Little_Sheep_Creek_Bridge_Hydraulics_TSL_Report.pdf

Memorandum

Western Federal Lands Highway Division 610 E. Fifth Street

Vancouver, WA 98661-3801

LITTLE SHEEP CREEK BRIDGE

TSL BRIDGE HYDRAULICS MEMO

To: Susan Ellis, WFLHD Project Manager From: Sven Leon, P.E., WFLHD Hydraulics Engineer Date: June 15, 2017 Project: OR WALLOWA 4602(1) – Wallowa Mountain Loop Road

Background

Wallowa County (County), Oregon, is reconstructing five miles of the Wallowa Mountain Loop Road (NSFR 39) between State Highway 350 and the Wallowa National Forest Boundary. The proposed work will widen the roadway, add ditch relief culverts, and repair localized subgrade areas. Culverts in Little Sheep Creek will be replaced with a bridge (Fig. 1). The County will maintain the road and bridge structure. Western Federal Lands Highway Division (WFLHD) is designing the road improvements and new bridge. WFLHD completed a morphologic, hydrologic, and hydraulic analysis for supporting the TS&L development. Results and recommendations are presented.

Recommendations

Bridge waterway and riprap plan and details are attached (Sheets H.3 and H.4).

Bridge Low Chord, Length, and Alignment

Minimum low chord elevation 4193.5 feet (project datum) (50-year waster surface elevation plus 3 feet for woody debris passage.

Minimum 50 feet distance between vertical abutment faces.

Construct new channel with 2(h):1(v) side-slopes and minimum 25 feet waterway bottom width.

Slope new channel to match upstream and downstream channel gradients.

Angle between bridge centerline and channel centerline 10 degrees.

Set new channel elevation at channel centerline and bridge centerline crossing to 4185 feet.

Ensure the new channel has a streambed material gradation consistent with what is in the natural channel immediately upstream of the bridge.

Scour

Based on the hydraulic analysis and geotechnical borings, use;

100-year abutment scour elevation – 4180.8 feet.

500-year abutment scour elevation – 4179.7 feet.

Set the bottom of the GRS wall to elevation 4180.0 feet.

Memo to: Susan Ellis, WFLHD Project Manager June 15, 2017

Abutment Erosion Protection

Install riprap Class 5 (FHWA FP-14), 4 feet thick, and sloped 2(h):1(v).

Set riprap crest elevation to 4192.5 feet (project datum) (50-year waster surface elevation plus 2 feet).

Install riprap toe along abutment wall front face, 10 feet wide and 4 feet thick.

Set riprap toe bottom elevation equal to GRS wall bottom.

Install separation geotextile, class 1-C under all the placed riprap.

Place conserved gravel-cobble streambed material over the placed riprap for creating a smooth, natural appearing bank line transition.

Abutment Type

Based on the hydraulic, scour, and geomorphic analysis, a Geosynthetic Reinforced Soil Integrated (GRS) abutment system appears appropriate for the site.

Stream Impacts

Flow conveyance, sediment transport, sediment deposition, and woody debris conveyance through the bridge waterway will be dramatically improved over existing conditions. It is expected to be equal to what is occurring in the upstream and downstream natural channels. Increased woody debris passage will allow more wood to be embedded in the downstream channel, increasing habitat complexity. Aquatic organism passage through the new bridge waterway is expected to be equivalent to the upstream and downstream natural channels for all range of flow conditions.

Floodplain and Flood-rise Impacts

Based on the hydraulic modeling, the proposed bridge is not expected to increase flooding of adjacent property and insurable structures.

Construction

Constructing the new bridge requires access on the channel bottom with heavy, track-mounted equipment.

Flow diversion is necessary. Flow diversion used from late April through early July should have a minimum capacity of 452 cfs (2-year flood). Flow diversion used from middle July through middle April should have a minimum capacity of 100 cfs. Work areas for placing bridge foundation elements and riprap may be isolated with conserved streambed material berms. GRS abutment foundation elements must not be placed in ponded water. Dewatering is required for GRS installation. Geotextile and riprap may be placed in ponded water. Dewatering is not required for riprap placement. Pull the conserved streambed material berm back over the placed riprap.

