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Frequently used road treatments used by BAER specialists by region (Foltz and others 2008)
| Region |
|||||||
| Treatment |
Overall |
1 |
2 |
3 |
4 |
5 |
6 |
| |
|||||||
| Percent |
|||||||
| |
|||||||
| Rolling dip/water bar | 29 |
29 |
-- |
27 |
30 |
19 |
42 |
| Culvert upgrading | 20 |
33 |
-- |
-- |
48 |
-- |
17 |
| Ditch cleaning/armoring | 16 |
25 |
-- |
14 |
13 |
17 |
-- |
| Culvert removal | 10 |
6 |
-- |
36 |
-- |
-- |
25 |
| Debris/trash rack | 6 |
-- |
-- |
9 |
-- |
19 |
-- |
| Armored ford crossing | 5 |
-- |
33 |
5 |
4 |
6 |
8 |
| Culvert risers | 5 |
-- |
-- |
-- |
-- |
19 |
-- |
| Storm patrol | 3 |
-- |
50 |
9 |
-- |
-- |
-- |
| Culvert overflow bypass | 2 |
-- |
-- |
-- |
4 |
6 |
-- |
| Hazard/warning sign | 1 |
2 |
17 |
-- |
-- |
-- |
-- |
| Flared inlet | 1 |
-- |
-- |
-- |
-- |
6 |
-- |
| Channel debris cleaning | 1 |
-- |
-- |
-- |
-- |
6 |
-- |
| Culvert inlet/outlet armoring | 1 |
2 |
-- |
-- |
-- |
-- |
-- |
| Additional relief culvert | 1 |
2 |
-- |
-- |
3 |
-- |
-- |
| Outsloping road | 1 |
-- |
-- |
-- |
-- |
3 |
-- |
| Fillslope armoring | 1 |
-- |
-- |
-- |
-- |
-- |
8 |
| No. of BAER interviewee responses | 30 |
8 |
1 |
6 |
5 |
8 |
2 |
Flow capacity for circular and pipe-arch culverts (Robison and others 1999)
| circular culverts |
pipe-arch culverts |
||||
| Diameter |
Cross-section area culvert |
Maximum flow in culvert |
Span × Rise |
Cross-section area culvert |
Maximum flow in culvert |
| (inches) |
(ft2) |
(cfs) |
(ft or inches) |
(ft2) |
(cfs) |
| |
|||||
| 15 |
1.2 |
3.5 |
22" × 13" |
1.6 |
4.5 |
| 18 |
1.8 |
5 |
25" × 16" |
2.2 |
7 |
| 21 |
2.4 |
8 |
29" × 18" |
2.9 |
10 |
| 24 |
3.1 |
11 |
36" × 22" |
4.3 |
16 |
| 27 |
4.0 |
15 |
43" × 27" |
6.4 |
26 |
| 30 |
4.9 |
20 |
50" × 31" |
8.5 |
37 |
| 33 |
5.9 |
25 |
58" × 36" |
11.4 |
55 |
| 36 |
7.1 |
31 |
65" × 40" |
14.2 |
70 |
| 42 |
9.6 |
46 |
72" × 44" |
17.3 |
90 |
| 48 |
12.6 |
64 |
6'-1" × 4'-7" |
22.0 |
130 |
| 54 |
15.9 |
87 |
7'-0" × 5'-1" |
28.0 |
170 |
| 60 |
19.6 |
113 |
8'-2" × 5'-9" |
38.0 |
240 |
| 66 |
23.8 |
145 |
9'-6" × 6'-5" |
48.0 |
340 |
| 72 |
28.3 |
178 |
11'-5" × 7'-3" |
63.0 |
470 |
| 78 |
33.2 |
219 |
12'-10" × 8'-4" |
85.0 |
650 |
| 84 |
38.5 |
262 |
15'-4" × 9'-3" |
107.0 |
930 |
| 90 |
44.2 |
313 |
|||
| 96 |
50.3 |
367 |
|||
| 102 |
56.7 |
427 |
|||
| 108 |
63.6 |
491 |
|||
| 114 |
70.9 |
556 |
|||
| 120 |
78.5 |
645 |
|||
| 132 |
95.0 |
840 |
|||
| 144 |
113.1 |
1,000 |
|||
A typical case of ditch relief culverts on forestlands was assumed, which is that the culvert is inlet-controlled, and projecting inlet and headwater depth is equal to diameter or height of culvert.
