40-ft high raw bank near upstream end of
5,500 LF reach
3

4. Platter Kill/Flat Creek Road (5,500 LF reach)
 Loose, saturated, highly-erodible bank
 Bed & bank armoring washed away by flood
4

5. Platter Kill/Flat Creek Road (5,500 LF reach)
 Approx. 50-ft high near vertical bank
 Bed & lower bank armoring washed away by flood
5

6. Platter Kill/Flat Creek Road (5,500 LF reach)
 Home site destroyed by channel relocation
6

7. Platter Kill/Flat Creek Road (5,500 LF reach)
 15-ft wide x 7-ft high box culvert beneath roadway
7

8. Little Schoharie Reach A (9,600 LF reach)
 Overwidened channel w/ loose berms
8

9. Little Schoharie Reach B (8,200 LF reach)
 40-ft high raw bank below laboratory facility
9

10. Little Schoharie Reach B (8,200 LF reach)
 Downcutting of exposed clay/silt material
10

11. Little Schoharie Reach C (6,000 LF reach)
 Original meandering channel, abandoned by flood
11

12. Little Schoharie Reach C (6,000 LF reach)
 Approx. 20-ft high eroding bank near Brooky Hollow
 Evidence of considerable downcutting
12

13. Little Schoharie Reach D (6,700 LF reach)
 Sharp bend @ Huntersland Rd., 10’ – 15’ downcutting
13

14. Little Schoharie Reach D (6,700 LF reach)
 Conditions on 1/24/12 (~ 5 mos. after Irene)
14

15. Little Schoharie Reach D (6,700 LF reach)
15
 Conditions on 3/06/13 (~ 18 mos. after Irene)

16. Little Schoharie Reach D (6,700 LF reach)
 Sloughing of bank near residence as stream downcutsg
16

17. 17

18. Line Creek/Mill Valley Rd. (10,400 LF reach)
 Home site destroyed by channel relocation
18

19. Line Creek/Mill Valley
Rd. (10,400 LF reach)
 Stream adjacent to road
& residences
 Some hard-armoring or
structural solutions may
be required
19

20. Damage Survey Report (DSR) Process
 Field Procedures (began in Jan. 2012)
 GPS-locate features & estimate lengths & heights
 Office Procedures (Conceptual – Level)
 Enter field data into GIS system
 Preliminary Hydrologic & Hydraulic analyses
 Conceptual solution (reconnect stream w/ floodplain,
remove berms, restore meander pattern, size channel
for 1 to 2 year flows, provide grade-control, revegetate
banks, hard-armoring only where necessary)
 Quantity estimates
 Cost Estimating (completed 3/27/12)
20

21.  Loss of stream meander
 Raw Bank Height & Area
estimates
 ~ 885,000 sq. ft. of raw
bank along 5.6 miles
(Reaches A – D)
21

22. Project Finances (NRCS estimates)
 10 Project sites on 6 streams covering approximately
47,300 LF (9 miles) of stream
 Construction Cost estimated at $21.2M
 NRCS share (75%) = $15.9M
 NYS has agreed to fund Local share (25%) = $5.3M
 NRCS will fund up to $1.59M for allowable non-
construction costs (administration, engineering, etc.)
22

23. Project Plan – Schoharie County EWP
 County under contract with AECOM to “Provide
Assessment, Design and Construction Administration
for Support of Natural Stream Restoration Projects”
 Assessment & Design in 1st half of 2013
 Construction to begin this summer, with completion by
mid-January, 2014 (EWP condition)
23

24. Fluvial Geomorphology
 The study of how landforms change with time under
the influence of rivers and streams
 Frequently takes a “watershed scale approach”
 Attempts to work with a river’s natural processes
vs. Conventional Channelization
 Tends to make the river conform to a preconceived
regular shape
 Often used in short reaches, to meet very specific
criteria (e.g. 100-year flood)
24

25. Conventional Channelization
 Wide, trapezoidal
channel
 Often straight
25
• Contain Floods

26. Conventional Channelization
 Wide, trapezoidal
channel
 Often straight
26
• Contain Floods
• Levees sometimes
used

27. Conventional Channelization
 Wide, trapezoidal
channel
 Often straight
27
• Contain Floods
• Levees sometimes
used
• Low flows wide &
shallow

28. Natural Channel Design
28
• Irregular shape w/
low-flow channel
• Meandering
• Channel contains
~ 1.5 year flood
(Bankfull Flow)

29. Natural Channel Design
29
• Irregular shape w/
low-flow channel
• Meandering
• Channel contains
~ 1.5 year flood
(Bankfull Flow)
• Higher flows use
floodplain

30. Natural Channel Design
30
• Irregular shape w/
low-flow channel
• Meandering
• Channel contains
~ 1.5 year flood
(Bankfull Flow)
• Higher flows use
floodplain
• Low flows confined

31. Side-by-side Comparison
31
• Natural Channel Design •Conventional Channelization
Low Flows
Low Flows

32. Side-by-side Comparison
32
• Natural Channel Design •Conventional Channelization
Bankfull
(~ 1.5 yr Flood)
Design Flood
(>>1.5 yr flood)

33. Side-by-side Comparison
33
• Natural Channel Design •Conventional Channelization
Large Floods
Large Floods
(if berms are used)

34. Energy Balance of Streams (Lane, 1955)
34

35. Regional Curves – Flow
35

36. Energy Dissipation in Stable Streams
 Bed Roughness
 Form Resistance
- Step Pools (steeper streams)
- Riffle/Pool sequences (moderate slope streams)
- Meander Pattern (flatter streams)
 Floodplain acts like an “Energy Relief Valve”
36

37.  Rock cross-vanes for
energy redirection,
grade control &
sediment transport
37
Man-made
approaches

38. Bed Material is Important!
38

39. Summary – Natural Channel Design
 puts the ~ 1.5 year flood in the channel and larger floods
out onto a floodplain
 Low-Flow conditions, Water Quality, Habitat, Ecosystem
Function, and Resilience are all important
 In areas w/out an adequate floodplain, other methods (or
a combination of methods) may be necessary
 Requires extensive data collection & analysis
 should provide Schoharie County with many stream
corridor benefits
39

40. Slide 40
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