hms2cng — HMS to Cloud Native GIS

Full project access and archival for HEC-HMS. Exports geometry, simulation results, and project metadata to cloud-native GeoParquet — enabling cross-project DuckDB analytics, PMTiles web visualization, and PostGIS integration.

Documentation: rascommander.info/hms2cng

Built on top of hms-commander by CLB Engineering Corporation.

Installation

# Base installation (GeoParquet export only)
pip install hms2cng

# All features (DuckDB, PostGIS, PMTiles)
pip install "hms2cng[all]"

PMTiles Generation

PMTiles generation requires external CLI tools:

• tippecanoe — conda install -c conda-forge tippecanoe
• pmtiles — go install github.com/protomaps/go-pmtiles/pmtiles@latest

Quick Start

Full Project Export

Export an entire HMS project — all basin models, all runs, all layers:

# Preview the project structure (runs, basin models, met models)
hms2cng manifest MyProject.hms

# Export everything to a hierarchical GeoParquet archive
hms2cng project MyProject.hms out/my_archive/

Output structure:

out/my_archive/
  manifest.parquet          # project-level metadata (1 row)
  run_registry.parquet      # basin + met + control lineage per run
  basin_inventory.parquet   # element counts per basin model
  geometry/
    {basin_slug}/
      subbasins.parquet
      reaches.parquet
      junctions.parquet
      ...
  results/
    {run_slug}/
      outflow.parquet       # peak, min, mean, time of peak

Query across all runs with DuckDB:

import duckdb
df = duckdb.sql("""
    SELECT project_name, run_name, name, max_value, units
    FROM read_parquet('out/my_archive/results/*/*.parquet', union_by_name=true)
    ORDER BY max_value DESC
    LIMIT 20
""").df()

Single-Layer Export

# Export a specific geometry layer
hms2cng geometry model.basin subbasins.parquet --layer subbasins

# Export simulation results
hms2cng results project/results results.parquet --type subbasin --var Outflow

# Query with DuckDB
hms2cng query results.parquet "SELECT name, max_value FROM _ ORDER BY max_value DESC"

# Generate PMTiles (requires tippecanoe + pmtiles)
hms2cng pmtiles subbasins.parquet subbasins.pmtiles --layer subbasins

# Sync to PostGIS
hms2cng sync subbasins.parquet "postgresql://user:pass@host:5432/db" hms_subbasins

Python API

from hms2cng import (
    export_full_project,          # export entire HMS project
    get_project_manifest,         # read project structure as dict
    export_all_basin_geometry,    # batch geometry export
    export_all_results,           # batch results export
    export_basin_geometry,        # single layer export
    export_hms_results,           # single run export
    DuckSession,
)

# Full project archive
summary = export_full_project("MyProject.hms", "out/archive/")
print(f"Geometry files: {len(summary['geometry_files'])}")
print(f"Results files:  {len(summary['results_files'])}")

# Project manifest
manifest = get_project_manifest("MyProject.hms")
print(manifest["run_names"])  # JSON list of run names

# Single layer (original API unchanged)
from hms2cng.geometry import get_basin_layer_gdf
gdf = get_basin_layer_gdf("project.basin", layer="subbasins")

Cloud Native GIS Stack

Development

git clone https://github.com/gpt-cmdr/hms2cng
cd hms2cng
uv pip install -e ".[all]"

# Run tests
uv run pytest tests/

# Interactive examples (marimo)
uv run marimo edit examples/06_full_project_export.py

# Preview docs
uv run mkdocs serve

About CLB Engineering

hms2cng is an open-source project of CLB Engineering Corporation, the creators of hms-commander and ras-commander.

CLB pioneered the LLM Forward approach to civil engineering — a framework where licensed professional engineers leverage Large Language Models to accelerate H&H modeling workflows while maintaining full professional responsibility.

Contact: info@clbengineering.com | Website: clbengineering.com

License

MIT — See LICENSE

Author: William M. Katzenmeyer, P.E., C.F.M. — CLB Engineering Corporation