Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation:...
-
Upload
arianna-lynch -
Category
Documents
-
view
254 -
download
5
Transcript of Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation:...
![Page 1: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/1.jpg)
Hydrology & Hydraulicsfor
Bridge Design
![Page 2: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/2.jpg)
Bridge Hydraulics Overview
Topics for this presentation:Item 1 – Design discharges (Hydrology)Item 2 – Channel & Bridge CharacteristicsItem 3 – Hydraulic Analysis using HEC-RASItem 4 – National Flood Insurance ProgramItem 5 – Scour Analysis & Channel ProtectionItem 6 – ODOT Submittal Requirements
![Page 3: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/3.jpg)
Item 1: Hydrology
Two primary methods used by ODOT to calculate flood discharges:
• USGS report 89-4126 (rural)• USGS report 93-135 (small urban)
![Page 4: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/4.jpg)
USGS Report 89-4126:
Techniques for Estimating Flood-Peak Discharges of Rural, Unregulated Streams in Ohio
• Provides multiple-regression equations to calculate discharges for gaged and ungaged streams
• Provides a method to adjust discharges for gaged streams
• Contains data from streamflow gaging stations
![Page 5: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/5.jpg)
USGS Report 89-4126:
![Page 6: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/6.jpg)
Drainage Area
![Page 7: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/7.jpg)
Supplement to the Gazetteer
• Useful for calculating larger drainage areas
• Available from ODNR, listed as an “out of print” publication on website
![Page 8: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/8.jpg)
Supplement to the Gazetteer
![Page 9: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/9.jpg)
Main Channel Slope
![Page 10: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/10.jpg)
Storage
![Page 11: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/11.jpg)
Region for Drainage Area
![Page 12: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/12.jpg)
Discharge Calculation for Ungaged Stream:
The Region C multiple-regression equation for 100-year flood peak discharges is chosen:
Q100 = (RC)(CONTDA)0.756(SLOPE)0.285(STORAGE+1)-0.363
Basic characteristics for the ungaged site are determined:CONTDA = 0.290 square miles
SLOPE = 93.0 feet per mile
STORAGE = 0.0 percent
These values are substituted into the Region C equation:
Q100 = 236(0.290)0.756(93.0)0.285(0.0+1)-0.363
Q100 = 337 cubic feet per second
![Page 13: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/13.jpg)
Confirm Suitability of Rural Equations• Check basin characteristics with ranges for region
• Characteristics outside range occur infrequently
![Page 14: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/14.jpg)
Use of Gaging Station Data• For ungaged sites on gaged streams• Confirm that drainage basin is rural and stream is
unregulated• Site can be upstream or downstream of gauging station• Results of regression equations are adjusted to agree with
data from nearby gaging stations
![Page 15: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/15.jpg)
Peakflow Software• Applies regression equations• Performs gauging station adjustments• Download from ODOT website
![Page 16: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/16.jpg)
USGS Report 93-135:Estimation of Peak-Frequency Relations, Flood Hydrographs, and Volume-Duration-Frequency Relations of Ungaged Small Urban Streams in Ohio
• Procedure similar to that used for rural streams• Equations are not suitable for all urban streams• Q = f (Area, Slope, BDF)
![Page 17: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/17.jpg)
Basin Development Factor (BDF):
• A measure of urban development within a drainage basin
0 = No development
12 = Maximum development• Divide basin into three subdivisions• Estimate development in each subdivision
![Page 18: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/18.jpg)
044TOTAL
011Curb & Gutter Streets
011Storm Drains
011Channel Linings
011Channel Improvements
Lower 1/3Middle 1/3Upper 1/3
BDF=4+4+0=8
Basin Development Factor (BDF):
![Page 19: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/19.jpg)
Confirm Suitability of Urban Equations
120BDF
41.231.5Precipitation
4.090.026Drainage Area
MaximumMinimumBasin Characteristics
![Page 20: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/20.jpg)
Other Sources for Discharge Estimates
• HUD Flood Insurance Studies• U.S. Corps of Engineers Flood Studies• U.S. Soil Conservation Studies• Agencies responsible for flood control facilities
(regulated streams)
![Page 21: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/21.jpg)
ODOT Design Discharges
Design Flood Frequency:
Freeways/Controlled Access Facilities 50 years