Operation and Maintenance

Riprap placed for controlling bank erosion should be inspected annually and after each extreme flood event. Replace or reposition dislodged stone. The presence of woody debris trapped upstream, beneath, and downstream of the bridge should be inspected annually and after each extreme flood event. Remove woody debris as needed for maintaining flow conveyance capacity and preventing logs deflecting flow towards riprap or the GRS abutments.

Site Conditions

Two 6-foot diameter CMP culverts convey the stream flow. The twin 6-foot diameter culverts are half filled with sediment and are in poor condition (Photos 1 and 2). Backwater caused by the twin culverts has induced sediment deposition immediately upstream of the culverts (Photo 1). The twin culverts also reduce large woody debris conveyance. Another 6-foot diameter CMP culvert on the left floodplain conveys overbank flow (Photo 3). It is in good condition.

The channel generally has low sinuosity, but is relative straight immediately upstream and downstream of the proposed bridge (Photos 4 and 5). Active channel width (ordinary-high-water) is approximately 20 to 25 feet. Active channel depth (ordinary-high-water) is approximately 2 to 3 feet. Flood-prone (50-year flood event) depth is approximately 5 feet. Flood-prone width is estimated to be 120 to 180 feet. The floodplain is moderately vegetated with grasses, shrubs, willows, and cottonwoods. Channel slope is to 1 to 2 percent. Pool-riffle is the dominant bed form. Based on visual observation, sand, gravel, cobble, and small boulders comprise the streambed material.

The stream banks appear moderately stable where vegetated. Based on Goggle Earth imagery, the channel has not migrated since 1994. It appears to be confined to the south valley wall, an erosion resistant colluvium (Fig. 1, Photo 6). The potential for catastrophic lateral bank migration or channel avulsion is low. Based on observed woody debris, available bank-side vegetation, and expected flood flow depths, the stream can carry a large amount of large woody debris. Height of debris entangled on boulders, bank vegetation, and gravel-bars indicate the site has experienced floodwater depths of 3 to 4 feet (Photo 7).

Hydrology

The Little Sheep Creek originates near Wing Ridge and Ferguson Ridge in the Wallowa Mountains and flows north to merge with Big Sheep Creek and the Imnaha River, approximately 20 miles from the bridge site. Elevations range from 4200 feet at the bridge site to 9650 feet in the mountains. The drainage area is steeply mountainous with moderately incised drainages. Approximately one-half of the watershed is in the Wallowa-Whitman National Forest and approximately one-fourth is in the Eagle Cap Wilderness. Clear-cut logging has occurred and can occur in the future. Development is sparse, primarily rural residences and ranching. No significant flow diversions or lake areas occur. Extreme flooding typically occurs with heavy snow-melt late April, May, June, and early July.

No stream gage station data is available for Little Sheep Creek near the bridge site. USGS StreamStats (version 3) web-based application was used for delineating the watershed and calculating drainage area (39.1 sq. miles), mean annual precipitations (33.1 inches), forest cover (36.1 percent), and maximum elevation (9650 feet, NAD83). Peak discharges were estimated using USGS regression equations from “Estimating Flow-Duration and Low-Flow Frequency Statistics for Unregulated Streams in Oregon" (USGS SIR 2008-5126, 2008). Watersheds are within northeast regression equation area. Peak discharges estimates are presented in Table 1.

Water Surface Elevations and Flow Velocities

Hydrologic Engineering Center River Analysis System (HEC-RAS 5.0) two-dimensional, unsteady flow model was used for estimating the proposed bridge water surface elevations, flow depths, and flow velocities. Terrain for the proposed bridge model was created by modifying existing ground topography obtained from project mapping to reflect the proposed bridge and road embankment. The model uses a mesh with 4 feet by 4 feet grid spacing extending 140 feet upstream and downstream (Fig. 3). Normal flow depth with 0.01 feet/feet friction slope was set for the downstream boundary condition. Twelve-hour duration, 1-minute interval hydrograph was used for the upstream boundary condition. The hydrograph includes the 2, 10, 25, 50, 100, and 500-year flood flows. A Manning’s Roughness Coefficient of 0.06 was selected for the main channel areas and overbank areas. The model was calibrated with apparent bankfull and high water levels determined in the field. The model uses a 4 second computation interval, full momentum equation set, and 2-hour warmup time. Flow depths, water surface elevations, and design flow velocities are summarized in Table 2 and Figures 4, 5, and 6.

