Exact answer known1D2D · mixedCandidate

Manhole overflowing onto a street

Does a coupled model put all of the sewer's overflow onto the street?

Test A12-010
Chen (2007)
Version 1.0.0

Right answer: Exact, from conservation · Chen (2007)
Results: 4 models · closest 0.14 % off · see them ↓
Must: release the full pipe flow onto the street

Sketch, not to scale.

What happens

A pipe delivers a steady flow to a manhole with no way out but up. It overflows onto a sloping street, and downstream the street carries the whole flow as a thin sheet whose depth is fixed exactly by the slope and roughness.

Why it matters

Surcharging manholes are where urban flooding starts. If the coupling loses or invents water here, every flood map built on it is wrong.

A good model must

release the full pipe flow onto the street
get the street depth within 3 mm
end with the water accounted for (0.5 %)

Exact answer and models

Water balance over time

Water stored on the surface and in the pipes, minus what came in, plus what went out: zero for a model that neither makes nor loses water. Shaded: the pass limit at the end of the run, ±4.4 m³ (0.5 %).

Point at the chart to read every model's value; click a name to hide or show it.

Flow out of the manhole onto the street

At steady state the manhole must release the whole pipe inflow, 0.5 m³/s.

Point at the chart to read every model's value; click a name to hide or show it.

How models did

In rank order: by each model's percent difference from the right answer, the largest over the test's accuracy checks (lower is better; results within 10 % of each other share a rank). Mass error, timing and NSE are shown beside it, not folded in. Each model runs the same inputs. Compare them in the results viewer →

Rank	Model	Difference	Largest difference in	Mass error	Run time
1	SWMM + ANUGA coupled 1D/2D	0.14 %	Street depth	0.56 %	44.8 s
2	OpenSWMM 6 coupled 1D/2D	0.79 %	Street depth	<0.01 %	4.0 s
3	HEC-RAS 7.0 pipe networks · 1D/2D	7.6 %	Street depth	0.48 %	31.9 s
4	OpenSWMM 6 coupled 1D/2D · cross mesh	10 %	Street depth	<0.01 %	11.0 s

SWMM + ANUGA

EPA SWMM 5.2.4 pipes coupled to an ANUGA 4.0.1 surface by the suite's own explicit coupler (1 s weir/orifice exchange at the manholes): a worked example of a 1D/2D model, not a product

#1 0.14 % off

Run time, finest grid: 44.8 s · AMD EPYC 9V74 80-Core Processor, 2 cores, 15.6 GB, Linux 6.17.0-1022-azure (GitHub Actions (github-hosted, ubuntu24))

Settings: suite coupler: explicit 1 s weir/orifice exchange (Chen et al. 2007), levelling-limited

Manhole outflow

• < 0.0001 % off

Street depth

• 0.11 mm off

0.14 % of the 77.7 mm normal depth

Water balance

· 0.56 % off

conservation, reported beside the score

The street carries exactly what the manhole releases (0.5 m³/s, depth 0.1 mm from exact), but 5 m³ of the 885 m³ is missing at the end (0.56 %). The coupler moves water exactly; the loss is SWMM's own continuity error (0.50 % in its report), made as the dead-end pipe filled and surcharged.

Scored with method 3.0 · Score card: SWMM–ANUGA coupled (SWMM 5.2.4 + ANUGA 4.0.1)

Run it yourself

SWMM–ANUGA coupled (SWMM 5.2.4 + ANUGA 4.0.1) · runs on Linux · produced by scripts/run_coupled_cases.py in open-solvers.yml.

git clone https://github.com/scott-jeffers/benchmark1d2d && cd benchmark1d2d
git checkout 71dc10fc07a9
conda create -n anuga -c conda-forge anuga=4.0.1 python=3.12 pip scipy
conda activate anuga
python -m pip install -e ".[dev]" swmm-toolkit==0.17.0
python scripts/run_coupled_cases.py A12-010

The model files the suite wrote for this run (.zip, 0.86 KB): the exact inputs the solver read (one folder per grid, where the test has several), with their SHA-256.

The suite's own coupler moves the water; its code is the script.

The test itself (inputs, exact answer, checks): A12-010.zip. Check the score card with benchmark1d2d verify-card: its signature by the suite's public development key shows the card has not changed since it was written, not who wrote it.

OpenSWMM 6

OpenSWMM Engine v6 (pre-release) with its own 1D/2D coupling: a local-inertial 2D surface with each manhole tied to a mesh vertex, run with its defaults; the surface is the case's grid with each square cut into two triangles

#2 0.79 % off

Run time, finest grid: 4.0 s · INTEL(R) XEON(R) PLATINUM 8573C, 2 cores, 15.6 GB, Linux 6.17.0-1022-azure (GitHub Actions (github-hosted, ubuntu24))

Settings: OpenSWMM's own 1D/2D coupling, defaults; vertex-coupled manholes; two triangles per grid square

Manhole outflow

• 0.56 % off

Street depth

• 0.61 mm off

0.79 % of the 77.7 mm normal depth

Water balance

· 0.0012 % off

conservation, reported beside the score

With OpenSWMM's own coupling and defaults: the manhole passes 0.503 m³/s onto the street (0.5 exact), the street runs 0.6 mm from normal depth, and the water balances to 0.01 m³ of 900 m³.