Other Highways (≥2000 ADT) 25 years
Other Highways (<2000 ADT) 10 years
![Page 22: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/22.jpg)
Item 2: Channel & Bridge Characteristics• Perform channel survey• Data Requirements:
– Cross section geometry– Roughness values– Bridge characteristics
![Page 23: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/23.jpg)
Field Survey for Waterway Crossings• Used to obtain channel cross-section data and establish
roughness coefficients (“n” values)• Photographs are required• Determine and document nature of upstream property• Assess flood potential and Headwater controls• Look for evidence of scour
![Page 24: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/24.jpg)
Channel Cross-Sections
• Number of sections depends on uniformity of channel• Locate sections where bed profile, channel width or
depth, or roughness change abruptly• Orientation perpendicular to direction of flow
![Page 25: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/25.jpg)
Bridge Cross Section Requirements
![Page 26: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/26.jpg)
Manning’s Roughness Coefficients
• Various sources for “n” values• Roughness varies with season (Use worst case)
![Page 27: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/27.jpg)
FHWA-TS-84-204:Guide for Selecting Manning's Roughness Coefficientsfor Natural Channels and Flood Plains
(http://www.fhwa.dot.gov/bridge/wsp2339.pdf)
![Page 28: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/28.jpg)
U.S.G.S Water Supply Paper 1849(Available online, link found in HEC-RAS help menu)
http://wwwrcamnl.wr.usgs.gov/sws/fieldmethods/Indirects/nvalues/index.htm
![Page 29: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/29.jpg)
Item 3 – Hydraulic Analysis
HEC-RAS Software – US Army Corps of Engineers(Hydraulic Engineering Center - River Analysis System).
![Page 30: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/30.jpg)
• Software and Users Manuals are downloadable for free from Corps of Engineers website (www.hec.usace.army.mil)
• User inputs design flood flows, channel and structure survey information
• HEC-RAS uses the Standard Step method to compute steady flow water surface profiles
• HEC-RAS is capable of modeling subcritical, supercritical, and mixed flow
HEC-RAS Software
![Page 31: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/31.jpg)
Standard Step Method• Also known as the “Step Backwater Method”• Uses the Energy Equation and Manning’s Equation to
evaluate points along the water surface profile.
Basic Assumptions1. Steady flow2. Flow type constant between sections3. Normal depths considered vertical depths4. Level water surface across channel5. Sediment and air entrainment are negligible
![Page 32: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/32.jpg)
Standard Step Method
![Page 33: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/33.jpg)
Defining flow data in HEC-RAS
Required input for steady flow analysis:
- Discharge at cross sections with a change in flow.
- Boundary condition
• Downstream Channel Slope (Used to calculate Normal Depth)
• Known value (If available)
![Page 34: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/34.jpg)
Cross Section Geometry
![Page 35: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/35.jpg)
Bridge Geometry
![Page 36: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/36.jpg)
Cross Section Layout
![Page 37: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/37.jpg)
HEC-RAS Output
![Page 38: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/38.jpg)
HEC-RAS Output
![Page 39: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/39.jpg)
Allowable Backwater
• In general, the bridge should be designed to clear the design frequency flood
• Meet NFIP (National Flood Insurance Program) requirements
• Meet Conservancy District requirements• Limited to 1-foot raise in 100-year backwater if outside
of NFIP jurisdiction (Ohio Revised Code, section 1521.13)
• Backwater should not be allowed to flood “Unreasonably large areas of usable land”
• Backwater should not be increased in urban areas
![Page 40: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/40.jpg)
Item 4 - National Flood Insurance Program (NFIP)
• Most Ohio communities participate• Each community adopts local ordinances• Enforced by local floodplain coordinator
(see ODNR website for listing)
![Page 41: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/41.jpg)
Floodways
No encroachment allowed in the designated floodway unless analysis shows no increase in flood levels
![Page 42: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/42.jpg)
NFIP Compliance
• Obtain floodway map, flood insurance rate map, and flood insurance study for site. (All available on FEMA website)