Scour

A HEC-18 (5th ED., April 2012) scour analysis was completed using the HECRAS two-dimensional hydraulic model results (attached). The analysis includes abutment scour for the 100-year and 500-year flood events. Abutment scour was estimated using the NCHRP 24-20 approach. Abutment scour computed from the NCHRP approach is total scour at the abutment. It includes contraction scour. Based on review of site conditions, the channel profile appears stable. Long-term channel degradation was assumed zero. Streambed material gradations were developed with two digital photographs of gravel bar surfaces taken immediately upstream of the bridge. The photographs were processed using the FHWA Hydraulic Toolbox, version 4.2, gradation analysis tool (Photos 8 and 9). The distance between the yellow circles is 3 feet. D50 is approximately 2.5 inches. D100 is approximately 8 to 10 inches. D15 is approximately 1.5 inches. A D50 of 2.5 inches was used for the scour analysis. Two geotechnical borings indicate the abutments will be founded on approximately 20 feet of poorly graded gravel with sand, cobbles, and boulders. A summary of predicted scour is included in Table 2.

Riprap Sizing

The riprap was sized using the approach from USACE EM 1110-2-1601, June, 1994. Based on the two-dimensional HECRAS modeling, maximum expected flow velocity along the downstream right and left bank revetment is approximately 12 feet/sec for the 50-year flood event (Fig. 6). A stability factor of 0.3 was used for angular rock. Specific gravity of the stone was assumed to be 2.65. Slope of finished riprap surface is 2(h):1(v). To account for unknown flow impingement angles caused by shifting debris and mid-channel sediment deposits, a design factor-of-safety of 1.5 was selected. Riprap sizing analysis is attached.

Floodplain and Flood-rise Limitations

The site is not mapped by Federal Emergency Management Agency (FEMA) as being in a special flood hazard area. A detailed FEMA mapping study has not been completed for the site. No base flood elevations have been determined. There are no insurable structures near the bridge. A house and barn structure is located approximately 2,200 feet upstream along the left bank.

attachments: Tables 1 and 2 Figures 1, 2, 3, 4, 5, and 6 Photographs 1 to 9 Bridge/Riprap Plan Sheet Bridge/Riprap Section Sheet Peak Discharge Estimates Scour Analysis Riprap Design

Estimate Drainage

Method Area (mi2) 2 5 10 25 50 100 500

Little Sheep Creek 39.1 452 678 834 1023 1207 1362 2180

Bridge

Notes:

1. USGS Regression Equations, “Estimating Flow-Duration and Low-Flow Frequency Statistics for

Unregulated Streams in Oregon", USGS SIR 2008-5126, 2008.

2 5 10 25 50 100 500

Abut Low Chord Elev (Feet) 4193.8 4193.8 4193.8 4193.8 4193.8 4193.8 4193.8

WS Elevation (Feet) 4188.7 NA 4189.4 4189.9 4190.5 4191.0 4191.4

Clearance LC to WS (Feet) 5.1 NA 4.4 3.9 3.3 2.8 2.4

Long-term Degradation (Feet) NA NA NA NA NA 0.0 0.0

Contraction Scour (Feet) NA NA NA NA NA 0.0 0.0

Abutment Scour (Feet) NA NA NA NA NA 4.2 5.3

Total Scour Elevation (Feet) NA NA NA NA NA 4180.8 4179.7

Design Flow Velocity (Feet/sec) 7.8 NA 9.2 9.9 10.7 11.4 11.8

Notes:

1. Elevations in local project datum.

NA - Not analyzed.

Table 1. Peak Discharges (ft3/sec)

Location

Recurrence Intervals (years)

Recurrence Intervals (years)

Table 2. Water Surface Elevations, Scour, and Flow Velocities

Image date: 7/29/2016

Project Site Location

Map printed from National Geographic TOPO

FIGURE 1

LOCATION MAP

Wallowa Mountain Loop Road

200 feet

N

Little Sheep Creek Bridge

45.340/-117.074 NAD83

Bridge Site

Map printed from Google Earth Pro, image date 7/29/2016

2 miles

N

0 100 feet

FIGURE 2

LITTLE SHEEP CREEK BRIDGE

DRAINAGE AREA MAP

DA = 39.1 sq. mi.

