Geometry Operations

RAS Commander provides comprehensive geometry parsing and modification for HEC-RAS projects.

Overview

Class	Purpose
RasGeometry	1D geometry parsing (cross sections, storage areas, connections)
RasGeometryUtils	Parsing utilities (fixed-width, count interpretation)
RasStruct	Inline structure parsing (bridges, culverts, weirs)
RasGeo	2D Manning's n land cover operations
HdfHydraulicTables	Cross section property tables (HTAB) from HDF

Cross Sections

List Cross Sections

Python

from ras_commander import RasGeometry, init_ras_project

init_ras_project("/path/to/project", "6.5")

# Get all cross sections
xs_df = RasGeometry.get_cross_sections("01")  # geometry number
print(xs_df[['river', 'reach', 'station', 'description']])

Station-Elevation Data

Python

# Get station-elevation for a specific cross section
river = "Big Creek"
reach = "Upper"
station = "1000"

sta_elev = RasGeometry.get_station_elevation("01", river, reach, station)
print(sta_elev)  # DataFrame with 'station' and 'elevation' columns

Manning's n Values

Python

# Get Manning's n for a cross section
mannings = RasGeometry.get_mannings_n("01", river, reach, station)
print(mannings)  # Returns LOB, Channel, ROB values

Modify Cross Sections

Python

import pandas as pd

# Create modified station-elevation
new_sta_elev = pd.DataFrame({
    'station': [0, 50, 100, 150, 200],
    'elevation': [105, 100, 98, 100, 105]
})

# Update the cross section
RasGeometry.set_station_elevation(
    "01", river, reach, station,
    new_sta_elev
)

Critical Limits

• Maximum 450 points per cross section
• Bank stations are automatically interpolated if not on existing points
• Always verify results after modification

Storage Areas

Python

# List all storage areas
sa_df = RasGeometry.get_storage_areas("01")
print(sa_df[['name', 'max_elevation']])

# Get elevation-volume curve
sa_name = "Storage Area 1"
elev_vol = RasGeometry.get_storage_elevation_volume("01", sa_name)
print(elev_vol)  # DataFrame with elevation, area, volume

Lateral Structures

Python

# List lateral structures
lat_df = RasGeometry.get_lateral_structures("01")
print(lat_df)

# Get weir profile for a lateral structure
profile = RasGeometry.get_lateral_weir_profile("01", "Lateral Weir 1")
print(profile)  # Station and elevation

SA/2D Connections

Python

# List connections
conn_df = RasGeometry.get_connections("01")
print(conn_df)

# Get weir profile
weir_profile = RasGeometry.get_connection_weir_profile("01", "SA-2D Conn 1")

# Get gate data
gates = RasGeometry.get_connection_gates("01", "SA-2D Conn 1")

Inline Structures

Inline Weirs

Python

from ras_commander import RasStruct

# List inline weirs
weirs = RasStruct.get_inline_weirs("01")
print(weirs)

# Get weir profile
profile = RasStruct.get_inline_weir_profile("01", river, reach, station)
print(profile)

# Get gate data
gates = RasStruct.get_inline_weir_gates("01", river, reach, station)

Bridges

Python

# List bridges
bridges = RasStruct.get_bridges("01")
print(bridges)

# Get bridge deck profile
deck = RasStruct.get_bridge_deck("01", river, reach, station)

# Get pier data
piers = RasStruct.get_bridge_piers("01", river, reach, station)

# Get abutment data
abutment = RasStruct.get_bridge_abutment("01", river, reach, station)

# Get approach sections
approach = RasStruct.get_bridge_approach_sections("01", river, reach, station)

# Get bridge coefficients
coeffs = RasStruct.get_bridge_coefficients("01", river, reach, station)

# Get HTAB settings
htab = RasStruct.get_bridge_htab("01", river, reach, station)

Culverts

Python

# List all culverts
culverts = RasStruct.get_culverts("01")
print(culverts)

# Get detailed culvert data for all at a location
all_culverts = RasStruct.get_all_culverts("01", river, reach, station)

Culvert Shape Codes:

Code	Shape
1	Circular
2	Box
3	Pipe Arch
4	Ellipse
5	Arch
6	Semi-Circle
7	Low Profile Arch
8	High Profile Arch
9	Con Span

2D Manning's n (Land Cover)

Python

from ras_commander import RasGeo

# Get base Manning's n table
base_n = RasGeo.get_base_mannings_table("01")
print(base_n)

# Get regional overrides
regional = RasGeo.get_regional_mannings("01", "2D Flow Area")

# Update Manning's n
RasGeo.set_base_mannings_table("01", updated_table)

Hydraulic Tables (HTAB)

Extract property tables from preprocessed geometry HDF:

Python

from ras_commander import HdfHydraulicTables

# Get geometry HDF path
geom_hdf = "/path/to/project.g01.hdf"

# Get cross section HTAB
htab = HdfHydraulicTables.get_xs_htab(geom_hdf, river, reach, station)
print(htab)
# Contains: elevation, area, conveyance, wetted_perimeter, top_width

This enables rating curve generation without re-running HEC-RAS.

Geometry Preprocessor Files

Clear .c## files to force HEC-RAS to recalculate hydraulic tables:

Python

from ras_commander import RasGeo, RasPlan

# Clear for specific plan
plan_path = RasPlan.get_plan_path("01")
RasGeo.clear_geompre_files(plan_path)

# Or clear for all plans
RasGeo.clear_geompre_files()

File Format Notes

HEC-RAS geometry files use FORTRAN-style fixed-width formatting:

• 8-character fields (common)
• Comma-separated values (some sections)
• Bank stations require interpolation to match points

The RasGeometryUtils class handles these formats internally.

Best Practices

1. Backup first: Always backup geometry files before modification
2. Clear preprocessor: Run clear_geompre_files() after geometry changes
3. Validate changes: Re-open in HEC-RAS GUI to verify modifications
4. Point limits: Keep cross sections under 450 points
5. Bank stations: Let the library handle interpolation automatically

Example: Modify Cross Section Elevations

Python

from ras_commander import RasGeometry, RasGeo, RasCmdr, init_ras_project
import pandas as pd

init_ras_project("/path/to/project", "6.5")

# Get current data
river, reach, station = "Big Creek", "Upper", "1000"
sta_elev = RasGeometry.get_station_elevation("01", river, reach, station)

# Lower the channel by 2 feet
sta_elev['elevation'] = sta_elev['elevation'] - 2.0

# Update geometry
RasGeometry.set_station_elevation("01", river, reach, station, sta_elev)

# Clear preprocessor and recompute
RasGeo.clear_geompre_files()
success = RasCmdr.compute_plan("01", dest_folder="./modified_run")