• If the site falls within a special flood hazard area, any construction must be approved by local floodplain coordinator
• Obtain local floodplain ordinances for community
![Page 43: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/43.jpg)
Floodway Map
![Page 44: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/44.jpg)
Flood Insurance Rate Map
![Page 45: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/45.jpg)
Flood Insurance Study
![Page 46: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/46.jpg)
NFIP Compliance
Condition Requirement
Construction in the floodway
Analysis showing that proposed condition will not increase 100-year water surface elevations
Construction in floodway fringe
Embankment is permitted in the floodway fringe
Construction in Flood Hazard Zone A
See local floodplain regulations for requirements
![Page 47: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/47.jpg)
NFIP Compliance – HEC RAS Analysis
• Obtain original model used for FIS, if possible• If original model cannot be obtained, use water
surface elevations and flow rates from FIS to initiate analysis
• If flow rates and water surface elevations are substantially different those based on the regression equations, include both on the structure site plan
![Page 48: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/48.jpg)
Ohio’s Conservancy Districts
http://www.miamiconservancy.org/Who_We_Are/What_Is_A_Conservancy_District/Ohios_Conservancy_Districts.htm
![Page 49: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/49.jpg)
Item 5 – Scour Analysis and Channel Protection
Hydraulic Engineering Circular No. 18 (HEC-18):Evaluating Scour at Bridges
Published by FHWA
Best source of information on scour analysis & countermeasures
![Page 50: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/50.jpg)
Total Scour –three components:1. Long term aggradation and degradation
2. Contraction scour
3. Local scour
![Page 51: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/51.jpg)
Long-Term Aggradation and Degradation
• Not computed by HEC-RAS
• What is the long-term trend?
• Trends can change due to natural or man-made causes.
• Evaluate using HEC-18 before performing analysis
• ODOT District personnel and County Engineers are a good source of information.
![Page 52: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/52.jpg)
Contraction Scour
• Occurs when the flow area of a stream is reduced by a natural contraction or a bridge restricting the flow
![Page 53: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/53.jpg)
Contraction Scour
![Page 54: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/54.jpg)
Contraction Scour
![Page 55: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/55.jpg)
Local Scour at Piers• Occurs due to the acceleration of flow around the pier and
the formation of flow vortices.
![Page 56: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/56.jpg)
Local Scour at Piers
![Page 57: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/57.jpg)
Local Scour at Piers
![Page 58: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/58.jpg)
Local Scour at Piers
![Page 59: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/59.jpg)
Local Scour at Abutments
![Page 60: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/60.jpg)
Local Scour at Abutments
![Page 61: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/61.jpg)
Local Scour at Abutments
![Page 62: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/62.jpg)
Local Scour at Abutments
![Page 63: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/63.jpg)
Scour with HEC-RAS
![Page 64: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/64.jpg)
Scour with HEC-RAS
![Page 65: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/65.jpg)
ODOT Scour Protection Requirements
• Deep foundations (piles or drilled shafts) or spread footings in rock
• Spill-through earth slopes armored with rock channel protection
– Minimum size and thickness of RCP given in ODOT Bridge Design Manual
– Increase thickness of RCP outside portion of curved channels or where ice flow is concern
![Page 66: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/66.jpg)
Rock Channel Protection at Bridges
![Page 67: Hydrology & Hydraulics for Bridge Design. Bridge Hydraulics Overview Topics for this presentation: Item 1 – Design discharges (Hydrology) Item 2 – Channel.](https://reader034.fdocuments.net/reader034/viewer/2022050905/5515acd855034691418b62b0/html5/thumbnails/67.jpg)
Item 6 - ODOT Submittal Requirements:
Include a “Hydraulic Report” with the Structure Type Study. This report should include:
1. Computation of flood flows
2. Hydraulic analysis of existing and proposed structure (include both hard copy and HEC-RAS files)
3. Information on NFIP floodmaps and flood insurance studies referenced
4. Scour analysis of proposed structure