Project Road

Little Sheep Creek Bridge

Bridge Site

HECRAS 5.0 - Two-Dimensional hydraulic model.

N

0 100 feet

Model Mesh

FIGURE 3

LITTLE SHEEP CREEK BRIDGE

HECRAS 2-D MODEL TERRAIN

N

Flow Depth Plot Location

Flow Depth (Feet)

FIGURE 4

LITTLE SHEEP CREEK BRIDGE

50-YEAR FLOW DEPTH

2-yr

500-yr

100-yr

50-yr

25-yr

10-yr

Water Surface Elevation Plot Location

4186.5

4187.5

4188.5

4189.5

4190.5

4191.5

Water Surface Elevation (Feet‐project datum)

FIGURE 5

LITTLE SHEEP CREEK BRIDGE

50-YEAR WS ELEVATION

2-yr

500-yr

100-yr

50-yr

Velocity Plot Location

Flow Velocity (Feet/sec)

FIGURE 6

LITTLE SHEEP CREEK BRIDGE

50-YEAR FLOW VELOCITY

2-yr

500-yr100-yr 50-yr

Photos Wallowa Mountain Loop Road

PHOTO 1

PHOTO 2

PHOTO 3

10/6/2016

Culvert in good condition.

Culverts filled one-half with sediment and in poor condition.

Little Sheep Creek Overflow Culvert inlet.

Little Sheep Creek Culverts inlets.

Culverts filled one-half with sediment and in poor condition.

Little Sheep Creek Culverts outlets.

PHOTO 4

PHOTO 5

PHOTO 6

10/6/2016

Stream adjacent to road embankment.

Flood-prone depth 3 to 4 feet. Active channel width 20 feet. Banks stable.

Pool-riffle dominant bed form. Cobble-gravel streambed material.

Little Sheep Creek - Channel upstream of culverts.

Active channel width 20 feet. Banks stable. Pool-riffle dominant bed form.

Cobble-gravel streambed material.

Little Sheep Creek - Channel downstream of culverts.

Active channel width 20 feet. Banks stable. Pool-riffle dominant bed form.

Cobble-gravel streambed material.

Little Sheep Creek - Channel upstream of culverts.

PHOTO 7

PHOTO 8

PHOTO 9

10/6/2016

Gradation photo, yellow dots 3 feet apart.

Little Sheep Creek - Channel upstream of culverts.

Gradation photo, yellow dots 3 feet apart.

Little Sheep Creek - Channel upstream of culverts.

Little Sheep Creek - Channel upstream of culverts.

Woody debris indicates maximum flooding depth.

10 200510

SCALE IN FEET

PLAN

SCOUR MITIGATION

LITTLE SHEEP CREEK BRIDGE

N Temporary flow barrier

Temporary flow barrier

F lo w Existing grade contour

Stream edge

H.3

STATE PROJECT

NUMBER

SHEET

I n t_ ft

D c m y fi le s p w p r o d u c ti o n d v S h e e p C r e e k R ip r a p S e c ti o n .d g n

OR WALLOWA 4602(1)

A

M

J u n e

C h e c k e d b y

D e s ig n e d b y

11+00 12+00

Elev. 4196.59

11+12.03

Begin bridge

Placed riprap, class 5 16'-0"10'-0" 9'-0"

15'-0"

Remove existing culverts erosion control, class 1

Placed riprap

Proposed channel CL

Elev. 4199.13

11+75.14

End bridge shape to finished road embankment

Placed riprap erosion control, class 1, GRS Abutment

Placed riprap, class 5

GRS Abutment

Proposed road CL

Existing road CL

Remove existing culvert

Elev 4185.0

11 + 43.1

Proposed channel CL, ° AA

B

B

C

C

OR WALLOWA 4602(1)

Varies

SECTIONS

SCOUR MITIGATION

LITTLE SHEEP CREEK BRIDGE

erosion control, class 1

Placed riprap cobbles

Conserved class 5 riprap, Placed

Conserved cobbles

Placed riprap

Select fill

8'-0"12'-0"

SECTION B

SECTION C

NO SCALE

HYDRAULIC & HYDROLOGIC SUMMARY

50 100 500

2 0.2

4190.5 4191.0 4191.4

0 0

Total Scour (Ft)

