Terrain Modules

Classes for terrain creation, terrain modification writing, and terrain modification analysis.

Platform Requirements

RasTerrainMod requires Windows with pythonnet and a HEC-RAS installation (uses RasMapperLib.dll via .NET interop). RasTerrain and RasTerrainModWriter work on all platforms.

RasTerrain

Terrain HDF creation from rasters using RasProcess.exe CreateTerrain.

Terrain Creation Methods

• create_terrain_hdf(input_rasters, output_hdf, projection_prj, units="Feet", stitch=True, hecras_version="7.0", timeout_seconds=600) - Create HEC-RAS terrain HDF from input rasters
• create_terrain_from_rasters(input_rasters, output_folder, terrain_name="Terrain", units="Feet", stitch=True, hecras_version="7.0", generate_prj=True) - Convenience wrapper with automatic PRJ generation

Utility Methods

• vrt_to_tiff(vrt_path, output_path, compression="LZW", create_overviews=True, overview_levels=None, nodata_value=None, hecras_version="7.0") - Convert VRT to single optimized TIFF using HEC-RAS bundled GDAL
• get_available_versions() - List installed HEC-RAS versions with terrain creation support

Bank Line Generation

• compute_bank_lines(geom_path, crs=None, ras_object=None) - Generate bank-line geometry from cross-section bank stations

Usage

Python

from ras_commander import RasTerrain

# Create terrain from rasters
terrain_hdf = RasTerrain.create_terrain_from_rasters(
    input_rasters=["dem_north.tif", "dem_south.tif"],
    output_folder="terrain/",
    terrain_name="Project_Terrain",
    units="Feet",
    hecras_version="7.0",
)

RasTerrainModWriter

Line and polygon terrain modification HDF/.rasmap writing. Also available as the alias RasTerrainModification.

Line Modification Methods

• add_high_ground_modification(terrain_hdf_path, rasmap_path, name, polyline_points, top_width=20.0, side_slope=2.0, ...) - Add levee/road terrain modification with trapezoidal profile along polyline (TakeHigher mode)
• add_fill_surface_modification(terrain_hdf_path, rasmap_path, name, polyline_points, top_width=20.0, side_slope=2.0, ...) - Add fill-surface (SetValue) modification along polyline
• add_channel_modification(terrain_hdf_path, rasmap_path, name, polyline_points, width=50.0, depth=10.0, left_slope=3.0, right_slope=3.0, ...) - Add trapezoidal channel modification (TakeLower mode)

Polygon Modification Methods

• add_modification_polygon(terrain_hdf_path, name, polygon_coords, elevation_method="boundary_from_terrain", control_points=None, ...) - Add polygon multipoint modification (detention pond/wetland grading)

Group Management

• add_modification_group(terrain_hdf_path, rasmap_path, group_name="Modifications") - Add empty modification group to terrain HDF and .rasmap

Query Methods

• list_modifications(terrain_hdf_path) - List all terrain modifications stored in HDF sidecar group
• get_modification_profile(terrain_hdf_path, name) - Read modification station/elevation profile

Analysis Methods

• sample_modification_surface(terrain_hdf_path, name, points, existing_elevations=None, ...) - Evaluate line modification surface at XY points
• apply_modification_to_profile(terrain_hdf_path, name, profile, ...) - Apply line modification to existing terrain profile
• compare_before_after_profiles(rasmap_existing, rasmap_modified, geom_hdf_path, x_coords, y_coords, ...) - Compare terrain profiles before/after modification

Usage

Python

from ras_commander import RasTerrainModWriter

# Add a levee (high ground)
RasTerrainModWriter.add_high_ground_modification(
    terrain_hdf_path="Terrain/Terrain.hdf",
    rasmap_path="Project.rasmap",
    name="Proposed Levee",
    polyline_points=[(x1, y1), (x2, y2), (x3, y3)],
    top_width=20.0,
    side_slope=3.0,
    elevation=25.0,
)

# Add a detention pond (polygon)
RasTerrainModWriter.add_modification_polygon(
    terrain_hdf_path="Terrain/Terrain.hdf",
    name="Detention Pond",
    polygon_coords=[(x1, y1), (x2, y2), (x3, y3), (x4, y4)],
    control_points=[(cx, cy, target_elev)],
    mode="set_value",
    rasmap_path="Project.rasmap",
)

RasTerrainMod

Terrain profile and volume comparison with modifications applied. Uses RasMapperLib.dll via pythonnet to sample the actual modified terrain surface.

Windows Only

Requires Windows, pythonnet, and an installed HEC-RAS version. Call setup_gdal_bridge() once before other methods.

Setup

• setup_gdal_bridge(hecras_version="7.0", python_dir=None, create_junction=True) - Configure HEC-RAS GDAL runtime for pythonnet before loading

Terrain Sampling

• get_terrain_extent(rasmap_path, geom_hdf_path, ras_object=None) - Get terrain bounding box with modifications applied
• get_terrain_profile(rasmap_path, geom_hdf_path, x_coords, y_coords, filter_tolerance=0.01, ras_object=None) - Sample terrain elevation along polyline
• get_terrain_volume_elevation(rasmap_path, geom_hdf_path, x_coords, y_coords, ...) - Compute elevation-volume curve for polygon

Comparison Methods

• compare_terrain_profiles(rasmap_existing, rasmap_proposed, geom_hdf_path, x_coords, y_coords, ...) - Compare terrain profiles between existing and proposed (cut/fill analysis)
• compare_terrain_volumes(rasmap_existing, rasmap_proposed, geom_hdf_path, x_coords, y_coords, ...) - Compare elevation-volume curves for no-net-fill analysis

Raster Export

• compute_modified_terrain_raster(rasmap_path, geom_hdf_path, terrain_tif_path, output_tif_path=None, ...) - Compute full-resolution raster of terrain with modifications applied

Usage

Python

from ras_commander.terrain import RasTerrainMod

# One-time setup
RasTerrainMod.setup_gdal_bridge("7.0")

# Compare existing vs proposed terrain along a profile
comparison = RasTerrainMod.compare_terrain_profiles(
    rasmap_existing="Existing.rasmap",
    rasmap_proposed="Proposed.rasmap",
    geom_hdf_path="Model.g01.hdf",
    x_coords=[x1, x2, x3],
    y_coords=[y1, y2, y3],
)
print(comparison[['station', 'existing_elevation', 'proposed_elevation', 'difference']])

Related Examples

Notebook	Description
316_terrain_modifications.ipynb	Terrain modification writer: high ground, channel, polygon
920_terrain_creation.ipynb	Terrain HDF creation from rasters
930_terrain_modification_analysis.ipynb	Cut/fill analysis with RasTerrainMod