Evaluation of Drainage Management Software
The following sections outline the input requirements, computational methods and output options available with this software. The package was run through various tests for comparison with MTO drainage management practices provided by the MTO Drainage Management Manual (1997). A summary of out results and the requirements for using this software for MTO design, analysis or approvals is provided.The following sections outline the input requirements, computational methods and output options available with this software. The package was run through various tests for comparison with MTO drainage management practices provided by the MTO Drainage Management Manual (1997). A summary of the evaluation results and the requirements for using this software for MTO design, analysis or approvals is provided.
Use in MTO Drainage Management Practices:
Model Capabilities
What does it do?
HECRAS is a hydraulic modelling application developed by the US Army Corps of Engineers to simulate water surface profiles for steady and gradually varied flow in open channel watercourses. The application will estimate water surface elevation and related output along a channel reach under subcritical, supercritical ormixed flow regimes. The program is capable of modelling complicated networks with multiple reaches and tributaries. Flow through culverts, bridges, weirs and gated spillways is accommodated. Levees, blocked obstructions, lids and ineffective flow areas can also be modelled as can ice jam and debris flow conditions. The program includes an option for estimating scour at bridges for design.
With extensive input data manipulation tools and output options, HECRAS is an appropriate design and/or analysis tool.
Flow Definitions
 Steady:
 A flow condition for which the flow rate at a given point remains constant with time.
 Subcritical:
 A flow condition where the velocity is less than the critical velocity and the depth is greater than the critical depth.
 Supercritical:
 A flow condition where the velocity is less than the critical velocity and the depth is less than the critical depth.
 Critical Depth:
 The depth in a channel for which the specific energy is a minimum.
How does it do it?
Input data is entered through a series of input tables/windows. A watercourse is represented by a series of cross sections. Various tools are included in the program to facilitate inputting the geometric data (Geometric Data (Table 1)) including cross section interpolation, GIS/CADD file importing and graphical and tabular editors. The user then inputs design details of any structures in the watercourse (Culverts and Bridges (Table 2), Weirs (Table 3), Gated Spillways (Table 4)). The steady flow data (Steady Flow Data (Table 5)) is then entered followed by the data for at least one set of boundary condition. The program uses the standard step method to balance the energy equation or the momentum equation at each crosssection under the given flows based on the given depth of flow at the boundary crosssection. Optional computational methods are available throughout the program.
File Management
HECRAS includes comprehensive file management capability. A series of files are saved as a "project". A project consists of:
 Project file (title of the project; the units system of the project; a list of all the files that are associated with the project; and a list of default variables that can be set from the interface),
 Plan files (description and short identifier for the plan; a list of files that are associated with the plan; and a description of all the simulation options that were set for the plan),
 Run files (the necessary data to perform the computations that are requested by the associated file plan),
 Output files (all the computed results from the requested computational engine),
 Geometry files ( all of the geometric data for the river system being analyzed) and
 Steady Flow Data files (the number of profiles to be computed; flow data; and boundary conditions for each reach).
Output Options
HECRAS provides extensive options to view detailed information summaries and results through tables, plots, or curves. The following illustrates the available output and input options. (Select any of the hyperlinks to view a graphical representation of the information)
Figure #  Tabular Output: 