Pier Scour (Ft)

Abutment Scour (Ft)

Contraction Scour (Ft)

Flow Velocity (Ft/s)

Predicted Flood Rise (Ft)

Clearance above WS (Ft)

Design High Water (Ft)

Design Discharge (cfs)

Exceedance Probability (%)

Flood Frequency (Yr)

3.2 2.7 2.3

4.2 5.3

0 00

4180.8

4179.7

DESCRIPTIONITEM NO. UNIT QUANTITY

RIPRAP QUANTITIES

25101-0400

25101-0400

20701-0200

Placed riprap, method A, class 1

Placed riprap, method A, class 5

Separation- stabilization geotextile, class 1, type C

CY

CY

SQYD

20'-0"

16'-0" elev 4192.0

Riprap crest, class 1-C

Geotextile, footing bottom

GRS abutment footing bottom

GRS abutment elev 4180

GRS wall bottom, elev 4180

GRS wall bottom, class 1-C

Geotextile, Excavation limit

Existing grade

GRS abutmment bearing seat

GRS abutment wall top

GRS abutment wall

Existing grade

H.4

STATE PROJECT

NUMBER

SHEET

I n t_ ft

D c m y fi le s p w p r o d u c ti o n d v S h e e p C r e e k R ip r a p S e c ti o n .d g n

A

M

J u n e

C h e c k e d b y

D e s ig n e d b y

OHW Elev 4188.7

50-year W.S. Elev 4190.5

25' min.

Placed riprap, class 5 erosion control, class 1

Placed riprap

Placed riprap, class 5

SECTION A

elev 4185 channel bottom, Proposed stream

Elev. 4196.59

11+12.03

Begin bridge elev 4192.5

Riprap crest, Existing Ground at CL

Elev. 4199.13

11+75.14

End bridge elev 4184

Riprap toe, elev 4184

Riprap toe, Geotextile, class 1-C

Geotextile, class 1-C

GRS abutment wall

GRS wall bottom, elev 4180

GRS abutment footing bottom GRS abutment footing bottom

GRS abutment wall

GRS wall bottom, elev 4180

Riprap crest, elev 4192.5 Low chord, elev 4193.75

Select fill 10'-0" shape to finished road embankment

Placed riprap erosion control, class 1, 10'-0"

Proposed road profile9'-0"

11.811.410.7

CALCULATIONS

Peak Discharge Estimates

Scour Analysis

Riprap Sizing

Project: File:

Desc: By:

Region: Date:

Exceed Coefficients Error Equation: Q = K(A^a)*(p^b)*((1+F)^c)

Prob. K a b c +%/-% Source: Magnitude and Freq. Floods in Eastern Oregon

0.50 0.508 0.820 1.360 -0.270 82/45 (USGS WRIR 82-4078, 1983)

0.20 2.440 0.790 1.090 -0.300 79/44 A = Drainage area

0.10 5.280 0.780 0.960 -0.320 83/45 p = mean annual precipitation

0.04 11.800 0.770 0.830 -0.350 89/47 F = Percent DA covered by forest

0.02 19.800 0.760 0.750 -0.360 90/48

0.01 30.700 0.760 0.680 -0.380 101/50 Culvert Type HW/D K M a

CMP Projecting 1.0 0.5 0.667 2.827

Estimated Discharge (Q) Min.

Drain. p F Exceedance Probability 0.02 Culvert

Station Area 0.50 0.20 0.10 0.04 0.02 0.01 0.002 Design Dia

(sq mi) (in) (%) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (ft)

Minimum

39.1 33.1 36.1 452 678 834 1,023 1,207 1,362 2,180 1,207 12.4

0.56 20.4 25.5 8 15 21 29 38 44 71 38 3.1

Target Divide Rd 1.97 24.5 63.0 22 39 51 66 82 93 149 82 4.2

DA 3 0.69 26.2 80.8 10 17 22 29 35 40 64 35 3.0

0.1 25.0 40.0 2 4 6 8 10 12 10 1.8

0.3 25.0 40.0 6 10 14 18 23 27 23 2.6

0.5 25.0 40.0 8 15 21 27 34 39 34 3.0

0.7 25.0 40.0 11 20 27 35 44 51 44 3.3

0.9 25.0 40.0 14 25 33 43 54 62 54 3.6

1.1 25.0 40.0 16 29 38 50 63 72 63 3.8

1.5 25.0 40.0 21 37 49 64 79 91 79 4.2

Notes:

K = Constant from Table 9, HDS-5

M = Constant from Table 9, HDS-5

D = [Q/(0.7844x(1/K^1/M))]^.4 from HDS-5, equation 27. Assumes HW/D < 1.2 ,unsubmerged.

