My Projects
A drainage design is rarely one calculation — it is a chain of them. On any calculator, use Save to project to keep that result, then group related calculations under a named project so the whole site design stays together. Projects are stored in your browser and are available whenever you return to this site.
No saved projects
Use any calculator and click "Save to Project" in the results section to get started.
Browse CalculatorsHow the project workflow works
1. Calculate
Run any calculator with your site inputs and confirm the result.
2. Save to a project
Save the result to a new or existing project. Inputs and outputs are stored together.
3. Return anytime
Reopen a project here to review, rename, or continue where you left off.
Projects live only in this browser (they use local storage, not an account), so clearing your browser data or switching devices will remove them. Nothing is uploaded.
A typical drainage project, step by step
Most site drainage designs follow the same sequence — estimate the flow, collect it, convey it, then store or infiltrate the excess. Save each calculator's result to the same project so the numbers carry forward.
- 1
Estimate the runoff
Start with the contributing area and land use. Pick a runoff coefficient, then find the peak flow with the Rational Method.
- 2
Collect the water
Size the inlets, gutters, and surface collectors that gather runoff before it is conveyed.
- 3
Convey it
Route the collected flow through pipes or channels sized with Manning's equation.
- 4
Store or infiltrate
Detain or infiltrate the excess so post-development flow does not exceed pre-development conditions.