01  Culverts  provides detailed culvert information. 
02  Bridge  provides detailed bridge information. 
03  Flow Distribution  provides information of flow distribution output at any cross section. 
04  Profile  displays hydraulic variables for each cross section. 
Graphical Output:  
05  Cross section plots  displays XY perspective of a cross section. 
06  Profile plots  displays variables used for computations. 
07  Rating Curve  displays various graphs. 
08  XYZ Perspective Plot  provides a 3D view of the river system. 
Input Summary:  
09  Manning's n and k values  displays Manning's n and roughness heights values for each cross section. 
10  Reach Lengths  provides the cross section between reach lengths. 
11  Contraction & Expansion Coefficients  provides contraction & expansion coefficients for each cross section. 
12  River Stationing  displays cross section river stationing. 
13  Ice Cover  displays detailed ice cover information. 
Functionality
Experience Required
A high level of understanding of open channel hydraulic processes is required for appropriate definition of input parameters, selection of calculation options and interpretation / remediation of output errors, notes and warnings.
Using the program
Use of the program itself requires basic familiarity of window based programs. The program is easy to navigate and has extensive on line help and user manuals.
Comparison to Previous Version
HECRAS is based on the previous hydraulic modelling application, HEC2 developed by the US Army Corps of Engineers. Comprehensive graphical user interface functionality, improved file management capabilities and extensive output options have been added making it a much easier program to navigate and report from. As well, several changes have been incorporated in the modelling approach. These are summarized below:
Cross Section Conveyance Calculations
In both programs, crosssections are subdivided into multiple segments and total conveyance is calculated as the sum of the conveyance in each segment. In HEC2, the crosssections are subdivided at each coordinate in the overbanks and the main channel is one segment. In HECRAS the default is to subdivide the crosssections at each coordinate where there is a change in nvalues. HECRAS has the option to perform calculations using the HEC2 method.
Critical Depth Calculations
HEC2 has only one method of calculating critical depth, which is similar to the"parabolic" method in HECRAS. HECRAS has two methods: a "parabolic" method (default) and a "secant" method. A smart feature in HECRAS is it automatically switches to the secant method if the parabolic method does not converge. Critical depth answers from the two programs could therefore, be significantly different. HECRAS, in general, will provide the more accurate answer.
Bridge Hydraulic Computations  Special Bridge Method
The HEC2 special bridge routines use a trapezoidal approximation for low flow. The HECRAS program uses the actual bridge opening geometry for all of the low flow methodologies.
For low flow calculations HEC2 combines all the pier widths and uses a single equivalent pier width placed at the centre of the trapezoid. HECRAS evaluates the impact of each pier individually.
HEC2 assumes a fully submerged condition for pressure flow calculations while HECRAS uses the equation for fully submerged flow conditions as well as a sluice gate equation when only the upstream end of the bridge is submerged. (For further detail, please refer to C5 of the HECRAS manual)
When importing a HEC2 special bridge data into HECRAS, the user must input the low chord information to define the actual opening.
When defining the crosssection at a bridge, in HEC2, the user is required to input stations that followed along the ground of the LOB, then across the bridge deck/roadway embankment; and then along the ground of the ROB. In HECRAS, the user only needs to define the blocked out area that is not part of the ground.
Bridge Hydraulic Computations  Normal Bridge Method
In HEC2 pier information is either entered as part of the bridge table (BT data) or the ground information. If the user stays the energy based methods in HECRAS the results will be about the same. If the user wishes to use either the Momentum or Yarnell methods for low flow, they must first delete the pier information in HECRAS. If this is not done, HECRAS will not know about the pier information, and will therefore incorrectly calculate the losses with either the Momentum or Yarnell methods.
HEC2 Normal bridge method utilizes six user input cross sections. HECRAS uses four user input cross sections in the vicinity of the bridge and automatically formulates 2 internal crosssection. When importing HEC2 data, depending on how the cross sections were defined in HEC2, HECRAS may end up with extra sections and thus calculate additional losses.
Stationing of the bridge table in HEC2 had to match stations on the ground. This is not required in HECRAS.
Culvert Hydraulic Computations
HEC2 can only perform culvert calculations for box and circular culvert shapes. HECRAS can handle the following shapes: box; circular pipe; semicircle; arch; pip arch; vertical ellipse; horizontal ellipse; low profile arch; and high profile arch.
HECRAS also has the ability to mix the culvert shapes, sizes, and all other parameters at any single culvert crossing. In HEC2 the user is limited to the same barrel shape and size.
Floodway Encroachment Computations
Floodway Encroachment capabilities in HECRAS were adapted from those in HEC2. HECRAS, similar to HEC2, has five optional methods for specifying flood plain encroachment. Methods 13 are basically the same in the 2 models. The following is a list of the differences.
HECRAS has an additional capability of allowing the user to specify a left and right encroachment offset.
HECRAS method 4 will locate the final encroachment to an accuracy of 0.01 feet, while the HEC2 method 4 uses a parabolic interpolation method between the existing cross section points and therefore does not always find the encroachment station as accurately.
Method 5 in HECRAS is a combination of HEC2's methods 5 and 6. HECRAS can be used to optimize for a change in water surface, a change in energy, or both parameters at the same time.
At bridges and culverts, the default in HECRAS is to perform the encroachment, while in HEC2 the default is not to perform the encroachment.
At bridges where the energy based modelling approach is being used HECRAS will calculate the encroachment for each of the cross sections through the bridge individually. HEC2 will take the encroachments calculated at the downstream side of the bridge and fix those encroachments stations the whole way through the bridge.
In HEC2, if the user specifies a fixed set of encroachments on the X3 record, this would override anything on the ET record. In HECRAS, when the data is imported the X3 record encroachment is converted into a blocked obstruction. Therefore information on the ET record will be used in addition to the blocked obstruction.
New Computational Features in HECRAS
HECRAS can perform subcritical, supercritical, or mixed flow regime calculations all in a single execution of the program.
HECRAS has the ability to perform multiple bridge and/or culvert openings at the same road crossing.
At bridges, the user has the ability to use a momentum based solution for classA , B, and C low flow. In HEC2 the momentum equation was used for class B and C flow, and requires the trapezoidal approximation. The HECRAS momentum solution also takes into account friction and weight forces that HEC2 does not.
