# Presentation: 644708

## CONCEPTS – Conservational Channel Evolution and Pollutant Transport System

- Eddy J. Langendoen
- Robert E. Thomas
- USDA Agricultural Research Service
- National Sedimentation Laboratory
- Oxford, Mississippi

## Instructors

- Eddy Langendoen
- Research Hydraulic Engineer with USDA-ARS National Sedimentation Laboratory
- Developer of CONCEPTS
- Develop technologies that integrate fluvial hydraulics, sedimentation engineering, and computer modeling techniques to examine the effectiveness of stabilization and restoration practices
- Background in computational hydraulics
- M.S. in Civil Engineering and Ph.D. from Delft University of Technology, The Netherlands

## Instructors (cont.)

- Rob Thomas
- Research Associate with USDA-ARS National Sedimentation Laboratory
- Investigating lateral and vertical adjustment of channels to disturbances, including monitoring and modeling of the upstream migration of knickpoints.
- Application of CONCEPTS to Goodwin Creek and the Yalobusha River, Mississippi.
- B.S. in Geography from University of Nottingham, England

## Course Outline

- Introduction
- Why CONCEPTS?
- An application of CONCEPTS
- CONCEPTS overview
- Hydraulics
- Sediment transport and bed adjustment
- Streambank erosion mechanics

## Course Outline (cont.)

- Input data
- Required data
- How do we get it?
- Output data
- Output types
- Output options
- Execution of CONCEPTS using sample applications
- Preparing input files
- Running CONCEPTS
- Viewing/interpreting output files

## Why Do We Use/Develop CONCEPTS?

- Most of our work is in the Mid-Continental USA
- Highly erodible soils
- Channelized stream systems
- Unstable stream systems
- How can we reduce impact or stabilize these stream systems

## Characteristics of Unstable Streams

- Migrating knickpoints
- Mass wasting of streambanks
- Recruitment of large woody debris
- Impairment
- Stream
- Habitat
- Infrastructure

## Stream Rehabilitation/Restoration

- Stabilize stream
- ‘Hard’ structures (concrete, rock)
- ‘Soft’ bioengineered or vegetative solutions
- Combination
- (Re)construct channel
- Does our design work?
- Need to evaluate design
- CONCEPTS

## Sample Application of CONCEPTS – Yalobusha River, Mississippi

## Yalobusha River – Background

- European agricultural development early 19th century
- Channel capacity restricted by silt and debris accumulation
- Excavation of 12-mile ditch through the river’s valley early 20th century
- Sand, silt, and debris closed lower part of the channel
- Clearing in the 1940s
- New channelization in the 1960s
- Extending ditch downstream
- Realigned and dredged the mouths of all major tributaries
- Construction of erosion control structures

## Yalobusha River – Background (cont.)

- Channel response:
- Headward migrating knickpoints in all tribs
- Extensive streambank erosion
- Recruitment of large woody debris
- Deposition of sands and debris at the terminus of channelization
- Flooding problems at Calhoun City
- Mitigation: plug removal

## Channel Evolution

- Channels respond to:
- Hydrologic changes
- Changes in sediment loadings
- Man-made changes
- How do channels adjust?
- Vertically: scour – fill, degradation – aggradation
- Horizontally: widening & migration
- Models must capture these processes
- Hydraulics
- Sediment transport and bed adjustment
- Streambank mechanics

## CONCEPTS – CONservational Channel Evolution and Pollutant Transport System

- CONCEPTS simulates long-term response of channels to loadings of water and sediments, and to instream structures

- Output:
- Changes in channel geometry
- Time series of hydraulic variables and sediment yield

- Input:
- Channel geometry
- Composition of bed and bank materials
- Erosion resistance and shear strength of bed and bank materials
- Rates of flow and sediments entering the channel

## Hydraulics

## Hydraulics

- Unsteady
- One-dimensional
- Long term simulations
- Cross-stream variations are neglected
- Gradually-varying
- St. Venant equations
- Special techniques to handle ‘flashy’ runoff events
- Solution method
- Generalized Preissmann scheme
- Gaussian elimination