Permissible velocities to withstand erosion (Watkins and Fiddes 1984; Novak and others 2001)
| Surface type | D50 |
Permissible velocity |
| (mm) |
(ft/s) |
|
| |
||
| Asphalt |
-- |
23.0 |
| Bitumen-bound macadam1 | -- |
19.7 |
| Cobbles | 100 |
11.8 |
| Cobbles | 40 |
7.9 |
| Coarse gravel and cobbles | 25 |
6.2 |
| Gravel (coarse to medium) | 10 |
4.6 |
| Gravel (medium to fine) | 5.0 |
3.6 |
| Graded silt to cobbles (colloidal) | -- |
5.2 |
| Alluvial silt (colloidal) | -- |
4.9 |
| Graded loam to cobbles | -- |
4.9 |
| Stiff clay | -- |
4.9 |
| Coarse sand | 2.5 |
3.3 |
| Volcanic ash | -- |
3.3 |
| Dense clay | -- |
3.3 |
| Medium sand | 1.0 |
2.6 |
| Silt loam | -- |
2.6 |
| Sandy clay of medium density | -- |
2.6 |
| Sandy loam (non-colloidal) | -- |
2.3 |
| Fine sand (non-colloidal) | 0.25 |
2.0 |
| Coarse silt, fine sand | 0.05 |
1.3 |
| Sandy clay of low density | -- |
1.3 |
| Fine silt | -- |
0.8--2.6 |
| 1 | Type of road construction. It consists of three layers of stones that interlock each other. |
Permissible velocities in vegetated channels (Watkins and Fiddes 1984)
| Vegetation | % slope of drain |
Permissible velocities (ft/s) |
|
| In stable soils |
In erodible soils |
||
| |
|||
| Bermuda grass | 0--5 |
7.9 |
5.9 |
| (Cynodon dactylon) | 5--10 |
6.9 |
4.9 |
| Buffalo grass | 0--5 |
6.9 |
4.9 |
| (Buchloe dactyloides) | 5--10 |
5.9 |
3.9 |
Overflow Discharge for Rolling Dips/Water Bars (Novak and others 2001)
The overflow discharge over an embankment can be estimated using the following weir formula.
| Q = C b H 3/2 | ||||
| where | ||||
| Q | = | overflow discharge (cfs); | ||
| C | = | sill coefficient (ft1/2 s-1); | ||
| b | = | length of the flow section (ft); and, | ||
| H | = | total head upstream of the sill (ft). | ||
The coefficient of C is a function of h/L (h is the head over a sill of width L) for free flow or modular flow conditions. Free flow occurs where a man-made structure creates a drop in water level over the structure resulting in the major part of the total upstream energy head being converted into kinetic energy to obtain critical flow at the control section. Under this condition, the upstream head is independent of downstream conditions (Boiten 2002). The range of values of C for free flow over the embankment is presented below.
| Type of surface |
Range of h/L |
C value |
| (ft1/2/s) |
||
| |
||
| Paved surface |
0.15 |
3.04 |
| 0.20 |
3.06 |
|
| >0.25 |
3.08 |
|
| Gravel surface |
0.15 |
2.95 |
| 0.20 |
3.01 |
|
| 0.25 |
3.06 |
|
| 0.30 |
3.08 |
|
If the drop in water level over the structure becomes rather small, the flow above it remains sub-critical; therefore, the upstream head is affected by downstream conditions. This flow type is referred to as submerged flow, non-modular flow, or drowned flow (Boiten 2002). In such a case, a correction factor, f, as a function of hd/s/H (hd/sis the head drop of a sill to downstream), may be incorporated for submerged flow or non-modular flow conditions. The range of values of f for submerged flow over the embankment is presented below.
| Type of surface |
Range of hd/s/H
|
f value |
| |
||
| Paved surface |
<0.8 |
1.00 |
| 0.9 |
0.93 |
|
| 0.95 |
0.80 |
|
| 0.99 |
0.50 |
|
| Gravel surface |
<0.75 |
1.00 |
| 0.80 |
0.98 |
|
| 0.90 |
0.88 |
|
| 0.95 |
0.68 |
|
| 0.98 |
0.50 |
|
REFERENCES
Boiten, Wubbo. 2002. Flow measurement structures. Flow Measurement and Instrumentation. 13(5-6): 203-207.
Foltz, Randy B.; Robichaud, Peter R.; Rhee, Hakjun. 2008. A synthesis of post-fire road treatments for BAER teams: methods, treatment effectiveness, and decision-making tools for rehabilitation. Gen. Tech. Rep. RMRS-GTR. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station (in preparation).
Novak, P.; Moffat, A. I. B.; Nalluri, C.; Narayanan, R. 2001. Hydraulic structures (3rd ed.). London, UK: Taylor & Francis Group. 666 p.
Robison, E. George; Mirati, Albert; Allen, Marganne. 1999. Oregon road/stream crossing restoration guide: spring 1999. Salem, OR: Oregon Department of Forestry. 79 p.
Watkins, L. H.; Fiddes, D. 1984. Highway and urban hydrology in the tropics. London, UK: Pentech Press Limited. 206 p.
USDA Forest Service - RMRS - Moscow Forestry Sciences
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