CMS-Flow/Weirs

Introduction

A weir is an overflow structure built across a river or an open channel, allowing water to flow over the top. Weirs are commonly used for flow and flooding control and salinity and sediment management. Weirs are also constructed as nearshore coastal structures, such as weir jetties, to control longshore sediment transport, stabilize channel morphology, and protect harbors and navigation channels. In coastal applications, weirs represent unique features of solid structures and it is necessary to incorporate the structures into coastal hydrodynamic and sediment transport modeling systems.

Usage of Weirs for CMS in the SMS

Early SMS versions (< 13.4)

Previous documentation (Link given below) described the formulation and implementation of Weir structures in CMS, detailing input requirements for SMS versions up to 11.2. This implementation required hand-manipulation of the CMS-Flow parameter files to add in lists of cells and option values.

• Implementation of Structures in the CMS: Part II, Weir

Future SMS versions (13.4.x)

SMS 13.4 CMS-Flow model coverages.

• A "Structures" coverage has been added beneath the CMS-Flow model option in SMS 13.4 and later. This one coverage will handle Weir structures as well as three other types: Rubble Mounds, Culverts, and Tide Gates.
• The "Structures" coverage will need to be applied to the CMS Simulation in order to export the appropriate cards to the parameter file.

Values needed by the CMS for each Weir structure are listed in the table below. If there is a user-definable option in the dialog for the user to enter a value, the word 'Dialog' is shown in column 2, otherwise the words 'No dialog' are written.

List of weir structure parameters

Number of Cells	No dialog
Cell IDs	No dialog
Distribution Coefficient	Dialog
Orientation of Weir	Dialog
Type of Weir	Dialog
Flow Coefficient Bay to Sea	Dialog
Flow Coefficient Sea to Bay	Dialog
Elevation of Weir	Dialog
Weir Calculation Method	Dialog

SMS will handle the assignment of the appropriate values for Number of cells and Cell IDs.

CMS-Flow specific information for SMS 13.4+

The parameters/selections for each Weir structure polygon will be exported to the ‘.cmcards’ file in the form of a block of values.  This implementation has been confirmed to work with CMS 5.3.12 and later.

• The Weir parameter cards needed for each structure are added to a block with a corresponding BEGIN/END statement for each weir are listed in the table below.
• For readability and to be consistent with other cards in the .cmcards file, all values should start in column 36.

Cardname	Indent 2 spaces?	Type of value written	Notes
WEIR_STRUCT_BEGIN	NO	N/A
CELL_IDS	YES	<int> <multiple int>	Total number of cells (n) followed by a list of all cell ids (from 1 to n).
DISTRIBUTION_COEFFICIENT	YES	<real>
ORIENTATION	YES	1, 2, 3, or 4	Direction of Sea side: 1= North, 2= East, 3= South, 4= West
TYPE	YES	1 or 2	1= Sharp-crested, 2=Broad-crested
FLOW_COEFF_FROM_BAY	YES	<real>
FLOW_COEFF_FROM_SEA	YES	<real>
CREST_ELEVATION	YES	<real>	Positive is upward
METHOD	YES	1 or 2	1= Approach 1, 2= Approach 2 (see literature)
WEIR_STRUCT_END	NO	N/A

An example weir implementation is shown below. Line comments are preceded by a '!'.

WEIR_STRUCT_BEGIN
  CELL_IDS                           8   16864 16865 16866 16867 16868 16869 16870 16871
  ORIENTATION                        3   !1= North, 2= East, 3= South, 4= West
  FLOW_COEFFICIENT_FROM_BAY          0.05 
  FLOW_COEFFICIENT_FROM_SEA          0.05
  CREST_ELEVATION                    -0.22
  METH                               2   !1= Approach 1, 2= Approach 2
WEIR_END

Last update 9/25/2024
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