HECRAS can model single reaches, dentritic stream systems, or fully looped networked systems. HEC2 can only do single reaches and a limited number of tributaries (up to three stream orders).
At stream junctions, HEC2 has the ability to perform the calculations with either an energy based method or a momentum based method. HEC2 only has the energy based method.
HECRAS has the following new cross section properties: blocked ineffective flow areas; normal ineffective flow areas can be located at any station; blocked obstructions; and specification of levees.
In HECRAS you can add a maximum of 500 cross sections points while in HEC2 you had a maximum of 100 cross section points.
HECRAS has the ability to perform geometric cross section interpolation. HEC2 interpolation is based on a ratio of the current cross section and a linear elevation adjustment.
HECRAS has an improved flow distribution calculation routine.
General Considerations
The following notes should be considered as appropriate when using this program on MTO projects or projects requiring approavl by MTO.
 There is not always consistency between DMM and HECRAS variable naming conventions therefore special care should be taken in user input of coefficients etc. There is sufficient detail in the user manual to make appropriate modifications.
 For some culverts, HECRAS will provide a headwater depth for inlet control that is lower than that produced by use of DMM nomographs. The difference increases the greater the flow but was found to be within 5% for flow rates within normal design criteria. For analysis of existing culverts that are significantly undersized, this difference may need to be considered.
 If a culvert is flowing full HECRAS discards the inlet control solution and uses the outlet control solution as the governing energy gradeline
 When analysing more than 13 profiles in a run, the titles on the output scramble.
 The program can terminate successfully but not provide a valid solution. Careful attention should be given to warnings and notes.
 The program is applicable only to scenarios of steady, gradually varied flow (except at hydraulic structures) that is one dimensional and where river channels have small slopes (less than 1:10).
Use in MTO Drainage Management Practice
Overall, the use of this model is acceptable by MTO. The method and parameter options available throughout the program allow for compliance with the methodologies and parameters covered in the Drainage Management Manual.
Minimum Requirements for Inclusion in Report
This section provides some guidance to designers, analyst and reviewers on the type of information and minimum requirements for reporting the results of a HECRAS analysis. This by no means should be considered a comprehensive list of the information included in a drainage report.
Summary of input parameters:
Due to the fact that data input into HECRAS is done through a series of input windows, no printable input file can be provided (as is the case with HEC2). Therefore, summary tables should be provided listing the values of the various coefficients used in the analysis and which computational methods were chosen. As well, any variance from accepted practise should be explained.
When reviewing a report that includes a HECRAS analysis, careful attention should be given to the review of input parameters. In HECRAS, the user can set all parameters. However, some parameters are given default values (Parameters with Program Default Values (Table 6)). Parameters that have been left at their default values should be noted and an assessment made to whether this is appropriate. Refer to the DMM for values applicable to Ontario where available. The HECRAS manual also provides guidelines.
As well as input parameters, HECRAS provides various computational method options. Note which computational methods have been left at their default (Computational Methods (Table 7)) and assess whether this is appropriate. Refer to the DMM for methods applicable to Ontario where available. The HECRAS manual also provides guidelines.
Tabular and Graphical Output
The report should include both tabular and graphical output showing the water surface profile for the different flow rates assessed (2100 year) in both "profile" and "crosssections" views, at a minimum. HECRAS provides extensive output options therefore any recommendations from the analysis should be supported by including additional relevant output.
The output should have logical consistency between crosssections and whether the watercourse has been adequately represented.
The user/reviewer should ensure that a HECRAS analysis is valid. The program is applicable only to scenarios of steady, gradually varied flow (except at hydraulic structures) that is one dimensional and where river channels have small slopes (less than 1:10).
Summary of Calculation Tolerances
HEC_RAS relies on tolerance values to determine convergence of the numerical analysis. These values can be set by the user with a preset range. The accuracy of the results will depend on the tolerance values entered. Therefore the table summarizing calculation tolerances should be provided.
HECRAS defaults to a set of calculation tolerances (Calculation Tolerances (Table 8)) that will allow the program to converge on a solution in a reasonable time based on the recommended hardware. If the user has changed the default tolerances, the rationale should be provided for this change.
Summary of errors, warnings and notes
The model can provide an extensive array of messages to notify the user to pay attention to specific results. The messages can be either error messages, warnings, or notes.
Error messages (Sample Error Messages (Table 11)) will only occur when the program cannot complete a run. Generally this is due to missing data. If the program did not crash, you can view the error in the summary of Errors, Warnings, and Notes. If the program crashed, you can view a log file that will give you a detailed computational summary of the steps before it crashed. A completed analysis should not include error messages.
A summary of errors, warnings and notes associated with each scenario analyzed should be provided. If some warnings could not be resolved a justification of why the analysis is acceptable must be included. This should include an assessment of such warnings on the results of the analysis.
A warning message (Common Warning Messages (Table 9)) will occur when steady flow computations have been completed and the program has detected problems that may or may not require the user's attention. For example:
The program will often assume critical depth or minimum error depth when the energy equation cannot be determined. These are not valid solutions and the effect on the overall profile should be assessed.
Warning messages may also indicate the geometric data does not adequately represent the watercourse. Messages related to large changes in conveyance, velocity or energy might indicate that more cross sections are needed to accurately estimate energy losses between sections.
Therefore when reviewing the HECRAS output careful attention should be given to warnings. The program may "terminate successfully" and compile all output but not provide a valid solution. Note messages (Common Note Messages (Table 10)) inform the user about how the program is performing the computations. The notes should be reviewed to assess whether the way the program is performing the computations is as intended and is an accurate representation of the scenario being modelled.
Summary Evaluation
Go to the HTML version of the Summary Evaluation of HECRAS, or download the PDF version (39 KB)
To view PDF files, you will require Adobe Acrobat Reader.
Tables
Input Parameters  Geometric Data (Table 1)
Parameter  Purpose 

