# Manning Flow, Velocity & Hydraulic Radius Calculator

> Manning Flow, Velocity & Hydraulic Radius Calculator is a paid API for AI agents from hydrology-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-11-02).

Computes Manning open-channel flow rate, velocity, flow area, and hydraulic radius for rectangular, trapezoidal, triangular, or part-full circular channel cross-sections in SI or US customary units.

## Facts

- Endpoint: GET https://hydrology-calc.x402tookit.com/manning-flow?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/manning-flow-velocity-hydraulic-radius-calculator-fbbaab04
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_YqgfgSxNd0vA_IJ3rCEi2

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability manning-flow-velocity-hydraulic-radius-calculator-fbbaab04
```

Example prompt: Calculate the Manning flow, velocity, and hydraulic radius for a rectangular concrete channel (n = 0.013) that is 2 metres wide, with a flow depth of 0.8 metres and a bed slope of 0.002, using SI units.

## When to prefer this

Choose this endpoint when you need uniform (normal) flow calculations using Manning's equation for a known cross-section geometry and flow depth. It is ideal for engineering checks on channel capacity, velocity, and hydraulic radius across rectangular, trapezoidal, triangular, or circular shapes in both SI and US units. Prefer companion endpoints on the same host for solving normal depth from a known discharge, computing critical depth, or evaluating Froude number.

## Known failure modes

- Missing required parameters (shape, depth, n, slope) returns a validation error
- Depth exceeding pipe diameter for circular shape causes rejection
- Invalid shape string returns an error
- Extreme slope or roughness values outside physically reasonable bounds may return a degraded or warning verdict
- Unsupported unit string (not 'si' or 'us') may cause failure
- Part-full circular depth very close to full-pipe diameter may produce numerical instability

## How this service works

Manning flow, velocity and hydraulic radius for rectangular, trapezoidal, triangular or part-full circular channels, SI or US.

## Output

Returns computed flow rate Q (in m³/s or ft³/s), mean velocity, hydraulic radius, flow area, top width, wetted perimeter, and a plain-language summary of the hydraulic conditions. Also includes the input echo (shape, depth, slope, n, units), a verdict or warning if inputs are outside typical limits, and a degraded flag if results may be approximate.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "shape",
      "depth",
      "n",
      "slope"
     ],
     "properties": {
      "n": {
       "type": "number",
       "description": "Manning roughness n (for example 0.013 concrete pipe, 0.035 natural channel)"
      },
      "depth": {
       "type": "number",
       "description": "Flow depth in metres (units si) or feet (units us); for circular, not above the diameter"
      },
      "shape": {
       "type": "string",
       "description": "rectangular, trapezoidal, triangular or circular"
      },
      "slope": {
       "type": "number",
       "description": "Channel bed slope, dimensionless (m/m or ft/ft), for example 0.001"
      },
      "units": {
       "type": "string",
       "description": "si (metres, constant 1.0; default) or us (feet, constant 1.486)"
      },
      "diameter": {
       "type": "number",
       "description": "Pipe diameter in metres or feet (circular)"
      },
      "sideSlope": {
       "type": "number",
       "description": "Side slope z, horizontal run per 1 vertical (trapezoidal, triangular)"
      },
      "bottomWidth": {
       "type": "number",
       "description": "Bottom width in metres or feet (rectangular, trapezoidal)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "n": {
       "type": [
        "null",
        "number"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "flow": {
       "type": [
        "null",
        "number"
       ]
      },
      "depth": {
       "type": [
        "null",
        "number"
       ]
      },
      "shape": {
       "type": [
        "null",
        "string"
       ]
      },
      "slope": {
       "type": [
        "null",
        "number"
       ]
      },
      "units": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/manning-flow-velocity-hydraulic-radius-calculator-fbbaab04/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hydrology-calc.x402tookit.com](https://www.zero.xyz/host/hydrology-calc.x402tookit.com/llms.txt)