There is a choice of two polylines that allow for linear adjustments to the 2D Grid: Breakline and Road Centerline. Each grid cell that is intersected by a 2D Polyline is updated. To increase the number of cells updated, consider using two parallel Breakline elements. For roads, simply increase the Width attribute of a Road Centerline element or option to model the grid adjustment as a Road (2D Polygon) instead.

• Breakline – allows user to override the surface elevation of the corresponding grid cells.
• Road Centerline – supports modeling an impervious roadway, footpaths and the like as a polyline.

• Width: The overall width of the road, centered upon the polyline.
• Elevation Adjustment Operation: Lets you add or subtract a relative value from the current surface elevations of the corresponding grid cells.
• Elevation Adjustment: Is the amount of change in elevation that will be added to, or subtracted from, the current surface elevation of each matching grid cell. The operation of “Set To” will directly assign this value as the new surface elevation for each intersected grid cell.
• Impermeability Fraction Adjustment Type: Lets you select how the value for Impermeability Fraction that will be overridden for the corresponding 2D grid cells; using a User Defined amount or a value from a referenced catalog item.
• Impermeability Fraction: When the Impermeability Fraction Adjustment Type is User Defined, enter the value to assign to each of the 2D grid cells contained by this area.
• Manning’s n Adjustment Type: Lets you select how the value for Manning’s n will be assigned to each grid cell. Either a User Defined value, or referencing a value defined within a catalog item.
• Manning’s n: The value for overland roughness that will be assigned to the corresponding portion of the computational grid. The default is 0.013.
• SCS CN Adjustment Type: Lets you select how the value for SCS Curve Number will be provided; using a User Defined amount or a value from a referenced catalog item.
• SCS CN: Applicable when the SCS CN Adjustment Type is User Defined, enter the value that you wish to allocate to the corresponding 2D grid cells. The default value is 98.