Scored with method 3.0 · Score card: OpenSWMM Engine v6 1D/2D (two triangles per grid square) 6.0.0a4.dev1

Run it yourself

OpenSWMM Engine v6 1D/2D (two triangles per grid square) 6.0.0a4.dev1 · runs on Linux · produced by scripts/run_openswmm_coupled.py in open-solvers.yml.

git clone https://github.com/scott-jeffers/benchmark1d2d && cd benchmark1d2d
git checkout 71dc10fc07a9
python -m pip install -e ".[dev]" swmm-toolkit==0.17.0
python -m venv .venv-openswmm
.venv-openswmm/bin/python -m pip install "openswmm==6.0.0a4.dev1" numpy
python scripts/run_openswmm_coupled.py --openswmm-python .venv-openswmm/bin/python --mesh diagonal A12-010

The model files the suite wrote for this run (.zip, 28 KB): the exact inputs the solver read (one folder per grid, where the test has several), with their SHA-256.

HEC-RAS 7.0

HEC-RAS 7.0.1 with its own storm-drain pipe networks: nodes, conduits and top inlets joined to a 2D SWE-ELM surface, HEC-RAS's defaults; the network is written into the geometry file headless and HEC-RAS's compute builds its cells. HEC-RAS 7.0.1 leaves the pipe solver's settings out of what it hands its engine for these headless plans, so the suite adds HEC-RAS's defaults and runs the engine again (the run time includes both passes)

#3 7.6 % off

Run time, finest grid: 31.9 s · AMD EPYC 7763 64-Core Processor, 2 cores, 16 GB, Windows 2025Server (GitHub Actions (github-hosted, win25-vs2026))

Settings: hecras pipe network written into the geometry HDF (nodes, conduits, top inlets), 2D SWE-ELM surface, defaults

Manhole outflow

• 0 % off

Street depth

• 5.9 mm off

7.6 % of the 77.7 mm normal depth

Water balance

· 0.48 % off

conservation, reported beside the score

The manhole passes exactly 0.5 m³/s onto the street, but the street runs 83.6 mm deep where normal depth is 77.7 mm. The suite's balance (2D cells, the pipe cells' volume tables, the outflow line) is 4.3 m³ short of 900 m³ (0.48 %); HEC-RAS's own report closes to 0.017 %.

Scored with method 3.0 · Score card: HEC-RAS 7.0.1 pipe networks 1D/2D

Run it yourself

HEC-RAS 7.0.1 pipe networks 1D/2D · runs on Windows · produced by scripts/run_hecras_pipes.py in hecras.yml.

git clone https://github.com/scott-jeffers/benchmark1d2d && cd benchmark1d2d
git checkout 71dc10fc07a9
# Windows: HEC-RAS 7.0.1 from HEC (HEC-RAS_701_Setup.exe, SHA-256 1FE76297…3CEE73), silent install /S /v/qn
python -m pip install -e ".[dev]" "ras-commander==0.106.1" h5py psutil pywin32 pillow pythonnet tifffile
python scripts/run_hecras_pipes.py A12-010 --accept-hec-terms

The model files the suite wrote for this run (.zip, 285 KB): the exact inputs the solver read (one folder per grid, where the test has several), with their SHA-256.

The pipe network (nodes, conduits, top inlets) is written into the geometry HDF; HEC-RAS's preprocessor builds its cells.

OpenSWMM 6

The same OpenSWMM 6 1D/2D model on a finer-cut mesh: each grid square cut into four triangles by both diagonals (the mesh the suite's ANUGA surface uses)

#4 10 % off

Run time, finest grid: 11.0 s · Intel(R) Xeon(R) Platinum 8370C CPU @ 2.80GHz, 2 cores, 15.6 GB, Linux 6.17.0-1022-azure (GitHub Actions (github-hosted, ubuntu24))

Settings: OpenSWMM's own 1D/2D coupling, defaults; vertex-coupled manholes; four triangles per grid square

Manhole outflow

• 0.58 % off

Street depth

• 8 mm off

10 % of the 77.7 mm normal depth

Water balance

· 0.00084 % off

conservation, reported beside the score

Same exchange and balance as on the two-triangle mesh, but with each square cut into four triangles the street runs 85.7 mm deep instead of 77.7 mm. The same model on the simpler two-triangle mesh is 0.6 mm off: the sheet flow depends on how the grid is triangulated.

Scored with method 3.0 · Score card: OpenSWMM Engine v6 1D/2D (four triangles per grid square) 6.0.0a4.dev1

Run it yourself

OpenSWMM Engine v6 1D/2D (four triangles per grid square) 6.0.0a4.dev1 · runs on Linux · produced by scripts/run_openswmm_coupled.py in open-solvers.yml.

git clone https://github.com/scott-jeffers/benchmark1d2d && cd benchmark1d2d
git checkout 71dc10fc07a9
python -m pip install -e ".[dev]" swmm-toolkit==0.17.0
python -m venv .venv-openswmm
.venv-openswmm/bin/python -m pip install "openswmm==6.0.0a4.dev1" numpy
python scripts/run_openswmm_coupled.py --openswmm-python .venv-openswmm/bin/python --mesh cross A12-010

The model files the suite wrote for this run (.zip, 54 KB): the exact inputs the solver read (one folder per grid, where the test has several), with their SHA-256.

