District of Columbia · Northeast Atlantic Coast & Piedmont · river deposits country
Fall · September 16, 2026
Washington, District of Columbia
Where your water goes
Your sub-basin
Potomac
then
Atlantic Ocean Seaboard
It arrives here
Atlantic Ocean
Everything that falls here works its way east and north to the Atlantic. It is the drainage that carried the fur trade inland and the log drives back out, and the one Atlantic salmon and American eel still use — the eel travelling the whole length of it to spawn in the Sargasso Sea.
Basin 020700 (USGS hydrologic unit)
The river right now
127%
of the ten-year median for this date · 4.9 m³/s against 3.9 normally
normalAbout what it should be for the date. The river is doing its ordinary work — sorting gravel, feeding its banks and moving fish around at the pace everything in it is adapted to. It is rising — about 53% more water by the end of the week.
Under your feet
About 3 million years old — from the ice ages and since — the most recent chapter.
All the kinds of rock, and how each one forms →
Lowland Deposits · Pleistocene
colluvium · Pliocene
Bedrock and soil figures are modelled from national geological surveys and global soil mapping, at a resolution of a few hundred metres — right for the shape of a district, not for a particular garden. River discharge is modelled, not gauged. For anything that matters, dig a hole and look.
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Late Cretaceous sedimentary · Late Cretaceous
Mesozoic sedimentary rocks · Early Cretaceous
Chopawamsic Formation · Cambrian
The soil it made
What that means
Comfortable for woodland plants and a little tight for the vegetable garden. Brassicas sulk, and clubroot is worse at this end of the scale.
Happy here without a fight
Blueberries, raspberries, potatoes, rhubarb, carrots, most conifers, azaleas and hydrangeas — which come out blue here.
If you want the rest
A dressing of lime in autumn brings the vegetable beds up without touching the fruit. Leave the blueberries well alone.
Working it
A balance of sand, silt and clay — the texture that holds enough water to matter and still drains, which is why loam is the one everybody wants.