## Hydraulics – Boundary Conditions

- Boundary conditions
- External boundaries
- Upstream and downstream ends of stream corridor
- Internal boundaries
- Locations where the flow is rapidly varied
- Hydraulic structures
- Knickpoints
- Rapids

## Hydraulics – External Boundary Conditions

- Upstream boundary
- Discharge hydrograph
- Downstream boundary
- Rating curve
- User specified
- CONCEPTS’ generated loop-rating curve

*h* = flow depth (m)
*K *= conveyance (m3/s)
*Q *= flow discharge (m3/s)
*S**f* = friction slope (m/m)
*t *= time (s)
-  = coefficient of rating curve
-  = exponent of rating curve

## Hydraulics – Hydraulic Structures

- Hydraulic structures in CONCEPTS
- Box and pipe culverts
- Bridge crossings
- Grade control structures
- Generic structures
- We need two equations
- Continuity equation
- Dynamic equation

- Relate discharge with stages upstream and downstream of the structure

## Sediment Transport

## Sediment Transport

- Sediment transport rates are a function of:
- Flow hydraulics
- Bed composition
- Upstream sediment supply
- Sediment deposited on or scoured from the bed changes bed composition, flow hydraulics, and fractional transport rates

- Sediment discharge is therefore calculated using a transport (advection) equation with source terms representing loadings

- (entrainment and lateral contributions) and losses (deposition)

## Sediment Transport (cont.)

- Sediment mixtures
- 13 predefined size classes
- Sediment transport capacity is predicted by SEDTRA
- CONCEPTS tracks the composition of both surface and substrate
- Distinguish different erosion characteristics of cohesive and cohesionless bed material
- Cohesionless: local erosion or deposition is proportional to the difference between sediment transport rate and capacity
- Cohesive: excess shear stress approach

## Sediment Transport – Sediment Sizes and Transport Equations

| size class | upper bound
(mm) | representative diameter
(mm) | description | transport equation |
| --- | --- | --- | --- | --- |
| 1 | 0.010 |  | clay – very fine silt | wash load |
| 2 | 0.025 | 0.016 | fine – medium silt | Laursen |
| 3 | 0.065 | 0.040 | medium – coarse silt | Laursen |
| 4 | 0.250 | 0.127 | fine sand | Laursen |
| 5 | 0.841 | 0.458 | medium – coarse sand | Yang |
| 6 | 2.000 | 1.297 | very coarse sand | Yang |
| 7 | 3.364 | 2.594 | very fine gravel | Meyer-Peter & Mueller |
| 8 | 5.656 | 4.362 | fine gravel | Meyer-Peter & Mueller |
| 9 | 9.514 | 7.336 | fine gravel | Meyer-Peter & Mueller |
| 10 | 16.000 | 12.338 | medium gravel | Meyer-Peter & Mueller |
| 11 | 26.909 | 20.749 | coarse gravel | Meyer-Peter & Mueller |
| 12 | 38.055 | 32.000 | coarse gravel | Meyer-Peter & Mueller |
| 13 | 50.000 | 43.713 | very coarse gravel | Meyer-Peter & Mueller |

## Sediment Transport – Approximation

- Fractional step method.  The transport equation is split into an equivalent system of:
- Advection equation
- Sediment mass is transported downstream without the effects of sources and losses.
- Solved by the method of characteristics
- Rate-of-Change equation
- Sediment mass is adjusted by taking into account erosion and deposition
- Analytical solution assuming sediment transport capacity is constant during a time step

## Sediment Transport – Bed Adjustment

- erosion partly wetted bed

- deposition partly wetted bed

- erosion fully wetted bed

- deposition fully wetted bed

## Sediment Transport – Boundary Conditions

- Upstream boundary
- Sediment load as a fraction of local sediment transport capacity
- Time series of sediment load (kg/s)
- Downstream boundary
- Not required by the solution method, however only processes occurring in the reach then determine the evolution of the outlet. Change in bed elevation can be adjusted by multiplying it with a coefficient varying between 0 and 1.

