Repairing Geometry Issues

Lightweight skill for navigating ras-commander's geometry checking and repair capabilities.

This skill provides quick navigation to primary sources for RasCheck (validation) and RasFixit (repair). Do not duplicate content from primary sources - this file serves as an index only.

Primary Sources (Read These First)

Quality Validation (RasCheck)

C:\GH\ras-commander\ras_commander\check\CLAUDE.md (262 lines)

• 5 comprehensive checks (NT, XS, Structure, Floodway, Profiles)
• FEMA/USACE standards implementation
• Custom thresholds and state-specific surcharge limits
• Report generation (HTML, CSV, JSON)

Automated Repair (RasFixit)

C:\GH\ras-commander\ras_commander\fixit\AGENTS.md (119 lines)

• Blocked obstruction repair algorithm
• 0.02-unit gap insertion requirement
• Elevation envelope details
• Module organization and patterns

Complete Workflows

C:\GH\ras-commander\examples\200_fixit_blocked_obstructions.ipynb

• RasFixit demonstration with visualizations
• Before/after comparison workflow
• Engineering review requirements

C:\GH\ras-commander\examples\300_quality_assurance_rascheck.ipynb

• RasCheck validation workflow
• Multi-check execution and reporting
• Custom threshold configuration

Quick Start Patterns

Check → Fix → Verify Workflow

from ras_commander import RasCheck, RasFixit

# 1. CHECK: Detect issues
results = RasCheck.run_all("01")
print(f"Errors: {results.get_error_count()}")
print(f"Warnings: {results.get_warning_count()}")

# 2. FIX: Repair blocked obstructions (if detected)
fix_results = RasFixit.fix_blocked_obstructions(
    "model.g01",
    backup=True,      # ALWAYS create timestamped backup
    visualize=True    # ALWAYS generate verification PNGs
)
print(f"Fixed {fix_results.total_xs_fixed} cross sections")

# 3. VERIFY: Confirm repairs
verify_results = RasCheck.run_all("01")

Detection Only (Non-Destructive)

# Detect overlaps without modifying files
detect_results = RasFixit.detect_obstruction_overlaps("model.g01")
print(f"Cross sections with overlaps: {detect_results.total_xs_fixed}")

# Review affected stations
for msg in detect_results.messages:
    print(f"RS {msg.station}: {msg.original_count} → {msg.fixed_count}")

Custom Validation Thresholds

from ras_commander.check import create_custom_thresholds

# Override FEMA defaults for stricter standards
custom = create_custom_thresholds({
    'mannings_n.overbank_max': 0.150,        # Stricter limit
    'reach_length.max_length_ft': 2000.0,    # More conservative
    'floodway.surcharge_ft': 0.5,            # USACE standard (vs 1.0 ft FEMA)
})

results = RasCheck.run_all("01", thresholds=custom)

State-Specific Standards

from ras_commander.check import get_state_surcharge_limit

# Use state-specific floodway surcharge limits
il_limit = get_state_surcharge_limit('IL')  # Returns 0.1 ft (vs FEMA 1.0 ft)

results = RasCheck.run_all(
    "01",
    floodway_profile="Floodway",
    surcharge=il_limit
)

Report Generation

from ras_commander.check import ReportMetadata

# Generate HTML report with metadata
metadata = ReportMetadata(
    project_name=ras.project_name,
    plan_number="01",
    checked_by="Engineer Name"
)
results.to_html("validation_report.html", metadata=metadata)

# Export to CSV for Excel analysis
df = results.to_dataframe()
df.to_csv("validation_messages.csv", index=False)

Critical Technical Details

Blocked Obstruction Algorithm (Elevation Envelope)

Source: C:\GH\ras-commander\ras_commander\fixit\AGENTS.md (lines 40-60)

CRITICAL WARNING - 0.02-Unit Gap Requirement:

• HEC-RAS REQUIRES minimum 0.02-unit separation between adjacent obstructions
• This is a hard requirement in the HEC-RAS geometry preprocessor
• The gap size is defined in obstructions.py as GAP_SIZE = 0.02
• DO NOT modify this constant - changing it will cause preprocessing failures

Algorithm Steps:

1. Collect critical stations: All start/end points of obstructions
2. Maximum elevation wins: In overlap zones, use highest elevation (hydraulically conservative)
3. Merge adjacent segments: Combine segments with same elevation
4. Insert 0.02-unit gaps: Minimum separation where elevations differ

