Grid Modification

Grid Modification#

This section outlines a process to port data after the domain has been changed or the grid elements size has been changed but a project has many components developed. This scenario occurs when an old project is revisited or a new project is extended to a larger area or clipped to a smaller area.

Note

The process will be outlined based on the available layers and procedures in the QGIS FLO-2D Plugin order.

1. Computational Domain Layer#

  • Update polygon to cover complete project extent.

  • Set cell size.

2. Grid#

  • Create the grid.

3. Interpolate Elevation#

  • Import full coverage raster.

    • If a new area is needed, it is easy to create a mosaic of the two rasters.

    • Export the grid layer as a raster and use a mosaic tool to combine the two rasters.

    • It is a good idea to use the new grid element resolution and alignment as the extent and size for the raster.

  • Sample full coverage raster with the Sampling grid elevation from raster layer.

4. Roughness#

  • Recalculate from a full coverage shapefile/raster.

  • If shapefile is not available,

    • Export the old grid and intersect it with roughness polygons for the new grid.

    • Use a Dissolve tool to simplify the shapefile so it combines like polygons with the same n-value.

5. Buildings#

  • Recalculate from Blocked Areas layer.

  • It may be necessary to add buildings from additional area.

  • The open street map downloader can download buildings. See the Building section of the Self Help Training for more info.

6. Extra Grid features#

  • Run separate tools for Spatial Tol, Spatial Froude, Spatial Shallow n, and Gutters.

7. Infiltration#

  • Recalculate from external layers.

  • It may be necessary to add infiltration areas to the infiltration shapefile.

    • If extra data is needed, intersect the new data into the Soil and Landuse shapefiles.

8. Hydraulic Structures#

  • Copy polyline features from Structures Schematic Layer.

  • Paste into Structures User Layer.

  • Run structures schematize tool to refresh data.

  • Add new structures using the editor tool and table editor after refreshing the data.

  • Rerun schematize tool to add new data to final Schematic Layer.

9. Levees#

  • If User Layers Levee Lines are available, use them to recalculate the levees.

  • If Levee Lines User Layer is not present, use this simple process to copy them from the Schematized Levees.

    • Create levee lines the center of the levee. This is just the standard create levee polyline using the editor add polyline process.

    • Make certain these lines cross the Schematic Levees frequently.

    • Intersect the Levee Lines Layer and Levees Layer to generate a point file with crest elevation.

    • Copy that to the Elevation Points Layer.

    • Run the Levee Calc tool with Levee Lines and Points.

    • The idea is to intersect the schema lines and get the crest elevation for the points layer.

    Note

    This does not work for walls.

  • Walls

    • Recalculate walls from wall data.

10. Boundary Conditions#

  • Run schematize button.

  • The downstream boundary might need to be edited or repositioned.

11. Rain#

  • Rerun depth Area Reduction sampler if used.

  • Save and export data.

12. Channels#

  • Rerun schematize.

  • Export .DAT files.

  • Run Interpolator.

  • Import interpolated channels.

  • It may be necessary to make left and right bank alignment corrections.

13. Floodplain cross sections#

  • Rerun schematize.

  • It may be necessary to add new cross sections.

Storm Drain#

  • Add new data to the storm drain shapefiles.

  • Rerun storm drain calculator tool to convert to the FLO-2D User layers.

  • Run schematize.

  • Export swmm.inp.

FLO-2D Pro#

  • Export Data

  • Run Model

    • It is probably wise to export the data and test run at more convenient points along this outline.

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