## Sediment Transport – Internal Boundary Conditions

- Sediment transport rate at a hydraulic structure is a function of the supply of sediment and the invert of the structure
- If invert is above channel bed, particles transported as bed load are deposited
- If invert is below or at the channel bed all sediment passes the structure

## Streambank Erosion

## Streambank Erosion

- Channel-width adjustment occurs in a wide variety of geomorphic contexts
- Equilibrium approaches are unlikely to accurately predict width adjustment over time
- Fundamental processes responsible for bank retreat
- Hydraulic erosion
- Mass bank failure

## Streambank Erosion – Hydraulic Erosion

- Transport, deposition, and erosion of cohesive sediments are extremely complex
- Erosion rate is given by an excess shear stress relation
- Critical shear stress:
- Arulanandan et al. (1980) if sodium adsorption ratio, dielectric dispersion, and pore fluid salt concentration are known
*In situ* measurements (Hanson and Simon 2001)
- Historical data on the retreat of the base of the bank combined with flow data
- The effects of weathering processes and vegetation can be included by adjusting critical shear stress

## Streambank Erosion – Hydraulic Erosion (cont.)

- Average shear stress *i* on each soil layer
- Average erosion distance *E**i*

## Streambank Erosion – Rotational Streambank Failure

## Streambank Erosion – Planar Streambank Failure

## Streambank Erosion – Cantilever Streambank Failure

## Streambank Erosion – Piping Streambank Failure

## Streambank Erosion – Streambank Stability

- Weight is the primary force tending to move the failure block
- Mobilized shear at the slip surface is the primary resisting force
- Shear strength is affected by
- Pore-water pressures
- Vegetation
- Mechanical reinforcement
- Reduction of soil moisture through canopy interception and evapotranspiration
- Increase soil moisture through stem flow

## Streambank Erosion – Planar Failure Analysis

- Stability is analyzed using limit equilibrium methods => FOS
- Methods are based upon static equilibriums of forces and/or moments
- Method of slices

*F**w* = confining force (N/m)
*N* = normal force (N/m)
*S* = mobilized shear force (N/m)
*W* = weight of composite soil (N/m)
-  = angle of slip surface

## Streambank Erosion – Inclination of Failure Surface

- The inclination of the failure plane is that for which the factor of safety is a minimum
- CONCEPTS uses a search method to find smallest FOS
- Factor of safety is evaluated at *N**e* number of points along the bank profile

## Test Cases

## Test Case 1

- Prismatic channel
- 25 km long
- 0.002 m/m bed slope
- Manning *n* is 0.04
- 51 Cross sections composed of a rectangular main-channel right-overbank sections at 500 m intervals
- Single runoff event

## Test Case 1 – Run Control File

## Run Control File

- The Run Control file sets:
- case name,
- project title,
- lateral inflow due to tributaries,
- downstream rating curve,
- the proportion of sediment transport capacity for all the sediment size classes being transported into the upstream end of the reach,
- the silt fraction and degree of downstream bed control,

## Run Control File (Cont.)

- The Run Control file sets:
- selection of the bank failure options, such as whether positive pore-water pressures, confining pressures, and matric suction are accounted for, and the complexity of the analysis- the number of time steps at which factor of safety is computed plus the number of potential failure planes in the bank,
- selection of the flow resistance formulation,
- water temperature,
- activation of sediment transport mechanisms and streambank mechanics,
- sets the start and end time of the simulation, the initial time step length
- the makeup of the modeling reach (the number of links, cross-sections and their names),
- output options.