Maximum

Little Sheep Ck

DA 1

General Minor

Major Drainage Peak Flow S. Leon

Northeast 7/1/2016

FLOOD DISCHARGE ESTIMATES

UNGAGED OREGON SITES

OR WALLOWA 4602(1) - Wallowa Mountain Loop Road reg-spec2014

SCOUR ESTIMATE

Project: OR WALLOWA 4602(1) – Wallowa Mountain Loop Road File:

Desc: Little Sheep Creek Bridge Date:

Units: ENG By:

Location Description

0-ye ar

0-ye ar

0-ye ar

0-ye ar

CONSTANTS

UNITS SI or ENG ENG ENG ENG ENG g ACCELERATION OF GRAVITY, 9.81 m/s2, 32.2 ft/s2 32.20 32.20 32.20 32.20

Du D UNIT CONVERSION, 0.001 SI, 0.00328 English 0.00328 0.00328 0.00328 0.00328

LIVE-BED OR CLEAR-WATER DETERMINATION

y AVERAGE FLOW DEPTH, m, ft 4.9 5.1

D50 DIAMETER 50% FINER BED PARTICLES, mm 60 60

V AVERAGE VELOCITY, m/s, ft/s 8.2 8.0

Ku UNIT COEFFICIENT, 6.19 SI, 11.17 English 11.170 11.170 11.170 11.170

Vc (6.1) CRITICAL VELOCITY, m/s, ft/s 0.00 0.00 8.47 8.53

LB / CW LIVE BED or CLEAR WATER CW CW

LIVE-BED CONTRACTION SCOUR

y1 AVERAGE U/S DEPTH, MAIN CHANNEL, m, ft 4.9 5.1 y0 AVERAGE CONTRACTED DEPTH BEFORE SCOUR, m, ft 5.0 5.4

Q1 FLOW IN UPSTREAM CHANNEL, m3/s, ft3/S 1362.0 2180.0

Q2 FLOW IN CONTRACTED CHANNEL, m3/s, ft3/S 1362.0 2180.0

W1 WIDTH OF THE UPSTREAM CHANNEL, m, ft 25.0 25.0

W2 WIDTH OF THE CONTRACTED SECTION, m, ft 25.0 25.0

S1 ENERGY SLOPE OF MAIN CHANNEL, m/m, ft/ft 0.0100 0.0100 w (Fig 6.8) D50 FALL VELOCITY, m/s 0.500 0.500

UNIT COEFFICIENT, 1.0 SI, 3.28 English 3.28 3.28 3.28 3.28

D50 FALL VELOCITY, m/s, ft/s 0.000 0.000 1.640 1.640 k1 (p6.10) TRANSPORT COEFFICIENT 0.00 0.00 0.64 0.64

BED MATERIAL TRANSPORT MODE BL/SL BL/SL

V* SHEAR VELOCITY, m/s, ft/s 0.00 0.00 1.26 1.28 y2 (6.2) AVERAGE DEPTH, CONTRACTED SECTION, m, ft 0.00 0.00 4.90 5.10 yS (6.3) AVERAGE SCOUR DEPTH, m, ft 0.00 0.00 0.00 0.00

As AVERAGE SCOUR AREA, m2, ft2 0.00 0.00 0.00 0.00 scour18-5.xls

6/10/2017

S. Leon

CLEAR-WATER CONTRACTION SCOUR

y0 AVERAGE CONTRACTED DEPTH BEFORE SCOUR, m, ft 0.0 0.0 5.0 5.4

D50 MEDIAN DIAMETER BED MATERIAL, mm 0.0 0.0 60.0 60.0

Q DISCHARGE THROUGH THE BRIDGE, m3/s, ft3/s 0.0 0.0 1362.0 2180.0

W BOTTOM WIDTH OF THE CONTRACTED SECTION, m, ft 0.0 0.0 25.0 25.0

Ku UNIT COEFFICIENT, 0.025 SI, 0.0077 English 0.0077 0.0077 0.0077 0.0077

Dm DIA. SMALLEST NONTRANSPORT PARTICLE, m, ft 0.0000 0.0000 0.2460 0.2460 y2 (6.4) AVERAGE DEPTH, CONTRACTED SECTION, m, ft 0.00 0.00 5.71 8.54 yS (6.5) AVERAGE SCOUR DEPTH, m, ft 0.00 0.00 0.71 3.14