Crosssection station & elevation  Defines channel shape 
Reach lengths (left,right,channel)  Defines path of watercourse 
Manning's n values  Used for friction loss calculations 
Expansion / Contraction coefficients  Used for expansion or contraction loss calculations 
Ineffective Flow areas  Defines the flow area 
Levees  Defines the flow area 
Blocked obstructions  Defines the flow area 
Thickness of ice  Used for ice jam calculations 
Manning's n for ice  Used for ice jam calculations 
Ice cover specific gravity  Used for ice jam calculations 
Internal friction angle of jam  Used for ice jam calculations 
Coefficient K1  Used for ice jam calculations 
Ice jam porosity  Used for ice jam calculations 
Max mean velocity under ice  Used for ice jam calculations 
Input Parameters  Culverts and Bridges (Table 2)
Parameter  Purpose 

Bridge Data (and Culvert Deck)  
Station ,high & low cord elevations  Defines bridge opening and weir flow 
width  
Distance to upstream station  Locates bridge/culvert on watercourse 
Centreline elevation and station of piers  Defines bridge opening 
Skew angle of piers  Defines bridge opening 
Station & elevation of abutments  Defines bridge opening 
Skew angle of abutments  Defines bridge opening 
Upstream / Downstream embankment slopes  Defines bridge opening 
Weir coefficient (for deck)  For overtopping calculation 
Max submergence  Used for conveyance calculations 
Minimum weir flow elevation  For overtopping calculation 
Pressure Flow Cd :