## Output Data.

- CONCEPTS creates three types of output:
- output at a certain cross-section and for a certain runoff event
- time-series output at a chosen cross-section
- output for a certain runoff event along a section of the modeling reach
- Names of the output files are in the form: run identifier + ‘ ’ + number + ‘.TXT’. e.g., if run identifier is SIMULATION, then output file names are ‘SIMULATION 050.TXT’, ‘SIMULATION 051.TXT’, etc..

## Output at a Certain Location and for a Certain Runoff Event 

- To request data for a chosen cross-section and runoff event, user has to:
- enter number of locations at which output is requested.
- for each location, user must enter:
- type of data required,
- location of required cross-section within modeling reach,
- number of runoff events for which output is requested,
- dates of those events,
- repeated for however many output cross-sections are required.

## Output at a Location and a Runoff Event (Parameters)

## Output at a Location and a Runoff Event (Parameters Cont.)

## Time-Series Output at a Certain Location

- CONCEPTS checks if time falls between start and end time of all requested time series. When model time is within time series boundaries, the requested parameters are printed.
- To request output at a certain cross-section over a period of time, the user has to:
- enter number of locations at which output is requested.
- for each location, user must enter:
- type of data required,
- the location of the required cross-section within the modeling reach,
- number of time series for which output is requested,
- the start and end dates of the time series,
- repeated for however many output cross-sections are required.

## Time-Series Output at a Location (Parameters)

## Time-Series Output at a Location (Parameters- Cont.)

## Time-Series Output at a Location (Parameters- Cont.)

## Output for a Certain Runoff Event along a Section of the Modeling Reach

- In order to request output for a certain runoff event along a profile, the user must enter:
- number of profiles at which output is requested,
- type of data,
- locations of first and last cross-section of the profile are entered, with the link number and in-link cross-section number,
- number of storm events for which output is requested for that particular profile,
- dates of the storm events,
- repeated for however many output profiles are required.

## Output for Runoff Events along a Profile (Parameters)

## Test Case 1 – Discharge File

## Discharge File

- Discharges inputted into the upstream end of the reach.
- Includes:
- baseflow (in m3s-1),
- all discharge records (in m3s-1),
- date and time,
- identifier signifying the start of a storm event, the end of a storm event or between storm events for each record.

## Downstream boundary condition

- Downstream (outlet) rating curve (stage-discharge)
- USGS has 7,292 stations, of which 4,200 are realtime
- Basic piece of data obtained at station is stage
- Stage measured by (among others): stilling well, bubbler system and pressure transducers
- Converted to discharge by velocity-area method (measure average velocity in 25 flow segments)

## Developing a rating curve

- Developed Stage-Discharge relationship for Goodwin Creek Bendway. Stage measured with crest stage gauge then a transducer, while discharge was obtained from stations

## What if there are no gaging stations nearby?

- Interpolation between or extrapolation from gauging points on the same stream on the basis of drainage-area size.
- Regional relations
- Rational Method
- Hydrological watershed models, e.g. variants of HEC-1 (including HEC-HMS, HEC-geoHMS), BASINS, SWAT, HSPF, the Watershed Modeling System, and USDA-ARS’s AnnAGNPS 2001

## Hydrological Models

- HEC packages
- Unit hydrographs via direct ordinates, Clark, Snyder, SCS or kinematic wave transforms. Routing via level-pool reservoir, average-lag, modified Puls, Muskingum, Muskingum-Cunge
- HSPF
- TR-55 (curve number method) and unit hydrograph
- WMS
- DEMs linked to HEC-1, TR-20, TR-55 or HSPF. Unit hydrograph theory
- BASINS
- HSPF and SWAT.
- SWAT = modified rational equation, TR-55 – Large basins, long time periods, not recommended for detailed flood routing

## Hydrological Models (cont.)

- AGricultural NonPoint Source model (AGNPS).
- suite of models developed to assist in quantifying impacts of agricultural non-point source pollution on water quality and environment.
- model concerned with runoff modeling is AnnAGNPS.
- utilizes TR-55 (USSCS, 1986) to simulate runoff generation.
- uses distributed parameter inputs and operates on a cell basis.
- AnnAGNPS data-intensive but contains tools such as a geographic information system and a database management system.