As AVERAGE SCOUR AREA, m2, ft2 0.00 0.00 17.73 78.61

PRESSURE FLOW CONTRACTION SCOUR

Hb DISTANCE LOW CHORD TO STREAM BED, m, ft y1 FLOW DEPTH UPSTREAM FACE OF BRIDGE, m, ft

D50 D50 OF BED MATERIAL IN OPENING, mm

Va AVERAGE VELOCITY THROUGH OPENING, m/s, ft/s

Ku UNIT COEFFICIENT, 6.19 SI, 11.17 English 11.170 11.170 11.170 11.170

Vc (5.1) CRITICAL VELOCITY, m/s, ft/s 0.00 0.00 0.00 0.00 ys VERTICAL SCOUR DEPTH, m, ft #DIV/0! #DIV/0! #DIV/0! #DIV/0!

PIER SCOUR

y1 FLOW DEPTH U/S OF THE PIER, m, ft

V1 APPROACH VELOCITY, m/s, ft/s a PIER WIDTH, m, ft

L PIER LENGTH, m, ft

FA FLOW ANGLE, degrees

K1 (Tbl 7.1) CORRECTION FOR PIER SHAPE (0.9 to 1.1, >5deg, 1)

K3 (Tbl 7.3) CORRECTION FOR BED FORM (1.1 to 1.3)

Sg SEDIMENT SPECIFIC GRAVITY 2.65 2.65 2.65 2.65

D50 DIAMETER 50% FINER BED PARTICLES, mm

D84 DIAMETER 95% FINER BED PARTICLES, mm

Ku UNIT COEFFICIENT, 6.19 SI, 11.17 English 11.17 11.17 11.17 11.17

Vc50 (6.1) CRITICAL VELOCITY D50, m/s, ft/s 0.00 0.00 0.00 0.00

L/a PIER LENGTH/WIDTH RATIO (MAX. L/a = 12)) 0.00 0.00 0.00 0.00

Fr FROUDE RATIO 0.00 0.00 0.00 0.00

GC SEDIMENT GRADATION COEFFICIENT, D84/D50 #DIV/0! #DIV/0! #DIV/0! #DIV/0!

H DENSIMETRIC PARTICLE FROUDE NUIMBER #DIV/0! #DIV/0! #DIV/0! #DIV/0!

K2 (7.4) CORRECTION FOR FLOW ANGLE (1 to 5) 0.00 0.00 0.00 0.00 y1/a #DIV/0! #DIV/0! #DIV/0! #DIV/0!

a/D50 #DIV/0! #DIV/0! #DIV/0! #DIV/0!

V1/Vc #DIV/0! #DIV/0! #DIV/0! #DIV/0!

Kw (7.20-21) WIDE PIER CORRECTION FAC (y1/a<0.8, a/D50>50, Fr<1) #DIV/0! #DIV/0! #DIV/0! #DIV/0!

yS (7.3) SCOUR DEPTH, m, ft 0.00 0.00 0.00 0.00 yS (7.34) SCOUR DEPTH-COARSE BED, m, ft (D50>20mm & GC>1.5) #DIV/0! #DIV/0! #DIV/0! #DIV/0!