Used for conveyance calculations 
Coefficient of Drag  Used for conveyance calculations 
Pier Shape K  Used for conveyance calculations 
Weir Crest Shape  Used for conveyance calculations 
Culvert Data  
Shape  Defines culvert 
Diameter (or rise & span )  Defines culvert 
Length  Defines culvert 
Chart #  Refers to Federal Highway Admin. HDS 5 (1985) 
Scale #  Refers to Federal Highway Admin. HDS 5 (1985) 
Entrance loss coefficient  Used to calculate headloss for outlet control 
Exit loss coefficient  Used to calculate headloss for outlet control 
Culvert 'n' value  Used to calculate headloss for outlet control 
Centreline stations  Locates culvert on watercourse 
# of Barrels  For total conveyance 
Upstream & Downstream invert  Used to calculate slope 
Input Parameters  Inline Weir (Table 3)
Parameter  Purpose 

Distance to upstream station  Locates inline weir on watercourse 
Station , elevation  Defines weir geometry 
Upstream & downstream embankment sideslope  Defines weir geometry 
width  Defines weir geometry 
Weir Coefficient  Used for conveyance calculations 
Weir Crest Shape  Used for conveyance calculations 
Input Parameters  Inline Gated Spillway (Table 4)
Parameter  Purpose 

Height  Defines gated spillway geometry 
width  Defines gated spillway geometry 
Invert and centreline stations  Defines gated spillway geometry 
Discharge coefficient  Defines gated spillway geometry 
Gate Type  Used for conveyance calculations 
Trunnion Exponent  Used for conveyance calculations 
Opening Exponent  Used for conveyance calculations 
Head Exponent  Used for conveyance calculations 
Orifice Coefficient  Used for conveyance calculations 
Trunnion Height  Used for conveyance calculations 
Weir Coefficient  Used for conveyance calculations 
Weir Crest Shape  Used for conveyance calculations 
Steady Flow Data (Table 5)
Parameter  Purpose 

Steady flow rate(s) analized  Sets flow rates to be analyzed 
Starting water surface elevation  Boundary condition to start calculations from 
Flow regime  Determines bakcwater or frontwater calculations, or both 
Input Parameters with Program Default Values (Table 6)
Parameter  Default Value 

Geometric Data  
Crosssection station & elevation  May use interpolation tool 
Reach lengths (left,right,channel)  No default 
Manning's n values  No default 
Expansion / Contraction coefficients 
Expansion = 0.1
Contraction = 0.3 
Ineffective Flow areas  At left and right overbanks 
Levees  At left and right overbanks 
Blocked obstructions  At left and right overbanks 
Thickness of ice  No default 
Manning's n for ice  No default 
Ice cover specific gravity  0.916 
Internal friction angle of jam  45 degrees 
Coefficient K1  0.33 
Ice jam porosity  0 
Max mean velocity under ice  1.524 m/s 
Bridge Data (and Culvert Deck)  
Station ,high & low cord elevations  No default 
width  No default 
Distance to upstream station  No default 
Centreline elevation and station of piers  No default 
Skew angle of piers  No default 
Station & elevation of abutments  No default 
Skew angle of abutments  No default 
Upstream / Downstream embankment slopes  0 
Weir coefficient (for deck)  1.44 
Max submergence  0.95 
Minimum weir flow elevation  Lowest upstream highcord 
Pressure Flow Cd :