## Test Case 1 – Cross Section File

## Cross-sections

- File for each cross-section in the reach.
- Cross-section files contain:
- cross-section name and its location within the reach,
- initial Manning’s *n* value,
- the fraction of additional discharge due to tributary inflow at the cross section,
- details of the geometry of the cross-section: number of points, station and elevation to be entered for each point within the left floodplain, left bank, channel bed, right bank, and right floodplain,

## Cross-sections (Cont.)

- Cross-section files contain:
- Manning’s *n* of the surface.
- elevation of the top of the bank,
- geotechnical parameters, including *c*', ', *b*,*s*, and the critical shear stress for erosion of the material,
- sediment composition of the bank is then detailed, in terms of the thirteen size classes employed by CONCEPTS,
- elevation of the groundwater table (to calculate pore-water pressures).

## Cross-sections (Cont.): Channel Bed

- The channel bed requires information on:
- elevation of bedrock (for restriction of amounts of bed degradation),
- porosity of the bed,
- hiding factors for the silt, sand and gravel fractions that make up the bed.
- layer data, to allow the input of numerous layers within the bed, including the bed composition in the thirteen size classes, critical shear stress for erosion and deposition of the bed and the empirical erodibility coefficient.

## Geometries- How can we get it?

- Many methods of terrestrial surveying exist, these include, but are not limited to:
- Tape, band or equivalent
- Leveling
- Total station
- Photogrammetry
- Global positioning system

## Surveying methods

|  |   |
| --- | --- |
| Dumpy Level (courtesy of Leica UK Ltd.)  | (left) Leica TC605 total station; (right) reflectance prism (both courtesy of Leica UK Ltd.)  
 |

## Typical values for bank material parameters (from Selby, 1982).

| Description | Friction angle          ' | Cohesion c'       (kPa) | Saturated unit weight
(N/m3) | b (degrees) |
| --- | --- | --- | --- | --- |
| Gravel | 36 | 0 | 20000 | 10 |
| Angular sand | 36 | 0 | 18000 | 15 |
| Rounded sand | 27 | 0 | 18000 | 15 |
| Silt | 25 | 5 | 18000 | 15 |
| Stiff clay | 10 | 15 | 18000 | 15 |
| Soft clay | 30 | 10 | 16000 | 15 |

## Cohesion and Friction Angle: Methods

*in situ* field techniques:
- borehole shear tester (BST)
- shear vane
- laboratory techniques:
- shear box,
- triaxial shear test
- all (except shear vane) produce plots of shear stress vs normal stress

## BST and Shear box configuration

- (a) Schematic of borehole shear test assembly. (b) Detail of shear head in borehole (from Simon and Hupp, 1990, Fig. 11.2, p.148) and Illustration of the principle of a shear box (from Selby, 1982, Fig. 4.16, p.54)

## BST and Shear box

- Measure drained, geotechnical parameters (apparent cohesion, *c**a*, and friction angle, ) *in situ*
- Sufficient number of shearing trials are made at successively incrementing normal stresses to form a failure envelope
- BST:
- 10 times faster than laboratory tests;
- test data are plotted on site;
- relatively inexpensive;
- shear head may clog, giving false results
- requires monitoring of pore-water pressure to obtain *c*’

## Shear box-features

- Shear box:
- soil matrix disturbed during sampling;
- stress distribution across a test sample is complex which may mean that the value of shearing resistance is approximate;
- time consuming, depending on sample properties;
- Pore-water pressures can be monitored with a modified version so matric suction and *b* can be obtained

## Triaxial Cell-features

- granular soils derive much of their strength from lateral confinement;
- minimum of three tests are normally carried out at different lateral pressures;
- pore-water pressure changes can be measured.
- disturbance of the soil matrix during sample collection;
- cost;
- time consuming

## Determining b

- *b* = angle indicating the rate of increase in shear strength relative to matric suction.
- matric suction can be measured by both direct testing or indirect testing.
- Direct tests include tensiometers (jet fill, small tip, quick draw or osmotic) and axis translation.
- tensiometers are a high-air entry, porous ceramic cup connected to a pressure measuring device through a small bore tube.