ABUTMENT SCOUR - NCHRP 24-20

y1 AVERAGE U/S DEPTH, MAIN CHANNEL, m, ft 4.9 5.1 v1 AVERAGE U/S VELOCITY, MAIN CHANNEL, m/s, ft/s 8.2 8.0 y0 AVERAGE CONTRACTED DEPTH BEFORE SCOUR, m, ft 5.0 5.4

Vbr AVERAGE VELOCITY THROUGH BRIDGE, m/s, ft/s 9.4 9.7

Bf FLOODPLAIN WIDTH, m, ft 95.0 100.0

FLOW THROUGH BRIDGE, m3/s, ft3/s 1362.0 2180.0

WW WATERWAY WIDTH, m, ft 45.0 45.0

L PROJECTED LENGTH EMBANKMENT, m, ft 90.0 95.0

D50 DIAMETER 50% FINER BED PARTICLES, mm 60 60 alpha SCOUR AMPLIFICATION FACTOR (FIG. 8.9 - 8.12) 1.65 1.70

Ku UNIT COEFFICIENT, 6.19 SI, 11.17 English 11.17 11.17 11.17 11.17

L/Bf L/Bf > 0.75 USE LB, < 0.75 USE CW #DIV/0! #DIV/0! 0.95 0.95 q1 UPSTREAM UNIT DISCHARGE, m3/s, ft3/s 0.00 0.00 40.18 40.80 q2 UNIT DISCHARGE IN CONSTRICTED OPENING, m3/s, ft3/s 0.00 0.00 47.00 52.38 q2/q1 #DIV/0! #DIV/0! 1.17 1.28 ymax (8.3) MAXIMUM FLOW DEPTH RESULTING FROM SCOUR, ft, m #DIV/0! #DIV/0! 9.25 10.74 yS (8.4) ABUTMENT SCOUR DEPTH, m, ft #DIV/0! #DIV/0! 4.25 5.34

TOTAL SCOUR

Base Elevation 4,185.0 4,185.0

Contraction Scour

Live Bed 0.0 0.0 0.0 0.0

Clear Water 0.0 0.0 0.7 3.1

Pressure Flow (assumes clear water) 0.0 0.0 0.0 0.0

Contraction + Pier (without Pressure Flow Scour)

Pier (max 2.4 x pier width) 0.0 0.0 #DIV/0! #DIV/0!

Total Live Bed 0.0 0.0 #DIV/0! #DIV/0!

Live Bed Scour Elevation 0.0 0.0 #DIV/0! #DIV/0!

Total Clear Water 0.0 0.0 #DIV/0! #DIV/0!

Clear Water Scour Elevation 0.0 0.0 #DIV/0! #DIV/0!

Contraction + Pier (with Pressure Flow Scour)

Pier (max 2.4 x pier width) 0.0 0.0 #DIV/0! #DIV/0!

Total Live Bed 0.0 0.0 #DIV/0! #DIV/0!

Live Bed Scour Elevation 0.0 0.0 #DIV/0! #DIV/0!

Total Clear Water 0.0 0.0 #DIV/0! #DIV/0!

Clear Water Scour Elevation 0.0 0.0 #DIV/0! #DIV/0!

Abutment

Abutment #DIV/0! #DIV/0! 4.2 5.3

Total Bed Scour Elevation #DIV/0! #DIV/0! 4,180.8 4,179.7

Note: S. Leon 7/12/12

HEC 18, 5th ED. 4/2012 (EQUATIONS SHOWN IN PARENTHESIS)

Hydraulic Analysis Report

Riprap Analysis

Input Parameters

Riprap Type: Revetment

The channel is a natural channel

Local Depth of Flow: 5 ft

Riprap Shape is Angular

Stability Coefficient: 0.3

This value is updated by the selected Riprap Shape

Blanket Thickness Coefficient: 1

Channel Cross-sectional Average Velocity: 12 ft/s

Which is the Average Velocity with Spurs

Centerline Radius of Curvature of Channel Bend: 1e+009 ft

Width of Water Surface at Upstream End of Channel Bend: 190 ft

Bank Angle: 2 :1 H:V

.966 < Bank Angle < 4.011

The location of the revetment protection is on a straight channel

Specific Gravity of Riprap: 2.65

Safety Factor: 1.5

Result Parameters

Side slope Correction Factor: 0.871418

Velocity Distribution Coefficient: 1

Design Velocity: 12 ft/s

Design velocity never less than average channel velocity

Computed D30: 14.9309 in

Computed D50: 17.917 in

Riprap Class

Riprap Class Name: CLASS V

Riprap Class Order: 5

The following values are an 'average' of the size fraction range for the selected riprap class.

d100: 36 in d85: 25.5 in d50: 18.5 in d15: 13 in