# CONCEPTS – Conservational Channel Evolution and Pollutant ... · Input Data – Hydraulics Data...

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CONCEPTS – Conservational Channel Evolution and Pollutant Transport System Eddy J. Langendoen Watershed Physical Processes Research Unit National Sedimentation Laboratory USDA Agricultural Research Service Oxford, Mississippi

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Input Data

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Input data required by CONCEPTS n Geometries n Bank strength parameters- c’, φ’,φb, γs, τc n Bed parameters- porosity, χ, bed layers,

elevation of bedrock n Manning’s n n Upstream and downstream boundary

conditions

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Input Data – Hydraulics Data Requirements n Stream corridor geometry, i.e. cross

section locations and profiles, and roughness

n Hydraulic structure location, geometry, roughness, energy loss coefficients

n Upstream discharge hydrograph n Downstream rating curve (optional) n Initial (base flow) conditions

5

Input Data – Sediment Transport Data Requirements n Bed material stratigraphy, composition, and

porosity n Percentage of fines (clay &silt) for which the bed

can be assumed cohesive n Hiding coefficient n Critical shear stresses for erosion and deposition n Sediment load at upstream boundary n Percentage of bed control at the outlet

6

Input Data – Streambank Erosion Data Requirements n Bank material properties

¨ Composition ¨ Unit weight ¨ Erodibility ¨ Shear strength

n Bank roughness n Bank stability analysis options

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Input Data – Hydraulics Data Requirements n Stream corridor geometry, i.e. cross

section locations and profiles, and roughness

n Hydraulic structure location, geometry, roughness, energy loss coefficients

n Upstream discharge hydrograph n Downstream rating curve (optional) n Initial (base flow) conditions

8

Geometries- How can we get it?

n Many methods of terrestrial surveying exist, these include, but are not limited to: ¨ Tape, band or equivalent ¨ Leveling ¨ Total Station ¨ RTK Global Positioning System ¨ Terrestrial-based LIDAR ¨ Photogrammetry

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Manning n – Equation

n The Manning equation calculates discharge as:

2 31Q K S AR S

n= =

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Manning n

n Many different equations. Most link n to Slope, Hydraulic Radius or Bed Particle Size

n Descriptive methods. References: Chow (1959), USSCS (1975), USFHWA (1979), Coon (1998)

n Cowan (1956) – Component method.. n due to sediment size, surface irregularity, cross-sectional variation, obstruction, vegetation, sinuosity

n Photographic method – Barnes (1967), Hicks and Mason (1999)

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Reference Equation Jarrett (1984, 1990) Keulegan (1938)

Limerinos (1970)

Sauer (1990) Strickler (1923)

0.16

84

0.113

1.16 2.0log

RnRD

=⎛ ⎞

+ ⎜ ⎟⎝ ⎠

Manning n – Equations

1 6900.035n D=

0.38 0.160.32n S R−=

0.18 0.080.12097n S R=1 6500.039n D=

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Input Data – Hydraulics Data Requirements n Stream corridor geometry, i.e. cross

section locations and profiles, and roughness

n Hydraulic structure location, geometry, roughness, energy loss coefficients

n Upstream discharge hydrograph n Downstream rating curve (optional) n Initial (base flow) conditions

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Hydraulic Structures

n 4 types of hydraulic structures (culvert, bridge crossing, drop structure, and generic structure)

n 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).

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Hydraulic Structures- Culverts

n Flow computation based on U.S. Federal Highway Administration's (1985) nomographs.

n CONCEPTS can simulate the flow at box and pipe culverts.

n Culverts require: ¨ USFHWA (1985) 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.

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Hydraulic Structures- Bridge Crossings n Shape of bridge crossing assumed to be

trapezoidal with a horizontal bed. n Bridge crossings require:

¨ bottom width (m), ¨ side slope, ¨ total pier width (m), ¨ pier shape coefficient, ¨ pier loss coefficient.