## In Situ Jet test device for determining critical shear stress

- Developed by the Agricultural Research Service (Hanson, 1990).
- Based on knowledge of hydraulic characteristics of a submerged jet and the characteristics of soil-material erodibility.
- Apparatus: pump, adjustable head tank, jet submergence tank, jet nozzle, delivery tube, and point gage.
- The stress range = 4 - 1500 Pa.
- Maximum scour measurements are taken at five to ten minute intervals over a period of 60 to 120 minutes.

## Material properties (Particle size and Unit weight)

- Particle size distributions.. method:
- Broken up, weighed dry sample washed over a 2.0 mm sieve, dried and reweighed;
- Coarse fraction sieved using 75, 50, 37.5, 25.0, 19.0, 9.5, 4.75 and 2.0 mm sieves, fine fraction passed over for hydrometer analysis.
- Unit weight, *s*
- defined as ratio of the weight of soil solids, *W**s* to the total volume of the soil, *V*;
- found by drying a sample of known weight and volume for over 16 hours at 110 oC, before reweighing

## Material properties (Porosity)

- Porosity, 
- defined as the volume of air- and water-filled voids in a soil divided by the total volume of the soil;
- This equals:
- 	where *b* is bulk density and *m* is particle density (assumed to be equal to 2600 kg m-3 for organic materials, 2650 kg m-3 for granular materials and 2700 kg m-3 for clays);
- porosity derived from laboratory values of bulk density

## Typical porosity and unit weight values for a range of sediments.

|  | Unit weight,
s, KNm-3  |  | Porosity,
  |  |
| --- | --- | --- | --- | --- |
| Soil Type | Max. | Min. | Max. | Min. |
| Clay (30-50% clay sizes) | 17599 | 7858 | 0.71 | 0.33 |
| Skip-graded silty clay with stones or rock fragments | 22004 | 13204 | 0.50 | 0.17 |
| Uniform, inorganic silt | 18541 | 12567 | 0.52 | 0.29 |
| Silty sand | 19954 | 13675 | 0.47 | 0.23 |
| Clean uniform sand (fine or medium) | 18541 | 13047 | 0.50 | 0.29 |
| Clean, fine to coarse sand | 21680 | 13361 | 0.49 | 0.17 |
| Micaceous sand | 18855 | 11939 | 0.55 | 0.29 |
| Sandy or silty clay | 21209 | 9427 | 0.64 | 0.20 |
| Silty sand and gravel | 21965 | 13989 | 0.46 | 0.12 |
| Well-graded gravel, sand, silt, and clay mixture | 23260 | 15716 | 0.41 | 0.11 |

## Manning’s n – pp. 78-80 in the manual

- Many different equations. Most link *n* to Slope, Hydraulic Radius or Bed Particle Size
- Descriptive methods. References: Chow (1959), USSCS (1975), USFHWA (1979), Coon (1998)
- Cowan (1956) – Component method.. *n* due to sediment size, surface irregularity, cross-sectional variation, obstruction, vegetation, sinuosity
- Photographic method – Barnes (1967), Hicks and Mason (1999)

## Hiding Coefficient, , (adapted from Kuhnle et al., 1996)

| Mixture name | Reference | dmean
(mm) | Distribution type | B |  |
| --- | --- | --- | --- | --- | --- |
| SG10 (laboratory) | Kuhnle (1993a)
 | 0.616 | Bimodal | 2.49 | 0.7 |
| SG25 (laboratory) | Kuhnle (1993a) | 0.927 | Bimodal | 2.6 | 0.7
 |
| SG45 (laboratory) | Kuhnle (1993a) | 1.454 | Bimodal | 2.73 | 0.6 |
| 1/2  (laboratory) | Wilcock & Southard (1988) | 1.82 | Unimodal | 0.67 | 1.0 |
| 1  (laboratory) | Wilcock & Southard (1988) | 1.85 | Unimodal | 0.37 | 1.0 |
| Goodwin Creek (GC) (field) | Kuhnle (1993b) | 1.189 | Bimodal | 3.1 | 0.5 |

