Open channel flow software

Describe the channel. Rischio shapes it, calculates it, and shows its work.

Any cross-section, from a lined trapezoid to a natural channel with floodplains: normal and critical depth, velocity, Froude number and whether the flow fits, with the calculation report ready to hand in. Describe the channel to the agent, or enter it yourself.

Design a channel, free How it calculates

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The same editor the agent works in. Pick a model, change a number and calculate: the engine answers right here.

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What it checks.

Every check with its rule and its limit, Rischio's defaults. In the studio, each result opens into its equation, with your numbers in it.

How it calculates, step by step

Check	Rule	Limit
Bank-full capacity The discharge fits below the lower bank $Q$	$Q$	$\le Q_{bank}$

Check

Limit

Bank-full capacity

The discharge fits below the lower bank

$Q$

\le Q_{bank}

What you can model

Any section, vertex by vertex
A roughness for every side
Compound sections with floodplains
Slope and discharge

How it's calculated

Uniform flow by Manning
The section divided where its roughness changes, each part with its own n
Normal depth solved for the discharge; critical depth, Froude number and specific energy
The rating curve, from the bed to the bank

The calculation report, ready to sign.

This is the one for the model the editor opens on, as the studio makes it. Read through it.

The checks' summary first, each with its margin
Every section with its equations and the values they take
The assumptions and warnings at the end, no small print

As PDF and Word, with your letterhead, in Professional.

Your engineering firmYour address · your license number

Calculation report

Model: Trapezoidal earth channel
Analysis: Open channel
Date: 15 October 2026
Units: SI · kN, m, kPa

1Summary

The model satisfies its check.

Check	Value	Limit	Margin	Result
Bank-full capacity	2.00 m³/s	≤ 3.41 m³/s	+41 %	OK

Limits are Rischio's defaults.

2Model

Figure 1. Section of the model.

Section

Trapezoidal earth channelCross-section

Vertex	$x$ m	$z$ m	$n$
1	1.00	1.00	0.030
2	2.00	0.10	0.030
3	3.10	0.10	0.030
4	4.00	0.10	0.030
5	5.00	1.00

$x$ Horizontal position · $z$ Elevation · $n$ Roughness of the segment to the next vertex

Flow

Flow conditionsUniform flow

Longitudinal slope

S

0.003 m/m

Discharge

Q

2.00 m³/s

3Normal flow

Figure 2. The section with the water surface at the normal depth.

Water surface elevation

\begin{aligned} Q(y_n) &= Q \quad \text{(normal depth, Manning)} \\ &= 0.770\;\text{m} \end{aligned}

where $Q$ = 2.00 m³/s

Normal depth

\begin{aligned} y_n &= WSE - z_{bed} \\ &= 0.670\;\text{m} \end{aligned}

Flow area

\begin{aligned} A &= \int (WSE - z) \, dx \\ &= 1.84\;\text{m}^{2}\text{} \end{aligned}

Wetted perimeter

\begin{aligned} P &= \Sigma P_i \\ &= 4.00\;\text{m} \end{aligned}

Hydraulic radius

\begin{aligned} R &= A / P \\ &= 0.459\;\text{m} \end{aligned}

where $A$ = 1.84 m², $P$ = 4.00 m

Equivalent roughness

\begin{aligned} n &= \left( \frac{\Sigma P_i n_i^{1.5}}{P} \right)^{2/3} \quad \text{(Horton–Einstein)} \\ &= 0.030\;\text{} \end{aligned}

where $P$ = 4.00 m

Mean velocity

\begin{aligned} V &= \frac{1}{n} R^{2/3} S^{1/2} \\ &= 1.09\;\text{m/s} \end{aligned}

where $n$ = 0.030 , $R$ = 0.459 m, $S$ = 0.003 m/m

4Flow regime

Figure 3. Normal depth (solid) and critical depth (dashed).

Top width

\begin{aligned} &T \\ &= 3.49\;\text{m} \end{aligned}

Froude number

\begin{aligned} Fr &= \frac{V}{\sqrt{g A / T}} \\ &= 0.478\;\text{} \end{aligned}

where $V$ = 1.09 m/s, $A$ = 1.84 m², $T$ = 3.49 m

Critical depth

\begin{aligned} \frac{Q^2 T_c}{g A_c^3} &= 1 \\ &= 0.430\;\text{m} \end{aligned}

where $Q$ = 2.00 m³/s

Specific energy

\begin{aligned} E &= y + \frac{V^2}{2g} \\ &= 0.731\;\text{m} \end{aligned}

where $y$ = 0.670 m, $V$ = 1.09 m/s

5Capacity of the section

Figure 4. Rating curve: water surface elevation against discharge, up to the lower bank.

Bank-full capacity

\begin{aligned} Q_{bank} &= \frac{1}{n} A R^{2/3} S^{1/2} \quad (y = y_{bank}) \\ &= 3.41\;\text{m}^{3}\text{/s} \end{aligned}

where $y_{bank}$ = 0.900 m, $S$ = 0.003 m/m

Check · Bank-full capacity

\begin{aligned} Q &\le Q_{bank} \\ Q &= 2.00\,\text{m}^{3}\text{/s} \; \le 3.41\,\text{m}^{3}\text{/s} \end{aligned}

margin +41 %

where $Q$ = 2.00 m³/s, $Q_{bank}$ = 3.41 m³/s

Learn more.

Questions, answered.

Which sections can it calculate?

Any cross-section drawn vertex by vertex: trapezoids, rectangles, gutters, compound sections with floodplains and natural channels, each side with its own Manning n.

Which method does it use?

Manning's equation for uniform flow, with the section divided where its roughness changes, as HEC-RAS does: a lined channel and its grassed floodplains each carry their own share. It solves the normal depth for the discharge, and gives the critical depth, the Froude number, the specific energy and the rating curve.

Does it calculate backwater profiles?

Not yet: it calculates uniform flow. Gradually varied flow, culverts and weirs are outside it.

What does the agent do, and what does the engine do?

The agent turns your words into a model and edits it. The engine, the same one behind the editor, does every calculation: no number comes from the agent. You review the model, open every equation and sign the report.

Is it free?

The Free plan has all four tools and up to 3 models. Professional, $49 a month, adds unlimited models, the report as PDF and Word with your letterhead, and your own agent through MCP. Every account starts with 14 days of Professional, no card needed.

What will you design today?

Describe it in a sentence. Rischio builds it, calculates it, and shows you every step.

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