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Hydraulic Structures- Drop Structures n Cross-section of drop structure assumed to be

trapezoidal with a horizontal bottom. n Bridge crossings require:

¨ bottom width (m), ¨ side slope, ¨ entrance loss coefficient.

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Hydraulic Structures- Generic Structures n Any structure for which a rating curve is available. n Cross-section of walls of structure assumed to consist of

linear elements. n Rating curve may comprise up to 4 segments, each

segment being a power function. n 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),

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Input Data – Hydraulics Data Requirements n Stream corridor geometry, i.e. cross

section locations and profiles, and roughness

n Hydraulic structure location, geometry, roughness, energy loss coefficients

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Upstream and Downstream boundary conditions n Upstream (input) discharge n Downstream (output) rating curve (stage-

discharge) n USGS has 7,292 stations, of which 4,200 are

realtime n Computer database currently holds mean daily-

discharge data for about 18,500 locations and more than 400,000 station-years of record, or more than 146 million individual mean daily-discharge values

n Basic piece of data obtained at station is stage

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What if there are no gaging stations nearby? n Interpolation between or extrapolation from

gauging points on the same stream on the basis of drainage-area size.

n Regional relations n Rational Method n 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

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Input Data – Streambank Erosion Data Requirements n Bank material properties

¨ Composition ¨ Unit weight ¨ Erodibility ¨ Shear strength

n Bank roughness n Bank stability analysis options

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

Description

Friction angle φ'

Cohesion c' (kPa

)

Saturated unit weight

(N/m3) φb

(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

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n in situ field techniques: ¨ borehole shear tester (BST) ¨ shear vane

n laboratory techniques: ¨ shear box, ¨ triaxial shear test

n all (except shear vane) produce plots of shear stress vs normal stress

Shear Strength Envelope - Clayc' = 12.5, φ' = 16 degrees

y = 0.296x + 12.5

0

10

20

30

40

50

0 10 20 30 40 50 60 70 80 90 100 110

Normal Stress (KPa)S

hear

Stre

ss a

t Fai

lure

(K

Pa)

Cohesion and Friction Angle: Methods

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Flume methods of determining critical shear stress

Device

Known Flow

Conditions Field Tests Bedload

Depth Range Armoring

Erosion Rate

Shear Stress Range

Annular Flume and

Shaker

Yes

No

No

0-2 mm

Yes

No

0-1 Pa

SEDFlume Yes

Yes

No

0-1 m No

Yes

0-10 Pa

SEDFlume w/ Trap

Channel

Yes

No1 Yes

0-1 m

No

Yes

0-10 Pa

Oscillatory Flume

Yes

Yes

No

0-1 m

Some

Yes

0-10 Pa

1from Gailani, personal communication, 2001

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In Situ Jet test device for determining critical shear stress n Developed by the Agricultural Research

Service (Hanson, 1990). n Based on knowledge of hydraulic

characteristics of a submerged jet and the characteristics of soil-material erodibility.

n Apparatus: pump, adjustable head tank, jet submergence tank, jet nozzle, delivery tube, and point gage.

n The stress range = 4 - 1500 Pa. n Maximum scour measurements are

taken at five to ten minute intervals over a period of 60 to 120 minutes.

26

Materials properties (Particle sizes, Unit weight and Porosity) n Particle size distributions.. method: n dry sample either in air at room temperature or with a

warming device not to exceed 60°C in temperature. n clumps of particles broken up using mortar and rubber-

coated pestle, before weighing the sample. n sample then washed over a 2.0 mm sieve, dried and

reweighed. n required minimum mass of soil retained on the 2.0 mm

sieve is dependent on the maximum particle size: ¨ gravels > 4 kg, sands = 0.115 kg, silts and clays = 0.065 kg.

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Materials properties (Particle sizes, Unit weight and Porosity) n Particle size distributions.. method: n separate retained portion into a series of fractions using

the 75 mm, 50 mm, 37.5 mm, 25.0 mm, 19.0 mm, 9.5 mm, 4.75 mm and 2.0 mm sieves.

n remainder (0.05-0.1 kg) prepared for hydrometer analysis.

n hydrometer readings should be taken at 2, 5, 15, 30, 60, 250, and 1440 minutes.

n transfer suspension to a 75-mm sieve and washed until the wash water is clear. diameter of a particle is calculated according to Stokes’ law.

