Project Review and Mapping

Set up culverts using Rating Tables and Culvert Equations using QGIS and the FLO-2D Plugin.

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Load Results and Maps

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Place holder video. Final version not ready.

This lesson introduces the setup of hydraulic structures in FLO-2D using QGIS. It includes visual styling, elevation considerations, and labeling, preparing the dataset for modeling.

Step 1: Load Hydraulic Structures

  • Load the hydraulic_structures.shp shapefile into your QGIS project.

  • Modify the layer style: - Change the symbol to an arrow line for visualizing flow direction. - Adjust the color to make structures more visible.

Note

Arrows indicate the direction of flow: inlet is the first vertex, outlet is the last.

Step 2: Understand Elevation Requirements

  • Each hydraulic structure must move flow from an inlet to an outlet grid element.

  • Elevations must match the invert elevations of culverts and connected features.

Tip

Use the Identify Features tool on your elevation raster and grid layers to find elevation mismatches.

Common adjustments:

  • Move the inlet/outlet point to the nearest correct elevation cell.

  • Use elevation correction polygons where necessary to model invert slopes and street flow paths.

  • Consider stilling basins or weirs where sediment control is necessary.

Step 3: Examples of Flow Adjustments

  • Evaluate upstream/downstream cells: - Example: Move from a 1428 ft grid cell to a 1425 ft cell to match invert.

  • Ensure continuity along trapezoidal channels feeding culverts.

Step 4: Assign Structures to Cross-Sections

  • For culverts connecting to channels: - Always assign outlet to the left bank of the cross-section. - FLO-2D exchanges discharge to cross-sections, not grid elements.

Note

Right bank assignments can cause ambiguity. Use left bank consistently.

Step 5: Label the Hydraulic Structures

  • Open Layer Properties > Labels tab.

  • Label each structure with the structure_name field.

  • Recommended settings: - Font size: 12 pt - Font color: white or a visible contrast color

Step 6: Check Attribute Table Fields

  • Ensure the attribute table contains: - structure_name - structure_type (floodplain-to-floodplain, floodplain-to-channel, etc.) - tailwater_switch (default = 0) - head_reference_elevation - Additional culvert parameters (used in the advanced setup)

Structure Types:

  • Floodplain to Floodplain: Flow between two grid cells

  • Floodplain to Channel: Connect to left bank of a cross-section

  • Channel to Channel: Set up previously in the Channel lesson

Next Step

In the next lesson, you’ll learn how to define hydraulic structure parameters in the layer attribute table and export your model data.

Review a Project Run

Note

Place holder video. Final version not ready.

In this lesson, we begin working with hydraulic structures in FLO-2D. This is the first part of a two-part lesson focusing on how to display and prepare culvert data for modeling using rating tables. The second, more advanced lesson will cover converting culverts to use the Generalized Culvert Equation (CT).

Step 1: Add the Hydraulic Structures Layer

  • Drag and drop the hydraulic structure shapefile onto your QGIS map canvas.

  • The default symbology may be muted. You should: - Change the line style to arrow to indicate flow direction. - Apply a brighter fill color for better visibility.

Note

Arrow symbology in QGIS applies an arrowhead at the last vertex of the polyline. This means: - First vertex = Inlet - Second vertex = Outlet

Step 2: Understand Flow Direction

  • FLO-2D hydraulic structures move water from inlet to outlet.

  • Even when reverse flow (e.g. tailwater conditions) is possible, always define flow in the expected direction.

Step 3: Elevation Considerations

  • Grid cell elevations are averages of underlying raster pixels.

  • Culverts often require invert elevations, not average elevations.

  • Use the Identify Features tool on the elevation raster to get correct values.

  • You may need to modify grid cell elevations at the inlet, outlet, and along small channels leading to the structures.

Tip

Use elevation correction polygons to modify grid cell elevations to match actual invert elevations.

Examples:

  • One culvert shows 1409 (grid cell average) while the actual invert is 1405.

  • Another structure has a weir at elevation 1396.5 to separate trash from flow before it enters a stilling basin.

Step 4: Label Hydraulic Structures

  • Open the attribute table and confirm each structure has a valid name.

  • Use the structure_name field to label structures on the map.

  • Adjust label font size and color for clarity.

Step 5: Classify Structure Types

Hydraulic structures can connect:

  • Floodplain to floodplain

  • Floodplain to channel (assign to Left Bank only)

  • Channel to channel

Make sure structure types and flow paths are clearly identified.

Important

FLO-2D links structures to cross-sections, not banks. Always connect to the Left Bank when targeting channels.

Step 6: Next Steps

  • All structures are initially set up with rating tables.

  • The tailwater switch is typically left at 0 (inlet-controlled flow).

  • More parameters (head reference, n-value, etc.) will be discussed before data export.

Note

The second part of this lesson will cover converting culverts to CT structures using the Generalized Culvert Equation.