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CALCULATORS / CIVIL, GEOTECHNICAL AND WATER SCREENING

Stormwater storage screening calculator

Rectangular storm pulse with constant outlet rate; no hydrograph routing.

civil-storm-storage.napkin / editable
✓ checks pass

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenariostoragem^3
13.5
9.9

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

storage capacity budget13.50 m^3✓ passes

BASELINE INPUTS

CALCULATED

storage13.5 m^3

Edits change the baseline source.

Calculated from your source · not saved
Baseline · Baseline
storage capacity budget13.50 m^3 ✓ passes
alternative · alternative
storage capacity budget9.90 m^3 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

storage
storage = max(0 L/s,inflow-outflow)*duration [m^3]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

inflow
20 L/s
outflow
5 L/s
duration
15 min

Calculated

storage
13.5 m^3

Assumptions and limits

Rectangular storm pulse with constant outlet rate; no hydrograph routing.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Stormwater storage screening. Inputs: inflow hydrograph; permitted outflow; initial storage. Outputs: required storage; overflow scenario. Model scope: Preliminary geometry and loads; site/code inputs supplied externally. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

  • Inputs: inflow hydrograph, permitted outflow, initial storage
  • Outputs: required storage, overflow scenario
  • Modes: calculate, compare, sweep
  • Drawing: Load and site section diagram

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS

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