 16 Aug 2022
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CES Section
 Updated on 16 Aug 2022
 4 Minutes to read

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CES (Conveyance Estimation System) Section offers an alternative method of calculating conveyance for a River Section, using the DepthIntegrated ReynoldsAveraged NavierStokes Method.
Data
Field in Data Entry Form  Description  Name in Datafile 

Section Label  Label1  Node label for cross section 
First Spill  Label2  First spill label 
Second Spill  Label3  Second spill label 
Distance to Next  dx  Distance to next cross section (a zero specifies the end of the reach) (m) 
Reach Slope  slope  slope estimate (m/m) 
Default Sinuosity  def_sinuosity  default sinuosity (m/m) 
 n_{1}  Number of ensuing data lines 
x  c  Cross chainage (m) 
y  z  Elevation of bed (mAD) 
Bank Marker  bank  One of the following:

Sinuosity  sinuosity  Sinuosity of the river between the current left bank and the next right bank, if different from the default sinuosity. Only used if there is a left bank marker on the same line 
Marker  lrb  The words LEFT', 'RIGHT', or 'BED' specifying the left bank top, right bank top and thalweg. These are for plotting purposes in the Flood Modeller UI only, and are not used in the calculation. Defaults are to the first, last and minimum levels specified respectively. A 'D' marker may also be used in this field to specify the lateral limits of dredging for the mobile bed sediment transport module, 1D Sediment Transport solver 
Easting  easting  Easting of point 
Northing  northing  Northing of point 
n/a  n_{2}  Number of ensuing roughness zone lines 
Zone Name  rz  Roughness zone name 
Roughness 
 Roughness in zone 
Notes
 The bank markers must appear in pairs separated only by lines without bank markers, as follows:
 LI must be followed by RO
 LO must be followed by RI
 LS must be followed by RS
 RO must be preceded by LI
 RI must be preceded by LO
 RS must be preceded by LS
Theory and Guidance
The CES Section offers a new, alternative method of calculating conveyance for a River Section. The approach uses the DepthIntegrated ReynoldsAveraged NavierStokes Method.
For advice on setting up CES sections e.g. positioning of bank markers, and the advanced options that are available, please refer to Conveyance User Manual.
Conveyance is calculated at a given water level through calculating the lateral unit flow rate q (m^{2}s^{1}) distribution, integrating q across the section to determine the total flow rate Q (m^{3}s^{1} ) and then dividing by the square root of the longitudinal slope S to obtain the total section conveyance K (m^{3}s^{1}) i.e.


Here, S is approximated from the reachaveraged longitudinal bed slope. The unit flow rate distribution is based on the depthintegrated ReynoldsAveraged NavierStokes [RANS] equation for flow in the streamwise direction, with empirical closure for the estimation of certain depthintegrated stresses, i.e.

1.0 = s (inbank) 1.0 £ s £ 1.015 (overbank)
s > 1.0 (inbank) s > 1.015 (overbank) where: g is the gravitational acceleration (m.s2) H is the local depth normal to the channel bed (m) h is the surface water level (m) y is the lateral distance across the channel (m) b is the coefficient to account for influence of local bedslope on the bed shear stress s is the reachaveraged sinuosity 
For solution of Equation (2), the crosssection is discretised laterally (Figure 1) into 100 divisions (default value) and there are 25 (default value) depths for solution.
Equation (2) has four calibration coefficients: the local friction factor f, the dimensionless eddy viscosity l , the secondary flow parameter G and the coefficient of meandering C_{uv}. For detailed descriptions of the models for estimating these calibration coefficients see DEFRA/EA (2003, 2004a & 2004b)[1]. Variation of the calculation parameters is permissible. Advice on how these parameters may be varied to optimise model predictions is available in DEFRA/EA (2004b).
[1] DEFRA/EA, 2003, Reducing Uncertainty in River Flood Conveyance, Interim Report 2: Review of Methods for Estimating Conveyance, Project W5A 057, HR Wallingford Ltd., United Kingdom.
DEFRA/EA, 2004, Reducing Uncertainty in River Flood Conveyance, Interim Report 3:Further Validation of stagedischarge prediction, application within Flood Modeller and Development and Statement of Advice on Uncertainty, Project W5A 057, HR Wallingford Ltd., United Kingdom.
EA/DEFRA, 2004b, Reducing Uncertainty in River Flood Conveyance: Conveyance Manual, Project W5A 057, HR Wallingford Ltd., United Kingdom.
Datafile Format
General Parameters
The general parameters section of the DAT file contains an absolute path to the roughness file:
Line 1  Title  Up to 40 characters
Line 2  #REVISION#1
Line 3  N_{nodes} Fr_{min} Fr_{max }D_{min }S_{tol}
Line 4  T Q_{tol} H_{tol} Θ P α η
Line 5  RAD FILE
Line 6  Absolute path to roughness file
Line 7  END GENERAL
CES Data
Items in square brackets are optional. Items in capitals are keywords.
Line 1  RIVER [comment]
Line 2  CES SECTION #REVISION#1
Line 3  Label1 [Label2] [Label3] [Lateral 1] [Lateral 2] [Lateral 3] [Lateral 4]
Line 4  dx [yshift] slope def_sinuosity
Line 5  n_{1}
Line 6 to Line 5+n_{1} c z [bank] [sinuosity] [lrb] [easting] [northing]
Line 6+n_{1} n_{2}
Line 7+n 1 to Line 6+ n_{1 }+ n_{2 } c rz
Notes
 Line 3 is in fields of either 8 or 12 characters, depending on a parameter set globally for the model. Lines 4 and 5 are in fields of 10 characters. The section data lines are F10.0, F10.0, A10, F10.0, A10, F10.0, F10.0. The roughness zone lines are F10.0, A.