## Test Case 2 – Goodwin Creek Bendway, MS

- Located in the loess hills of North-Central Mississippi
- Incised 3 meters to a depth of 5 meters
- Bank material
- 2 m of brown clayey silt
- 0.1-0.2 m manganese nodules
- 1.5 m of gray, blocky silt
- 1.5 m of packed sandy gravel

## Test Case 2 – Goodwin Creek Bendway, MS (cont.)

- Major failure episodes between 1996 and 2001 resulting in up to 5.5 m of top-bank retreat
- Planar and cantilever failures were relatively common
- Cantilevers were formed by:
- Fluvial undercutting about 3 – 3.5 m below the top bank
- Sapping and pop-out failures between the cohesive units about 1.6 – 2 m below the top bank
- Loss of matric suction may be as significant as the development of positive pore-water pressures

## Test Case 2 – Run Control File

## Test Case 2 – Discharge File

## Test Case 2 – Cross Section File

## Test Case 3

- Prismatic, rectangular channel
- 25 km long
- 0.002 m/m bed slope
- Manning *n* is 0.04
- 10 m deep and 300 m wide
- Single runoff event
- Test case 3a: baseline
- Test case 3b: culvert at 12.5 km
- Test case 3c: drop structure at 12.5 km

## Hydraulic Structures

- 4 types of hydraulic structures (culvert, bridge crossing, drop structure, and generic structure)
- Common parameters:
- name,
- river kilometer (km)
- Manning n,
- length (m),
- upstream and downstream inverts (m),
- upstream and downstream elevations of the structure above the streambed (m).

## Hydraulic Structures- Culverts

- Box and pipe culverts.
- Culverts require:
- U.S. Federal Highway Administration's (1985) nomographs chart and scale number,
- entrance loss coefficient,
- number of culvert barrels in road crossing and their dimensions: diameter (m) for a pipe culvert, and span (m) and rise (m) for a box culvert.

## Culvert Chart and Scale numbers

## Loss Coefficients

## Hydraulic Structures- Bridge Crossings

- Shape of bridge crossing assumed to be trapezoidal with a horizontal bed.
- Bridge crossings require:
- bottom width (m),
- side slope,
- total pier width (m),
- pier shape coefficient,
- pier loss coefficient.

## Bridge Pier Shape coefficients

## Hydraulic Structures- Drop Structures

- Cross-section of drop structure assumed to be trapezoidal with a horizontal bottom.
- Drop structures require:
- bottom width (m),
- side slope,
- entrance loss coefficient.

## Hydraulic Structures- Generic Structures

- Any structure for which a rating curve is available.
- Cross-section of walls of structure assumed to consist of linear elements.
- Rating curve may comprise up to 4 segments, each segment being a power function.
- Generic structures require:
- number of segments comprising walls of structure,
- bottom elevation (m) and slope of each segment,
- elevation of top of structure (m),
- details of rating curve, (number of segments, location of break points and coefficient and exponent of power function for each segment),

## Test Case 3 – Discharge File

## Test Case 3a – Run Control File

## Test Case 3a – Cross Section File

## Test Case 3b

- Culvert bridge crossing
- Ten pipes with a diameter of 8 m
- USFHWA chart # 1
- USFHWA scale # 1

## Test Case 3b – Run Control File

## Test Case 3b – Culvert File

## Test Case 3c

- Drop Structure
- 5 m long
- 75 m wide
- 1 m vertical drop

## Test Case 3c – Run Control File

## Test Case 3c – Drop Structure File