Not run yet: TUFLOW, InfoWorks ICM, MIKE+, PCSWMM 2D, Flood Modeller

Run it and add yours →

Status of this test

Candidate. To become frozen it needs: two independent codes pass; maintainer review recorded.

Download inputs (.zip)Check your results in the browser Cite this test View on GitHub

Technical details for reviewers Checks, reference, inputs, sources

Checks and why each limit was chosen

Check	Difference measured as a percentage of	Latest	Why this check
exchange_flow expected_state_error of Q · in the score	already a percentage	–	Steady manhole outflow within 1 % of the inflow.
street_depth expected_state_error of h · in the score	of the 77.7 mm normal depth	–	Street depth 75–125 m below the manhole within 3 mm (4 %) of normal depth: the sheet must carry exactly what the manhole released.
water_balance continuity_error of volume · conservation, beside the score	already a percentage	–	By the end of the run, the water stored on the surface and in the pipes has changed by exactly what came in minus what went out. A coupling that moves water between the two models must not make or lose any; each engine's own continuity error is allowed within this limit.
convergence not applicable	–	–	Scored on exact states that follow from conservation (exchanged and discharged volumes, settled levels): they do not depend on the grid.

Reference

Exact states that follow from the inputs by conservation and hydrostatics: exchanged and discharged volumes, settled levels and steady flows, plus the model's own volume balance.

Expected state	Value	Why it must hold
steady_exchange Q at M1	0.5 m3/s	At steady state the manhole has no outlet but the street, so it must pass the full pipe inflow (continuity).
normal_depth h at P1,P2	0.0777 m	Uniform sheet flow of q = Q/B = 0.05 m²/s on slope 0.005 with Manning n = 0.02 (hydraulic radius = depth in 2D shallow-water models): h = (n q / √S)^(3/5).

Promotion checklist

Only frozen tests have fixed inputs and answers. This list is computed from the manifest and the published score cards; the rules are in the method.

✓Data licence verifiedfor candidateanalytic-public
✓All inputs availablefor candidateall committed or fetched by SHA-256
✓Reference (truth) availablefor candidateexact states from conservation
✓Every tolerance justifiedfor candidateeach gating criterion has a rationale
✓A published run passesfor frozen1 passing score card(s)
✓Order of accuracy shownfor frozennot applicable: Scored on exact states that follow from conservation (exchanged and discharged volumes, settled levels): they do not depend on the grid.
✗Two independent codes passfor frozenpassing codes: OpenSWMM Engine v6 1D/2D — needs a second, independently written solver or engine
✗Maintainer review recordedfor frozenno maintainer review recorded

Inputs

File	Role	Format	SHA-256	Get it
`inputs/coupling.json`	coupling	json	`cd6872b93d6f…`	Download

About this test

Physics

A 0.6 m pipe brings a constant 0.5 m³/s to manhole M1, which has no outlet (its only other connection is a 1 m stub to a flap-gated outfall that never opens, because SWMM-family engines need an outfall). The manhole surcharges onto a 10 m wide, 200 m long street that falls at \(S = 0.005\) (Manning \(n = 0.02\)), walled on three sides and open at its foot.

Two answers follow exactly at steady state:

Exchange: the manhole must pass the whole inflow, \(Q = 0.5\) m³/s.
Street depth: below the manhole the flow becomes uniform sheet flow of \(q = Q/B = 0.05\) m²/s. With the depth as hydraulic radius (as in every 2D shallow-water model), \(h = (n q / \sqrt{S})^{3/5} = 77.7\) mm.

The street's foot is held at that normal depth, so the depth 75 and 125 m below the manhole tests what the manhole released, not the outflow boundary.

What it checks

That the network-to-surface exchange delivers the network's flow onto the 2D mesh, all of it and nothing more, and that the coupled model balances its water. The exchange coefficients in inputs/coupling.json (weir 0.5, orifice 0.6, a 0.6 m grate) are for engines that need them; the scored states do not depend on them.

Citation

Chen, A. S., Djordjević, S., Leandro, J., and Savić, D. A. (2007). The urban inundated area: a coupled 1D/2D model for the interaction between sewer and surface. Proc. NOVATECH 2007.

Sources

Chen, A. S., Djordjević, S., Leandro, J., Savić, D. A. (2007). The urban inundated area: a coupled 1D/2D model for the interaction between sewer and surface. www.researchgate.net/publication/257306339
Rubinato, M., Martins, R., Kesserwani, G., Leandro, J., Djordjević, S., Shucksmith, J. (2017). Experimental calibration and validation of sewer/surface flow exchange equations in steady and unsteady flow conditions. doi:10.1016/j.jhydrol.2017.06.024

Test A12-010_manhole_surcharge_onto_street · version 1.0.0 · data licence analytic-public