The Swale Desk

This desk watches one corner of the world: the shallow channels, ridges, and pipes that keep runoff out of basements and off pavement. Every page here starts from three numbers you can measure in an afternoon — grade, percolation rate, and catchment area. Any drainage decision made without them is a guess wearing a plan.

Checked 2026-09-10 · figures on this page re-verified against the sources below

Number one Grade % How fast your ground falls. Measure it with a line level. Number two Perk rate How fast your soil swallows water, in inches per hour. Number three Catchment How many square feet of roof and yard feed the wet spot.

The ledger

Entries as they were written or re-checked. The ledger is the desk's spine: nothing on this site claims to be fresher than its entry.

Date	Condition or question	Points to	Number
2026-09-10	Wet-season walk: measure before you buy anything	Measure yard grade	3 numbers
2026-09-05	Where pipes must go below frost, and where they never do	Frost line note	0–6 ft
2026-09-02	Why 72 hours of standing water is the rule, and where it comes from	72-hour rule	72 h
2026-09-01	Grass or rock in the channel — the trade-offs nobody states plainly	Grass or rock note	2 options
2026-08-25	Carry a downspout to the swale, or bury it: the arithmetic	Downspout math	1% min
2026-08-18	Perforated pipe: holes up or holes down, and who disagrees	Holes up or down	2 camps
2026-07-30	What “1 inch per hour” means in a perk test — and the unit trap	Inch per hour note	1 in/hr
2026-07-15	Sock-wrapped perforated pipe: what vendor pages omit	Sock marketing note	0 tests

Objects

Things with boundaries. Each object page defines one thing, lists its near kin, and shows where it stops working. No object page sells a fix; it sets the rules a fix must obey.

Swale — the planted channel. Boundary vs ditch, French drain, rain garden.
Berm — the ridge that makes a swale hold water.
French drain — the pipe system, and when it is the wrong fix.
Check dam — small rock or wood barriers inside a channel.
Grade — slope as percent, and how to read a level.
Percolation rate — the number that chooses swale or drain.
Catchment — roof and yard square footage that feeds the wet spot.
Catch basin — inlet, sump, and the trap of a buried pond.
Dry well — underground storage that only works on a passing perk rate.
Riprap — stone armor for fast water, and its sizing rules.

Jobs

Things you can finish today. Each job page runs on a real time box, lists tools, and marks the points where people stop.

Run a percolation test with a bucket — one afternoon, mostly waiting.
Measure yard grade with a line level — 30 minutes.
Calculate roof and yard catchment — 30 minutes of arithmetic.
Size a swale from three numbers — one hour at a table.
Build check dams in a swale — half a day, rock and stakes.
Plant a swale that does not wash out — seasonal, half a day.
Read your city's drainage code — one hour, no digging.
Diagnose standing water — the three-number check, one hour.

Notes

Dated judgments, disputes, and arithmetic. Notes can go stale, and say so in their header when they do.

Desk files

How the desk works, what it refuses, and who answers when a figure is wrong: method, refuse list, the desk, contact, privacy.

Sources behind this page

Minnesota Stormwater Manual — vegetated swale design chapters, stormwater.pca.state.mn.us
US EPA, NPDES stormwater program — epa.gov/npdes
USDA Natural Resources Conservation Service — nrcs.usda.gov