Example:

Original (overlapping):
  Segment 1: 100.0 - 200.0 ft, elev 35.0
  Segment 2: 150.0 - 250.0 ft, elev 36.0

Fixed (elevation envelope with 0.02 gap):
  Segment 1: 100.0 - 150.0 ft, elev 35.0
  Segment 2: 150.02 - 250.0 ft, elev 36.0  # 0.02 gap inserted

Fixed-Width FORTRAN Parsing

Source: C:\GH\ras-commander\ras_commander\fixit\AGENTS.md (lines 53-56)

• HEC-RAS geometry files use 8-character fixed-width columns
• FIELD_WIDTH = 8 constant must not be changed
• Overflow handled with asterisks (********)
• Section terminators: Bank Sta=, #XS Ineff=, #Mann=, XS Rating Curve=, XS HTab, Exp/Cntr=

When to Use This Skill

Use for:

• HEC-RAS geometry preprocessing failures
• FEMA/USACE model validation
• Fixing overlapping blocked obstructions
• Preparing models for peer review or submission
• FEMA Base Level Engineering (BLE) compliance
• Detecting Manning's n or cross section issues
• Validating structure (bridge/culvert) geometry
• Checking floodway surcharge limits
• Creating audit trails for engineering review

Don't use for:

• Simple file I/O operations (use basic ras-commander patterns)
• Model execution (use RasCmdr patterns)
• Data extraction (use HDF classes)

RasCheck Validation Categories

Source: C:\GH\ras-commander\ras_commander\check\CLAUDE.md (lines 13-60)

Check Type	Function	Validates
NT Check	check_nt()	Manning's n, transition coefficients, land cover standards
XS Check	check_xs()	Cross section spacing, station ordering, reach lengths, bank stations
Structure Check	check_structures()	Bridges, culverts, inline weirs, low chord elevations, pier spacing
Floodway Check	check_floodways()	Surcharge limits, conveyance reduction, encroachment methods
Profiles Check	check_profiles()	WSE ordering, discharge consistency, critical depth transitions

Run all checks:

results = RasCheck.run_all("01")  # Executes all 5 checks

Run individual check:

# Get HDF path from plan
plan_row = ras.plan_df[ras.plan_df['plan_number'] == "01"].iloc[0]
geom_hdf = Path(plan_row['Geom Path']).with_suffix('.hdf')

# Run specific check
nt_results = RasCheck.check_nt(geom_hdf)
xs_results = RasCheck.check_xs(geom_hdf)

RasFixit Repair Capabilities

Source: C:\GH\ras-commander\ras_commander\fixit\AGENTS.md (complete file)

Current Fix Types:

• fix_blocked_obstructions() - Repair overlapping/adjacent blocked obstructions
• detect_obstruction_overlaps() - Non-destructive detection only

Fix Results:

# FixResults dataclass contains:
# - total_xs_checked: Cross sections scanned
# - total_xs_fixed: Cross sections modified
# - messages: List of FixMessage objects
# - backup_path: Path to timestamped backup
# - visualization_folder: Path to PNG folder

# FixMessage contains:
# - station: River station (e.g., "12345.67")
# - action: FixAction enum (OVERLAP_RESOLVED, GAP_INSERTED, etc.)
# - original_data: List of original (start, end, elev) tuples
# - fixed_data: List of fixed (start, end, elev) tuples
# - original_count: Number of original obstructions
# - fixed_count: Number of fixed obstructions

Export to DataFrame:

df = fix_results.to_dataframe()
df.to_csv("obstruction_fixes.csv", index=False)

Engineering Review Requirements

CRITICAL: All automated fixes MUST be reviewed by a licensed professional engineer before use in production models.

Required Documentation

1. Timestamped backups: Always use backup=True
2. Before/after visualizations: Always use visualize=True
3. Audit trail: Export FixResults.to_dataframe() to CSV
4. Algorithm documentation: Include elevation envelope algorithm description

Verification Steps

1. Visual inspection: Review all PNG visualizations
2. Compare hydraulics: Run model with original and fixed geometry
3. Spot check: Manually verify critical cross sections in HEC-RAS GUI
4. Professional judgment: Ensure fixes align with engineering intent

Module Organization

RasCheck (check subpackage)

check/
├── __init__.py         # Exports RasCheck, CheckMessage, etc.
├── RasCheck.py         # Main static class (448 KB)
├── messages.py         # CheckMessage templates (106 KB)
├── report.py           # Report generation (23 KB)
├── thresholds.py       # CheckThresholds configuration (18 KB)
└── CLAUDE.md           # Primary source documentation (262 lines)