0.8 
Coefficient of Drag  No default 
Pier Shape K  No default 
Weir Crest Shape  Broadcrested 
Culvert Data  
Shape  Circular 
Diameter (or rise & span )  No default 
Length  No default 
Chart #  1  Concrete Pipe Culvert 
Scale #  1  Square edge entrance with headwall 
Entrance loss coefficient  No default 
Exit loss coefficient  1.0 
Culvert 'n' value  No default 
Centreline stations  No default 
# of Barrels  No default 
Upstream & Downstream invert  No default 
Inline weir data  
Distance to upstream station  No default 
Station , elevation  No default 
Upstream & downstream embankment sideslope  0 
width  No default 
Weir Coefficient  1.66 
Weir Crest Shape  Braodcrested 
Inline gated spillway data  
Height  No default 
width  No default 
Invert and centreline stations  No default 
Discharge coefficient  No default 
Gate Type  Sluice (Radial) 
Trunnion Exponent  0 (0.16) 
Opening Exponent  1 (0.72) 
Head Exponent  0.5 (0.62) 
Orifice Coefficient  0.8 
Trunnion Height  No default 
Weir Coefficient  3 
Weir Crest Shape  Broadcrested 
Default Computational Methods (Table 7)
Computational Method  Default 

Bridge Calculation Options  
Add friction and or weight component to momentum equation  Add friction component 
Set default location for critical depth during class B flow  Inside bridge at upstream end 
Set Criteria for computing pressure flow  Upstream energy gradeline 
Properties of ice jam through bridge  No ice jam computed 
Approach for low flow calculations  Energy equation 
Approach for high flow calculations  Energy equation 
Floating debris  none 
Culvert Calculation Options  
Solution criteria  Highest upstream energy gradeline 
Junction Options  
Computation mode  Energy equation 
Steady Flow Calculation Options  
Method for calculating average conveyance  At break in n values 
Method for calculating friction slope  Average conveyance 
Method for calculating critical depth  Parabolic method 
Default Calculation Tolerances (Table 8)
Factor  Tolerance 

Water surface calculation tolerance  .003 
Critical depth calculation tolerance  .003 
Maximum # of iterations  20 
Maximum difference tolerance  .1 
Flow Tolerance factor  .001 
Common Warning Messages (Table 9)
Warning Message  Explanation 

The velocity head has changed by more than 0.5 ft (0.15m). This may indicated the need for additional cross sections.  Implies there has been a significant change in the average velocity between this section and the section immediately downstream. This could reflect a significant change in slope or a dramatic change in crosssection shape. The user needs to assess whether the loss is appropriate. More sections may be supplied to allow the program to more accurately calculate energy losses 
The energy loss was greater than 1.0 ft (0.3m) between the current and previous cross section.  As a default, the program uses an average conveyance equation to determine energy loss. Actual rate of energy loss is usually not linear. Therefore if the cross sections are too far apart, an appropriate energy loss will not be determined. This warning is to flag a large energy loss and the user needs to assess whether the loss is appropriate. More cross sections or an alternate method to compute average friction slope may be warranted. May also indicate a misrepresentation of the effective flow area of the crosssection. 
The energy equation could not be balanced within the specified number of iterations. The program used critical depth for the water surface and continued on with the calculations.  During the computation of upstream water surface elevation the program could not compute energy losses to provide a flow depth in the specified flow regime. This may be due to poor cross section data, cross sections to far apart, wrong flow regime specified or the program is having trouble balancing a water surface elevation very close to the top of a levee or ineffective flow area. 
During standard step iterations, when the assumed water surface was set equal to critical depth, the calculated water surface came back below critical depth. This indicates that there is not a valid subcritical answer. The program defaulted to critical depth. 
This warning may be associated with too long of reach lengths between crosssections or the fact that the flow analysis should be performed in the supercritical or mixed flow regime. 
Divided flow computed for this crosssection 
Flow is occurring at more than one portion o the cross section. User must verify if this is possible. 
The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7 or greater than 1.4. This may indicate the need for additional cross sections. 
Implies that the crosssectional areas are change in dramatically between the two cross sections and additional cross sections may be added to more accurately calculate expansion and contraction losses. 
The parabolic search method failed to converge on critical depth. The program will try the cross section slice/secant method to find critical depth  The parabolic search method is the default method to calculate critical depth. If this method fails the program will automatically try the secant method and provide this warning. The user should examine closer the critical depth that was determined to ensure that the program supplied a valid answer 
Common Note Messages (Table 10)
Note Message  Explanation 

