![]() Ground surface elevations are extracted for the overbanks portion of the cross sections from the RAS Terrain layer.Įlevation Profiles from Terrain (Channel Only) Ground surface elevations are extracted from the RAS Terrain layer for the entire cross section.Įlevation Profiles from Terrain (Overbanks Only) Roughness coefficients are extracted based on the intersection of the Mannin's n layer and the cross section layer. A default "trigger" elevation is computed based on the highest elevation extracted from the Terrain layer at the intersection points. The begin and end location for blocked obstructions are computed based on the intersections of the Blocked Obstructions layer and the Cross Section layer. The begin and end location for ineffective flow area are computed based on the intersections of the Ineffective Flow Areas layer and the Cross Section layer. The Left and Right Overbank reach lengths are computed as the distance between cross sections based on the Flow Path Lines layer. The Channel reach length is computed as the distance between cross sections along the River line. The distance between the cross sections in stored as the Reach Length property. The intersection of the Bank Lines layer and Cross Section layer is used to compute the Bank Station locations for each cross section. This distance can be "overwritten" using the River Station Markers layer. The intersection of the River layer and the Cross Sections layer is used to compute the River Station based on the distance from the most downstream point on the river reach line. ![]() A summary of the update options along with description of the layers need to compute the properties is provided below. Properties can be updated at any time using the Update options on per cross section basis or doing the entire layer at once. XS PropertiesĬross section properties are assigned to the cross section as the cross section location lines are laid out. Individual or multiple selected cross sections can be updated by left-clicking on the cross section and choosing from the Update menu options. If you would like the cross section properties to automatically update, see the RAS Geometry Properties for the editing session as discussed in Updating Geometry section. To update the elevation profile data in subsequent sessions, you will need to manually update it through the menu system – right-click on the Cross Section layer and select Update and the property you would like to update, as shown the figure below. This may break linkages with other RAS data that depends on the river station.Ĭross section data will only be automatically updated during a cross section’s first edit session, while it is considered a “new” cross section. Therefore, the river station value will be updated as you edit the cross section layout, each time you finish editing the feature (close it). Cross section properties will continue to be updated each time a cross section cut line is edited. Elevation data will also be automatically extracted. Use the terrain, river centerline, bank lines, flow path lines, inundation mapping, and other data to properly place cross section lines.Īs each cross section is created, RAS Mapper will automatically compute the River Name, Reach Name, River Station, Bank Station, Reach Length and other data for the cross section (assuming the corresponding layers were already created). There are many considerations when developing cross section data for orientation, locating, and spacing, but keeping in mind that the cross sections should represent a smooth transition in geometry (elevation and area) and properties (conveyance, surface roughness, etc) is paramount. Cross sections will also be visualized when looking in the downstream direction therefore, they should be created from left to right when looking downstream (RAS Mapper will automatically flip the line to have the correct orientation). Therefore, most cross section lines should be created from a minimum of four points (the end points and points at the edge of the main channel). Cross sections should be laid out perpendicular to where water will flow in the channel and overbank areas. ![]() Cross sections are developed based on the location layout of cross section lines and properties from other layers such as the River, Bank Lines, and Terrain layers.
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