Source: https://guthlabs.ai/docs/instruments/open-channel-flow-manning-s-equation/implementation/

instrument implementation / implementation-contract

# Open-Channel Flow — Manning's Equation implementation

A source-bound implementation contract for Open-Channel Flow — Manning's Equation; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t6-120

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification has no stated validation for n=0 or negative slope. n=0 causes division by zero, while a signed negative slope makes the square-root argument invalid; both can produce undefined results unless rejected or assigned an explicit convention.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "system": "SI",
    "shape": "rectangular",
    "width_m": 3,
    "depth_m": 1,
    "mannings_n": 0.025,
    "slope": 0.001
  },
  "expected_outputs": {
    "hydraulic_area_m2": 3,
    "wetted_perimeter_m": 5,
    "hydraulic_radius_m": 0.6,
    "velocity_m_per_s": 0.899831,
    "discharge_m3_per_s": 2.69949
  },
  "working": "A=b y=3*1=3 m^2. P=b+2y=3+2(1)=5 m. R=A/P=3/5=0.6 m. V=(1/0.025)(0.6)^(2/3)(0.001)^(1/2). (0.6)^(2/3)=0.711378661 and sqrt(0.001)=0.0316227766, so V=40*0.711378661*0.0316227766=0.8998307 m/s, or 0.899831 m/s. Q=VA=0.8998307*3=2.699492 m^3/s, or 2.69949 m^3/s."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/open-channel-flow-manning-s-equation/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/open-channel-flow-manning-s-equation/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/open-channel-flow-manning-s-equation/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche6/tranche6-results.json`