Hydraulic Jump has occurred between this cross section and the previous upstream section.

Provides the location of a Hydraulic jump 
Program found supercritical flow starting at this cross section.

Provides the location of supercritical flow 
The energy method has computed a class B profile.  Whenever Class B low flow is found to occur the modeller should perform the analysis in the mixed flow regime.

The downstream water surface is below the minimum elevation for pressure flow. The sluice gate equations were used for pressure flow.  The sluice gate equation was used because the water surface elevation at the river station immediately below the bridge was less than the lowest value of the low cord for the bridge.

The downstream water surface is above the minimum elevation for pressure flow. The orifice equations were used for pressure flow.  The orifice equation was used because the water surface elevation at the river station immediately below the bridge was higher than the lowest value of the low cord for the bridge.

For the cross section inside the bridge at the upstream end, the water surface and energy have been projected from the upstream cross sections. The selected bridge modeling method does not compute answers inside the bridge. 

For the cross sections inside the bridge at the downstream end, the water surface is based on critical depth over the weir. The energy has been projected. 

Multiple critical depths were fond at this location. The critical depth with the lowest, valid, energy was used.  When the secant method is used to determine critical depth, this note will appear if more than one minimum energy point is found. This may occur for cross sections with large, flat overbanks. The user should examine closer the critical depth that was determined to ensure that the program supplied a valid answer. 
The momentum method has computed a class B profile.  Whenever Class B low flow is found to occur (ie a hydraulic jump is assumed to have occurred) the modeller should perform the analysis in the mixed flow regime. 
The culvert inlet is submerged and the culvert flows full over part or all of its length. Therefore, the culvert inlet equations are not valid and the supercritical result has been discarded. The outlet answer will be used 
Sample Error Messages (Table 11)
Errors Message  Explanation 

Error  Incomplete data, the following errors were found:
River: "Mimico Creek" Reach: "Tributary" RS:7.0  no Station Elevation Data. 
Station Elevation Data is missing. 
Error  Incomplete data, the following errors were found:
River: "Mimico Creek" Reach: "Tributary" RS:7.0  Main channel length not set. 
Main channel length of cross section is incomplete. 
Error  Incomplete data, the following errors were found:
River: "Mimico Creek" Reach: "Tributary" RS:6.97  Deck station data is not in increasing order on upstream side, stationing needs to maintain (vertical walls) or increase. 
Deck station numbers are missing 
Error  Incomplete data, the following errors were found:
River: "Mimico Creek" Reach: "Tributary" RS:7.0  No Manning's n data or friction height k set. 
Manning's n data for a cross section is missing. 
Error  Incomplete data, the following errors were found:
River: "Mimico Creek" Reach: "Tributary" RS:6.97  Culvert: Culvert #1 rise not set.  Culvert: Culvert #1 Length not set.  Culvert: Culvert #1 Distance from upstream cross section to culvert inlet not set.  Culvert: Culvert #1 Manning's n value not set.  Culvert: Culvert #1 entrance loss coefficient not set.  Culvert: Culvert #1 exit loss coefficient not set.  Culvert: Culvert #1 upstream invert elevation not set.  Culvert: Culvert #1 downstream invert elevation not set.  Culvert: Culvert #1 centreline stations not set so #Barrels = 0. 
Culvert Data is incomplete. 