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Materials properties (Particle sizes, Unit weight and Porosity) n Unit weight, γs n defined as ratio of the weight of soil solids,

Ws to the total volume of the soil, V. n found by drying a sample of known weight

and volume for over 16 hours at 110 ºC, before reweighing.

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Materials properties (Particle sizes, Unit weight and Porosity) n Porosity, n n defined as the volume of air- and water-filled voids in a

soil divided by the total volume of the soil. n Rearranging, this can be shown to equal

where ρb is bulk density and ρm 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).

n Therefore, porosity can be calculated by subtracting laboratory values of bulk density divided by one of these constants from 1.

mρbρ−1

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

Unit weight, γs, kNm-3

Porosity, n

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

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INPUT FILES

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Types of Input Files

n CONCEPTS requires two types of input files to be created in order to run. ¨ XML-based input file containing physical data,

channel models, and run data (*.concepts) ¨ Inflow files

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Input Files – XML data file

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Input Files – Inflow Files

n Discharges (water and sediment by size class) inputted into the upstream end of the reach and tributaries.

n Includes: ¨ 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.

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Input Files – Inflow Files (cont.)

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Input Files – Inflow Files (cont.)

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OUTPUT DATA

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Output Data.

n 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,

and ¨ output for a certain runoff event along a

section of the modeling reach (profiles).

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Output at a Certain Location and for a Certain Runoff Event n 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:

n type of data required, n location of required cross-section within modeling

reach, n dates of runoff events for which output is

requested, ¨ repeated for however many output cross-sections are

required.

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Output at a Location and a Runoff Event (Parameters)

Outputted parameter Value peak discharge 1 peak flow depth 2 peak stage 4 peak friction slope 8 sediment yield 16 cumulative sediment yield 32 change in bed elevation 64 cumulative change in bed elevation 128

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Output at a Location and a Runoff Event (Parameters cont.)

Outputted parameter Value lateral erosion 256 cumulative lateral erosion 512 cross-sectional geometry 1,024 in-bank top and bottom width 2,048 bank height 4,096

characteristic particle sizes 16,384 particle size distribution 32,768

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Time-Series Output at a Certain Location n 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.

n 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:

n type of data required, n the location of the required cross-section within the modeling

reach, n the start and end dates of the time series,

¨ repeated for however many output cross-sections are required.

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Time-Series Output at a Location (Parameters)

Outputted parameter Value discharge 1 velocity 2 flow depth 4 stage 8 flow area 16 flow top width 32 wetted perimeter 64 hydraulic radius 128 conveyance 256

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Time-Series Output at a Location (Parameters cont.)

Outputted parameter Value friction slope 512 energy head 1,024 Froude number 2,048 bed shear stress 4,096 sediment discharge (silt,sand,gravel,total) 8,192 cumulative sediment yield (silt,sand,gravel,total) 16,384 cumulative change in bed elevation 32,768 thalweg elevation 65,536 cumulative lateral erosion 131,072

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Time-Series Output at a Location (Parameters cont.)

Outputted parameter Value factor of safety 524,288 apparent cohesion 1,048,576 pore-water force 2,097,152 matric suction force 4,194,304 weight of failure block 8,388,608 weight of water on the bank 16,777,216 horizontal component of confining force 33,554,432 groundwater elevation 67,108,864 location of bank top 134,217,728

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Output for a Certain Runoff Event along a Section of the Modeling Reach n 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, ¨ dates of the storm events for which output is

requested for that particular profile, n repeated for however many output profiles are

required.

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Output for Runoff Events along a Profile (Parameters)

Outputted parameter Value peak discharge 1 peak stage 2 thalweg elevation 4 cumulative change in bed elevation 8 in-bank top width 16 bank height 32 sediment yield (silt,sand,gravel,total) 64 characteristic particle sizes 128