RasFixit (fixit subpackage)

fixit/
├── __init__.py         # Exports RasFixit, FixResults, FixMessage, FixAction
├── RasFixit.py         # Main static class with fix methods
├── obstructions.py     # BlockedObstruction and elevation envelope algorithm
├── results.py          # FixAction enum, FixMessage, FixResults dataclasses
├── visualization.py    # Lazy-loaded matplotlib PNG generation
├── log_parser.py       # HEC-RAS compute log parsing
└── AGENTS.md           # Primary source documentation (119 lines)

Common Issues and Solutions

Issue: Geometry preprocessing fails with obstruction errors

# 1. Detect obstructions
results = RasFixit.detect_obstruction_overlaps("model.g01")
if results.total_xs_fixed > 0:
    # 2. Fix obstructions
    fix_results = RasFixit.fix_blocked_obstructions(
        "model.g01",
        backup=True,
        visualize=True
    )
    print(f"Fixed {fix_results.total_xs_fixed} cross sections")

Issue: FEMA validation warnings

# Run validation and generate report
results = RasCheck.run_all("01")
results.to_html("fema_validation.html")

# Address errors (severity=ERROR)
df = results.to_dataframe()
errors = df[df['severity'] == 'ERROR']
print(errors[['station', 'message']])

Issue: Manning's n out of range

# Run NT check
nt_results = RasCheck.check_nt(geom_hdf)
df = nt_results.to_dataframe()

# Filter Manning's n issues
n_issues = df[df['message_id'].str.startswith('NT_RC')]
print(n_issues[['station', 'message']])

Issue: Cross section spacing too large

# Run XS check with custom threshold
custom = create_custom_thresholds({
    'reach_length.max_length_ft': 1500.0  # More conservative
})
xs_results = RasCheck.check_xs(geom_hdf, thresholds=custom)

Log Parsing for Automated Workflows

Source: C:\GH\ras-commander\ras_commander\fixit\AGENTS.md (line 18)

from ras_commander.fixit import log_parser

# Parse HEC-RAS compute log
with open("compute.log", 'r') as f:
    log_content = f.read()

# Detect obstruction errors
if log_parser.has_obstruction_errors(log_content):
    errors = log_parser.detect_obstruction_errors(log_content)
    stations = log_parser.extract_cross_section_ids(log_content)

    # Generate error report
    report = log_parser.generate_error_report(errors)
    print(report)

Performance Characteristics

RasCheck:

• Typical 1D model: 5-15 seconds
• Large 2D model: 30-60 seconds
• Low memory footprint (suitable for 10,000+ cross sections)
• Parallel checking supported for multiple plans

RasFixit:

• < 1 second per cross section repair
• Visualization: 2-3 seconds per PNG (optional)

Navigation Map

For validation questions → Read C:\GH\ras-commander\ras_commander\check\CLAUDE.md

For repair questions → Read C:\GH\ras-commander\ras_commander\fixit\AGENTS.md

For workflow examples → See notebooks:

• examples\200_fixit_blocked_obstructions.ipynb
• examples\300_quality_assurance_rascheck.ipynb

For API details → Read source code docstrings:

• ras_commander\check\RasCheck.py
• ras_commander\fixit\RasFixit.py

Related Skills

• quality-assurance subagent: .claude\agents\quality-assurance\SUBAGENT.md
• Testing approach: .claude\rules\testing\tdd-approach.md

State-Specific Floodway Surcharge Limits

Source: C:\GH\ras-commander\ras_commander\check\CLAUDE.md (lines 198-220)

States with non-standard surcharge limits (vs FEMA default 1.0 ft):

• IL: 0.1 ft
• WI: 0.0 ft (no surcharge allowed)
• MN: 0.5 ft
• NJ: 0.2 ft
• MI, IN, OH: 0.5 ft
• Default (TX, most states): 1.0 ft

from ras_commander.check import get_state_surcharge_limit

# Get state-specific limit
limit = get_state_surcharge_limit('IL')  # Returns 0.1
results = RasCheck.run_all("01", surcharge=limit)

---

Total Lines: ~390 (target: 300-400)

Primary sources contain: 262 + 119 = 381 lines of authoritative documentation This skill: Lightweight index with critical warnings and navigation guidance