stream1d 0.1.1

Stateless open-channel and river hydraulics solver

STREAM-1D

1D open-channel hydraulics solver (Rust). Steady gradually varied flow (Standard Step) and unsteady Saint-Venant routing on single reaches. Optional culverts, bridges, and one steady tributary junction.

Primary interface: Python extension (stream1d). Also compiles to WebAssembly. Stateless API: geometry and boundary inputs in, profile arrays out.

This repository is the solver only. It does not include a GUI, project database, or HEC-RAS file importer. stream1d.com is a separate hosted application built on this engine (see License).

Capabilities

Analysis	Structures	Limits
Steady GVF (subcritical, supercritical, mixed)	Culverts (FHWA inlet/outlet), bridges (HEC-RAS Class A/B/C, pressure, weir)	Single reach; one tributary junction (steady, subcritical)
Unsteady routing (single reach)	Inline culverts and bridges	Upstream Q(t), downstream WSEL(t); no multi-reach networks

Full HEC-RAS comparison: docs/reference/hecras_parity.md.

Python

Install

pip install stream1d

Requires Python ≥ 3.7. Wheels are published for Linux, macOS, and Windows (see PyPI).

Install from source

For unreleased changes, clone the repository and build with Rust + maturin:

python -m venv .venv
source .venv/bin/activate   # Windows: .venv\Scripts\activate
pip install maturin pytest
maturin develop --features python

Rebuild with maturin develop --features python after pulling solver changes. Release process: docs/development/publishing.md.

Steady profile

import stream1d as st

xs_us = st.CrossSection(
    station=1000.0,
    x=[0.0, 0.0, 10.0, 10.0],
    y=[6.0, 1.0, 1.0, 6.0],
    n_stations=[0.0],
    n_values=[0.025],
    unit_system="Metric",
)
xs_ds = st.CrossSection(
    station=0.0,
    x=[0.0, 0.0, 10.0, 10.0],
    y=[5.0, 0.0, 0.0, 5.0],
    n_stations=[0.0],
    n_values=[0.025],
    unit_system="Metric",
)

result = st.solve_steady(st.SteadyInputs(
    cross_sections=[xs_us, xs_ds],
    flow_rate=15.0,
    downstream_wsel=1.5,
    regime=0,
))
print(result["wsel"])
print(result["velocity"])

Unsteady routing

result = st.solve_unsteady(st.UnsteadyInputs(
    cross_sections=[xs_us, xs_ds],
    initial_wsel=[2.0, 1.5],
    initial_q=[14.0, 14.0],
    dt=60.0,
    num_steps=5,
    upstream_q_hydrograph=[14.0] * 5,
    downstream_wsel_hydrograph=[1.0] * 5,
))
print(result["wsel"][-1])

JSON fixtures

Load geometry from JSON with stream1d.import_utils.cross_section_from_dict. Example fixtures: tests/fixtures/wasm_steady_culvert_tier1.json, tests/fixtures/wasm_steady_bridge_bu_bd_v22.json.

Culvert, bridge, junction, and rating-curve examples: docs/python/getting_started.md.

Interactive notebook

python/stream1d_verification.ipynb — profiles and HEC-RAS comparison plots. First Binder build may take several minutes.

Inputs and outputs

Cross sections — river station; (x, y) cut polyline; Manning n zones (n_stations, n_values); optional is_overbank, blocked_obstructions, ineffective_flow_areas.

Steady — flow_rate, regime (0 subcritical, 1 supercritical, 2 mixed), downstream boundary (downstream_wsel, normal depth, rating curve, etc.). Structure fields: culvert_*, bridge_*.

Unsteady — initial_wsel, initial_q, dt, num_steps, upstream_q_hydrograph, downstream_wsel_hydrograph. Same structure fields as steady.

Results — wsel, velocity, area, froude_number, critical_wsel, energy_grade_slope. With culverts: control type, inlet/outlet HW, barrel and weir discharge. With bridges: flow regime, head loss. Unsteady structure outputs are [time_step][structure_index].

Field reference: python/stream1d/__init__.py, docs/wasm_api.types.ts. Equations: docs/reference/equations.md.

Verification

Case	Reference	Tolerance
ConSpan culvert 5/25/50 yr profiles	python/verification/hecras_conspan_profiles.json	±0.04 ft WSEL
Bridge abutments (WSPRO)	python/verification/bridge_abutment_hecras.json	±2 mm HW
Bridge BU/BD faces	python/verification/bridge_bu_bd_hecras.json	±2 mm HW

PYTHONPATH=python python python/test_hecras_culvert_verification.py
cargo test --test bridge_bu_bd_hecras_verification

Test commands: docs/development/testing.md.

Build targets

Target	Command	Notes
Python	maturin develop --features python	Default for research and scripting
WebAssembly	bash build_wasm.sh	Browser (pkg/) and Node (pkg-node/)

WASM API: docs/web/wasm_integration.md.

Documentation

Document	Contents
docs/python/getting_started.md	Culvert, bridge, unsteady Python examples
docs/reference/equations.md	GVF, Saint-Venant, culvert and bridge theory
docs/reference/hecras_parity.md	Scope vs HEC-RAS
docs/reference/api_changelog.md	Input schema versions
docs/BRIDGE_INTERIOR_SECTIONS_API.md	BU/BD interior sections
docs/web/wasm_integration.md	WASM build and JavaScript usage
docs/development/testing.md	Test suites and CI
docs/development/publishing.md	PyPI trusted publishing and releases
tech_spec.md	Host-application architecture

Repository layout

src/solvers/     steady, unsteady, culvert, bridge, junction
python/          stream1d bindings, verification data, notebook
docs/            reference manuals and WASM types
tests/           Rust integration tests and JSON fixtures
examples/wasm/   Node smoke tests and sample payloads

License

Engine (this repository): MIT License.

stream1d.com web application: separate proprietary product (Lillywhite Water Solutions LLC), not covered by this license.